From 5cdd42f3fd4cb6faa8670b53ead6a1e7fce062f1 Mon Sep 17 00:00:00 2001
From: liu fengyun <liufengyunchina@gmail.com>
Date: Wed, 11 May 2016 10:37:18 +0200
Subject: [PATCH 01/11] initial works

---
 .../tools/dotc/transform/PatternMatcher.scala |  10 +
 .../tools/dotc/transform/PostTyper.scala      |   9 +
 src/dotty/tools/dotc/transform/Space.scala    | 483 +++++++++++
 .../transform/PatmatExhaustivityTest.scala    |  58 ++
 tests/patmat/patmat-adt.check                 |  21 +
 tests/patmat/patmat-adt.scala                 |  53 ++
 tests/patmat/patmat-extractor.scala           |  17 +
 tests/patmat/patmat-ortype.check              |  13 +
 tests/patmat/patmat-ortype.scala              |  40 +
 tests/patmat/patmatexhaust-huge.check         |   5 +
 tests/patmat/patmatexhaust-huge.scala         | 806 ++++++++++++++++++
 tests/patmat/patmatexhaust.check              |  33 +
 tests/patmat/patmatexhaust.scala              | 131 +++
 tests/patmat/t3097.scala                      |  35 +
 tests/patmat/t3111.check                      |   8 +
 tests/patmat/t3111.scala                      |  13 +
 tests/patmat/t3163.check                      |   5 +
 tests/patmat/t3163.scala                      |   3 +
 tests/patmat/t3683.scala                      |  19 +
 tests/patmat/t4020.scala                      |  25 +
 tests/patmat/t4333.scala.ignore               |   7 +
 tests/patmat/t4408.check                      |   5 +
 tests/patmat/t4408.scala                      |  16 +
 tests/patmat/t4526.check                      |  13 +
 tests/patmat/t4526.scala                      |  16 +
 tests/patmat/t4691.check                      |   5 +
 tests/patmat/t4691.scala                      |  18 +
 tests/patmat/t5440.check                      |   5 +
 tests/patmat/t5968.scala                      |   7 +
 tests/patmat/t6008.scala                      |   5 +
 tests/patmat/t6420.check                      |   5 +
 tests/patmat/t6420.scala                      |  11 +
 tests/patmat/t6450.scala                      |   9 +
 tests/patmat/t6818.scala                      |  11 +
 tests/patmat/t7206.scala.ignore               |  19 +
 tests/patmat/t7285.check                      |  13 +
 tests/patmat/t7285.scala                      |  55 ++
 tests/patmat/t7285a.scala                     |  83 ++
 tests/patmat/t7298.scala                      |  11 +
 tests/patmat/t7353.scala                      |  11 +
 tests/patmat/t7437.scala                      |  17 +
 tests/patmat/t7466.check                      |   5 +
 tests/patmat/t7466.scala                      |  17 +
 tests/patmat/t7631.check                      |   5 +
 tests/patmat/t7631.scala                      |  11 +
 tests/patmat/t7669.check                      |   5 +
 tests/patmat/t7669.scala                      |  14 +
 tests/patmat/t7746.check                      |   5 +
 tests/patmat/t7746.scala                      |   5 +
 tests/patmat/t8068.scala                      |  14 +
 tests/patmat/t8178.check                      |  13 +
 tests/patmat/t8178.scala                      |  33 +
 tests/patmat/t8412.check                      |   5 +
 tests/patmat/t8412.scala                      |  14 +
 tests/patmat/t8430.check                      |   5 +
 tests/patmat/t8430.scala                      |  19 +
 tests/patmat/t8511.check                      |   5 +
 tests/patmat/t8511.scala                      |  25 +
 tests/patmat/t8546.scala                      |  49 ++
 tests/patmat/t8606.scala                      |  18 +
 tests/patmat/t9129.check                      |   5 +
 tests/patmat/t9129.scala                      |  29 +
 tests/patmat/t9232.check                      |   5 +
 tests/patmat/t9232.scala                      |  16 +
 tests/patmat/t9289.check                      |   9 +
 tests/patmat/t9289.scala                      |  28 +
 tests/patmat/t9351.check                      |  13 +
 tests/patmat/t9351.scala                      |  35 +
 tests/patmat/t9398.check                      |   5 +
 tests/patmat/t9398.scala                      |  13 +
 tests/patmat/t9399.scala                      |  16 +
 tests/patmat/t9573.check                      |   5 +
 tests/patmat/t9573.scala                      |  13 +
 tests/patmat/t9630.scala                      |  21 +
 tests/patmat/t9657.scala.ignore               |  28 +
 tests/patmat/t9672.check                      |   5 +
 tests/patmat/t9672.scala                      |  28 +
 tests/patmat/t9677.scala                      |  23 +
 78 files changed, 2693 insertions(+)
 create mode 100644 src/dotty/tools/dotc/transform/Space.scala
 create mode 100644 test/test/transform/PatmatExhaustivityTest.scala
 create mode 100644 tests/patmat/patmat-adt.check
 create mode 100644 tests/patmat/patmat-adt.scala
 create mode 100644 tests/patmat/patmat-extractor.scala
 create mode 100644 tests/patmat/patmat-ortype.check
 create mode 100644 tests/patmat/patmat-ortype.scala
 create mode 100644 tests/patmat/patmatexhaust-huge.check
 create mode 100644 tests/patmat/patmatexhaust-huge.scala
 create mode 100644 tests/patmat/patmatexhaust.check
 create mode 100644 tests/patmat/patmatexhaust.scala
 create mode 100644 tests/patmat/t3097.scala
 create mode 100644 tests/patmat/t3111.check
 create mode 100644 tests/patmat/t3111.scala
 create mode 100644 tests/patmat/t3163.check
 create mode 100644 tests/patmat/t3163.scala
 create mode 100644 tests/patmat/t3683.scala
 create mode 100644 tests/patmat/t4020.scala
 create mode 100644 tests/patmat/t4333.scala.ignore
 create mode 100644 tests/patmat/t4408.check
 create mode 100644 tests/patmat/t4408.scala
 create mode 100644 tests/patmat/t4526.check
 create mode 100644 tests/patmat/t4526.scala
 create mode 100644 tests/patmat/t4691.check
 create mode 100644 tests/patmat/t4691.scala
 create mode 100644 tests/patmat/t5440.check
 create mode 100644 tests/patmat/t5968.scala
 create mode 100644 tests/patmat/t6008.scala
 create mode 100644 tests/patmat/t6420.check
 create mode 100644 tests/patmat/t6420.scala
 create mode 100644 tests/patmat/t6450.scala
 create mode 100644 tests/patmat/t6818.scala
 create mode 100644 tests/patmat/t7206.scala.ignore
 create mode 100644 tests/patmat/t7285.check
 create mode 100644 tests/patmat/t7285.scala
 create mode 100644 tests/patmat/t7285a.scala
 create mode 100644 tests/patmat/t7298.scala
 create mode 100644 tests/patmat/t7353.scala
 create mode 100644 tests/patmat/t7437.scala
 create mode 100644 tests/patmat/t7466.check
 create mode 100644 tests/patmat/t7466.scala
 create mode 100644 tests/patmat/t7631.check
 create mode 100644 tests/patmat/t7631.scala
 create mode 100644 tests/patmat/t7669.check
 create mode 100644 tests/patmat/t7669.scala
 create mode 100644 tests/patmat/t7746.check
 create mode 100644 tests/patmat/t7746.scala
 create mode 100644 tests/patmat/t8068.scala
 create mode 100644 tests/patmat/t8178.check
 create mode 100644 tests/patmat/t8178.scala
 create mode 100644 tests/patmat/t8412.check
 create mode 100644 tests/patmat/t8412.scala
 create mode 100644 tests/patmat/t8430.check
 create mode 100644 tests/patmat/t8430.scala
 create mode 100644 tests/patmat/t8511.check
 create mode 100644 tests/patmat/t8511.scala
 create mode 100644 tests/patmat/t8546.scala
 create mode 100644 tests/patmat/t8606.scala
 create mode 100644 tests/patmat/t9129.check
 create mode 100644 tests/patmat/t9129.scala
 create mode 100644 tests/patmat/t9232.check
 create mode 100644 tests/patmat/t9232.scala
 create mode 100644 tests/patmat/t9289.check
 create mode 100644 tests/patmat/t9289.scala
 create mode 100644 tests/patmat/t9351.check
 create mode 100644 tests/patmat/t9351.scala
 create mode 100644 tests/patmat/t9398.check
 create mode 100644 tests/patmat/t9398.scala
 create mode 100644 tests/patmat/t9399.scala
 create mode 100644 tests/patmat/t9573.check
 create mode 100644 tests/patmat/t9573.scala
 create mode 100644 tests/patmat/t9630.scala
 create mode 100644 tests/patmat/t9657.scala.ignore
 create mode 100644 tests/patmat/t9672.check
 create mode 100644 tests/patmat/t9672.scala
 create mode 100644 tests/patmat/t9677.scala

diff --git a/src/dotty/tools/dotc/transform/PatternMatcher.scala b/src/dotty/tools/dotc/transform/PatternMatcher.scala
index 974053769233..9e3047645a34 100644
--- a/src/dotty/tools/dotc/transform/PatternMatcher.scala
+++ b/src/dotty/tools/dotc/transform/PatternMatcher.scala
@@ -50,8 +50,17 @@ class PatternMatcher extends MiniPhaseTransform with DenotTransformer {thisTrans
   private var _id = 0 // left for debuging
 
   override def transformMatch(tree: Match)(implicit ctx: Context, info: TransformerInfo): Tree = {
+    val Match(sel, cases) = tree
+
     val translated = new Translator()(ctx).translator.translateMatch(tree)
 
+    // check exhaustivity and unreachability
+    val engine = new SpaceEngine
+    if (!engine.skipCheck(sel.tpe)) {
+      engine.exhaustivity(tree)
+      engine.redundancy(tree)
+    }
+
     translated.ensureConforms(tree.tpe)
   }
 
@@ -1275,6 +1284,7 @@ class PatternMatcher extends MiniPhaseTransform with DenotTransformer {thisTrans
         case _                                                    => (cases, None)
       }
 
+
       // checkMatchVariablePatterns(nonSyntheticCases) // only used for warnings
 
       // we don't transform after uncurry
diff --git a/src/dotty/tools/dotc/transform/PostTyper.scala b/src/dotty/tools/dotc/transform/PostTyper.scala
index fcde59b24a03..4bfb79726aa6 100644
--- a/src/dotty/tools/dotc/transform/PostTyper.scala
+++ b/src/dotty/tools/dotc/transform/PostTyper.scala
@@ -38,6 +38,8 @@ import Symbols._, TypeUtils._
  *
  *  (9) Adds SourceFile annotations to all top-level classes and objects
  *
+ *  (10) Adds Child annotations to all sealed classes
+ *
  *  The reason for making this a macro transform is that some functions (in particular
  *  super and protected accessors and instantiation checks) are naturally top-down and
  *  don't lend themselves to the bottom-up approach of a mini phase. The other two functions
@@ -231,6 +233,13 @@ class PostTyper extends MacroTransform with IdentityDenotTransformer  { thisTran
                   ctx.compilationUnit.source.exists &&
                   sym != defn.SourceFileAnnot)
                 sym.addAnnotation(Annotation.makeSourceFile(ctx.compilationUnit.source.file.path))
+
+              if (!sym.isAnonymousClass) // ignore anonymous class
+                for (parent <- sym.asClass.classInfo.classParents) {
+                  val pclazz = parent.classSymbol
+                  if (pclazz.is(Sealed)) pclazz.addAnnotation(Annotation.makeChild(sym))
+                }
+
               tree
             }
             else {
diff --git a/src/dotty/tools/dotc/transform/Space.scala b/src/dotty/tools/dotc/transform/Space.scala
new file mode 100644
index 000000000000..30a297d0c6bc
--- /dev/null
+++ b/src/dotty/tools/dotc/transform/Space.scala
@@ -0,0 +1,483 @@
+package dotty.tools.dotc
+package transform
+
+import core.Types._
+import core.Contexts._
+import core.Flags._
+import ast.Trees._
+import ast.tpd
+import core.Decorators._
+import core.TypeApplications._
+import core.Symbols._
+import core.NameOps._
+import core.Constants._
+
+/** Space logic for checking exhaustivity and unreachability of
+ *  pattern matching.
+ */
+
+
+/** space definition */
+sealed trait Space
+case object Empty extends Space
+case class Typ(tp: Type, decomposed: Boolean) extends Space
+case class Kon(tp: Type, params: List[Space]) extends Space
+sealed trait Point extends Space
+case class Var(sym: Symbol, tp: Type) extends Point
+case class Const(value: Constant, tp: Type) extends Point
+case class Or(spaces: List[Space]) extends Space
+
+/** abstract space logic */
+trait SpaceLogic {
+  /** Is `tp1` a subtype of `tp2`? */
+  def isSubType(tp1: Type, tp2: Type): Boolean
+
+  /** Is `tp1` the same type as `tp2`? */
+  def isEqualType(tp1: Type, tp2: Type): Boolean
+
+  /** Is `tp` a case class? */
+  def isCaseClass(tp: Type): Boolean
+
+  /** Is the type `tp` decomposable? i.e. all values of the type can be covered
+   *  by its decomposed types.
+   *
+   * Abstract sealed class, OrType and Boolean can be decomposed.
+   */
+  def canDecompose(tp: Type): Boolean
+
+  /** Return parameters types of the case class `tp` */
+  def signature(tp: Type): List[Type]
+
+  /** Get components of decomposable types */
+  def partitions(tp: Type): List[Space]
+
+  /** Simplify space using the laws, there's no nested union after simplify */
+  def simplify(space: Space): Space = space match {
+    case Kon(tp, spaces) =>
+      val sp = Kon(tp, spaces.map(simplify _))
+      if (sp.params.exists(_ == Empty)) Empty
+      else sp
+    case Or(spaces) =>
+      val set = spaces.map(simplify _).flatMap {
+        case Or(ss) => ss
+        case s => Seq(s)
+      } filter (_ != Empty)
+
+      if (set.isEmpty) Empty
+      else if (set.size == 1) set.toList(0)
+      else Or(set)
+    case Typ(tp, _) =>
+      if (canDecompose(tp) && partitions(tp).isEmpty) Empty
+      else space
+    case _ => space
+  }
+
+  /** Flatten space to get rid of `Or` for pretty print */
+  def flatten(space: Space): List[Space] = space match {
+    case Kon(tp, spaces) =>
+      val flats = spaces.map(flatten _)
+
+      flats.foldLeft(List[Kon]()) { (acc, flat) =>
+        if (acc.isEmpty) flat.map(s => Kon(tp, Nil :+ s))
+        else for (Kon(tp, ss) <- acc; s <- flat) yield Kon(tp, ss :+ s)
+      }
+    case Or(spaces) =>
+      spaces.flatMap(flatten _)
+    case _ => List(space)
+  }
+
+  /** Is `a` a subspace of `b`? Equivalent to `a - b == Empty`, but faster */
+  def subspace(a: Space, b: Space): Boolean = (a, b) match {
+    case (Empty, _) => true
+    case (_, Empty) => false
+    case (Or(ss), _) => ss.forall(subspace(_, b))
+    case (Typ(tp1, _), Typ(tp2, _)) =>
+      isSubType(tp1, tp2)
+    case (Typ(tp1, _), Or(ss)) =>
+      ss.exists(subspace(a, _)) ||
+      (canDecompose(tp1) && subspace(Or(partitions(tp1)), b))
+    case (Typ(tp1, _), Kon(tp2, ss)) =>
+      isSubType(tp1, tp2) && subspace(Kon(tp2, signature(tp2).map(tp => Typ(tp, false))), b)
+    case (Kon(tp1, ss), Typ(tp2, _)) =>
+      isSubType(tp1, tp2) ||
+      simplify(a) == Empty ||
+      (isSubType(tp2, tp1) &&
+        canDecompose(tp1) &&
+        subspace(Or(partitions(tp1)), b))
+    case (Kon(_, _), Or(_)) =>
+      simplify(minus(a, b)) == Empty
+    case (Kon(tp1, ss1), Kon(tp2, ss2)) =>
+      isEqualType(tp1, tp2) && ss1.zip(ss2).forall((subspace _).tupled)
+    case (Const(v1, _), Const(v2, _)) => v1 == v2
+    case (Const(_, tp1), Typ(tp2, _)) => isSubType(tp1, tp2)
+    case (Const(_, _), Or(ss)) => ss.exists(subspace(a, _))
+    case (Const(_, _), _) => false
+    case (_, Const(_, _)) => false
+    case (Var(x, _), Var(y, _)) => x == y
+    case (Var(_, tp1), Typ(tp2, _)) => isSubType(tp1, tp2)
+    case (Var(_, _), Or(ss)) => ss.exists(subspace(a, _))
+    case (Var(_, _), _) => false
+    case (_, Var(_, _)) => false
+  }
+
+  /** Intersection of two spaces  */
+  def intersect(a: Space, b: Space): Space = (a, b) match {
+    case (Empty, _) | (_, Empty) => Empty
+    case (_, Or(ss)) => Or(ss.map(intersect(a, _)))
+    case (Or(ss), _) => Or(ss.map(intersect(_, b)))
+    case (Typ(tp1, _), Typ(tp2, _)) =>
+      if (isSubType(tp1, tp2)) a
+      else if (isSubType(tp2, tp1)) b
+      else Empty
+    case (Typ(tp1, _), Kon(tp2, ss)) =>
+      if (isSubType(tp2, tp1)) b
+      else if (isSubType(tp1, tp2)) a
+      else Empty
+    case (Kon(tp1, ss), Typ(tp2, _)) =>
+      if (isSubType(tp1, tp2) || isSubType(tp2, tp1)) a
+      else Empty
+    case (Kon(tp1, ss1), Kon(tp2, ss2)) =>
+      if (!isEqualType(tp1, tp2)) Empty
+      else if (ss1.zip(ss2).exists(p => simplify(intersect(p._1, p._2)) == Empty)) Empty
+      else
+        Kon(tp1, ss1.zip(ss2).map((intersect _).tupled))
+    case (Const(v1, _), Const(v2, _)) =>
+      if (v1 == v2) a else Empty
+    case (Const(_, tp1), Typ(tp2, _)) =>
+      if (isSubType(tp1, tp2)) a else Empty
+    case (Const(_, _), _) => Empty
+    case (Typ(tp1, _), Const(_, tp2)) =>
+      if (isSubType(tp2, tp1)) b else Empty
+    case (_, Const(_, _)) => Empty
+    case (Var(x, _), Var(y, _)) =>
+      if (x == y) a else Empty
+    case (Var(_, tp1), Typ(tp2, _)) =>
+      if (isSubType(tp1, tp2)) a else Empty
+    case (Var(_, _), _) => Empty
+    case (Typ(tp1, _), Var(_, tp2)) =>
+      if (isSubType(tp2, tp1)) b else Empty
+    case (_, Var(_, _)) => Empty
+  }
+
+  /** The space of a not covered by b */
+  def minus(a: Space, b: Space): Space = (a, b) match {
+    case (Empty, _) => Empty
+    case (_, Empty) => a
+    case (Typ(tp1, _), Typ(tp2, _)) =>
+      if (isSubType(tp1, tp2)) Empty
+      else if (isSubType(tp2, tp1) && canDecompose(tp1))
+        minus(Or(partitions(tp1)), b)
+      else a
+    case (Typ(tp1, _), Kon(tp2, ss)) =>
+      if (isSubType(tp1, tp2)) minus(Kon(tp2, signature(tp2).map(tp => Typ(tp, false))), b)
+      else if (isSubType(tp2, tp1) && canDecompose(tp1))
+        minus(Or(partitions(tp1)), b)
+      else a
+    case (_, Or(ss)) =>
+      ss.foldLeft(a)(minus)
+    case (Or(ss), _) =>
+      Or(ss.map(minus(_, b)))
+    case (Kon(tp1, ss), Typ(tp2, _)) =>
+      if (isSubType(tp1, tp2)) Empty
+      else if (simplify(a) == Empty) Empty
+      else if (isSubType(tp2, tp1) && canDecompose(tp1))
+        minus(Or(partitions(tp1)), b)
+      else a
+    case (Kon(tp1, ss1), Kon(tp2, ss2)) =>
+      if (!isEqualType(tp1, tp2)) a
+      else if (ss1.zip(ss2).exists(p => simplify(intersect(p._1, p._2)) == Empty)) a
+      else if (ss1.zip(ss2).forall((subspace _).tupled)) Empty
+      else
+        Or(
+          ss1.zip(ss2).map((minus _).tupled).zip(0 to ss2.length - 1).map {
+            case (ri, i) => Kon(tp1, ss1.updated(i, ri))
+          })
+    case (Const(v1, _), Const(v2, _)) =>
+      if (v1 == v2) Empty else a
+    case (Const(_, tp1), Typ(tp2, _)) =>
+      if (isSubType(tp1, tp2)) Empty else a
+    case (Const(_, _), _) => a
+    case (Typ(tp1, _), Const(_, tp2)) =>  // Boolean
+      if (isSubType(tp2, tp1) && canDecompose(tp1))
+        minus(Or(partitions(tp1)), b)
+      else a
+    case (_, Const(_, _)) => a
+    case (Var(x, _), Var(y, _)) =>
+      if (x == y) Empty else a
+    case (Var(_, tp1), Typ(tp2, _)) =>
+      if (isSubType(tp1, tp2)) Empty else a
+    case (Var(_, _), _) => a
+    case (_, Var(_, _)) => a
+  }
+}
+
+/** Scala implementation of space logic */
+class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
+  import tpd._
+
+  def debug(s: String): Unit = {
+    if (ctx.debug) println(s)
+  }
+
+  /** Return the space that represents the pattern `pat`
+   *
+   *  If roundUp is true, approximate extractors to its type,
+   *  otherwise approximate extractors to Empty
+   */
+  def project(pat: Tree, roundUp: Boolean = true)(implicit ctx: Context): Space = pat match {
+    case Literal(c) => Const(c, c.tpe)
+    case _: BackquotedIdent => Var(pat.symbol, pat.tpe)
+    case Ident(_) => Typ(pat.tpe.stripAnnots, false)
+    case Select(_, _) =>
+      if (pat.symbol.is(Module))
+        Typ(pat.tpe.stripAnnots, false)
+      else
+        Var(pat.symbol, pat.tpe)
+    case Alternative(trees) => Or(trees.map(project(_, roundUp)))
+    case Bind(_, pat) => project(pat)
+    case UnApply(_, _, pats) =>
+      if (pat.tpe.classSymbol.is(CaseClass))
+        Kon(pat.tpe.stripAnnots, pats.map(pat => project(pat, roundUp)))
+      else if (roundUp) Typ(pat.tpe, false)
+      else Empty
+    case Typed(pat @ UnApply(_, _, _), _) => project(pat)
+    case Typed(expr, _) => Typ(expr.tpe.stripAnnots, true)
+    case _ =>
+      debug(s"========unkown tree: $pat========")
+      Empty
+  }
+
+  /** Is `tp1` a subtype of `tp2`?
+   *
+   *  Ignore type parameters in comparison due to erasure, i.e., Some[Int] <: Some[T]
+   */
+  def isSubType(tp1: Type, tp2: Type): Boolean = (tp1, tp2) match {
+    case (tp1: RefinedType, tp2: RefinedType) => isSubType(tp1.parent, tp2.parent)
+    case (tp1: RefinedType, _) => isSubType(tp1.parent, tp2)
+    case (_, tp2: RefinedType) => isSubType(tp1, tp2.parent)
+    case (_, _) =>
+      val res = tp1 <:< tp2
+      debug(s"$tp1 <: $tp2 ? $res")
+      res
+  }
+
+  def isEqualType(tp1: Type, tp2: Type): Boolean = {
+    val res = tp1 =:= tp2
+    debug(s"$tp1 == $tp2 ? $res")
+    res
+  }
+
+  def signature(tp: Type): List[Type] = {
+    val ktor = tp.classSymbol.primaryConstructor.info
+
+    debug(s"=======ktor: $ktor")
+
+    val meth =
+      if (ktor.isInstanceOf[MethodType]) ktor
+      else
+      tp match {
+        case AppliedType(_, params) =>
+          debug(s"=======params: $params")
+          val refined = params.map {
+            // TypeBounds would generate an exception
+            case tp: TypeBounds => tp.underlying
+            case tp => tp
+          }
+          debug(s"=======refined params: $refined")
+          ktor.appliedTo(refined)
+        case _ =>
+          ktor
+      }
+
+    val sign = meth.firstParamTypes.map(_.stripTypeVar).map(paramTp => refine(tp, paramTp))
+
+    debug(s"====signature of $tp: $sign")
+    sign
+  }
+
+  def partitions(tp: Type): List[Space] = tp match {
+    case OrType(tp1, tp2) => List(Typ(tp1, true), Typ(tp2, true))
+    case _ if tp =:= ctx.definitions.BooleanType =>
+      List(
+        Const(Constant(true), ctx.definitions.BooleanType),
+        Const(Constant(false), ctx.definitions.BooleanType)
+      )
+    case _ =>
+      val children = tp.classSymbol.annotations.filter(_.symbol == ctx.definitions.ChildAnnot).map { annot =>
+        // refer to definition of Annotation.makeChild
+        val sym = annot.tree match {
+          case Apply(TypeApply(_, List(tpTree)), _) => tpTree.symbol.asClass
+        }
+
+        if (sym.is(ModuleClass))
+          sym.classInfo.selfType
+        else if (sym.info.typeParams.length > 0 || tp.isInstanceOf[TypeRef])
+          refine(tp, sym.classInfo.symbolicTypeRef)
+        else
+          sym.info
+      } filter(_ <:< tp) // child may not always be subtype of parent: SI-4020
+
+      debug(s"=========child of ${tp.show}: ${children.map(_.show).mkString(", ")}")
+
+      children.map(tp => Typ(tp, true))
+  }
+
+  /** Refine tp2 based on tp1
+   *
+   *  E.g. if `tp1` is `Option[Int]`, `tp2` is `Some`, then return
+   *  `Some[Int]`.
+   *
+   *  If `tp1` is `path1.A`, `tp2` is `path2.B`, and `path1` is subtype of
+   *  `path2`, then return `path1.B`.
+   */
+  def refine(tp1: Type, tp2: Type): Type = (tp1, tp2) match {
+    case (tp1: RefinedType, _) => tp1.wrapIfMember(refine(tp1.parent, tp2))
+    case (TypeRef(ref1: TypeProxy, _), tp2 @ TypeRef(ref2: TypeProxy, name)) =>
+      if (ref1.underlying <:< ref2.underlying) TypeRef(ref1, name) else tp2
+    case _ => tp2
+  }
+
+  /** Abstract sealed types,  or-types and Boolean can be decomposed */
+  def canDecompose(tp: Type): Boolean = {
+    tp.typeSymbol.is(allOf(Abstract, Sealed)) ||
+      tp.typeSymbol.is(allOf(Trait, Sealed)) ||
+      tp.isInstanceOf[OrType] ||
+      tp =:= ctx.definitions.BooleanType
+  }
+
+  def isCaseClass(tp: Type): Boolean = tp.classSymbol.isClass && tp.classSymbol.is(CaseClass)
+
+  /** Show friendly type name with current scope in mind
+   *
+   *  E.g.    C.this.B     -->  B     if current owner is C
+   *          C.this.x.T   -->  x.T   if current owner is C
+   *          X[T]         -->  X
+   *          C            -->  C     if current owner is C !!!
+   *
+   */
+  def showType(tp: Type): String = {
+    val enclosingCls = ctx.owner.enclosingClass.asClass.classInfo.symbolicTypeRef
+
+    def isOmittable(sym: Symbol) =
+      sym.isEffectiveRoot || sym.isAnonymousClass || sym.name.isReplWrapperName ||
+        ctx.definitions.UnqualifiedOwnerTypes.exists(_.symbol == sym) ||
+        sym.showFullName.startsWith("scala.") ||
+        sym == enclosingCls.typeSymbol
+
+    def refinePrefix(tp: Type): String = tp match {
+      case NoPrefix => ""
+      case tp: NamedType if isOmittable(tp.symbol) => ""
+      case tp: ThisType => refinePrefix(tp.tref)
+      case tp: RefinedType => refinePrefix(tp.parent)
+      case tp: NamedType => tp.name.show.stripSuffix("$")
+    }
+
+    def refine(tp: Type): String = tp match {
+      case tp: RefinedType => refine(tp.parent)
+      case tp: ThisType => refine(tp.tref)
+      case tp: NamedType =>
+        val pre = refinePrefix(tp.prefix)
+        if (pre.isEmpty) tp.name.show.stripSuffix("$")
+        else pre + "." + tp.name.show.stripSuffix("$")
+      case _ => tp.show.stripSuffix("$")
+    }
+
+    val text = tp match {
+      case tp: OrType => showType(tp.tp1) + " | " + showType(tp.tp2)
+      case _ => refine(tp)
+    }
+
+    if (text.isEmpty) enclosingCls.show.stripSuffix("$")
+    else text
+  }
+
+  /** Display spaces */
+  def show(s: Space): String = {
+    def doShow(s: Space, mergeList: Boolean = false): String = s match {
+      case Empty => ""
+      case Const(v, _) => v.show
+      case Var(x, _) => x.show
+      case Typ(tp, decomposed) =>
+        val sym = tp.widen.classSymbol
+
+        if (sym.is(ModuleClass))
+          showType(tp)
+        else if (ctx.definitions.isTupleType(tp))
+          signature(tp).map(_ => "_").mkString("(", ", ", ")")
+        else if (sym.showFullName == "scala.collection.immutable.::")
+          if (mergeList) "_" else "List(_)"
+        else if (tp.classSymbol.is(CaseClass))
+        // use constructor syntax for case class
+          showType(tp) + signature(tp).map(_ => "_").mkString("(", ",", ")")
+        else if (signature(tp).nonEmpty)
+          tp.classSymbol.name + signature(tp).map(_ => "_").mkString("(", ",", ")")
+        else if (decomposed) "_: " + showType(tp)
+        else "_"
+      case Kon(tp, params) =>
+        if (ctx.definitions.isTupleType(tp))
+          "(" + params.map(p => doShow(p)).mkString(", ") + ")"
+        else if (tp.widen.classSymbol.showFullName == "scala.collection.immutable.::")
+          if (mergeList) params.map(p => doShow(p, mergeList)).mkString(", ")
+          else params.map(p => doShow(p, true)).mkString("List(", ", ", ")")
+        else
+          showType(tp) + params.map(p => doShow(p)).mkString("(", ", ", ")")
+      case Or(_) =>
+        throw new Exception("incorrect flatten result " + s)
+    }
+
+    flatten(s).map(doShow(_, false)).distinct.mkString(", ")
+  }
+
+  /** Does the type t have @unchecked annotation? */
+  def skipCheck(tp: Type): Boolean = tp match {
+    case AnnotatedType(tp, annot) => ctx.definitions.UncheckedAnnot == annot.symbol
+    case _ => false
+  }
+
+  /** Widen a type and eliminate anonymous classes */
+  private def widen(tp: Type): Type = tp.widen match {
+    case tp:TypeRef if tp.symbol.isAnonymousClass =>
+      tp.symbol.asClass.typeRef.asSeenFrom(tp.prefix, tp.symbol.owner)
+    case tp => tp
+  }
+
+  def exhaustivity(_match: Match): Unit = {
+    val Match(sel, cases) = _match
+    val selTyp = widen(sel.tpe)
+
+    debug(s"====patterns:\n${cases.map(_.pat).mkString("\n")}")
+    val patternSpace = cases.map(x => project(x.pat)).reduce((a, b) => Or(List(a, b)))
+    debug(s"====selector:\n" + selTyp)
+    debug("====pattern space:\n" + show(patternSpace))
+    val uncovered = simplify(minus(Typ(selTyp, true), patternSpace))
+
+    if (uncovered != Empty) {
+      ctx.warning(
+        "match may not be exhaustive.\n" +
+        s"It would fail on the following input: " +
+        show(uncovered), _match.pos
+      )
+    }
+  }
+
+  def redundancy(_match: Match): Unit = {
+    val Match(sel, cases) = _match
+    val selTyp = widen(sel.tpe)
+
+    // starts from the second, the first can't be redundant
+    (1 until cases.length).foreach { i =>
+      // in redundancy check, take guard as false, take extractor as match
+      // nothing in order to soundly approximate
+      val prevs = cases.take(i).map { x =>
+        if (x.guard.isEmpty) project(x.pat, false)
+        else Empty
+      }.reduce((a, b) => Or(List(a, b)))
+
+      val curr = project(cases(i).pat)
+
+      if (subspace(curr, prevs)) {
+        ctx.warning("unreachable code", cases(i).body.pos)
+      }
+    }
+  }
+}
diff --git a/test/test/transform/PatmatExhaustivityTest.scala b/test/test/transform/PatmatExhaustivityTest.scala
new file mode 100644
index 000000000000..1ecaa2b1d14d
--- /dev/null
+++ b/test/test/transform/PatmatExhaustivityTest.scala
@@ -0,0 +1,58 @@
+package test.transform
+
+import java.io._
+import scala.io.Source._
+import scala.reflect.io.Directory
+import org.junit.Test
+
+import dotty.tools.dotc.Main
+import dotty.tools.dotc.reporting.ConsoleReporter
+
+class PatmatExhaustivityTest {
+  val testsDir = "./tests/patmat"
+  val options = "-Ystop-after:splitter"  // no need for code generation
+                                         // patmatexhaust-huge.scala crash compiler
+
+  private def compileFile(file: File) = {
+    val stringBuffer = new StringWriter()
+    val reporter = new ConsoleReporter(writer = new PrintWriter(stringBuffer))
+
+    try {
+      Main.process(Array(file.getPath, options), reporter, null)
+    } catch {
+      case e: Throwable =>
+        println(s"Compile $file exception:")
+        e.printStackTrace()
+    }
+
+    val actual = stringBuffer.toString.trim
+    val checkFilePath = file.getAbsolutePath.stripSuffix(".scala") + ".check"
+    val checkContent =
+      if (new File(checkFilePath).exists)
+        fromFile(checkFilePath).getLines.mkString("\n").trim
+      else ""
+
+    (file, checkContent, actual)
+  }
+
+  @Test def patmatExhaustivity: Unit = {
+    val res = Directory(testsDir).deepFiles.toList.filter(_.extension == "scala").map { f =>
+      compileFile(f.jfile)
+    }
+
+    val failed = res.filter { case (_, expected, actual) => expected != actual }
+    val ignored = Directory(testsDir).deepFiles.toList.filter(_.extension == "ignore")
+
+    failed.foreach { case (file, expected, actual) =>
+      println(s"\n----------------- incorrect output for $file --------------\n" +
+        s"Expected:\n-------\n$expected\n\nActual\n----------\n$actual\n"
+      )
+    }
+
+    val msg = s"Total: ${res.length + ignored.length}, Failed: ${failed.length}, Ignored: ${ignored.length}"
+
+    assert(failed.length == 0, msg)
+
+    println(msg)
+  }
+}
diff --git a/tests/patmat/patmat-adt.check b/tests/patmat/patmat-adt.check
new file mode 100644
index 000000000000..f4e1ce369e50
--- /dev/null
+++ b/tests/patmat/patmat-adt.check
@@ -0,0 +1,21 @@
+./tests/patmat/patmat-adt.scala:7: warning: match may not be exhaustive.
+It would fail on the following input: Bad(Good(_)), Good(Bad(_))
+  def foo1a(x: Odd) = x match { // warning: Good(_: Bad), Bad(_: Good)
+                        ^
+./tests/patmat/patmat-adt.scala:19: warning: match may not be exhaustive.
+It would fail on the following input: Some(_)
+  def foo2(x: Option[Int]) = x match { // warning: Some(_: Int)
+                               ^
+./tests/patmat/patmat-adt.scala:24: warning: match may not be exhaustive.
+It would fail on the following input: (None, Some(_)), (_, Some(_))
+  def foo3a[T](x: Option[T]) = (x, x) match { // warning: (Some(_), Some(_)), (None, Some(_))
+                                      ^
+./tests/patmat/patmat-adt.scala:29: warning: match may not be exhaustive.
+It would fail on the following input: (None, None), (Some(_), Some(_))
+  def foo3b[T](x: Option[T]) = (x, x) match { // warning: (Some(_), Some(_)), (None, None)
+                                      ^
+./tests/patmat/patmat-adt.scala:50: warning: match may not be exhaustive.
+It would fail on the following input: LetL(BooleanLit), LetL(IntLit)
+  def foo5(tree: Tree) : Any = tree match {
+                                    ^
+5 warnings found
\ No newline at end of file
diff --git a/tests/patmat/patmat-adt.scala b/tests/patmat/patmat-adt.scala
new file mode 100644
index 000000000000..acb4d3465ee6
--- /dev/null
+++ b/tests/patmat/patmat-adt.scala
@@ -0,0 +1,53 @@
+object PatmatADT {
+  abstract sealed class Odd(x: Odd)
+
+  case class Good(x: Odd) extends Odd(x)
+  case class Bad(x: Odd) extends Odd(x)
+
+  def foo1a(x: Odd) = x match { // warning: Good(_: Bad), Bad(_: Good)
+    case Good(_: Good) => false
+    case Bad(_: Bad) => false
+  }
+
+  def foo1b(x: Odd) = x match {
+    case Good(_: Good) => false
+    case Bad(_: Bad) => false
+    case Good(_: Bad) => false
+    case Bad(_: Good) => false
+  }
+
+  def foo2(x: Option[Int]) = x match { // warning: Some(_: Int)
+    case Some(_: Double) => true
+    case None => true
+  }
+
+  def foo3a[T](x: Option[T]) = (x, x) match { // warning: (Some(_), Some(_)), (None, Some(_))
+    case (Some(_), None) => true
+    case (None, None) => true
+  }
+
+  def foo3b[T](x: Option[T]) = (x, x) match { // warning: (Some(_), Some(_)), (None, None)
+    case (Some(_), None) => true
+    case (None, Some(_)) => true
+  }
+
+  sealed trait Base
+  case class Foo() extends Base
+
+  def foo4(x: Base) = x match {
+    case Foo() =>
+  }
+
+  sealed abstract class CL3Literal
+  case object IntLit extends CL3Literal
+  case object CharLit extends CL3Literal
+  case object BooleanLit extends CL3Literal
+
+
+  sealed abstract class Tree
+  case class LetL(value: CL3Literal) extends Tree
+
+  def foo5(tree: Tree) : Any = tree match {
+    case LetL(CharLit) =>
+  }
+}
\ No newline at end of file
diff --git a/tests/patmat/patmat-extractor.scala b/tests/patmat/patmat-extractor.scala
new file mode 100644
index 000000000000..02fde96dcb42
--- /dev/null
+++ b/tests/patmat/patmat-extractor.scala
@@ -0,0 +1,17 @@
+sealed trait Node
+case class NodeA(i: Int) extends Node
+case class NodeB(b: Boolean) extends Node
+case class NodeC(s: String) extends Node
+
+object Node {
+  def unapply(node: Node): Option[(Node, Node)] = ???
+}
+
+// currently scalac can't do anything with following
+// it's possible to do better in our case
+object Test {
+  def foo(x: Node): Boolean = x match { // unexhaustive
+    case Node(NodeA(_), NodeB(_)) => true
+    case Node(NodeA(4), NodeB(false)) => true // unreachable code
+  }
+}
\ No newline at end of file
diff --git a/tests/patmat/patmat-ortype.check b/tests/patmat/patmat-ortype.check
new file mode 100644
index 000000000000..2291da251994
--- /dev/null
+++ b/tests/patmat/patmat-ortype.check
@@ -0,0 +1,13 @@
+./tests/patmat/patmat-ortype.scala:8: warning: match may not be exhaustive.
+It would fail on the following input: _: String
+  def foo2a(x: Int | Double | String) = x match { // _: String not matched
+                                          ^
+./tests/patmat/patmat-ortype.scala:18: warning: match may not be exhaustive.
+It would fail on the following input: Some(_: String), None
+  def foo3(x: Option[Int | Double | String]) = x match { // warning: None, Some(_: String) not matched
+                                                 ^
+./tests/patmat/patmat-ortype.scala:36: warning: match may not be exhaustive.
+It would fail on the following input: Some(_: String)
+  def foo5b(x: Option[Int | Double | String]) = x match { // warning: Some(_: String) not matched
+                                                  ^
+three warnings found
\ No newline at end of file
diff --git a/tests/patmat/patmat-ortype.scala b/tests/patmat/patmat-ortype.scala
new file mode 100644
index 000000000000..c7419acd3b0f
--- /dev/null
+++ b/tests/patmat/patmat-ortype.scala
@@ -0,0 +1,40 @@
+object PatmatOrType {
+
+  def foo1(x: Int | Double) = x match {
+    case _: Int => true
+    case _: Double => true
+  }
+
+  def foo2a(x: Int | Double | String) = x match { // _: String not matched
+    case _: Int => true
+    case _: Double => true
+  }
+
+  def foo2b(x: Int | Double | String) = x match {
+    case _: Int => true
+    case _: (Double | String) => true
+  }
+
+  def foo3(x: Option[Int | Double | String]) = x match { // warning: None, Some(_: String) not matched
+    case Some(_: Int) => true
+    case Some(_: Double) => true
+  }
+
+  def foo4(x: Option[Int | Double | String]) = x match {
+    case Some(_: Int) => true
+    case Some(_: Double) => true
+    case Some(_: String) => true
+    case None => false
+  }
+
+  def foo5a(x: Option[Int | Double | String]) = x match {
+    case Some(_: (Int | Double)) => true
+    case Some(_: String) => true
+    case None => false
+  }
+
+  def foo5b(x: Option[Int | Double | String]) = x match { // warning: Some(_: String) not matched
+    case Some(_: (Int | Double)) => true
+    case None => false
+  }
+}
\ No newline at end of file
diff --git a/tests/patmat/patmatexhaust-huge.check b/tests/patmat/patmatexhaust-huge.check
new file mode 100644
index 000000000000..06cac90bd5e7
--- /dev/null
+++ b/tests/patmat/patmatexhaust-huge.check
@@ -0,0 +1,5 @@
+./tests/patmat/patmatexhaust-huge.scala:404: warning: match may not be exhaustive.
+It would fail on the following input: C397, C392
+  def f(c: C): Int = c match {
+                       ^
+one warning found
\ No newline at end of file
diff --git a/tests/patmat/patmatexhaust-huge.scala b/tests/patmat/patmatexhaust-huge.scala
new file mode 100644
index 000000000000..c4008b99542a
--- /dev/null
+++ b/tests/patmat/patmatexhaust-huge.scala
@@ -0,0 +1,806 @@
+abstract sealed trait C
+case object C1 extends C
+case object C2 extends C
+case object C3 extends C
+case object C4 extends C
+case object C5 extends C
+case object C6 extends C
+case object C7 extends C
+case object C8 extends C
+case object C9 extends C
+case object C10 extends C
+case object C11 extends C
+case object C12 extends C
+case object C13 extends C
+case object C14 extends C
+case object C15 extends C
+case object C16 extends C
+case object C17 extends C
+case object C18 extends C
+case object C19 extends C
+case object C20 extends C
+case object C21 extends C
+case object C22 extends C
+case object C23 extends C
+case object C24 extends C
+case object C25 extends C
+case object C26 extends C
+case object C27 extends C
+case object C28 extends C
+case object C29 extends C
+case object C30 extends C
+case object C31 extends C
+case object C32 extends C
+case object C33 extends C
+case object C34 extends C
+case object C35 extends C
+case object C36 extends C
+case object C37 extends C
+case object C38 extends C
+case object C39 extends C
+case object C40 extends C
+case object C41 extends C
+case object C42 extends C
+case object C43 extends C
+case object C44 extends C
+case object C45 extends C
+case object C46 extends C
+case object C47 extends C
+case object C48 extends C
+case object C49 extends C
+case object C50 extends C
+case object C51 extends C
+case object C52 extends C
+case object C53 extends C
+case object C54 extends C
+case object C55 extends C
+case object C56 extends C
+case object C57 extends C
+case object C58 extends C
+case object C59 extends C
+case object C60 extends C
+case object C61 extends C
+case object C62 extends C
+case object C63 extends C
+case object C64 extends C
+case object C65 extends C
+case object C66 extends C
+case object C67 extends C
+case object C68 extends C
+case object C69 extends C
+case object C70 extends C
+case object C71 extends C
+case object C72 extends C
+case object C73 extends C
+case object C74 extends C
+case object C75 extends C
+case object C76 extends C
+case object C77 extends C
+case object C78 extends C
+case object C79 extends C
+case object C80 extends C
+case object C81 extends C
+case object C82 extends C
+case object C83 extends C
+case object C84 extends C
+case object C85 extends C
+case object C86 extends C
+case object C87 extends C
+case object C88 extends C
+case object C89 extends C
+case object C90 extends C
+case object C91 extends C
+case object C92 extends C
+case object C93 extends C
+case object C94 extends C
+case object C95 extends C
+case object C96 extends C
+case object C97 extends C
+case object C98 extends C
+case object C99 extends C
+case object C100 extends C
+case object C101 extends C
+case object C102 extends C
+case object C103 extends C
+case object C104 extends C
+case object C105 extends C
+case object C106 extends C
+case object C107 extends C
+case object C108 extends C
+case object C109 extends C
+case object C110 extends C
+case object C111 extends C
+case object C112 extends C
+case object C113 extends C
+case object C114 extends C
+case object C115 extends C
+case object C116 extends C
+case object C117 extends C
+case object C118 extends C
+case object C119 extends C
+case object C120 extends C
+case object C121 extends C
+case object C122 extends C
+case object C123 extends C
+case object C124 extends C
+case object C125 extends C
+case object C126 extends C
+case object C127 extends C
+case object C128 extends C
+case object C129 extends C
+case object C130 extends C
+case object C131 extends C
+case object C132 extends C
+case object C133 extends C
+case object C134 extends C
+case object C135 extends C
+case object C136 extends C
+case object C137 extends C
+case object C138 extends C
+case object C139 extends C
+case object C140 extends C
+case object C141 extends C
+case object C142 extends C
+case object C143 extends C
+case object C144 extends C
+case object C145 extends C
+case object C146 extends C
+case object C147 extends C
+case object C148 extends C
+case object C149 extends C
+case object C150 extends C
+case object C151 extends C
+case object C152 extends C
+case object C153 extends C
+case object C154 extends C
+case object C155 extends C
+case object C156 extends C
+case object C157 extends C
+case object C158 extends C
+case object C159 extends C
+case object C160 extends C
+case object C161 extends C
+case object C162 extends C
+case object C163 extends C
+case object C164 extends C
+case object C165 extends C
+case object C166 extends C
+case object C167 extends C
+case object C168 extends C
+case object C169 extends C
+case object C170 extends C
+case object C171 extends C
+case object C172 extends C
+case object C173 extends C
+case object C174 extends C
+case object C175 extends C
+case object C176 extends C
+case object C177 extends C
+case object C178 extends C
+case object C179 extends C
+case object C180 extends C
+case object C181 extends C
+case object C182 extends C
+case object C183 extends C
+case object C184 extends C
+case object C185 extends C
+case object C186 extends C
+case object C187 extends C
+case object C188 extends C
+case object C189 extends C
+case object C190 extends C
+case object C191 extends C
+case object C192 extends C
+case object C193 extends C
+case object C194 extends C
+case object C195 extends C
+case object C196 extends C
+case object C197 extends C
+case object C198 extends C
+case object C199 extends C
+case object C200 extends C
+case object C201 extends C
+case object C202 extends C
+case object C203 extends C
+case object C204 extends C
+case object C205 extends C
+case object C206 extends C
+case object C207 extends C
+case object C208 extends C
+case object C209 extends C
+case object C210 extends C
+case object C211 extends C
+case object C212 extends C
+case object C213 extends C
+case object C214 extends C
+case object C215 extends C
+case object C216 extends C
+case object C217 extends C
+case object C218 extends C
+case object C219 extends C
+case object C220 extends C
+case object C221 extends C
+case object C222 extends C
+case object C223 extends C
+case object C224 extends C
+case object C225 extends C
+case object C226 extends C
+case object C227 extends C
+case object C228 extends C
+case object C229 extends C
+case object C230 extends C
+case object C231 extends C
+case object C232 extends C
+case object C233 extends C
+case object C234 extends C
+case object C235 extends C
+case object C236 extends C
+case object C237 extends C
+case object C238 extends C
+case object C239 extends C
+case object C240 extends C
+case object C241 extends C
+case object C242 extends C
+case object C243 extends C
+case object C244 extends C
+case object C245 extends C
+case object C246 extends C
+case object C247 extends C
+case object C248 extends C
+case object C249 extends C
+case object C250 extends C
+case object C251 extends C
+case object C252 extends C
+case object C253 extends C
+case object C254 extends C
+case object C255 extends C
+case object C256 extends C
+case object C257 extends C
+case object C258 extends C
+case object C259 extends C
+case object C260 extends C
+case object C261 extends C
+case object C262 extends C
+case object C263 extends C
+case object C264 extends C
+case object C265 extends C
+case object C266 extends C
+case object C267 extends C
+case object C268 extends C
+case object C269 extends C
+case object C270 extends C
+case object C271 extends C
+case object C272 extends C
+case object C273 extends C
+case object C274 extends C
+case object C275 extends C
+case object C276 extends C
+case object C277 extends C
+case object C278 extends C
+case object C279 extends C
+case object C280 extends C
+case object C281 extends C
+case object C282 extends C
+case object C283 extends C
+case object C284 extends C
+case object C285 extends C
+case object C286 extends C
+case object C287 extends C
+case object C288 extends C
+case object C289 extends C
+case object C290 extends C
+case object C291 extends C
+case object C292 extends C
+case object C293 extends C
+case object C294 extends C
+case object C295 extends C
+case object C296 extends C
+case object C297 extends C
+case object C298 extends C
+case object C299 extends C
+case object C300 extends C
+case object C301 extends C
+case object C302 extends C
+case object C303 extends C
+case object C304 extends C
+case object C305 extends C
+case object C306 extends C
+case object C307 extends C
+case object C308 extends C
+case object C309 extends C
+case object C310 extends C
+case object C311 extends C
+case object C312 extends C
+case object C313 extends C
+case object C314 extends C
+case object C315 extends C
+case object C316 extends C
+case object C317 extends C
+case object C318 extends C
+case object C319 extends C
+case object C320 extends C
+case object C321 extends C
+case object C322 extends C
+case object C323 extends C
+case object C324 extends C
+case object C325 extends C
+case object C326 extends C
+case object C327 extends C
+case object C328 extends C
+case object C329 extends C
+case object C330 extends C
+case object C331 extends C
+case object C332 extends C
+case object C333 extends C
+case object C334 extends C
+case object C335 extends C
+case object C336 extends C
+case object C337 extends C
+case object C338 extends C
+case object C339 extends C
+case object C340 extends C
+case object C341 extends C
+case object C342 extends C
+case object C343 extends C
+case object C344 extends C
+case object C345 extends C
+case object C346 extends C
+case object C347 extends C
+case object C348 extends C
+case object C349 extends C
+case object C350 extends C
+case object C351 extends C
+case object C352 extends C
+case object C353 extends C
+case object C354 extends C
+case object C355 extends C
+case object C356 extends C
+case object C357 extends C
+case object C358 extends C
+case object C359 extends C
+case object C360 extends C
+case object C361 extends C
+case object C362 extends C
+case object C363 extends C
+case object C364 extends C
+case object C365 extends C
+case object C366 extends C
+case object C367 extends C
+case object C368 extends C
+case object C369 extends C
+case object C370 extends C
+case object C371 extends C
+case object C372 extends C
+case object C373 extends C
+case object C374 extends C
+case object C375 extends C
+case object C376 extends C
+case object C377 extends C
+case object C378 extends C
+case object C379 extends C
+case object C380 extends C
+case object C381 extends C
+case object C382 extends C
+case object C383 extends C
+case object C384 extends C
+case object C385 extends C
+case object C386 extends C
+case object C387 extends C
+case object C388 extends C
+case object C389 extends C
+case object C390 extends C
+case object C391 extends C
+case object C392 extends C
+case object C393 extends C
+case object C394 extends C
+case object C395 extends C
+case object C396 extends C
+case object C397 extends C
+case object C398 extends C
+case object C399 extends C
+case object C400 extends C
+
+object M {
+  def f(c: C): Int = c match {
+    case C1 => 1
+    case C2 => 2
+    case C3 => 3
+    case C4 => 4
+    case C5 => 5
+    case C6 => 6
+    case C7 => 7
+    case C8 => 8
+    case C9 => 9
+    case C10 => 10
+    case C11 => 11
+    case C12 => 12
+    case C13 => 13
+    case C14 => 14
+    case C15 => 15
+    case C16 => 16
+    case C17 => 17
+    case C18 => 18
+    case C19 => 19
+    case C20 => 20
+    case C21 => 21
+    case C22 => 22
+    case C23 => 23
+    case C24 => 24
+    case C25 => 25
+    case C26 => 26
+    case C27 => 27
+    case C28 => 28
+    case C29 => 29
+    case C30 => 30
+    case C31 => 31
+    case C32 => 32
+    case C33 => 33
+    case C34 => 34
+    case C35 => 35
+    case C36 => 36
+    case C37 => 37
+    case C38 => 38
+    case C39 => 39
+    case C40 => 40
+    case C41 => 41
+    case C42 => 42
+    case C43 => 43
+    case C44 => 44
+    case C45 => 45
+    case C46 => 46
+    case C47 => 47
+    case C48 => 48
+    case C49 => 49
+    case C50 => 50
+    case C51 => 51
+    case C52 => 52
+    case C53 => 53
+    case C54 => 54
+    case C55 => 55
+    case C56 => 56
+    case C57 => 57
+    case C58 => 58
+    case C59 => 59
+    case C60 => 60
+    case C61 => 61
+    case C62 => 62
+    case C63 => 63
+    case C64 => 64
+    case C65 => 65
+    case C66 => 66
+    case C67 => 67
+    case C68 => 68
+    case C69 => 69
+    case C70 => 70
+    case C71 => 71
+    case C72 => 72
+    case C73 => 73
+    case C74 => 74
+    case C75 => 75
+    case C76 => 76
+    case C77 => 77
+    case C78 => 78
+    case C79 => 79
+    case C80 => 80
+    case C81 => 81
+    case C82 => 82
+    case C83 => 83
+    case C84 => 84
+    case C85 => 85
+    case C86 => 86
+    case C87 => 87
+    case C88 => 88
+    case C89 => 89
+    case C90 => 90
+    case C91 => 91
+    case C92 => 92
+    case C93 => 93
+    case C94 => 94
+    case C95 => 95
+    case C96 => 96
+    case C97 => 97
+    case C98 => 98
+    case C99 => 99
+    case C100 => 100
+    case C101 => 101
+    case C102 => 102
+    case C103 => 103
+    case C104 => 104
+    case C105 => 105
+    case C106 => 106
+    case C107 => 107
+    case C108 => 108
+    case C109 => 109
+    case C110 => 110
+    case C111 => 111
+    case C112 => 112
+    case C113 => 113
+    case C114 => 114
+    case C115 => 115
+    case C116 => 116
+    case C117 => 117
+    case C118 => 118
+    case C119 => 119
+    case C120 => 120
+    case C121 => 121
+    case C122 => 122
+    case C123 => 123
+    case C124 => 124
+    case C125 => 125
+    case C126 => 126
+    case C127 => 127
+    case C128 => 128
+    case C129 => 129
+    case C130 => 130
+    case C131 => 131
+    case C132 => 132
+    case C133 => 133
+    case C134 => 134
+    case C135 => 135
+    case C136 => 136
+    case C137 => 137
+    case C138 => 138
+    case C139 => 139
+    case C140 => 140
+    case C141 => 141
+    case C142 => 142
+    case C143 => 143
+    case C144 => 144
+    case C145 => 145
+    case C146 => 146
+    case C147 => 147
+    case C148 => 148
+    case C149 => 149
+    case C150 => 150
+    case C151 => 151
+    case C152 => 152
+    case C153 => 153
+    case C154 => 154
+    case C155 => 155
+    case C156 => 156
+    case C157 => 157
+    case C158 => 158
+    case C159 => 159
+    case C160 => 160
+    case C161 => 161
+    case C162 => 162
+    case C163 => 163
+    case C164 => 164
+    case C165 => 165
+    case C166 => 166
+    case C167 => 167
+    case C168 => 168
+    case C169 => 169
+    case C170 => 170
+    case C171 => 171
+    case C172 => 172
+    case C173 => 173
+    case C174 => 174
+    case C175 => 175
+    case C176 => 176
+    case C177 => 177
+    case C178 => 178
+    case C179 => 179
+    case C180 => 180
+    case C181 => 181
+    case C182 => 182
+    case C183 => 183
+    case C184 => 184
+    case C185 => 185
+    case C186 => 186
+    case C187 => 187
+    case C188 => 188
+    case C189 => 189
+    case C190 => 190
+    case C191 => 191
+    case C192 => 192
+    case C193 => 193
+    case C194 => 194
+    case C195 => 195
+    case C196 => 196
+    case C197 => 197
+    case C198 => 198
+    case C199 => 199
+    case C200 => 200
+    case C201 => 201
+    case C202 => 202
+    case C203 => 203
+    case C204 => 204
+    case C205 => 205
+    case C206 => 206
+    case C207 => 207
+    case C208 => 208
+    case C209 => 209
+    case C210 => 210
+    case C211 => 211
+    case C212 => 212
+    case C213 => 213
+    case C214 => 214
+    case C215 => 215
+    case C216 => 216
+    case C217 => 217
+    case C218 => 218
+    case C219 => 219
+    case C220 => 220
+    case C221 => 221
+    case C222 => 222
+    case C223 => 223
+    case C224 => 224
+    case C225 => 225
+    case C226 => 226
+    case C227 => 227
+    case C228 => 228
+    case C229 => 229
+    case C230 => 230
+    case C231 => 231
+    case C232 => 232
+    case C233 => 233
+    case C234 => 234
+    case C235 => 235
+    case C236 => 236
+    case C237 => 237
+    case C238 => 238
+    case C239 => 239
+    case C240 => 240
+    case C241 => 241
+    case C242 => 242
+    case C243 => 243
+    case C244 => 244
+    case C245 => 245
+    case C246 => 246
+    case C247 => 247
+    case C248 => 248
+    case C249 => 249
+    case C250 => 250
+    case C251 => 251
+    case C252 => 252
+    case C253 => 253
+    case C254 => 254
+    case C255 => 255
+    case C256 => 256
+    case C257 => 257
+    case C258 => 258
+    case C259 => 259
+    case C260 => 260
+    case C261 => 261
+    case C262 => 262
+    case C263 => 263
+    case C264 => 264
+    case C265 => 265
+    case C266 => 266
+    case C267 => 267
+    case C268 => 268
+    case C269 => 269
+    case C270 => 270
+    case C271 => 271
+    case C272 => 272
+    case C273 => 273
+    case C274 => 274
+    case C275 => 275
+    case C276 => 276
+    case C277 => 277
+    case C278 => 278
+    case C279 => 279
+    case C280 => 280
+    case C281 => 281
+    case C282 => 282
+    case C283 => 283
+    case C284 => 284
+    case C285 => 285
+    case C286 => 286
+    case C287 => 287
+    case C288 => 288
+    case C289 => 289
+    case C290 => 290
+    case C291 => 291
+    case C292 => 292
+    case C293 => 293
+    case C294 => 294
+    case C295 => 295
+    case C296 => 296
+    case C297 => 297
+    case C298 => 298
+    case C299 => 299
+    case C300 => 300
+    case C301 => 301
+    case C302 => 302
+    case C303 => 303
+    case C304 => 304
+    case C305 => 305
+    case C306 => 306
+    case C307 => 307
+    case C308 => 308
+    case C309 => 309
+    case C310 => 310
+    case C311 => 311
+    case C312 => 312
+    case C313 => 313
+    case C314 => 314
+    case C315 => 315
+    case C316 => 316
+    case C317 => 317
+    case C318 => 318
+    case C319 => 319
+    case C320 => 320
+    case C321 => 321
+    case C322 => 322
+    case C323 => 323
+    case C324 => 324
+    case C325 => 325
+    case C326 => 326
+    case C327 => 327
+    case C328 => 328
+    case C329 => 329
+    case C330 => 330
+    case C331 => 331
+    case C332 => 332
+    case C333 => 333
+    case C334 => 334
+    case C335 => 335
+    case C336 => 336
+    case C337 => 337
+    case C338 => 338
+    case C339 => 339
+    case C340 => 340
+    case C341 => 341
+    case C342 => 342
+    case C343 => 343
+    case C344 => 344
+    case C345 => 345
+    case C346 => 346
+    case C347 => 347
+    case C348 => 348
+    case C349 => 349
+    case C350 => 350
+    case C351 => 351
+    case C352 => 352
+    case C353 => 353
+    case C354 => 354
+    case C355 => 355
+    case C356 => 356
+    case C357 => 357
+    case C358 => 358
+    case C359 => 359
+    case C360 => 360
+    case C361 => 361
+    case C362 => 362
+    case C363 => 363
+    case C364 => 364
+    case C365 => 365
+    case C366 => 366
+    case C367 => 367
+    case C368 => 368
+    case C369 => 369
+    case C370 => 370
+    case C371 => 371
+    case C372 => 372
+    case C373 => 373
+    case C374 => 374
+    case C375 => 375
+    case C376 => 376
+    case C377 => 377
+    case C378 => 378
+    case C379 => 379
+    case C380 => 380
+    case C381 => 381
+    case C382 => 382
+    case C383 => 383
+    case C384 => 384
+    case C385 => 385
+    case C386 => 386
+    case C387 => 387
+    case C388 => 388
+    case C389 => 389
+    case C390 => 390
+    case C391 => 391
+//    case C392 => 392
+    case C393 => 393
+    case C394 => 394
+    case C395 => 395
+    case C396 => 396
+//    case C397 => 397
+    case C398 => 398
+    case C399 => 399
+    case C400 => 400
+  }
+}
diff --git a/tests/patmat/patmatexhaust.check b/tests/patmat/patmatexhaust.check
new file mode 100644
index 000000000000..5121b73638a8
--- /dev/null
+++ b/tests/patmat/patmatexhaust.check
@@ -0,0 +1,33 @@
+./tests/patmat/patmatexhaust.scala:7: warning: match may not be exhaustive.
+It would fail on the following input: Baz
+    def ma1(x:Foo) = x match {
+                       ^
+./tests/patmat/patmatexhaust.scala:11: warning: match may not be exhaustive.
+It would fail on the following input: Bar(_)
+    def ma2(x:Foo) = x match {
+                       ^
+./tests/patmat/patmatexhaust.scala:23: warning: match may not be exhaustive.
+It would fail on the following input: (Qult(), Qult()), (Kult(_), Kult(_))
+    def ma3(x:Mult) = (x,x) match { // not exhaustive
+                            ^
+./tests/patmat/patmatexhaust.scala:49: warning: match may not be exhaustive.
+It would fail on the following input: _: Gp
+    def ma4(x:Deep) = x match { // missing cases: Gu, Gp which is not abstract so must be included
+                        ^
+./tests/patmat/patmatexhaust.scala:75: warning: match may not be exhaustive.
+It would fail on the following input: _: B
+  def ma9(x: B) = x match {
+                    ^
+./tests/patmat/patmatexhaust.scala:100: warning: match may not be exhaustive.
+It would fail on the following input: _: C1
+    def ma10(x: C) = x match { // not exhaustive: C1 is not sealed.
+                       ^
+./tests/patmat/patmatexhaust.scala:114: warning: match may not be exhaustive.
+It would fail on the following input: _: C1
+    def ma10(x: C) = x match {  // not exhaustive: C1 has subclasses.
+                       ^
+./tests/patmat/patmatexhaust.scala:126: warning: match may not be exhaustive.
+It would fail on the following input: _: C1
+    def ma10(x: C) = x match { // not exhaustive: C1 is not abstract.
+                       ^
+8 warnings found
\ No newline at end of file
diff --git a/tests/patmat/patmatexhaust.scala b/tests/patmat/patmatexhaust.scala
new file mode 100644
index 000000000000..26f0c12a919c
--- /dev/null
+++ b/tests/patmat/patmatexhaust.scala
@@ -0,0 +1,131 @@
+class TestSealedExhaustive { // compile only
+    sealed abstract class Foo
+
+    case class Bar(x:Int) extends Foo
+    case object Baz extends Foo
+
+    def ma1(x:Foo) = x match {
+      case Bar(_) => // not exhaustive
+    }
+
+    def ma2(x:Foo) = x match {
+      case Baz    => // not exhaustive
+    }
+
+    sealed abstract class Mult
+    case class Kult(s:Mult) extends Mult
+    case class Qult() extends Mult
+
+    def ma33(x:Kult) = x match { // exhaustive
+      case Kult(_) => // exhaustive
+    }
+
+    def ma3(x:Mult) = (x,x) match { // not exhaustive
+      case (Kult(_), Qult())    => // Kult missing
+      //case (Kult(_), Kult(_))    =>
+      case (Qult(), Kult(_))    => // Qult missing
+      //case (Qult(), Qult())    =>
+    }
+
+    def ma3u(x:Mult) = ((x,x) : @unchecked) match { // not exhaustive, but not checked!
+      case (Kult(_), Qult())    =>
+      case (Qult(), Kult(_))    =>
+    }
+
+    sealed abstract class Deep
+
+    case object Ga extends Deep
+    sealed class Gp extends Deep
+    case object Gu extends Gp
+
+    def zma3(x:Deep) = x match { // exhaustive!
+      case _ =>
+    }
+    def zma4(x:Deep) = x match { // exhaustive!
+      case Ga =>
+      case _ =>
+    }
+
+    def ma4(x:Deep) = x match { // missing cases: Gu, Gp which is not abstract so must be included
+      case Ga =>
+    }
+
+    def ma5(x:Deep) = x match {
+      case Gu =>
+      case _ if 1 == 0 =>
+      case Ga =>
+    }
+
+  def ma6()  = List(1,2) match { // give up
+    case List(1,2) =>
+    case x :: xs =>
+  }
+
+  def ma7() = List(1,2) match { //exhaustive
+    case 1::2::Nil =>
+      case _ =>
+  }
+
+  sealed class B
+  case class B1() extends B
+  case object B2 extends B
+  def ma8(x: B) = x match {
+    case _: B => true
+  }
+  def ma9(x: B) = x match {
+    case B1() => true       // missing B, which is not abstract so must be included
+    case B2   => true
+  }
+
+  object ob1 {
+    sealed abstract class C
+    sealed abstract class C1 extends C
+    object C2 extends C
+    case class C3() extends C
+    case object C4 extends C
+
+    def ma10(x: C) = x match {  // exhaustive: abstract sealed C1 is dead end.
+      case C3()     => true
+      case C2 | C4  => true
+    }
+  }
+
+  object ob2 {
+    sealed abstract class C
+    abstract class C1 extends C
+    object C2 extends C
+    case class C3() extends C
+    case object C4 extends C
+
+    def ma10(x: C) = x match { // not exhaustive: C1 is not sealed.
+      case C3()     => true
+      case C2 | C4  => true
+    }
+  }
+  object ob3 {
+    sealed abstract class C
+    sealed abstract class C1 extends C
+    object D1 extends C1
+    case class D2() extends C1
+    object C2 extends C
+    case class C3() extends C
+    case object C4 extends C
+
+    def ma10(x: C) = x match {  // not exhaustive: C1 has subclasses.
+      case C3()     => true
+      case C2 | C4  => true
+    }
+  }
+  object ob4 {
+    sealed abstract class C
+    sealed class C1 extends C
+    object C2 extends C
+    case class C3() extends C
+    case object C4 extends C
+
+    def ma10(x: C) = x match { // not exhaustive: C1 is not abstract.
+      case C3()     => true
+      case C2 | C4  => true
+    }
+  }
+}
diff --git a/tests/patmat/t3097.scala b/tests/patmat/t3097.scala
new file mode 100644
index 000000000000..3ff61b3c7b87
--- /dev/null
+++ b/tests/patmat/t3097.scala
@@ -0,0 +1,35 @@
+sealed trait ISimpleValue
+
+sealed trait IListValue extends ISimpleValue {
+  def items: List[IAtomicValue[_]]
+}
+
+sealed trait IAtomicValue[O] extends ISimpleValue {
+  def data: O
+}
+
+sealed trait IAbstractDoubleValue[O] extends IAtomicValue[O] {
+}
+
+sealed trait IDoubleValue extends IAbstractDoubleValue[Double]
+
+case class ListValue(val items: List[IAtomicValue[_]]) extends IListValue
+
+class DoubleValue(val data: Double) extends IDoubleValue {
+  def asDouble = data
+}
+
+object Test {
+
+  /**
+   * @param args the command line arguments
+   */
+  def main(args: Array[String]): Unit = {
+    val v: ISimpleValue = new DoubleValue(1)
+    v match {
+      case m: IListValue => println("list")
+      case a: IAtomicValue[_] => println("atomic")
+    }
+
+  }
+}
\ No newline at end of file
diff --git a/tests/patmat/t3111.check b/tests/patmat/t3111.check
new file mode 100644
index 000000000000..46ff0a6a9376
--- /dev/null
+++ b/tests/patmat/t3111.check
@@ -0,0 +1,8 @@
+./tests/patmat/t3111.scala:4: warning: match may not be exhaustive.
+It would fail on the following input: false
+  bool match {
+       ^
+./tests/patmat/t3111.scala:11: warning: unreachable code
+    case _ => "cats and dogs living together... mass hysteria!"
+          ^
+two warnings found
\ No newline at end of file
diff --git a/tests/patmat/t3111.scala b/tests/patmat/t3111.scala
new file mode 100644
index 000000000000..8f2bc5a273a9
--- /dev/null
+++ b/tests/patmat/t3111.scala
@@ -0,0 +1,13 @@
+object Test {
+  val bool: Boolean = false
+
+  bool match {
+    case true => "true!"
+  }
+
+  bool match {
+    case true => "true!"
+    case false => "false!"
+    case _ => "cats and dogs living together... mass hysteria!"
+  }
+}
\ No newline at end of file
diff --git a/tests/patmat/t3163.check b/tests/patmat/t3163.check
new file mode 100644
index 000000000000..3da94e2c2a40
--- /dev/null
+++ b/tests/patmat/t3163.check
@@ -0,0 +1,5 @@
+./tests/patmat/t3163.scala:2: warning: match may not be exhaustive.
+It would fail on the following input: _: AnyVal
+  def foo(x : AnyVal) = x match {case b : Boolean => "It's a bool"}
+                          ^
+one warning found
\ No newline at end of file
diff --git a/tests/patmat/t3163.scala b/tests/patmat/t3163.scala
new file mode 100644
index 000000000000..2e0f2c1d9482
--- /dev/null
+++ b/tests/patmat/t3163.scala
@@ -0,0 +1,3 @@
+object Test {
+  def foo(x : AnyVal) = x match {case b : Boolean => "It's a bool"}
+}
\ No newline at end of file
diff --git a/tests/patmat/t3683.scala b/tests/patmat/t3683.scala
new file mode 100644
index 000000000000..44be9d6c63fe
--- /dev/null
+++ b/tests/patmat/t3683.scala
@@ -0,0 +1,19 @@
+sealed trait Foo
+sealed trait Bar extends Foo
+sealed trait W[T >: Bar <: Foo]
+sealed case class X() extends W[Foo]
+sealed case class Y() extends W[Bar]
+sealed case class Z[T >: Bar <: Foo](
+  z1: W[T]
+) extends W[T]
+
+object Main {
+  def func(w: W[Bar]): Int = {
+    w match {
+      // Error if I include it, warning if I do not!
+      // case X() => 2
+      case Y() => 1
+      case Z(z) => func(z)
+    }
+  }
+}
diff --git a/tests/patmat/t4020.scala b/tests/patmat/t4020.scala
new file mode 100644
index 000000000000..f9764601910a
--- /dev/null
+++ b/tests/patmat/t4020.scala
@@ -0,0 +1,25 @@
+class A {
+    sealed trait Foo
+}
+
+object a1 extends A {
+    case class Foo1(i: Int) extends Foo
+}
+
+object a2 extends A {
+    case class Foo2(i: Int) extends Foo
+}
+
+class B {
+    def mthd(foo: a2.Foo) = {
+        foo match {
+            case a2.Foo2(i) => i
+
+            // Note: This case is impossible.  In fact, scalac
+            // will (correctly) report an error if it is uncommented,
+            // but a warning if it is commented.
+
+            // case a1.Foo1(i) => i
+        }
+    }
+}
\ No newline at end of file
diff --git a/tests/patmat/t4333.scala.ignore b/tests/patmat/t4333.scala.ignore
new file mode 100644
index 000000000000..07d105c74e47
--- /dev/null
+++ b/tests/patmat/t4333.scala.ignore
@@ -0,0 +1,7 @@
+object Enum extends Enumeration { val A, B, C = Value }
+
+object Test {
+  def foo(v : Enum.Value) = v match {
+    case Enum.B => println("B")
+  }
+}
diff --git a/tests/patmat/t4408.check b/tests/patmat/t4408.check
new file mode 100644
index 000000000000..53bfe1c2c564
--- /dev/null
+++ b/tests/patmat/t4408.check
@@ -0,0 +1,5 @@
+./tests/patmat/t4408.scala:2: warning: match may not be exhaustive.
+It would fail on the following input: List(_, _, _)
+  def printList(in: List[String]): Unit = in match {
+                                             ^
+one warning found
\ No newline at end of file
diff --git a/tests/patmat/t4408.scala b/tests/patmat/t4408.scala
new file mode 100644
index 000000000000..419b6636971e
--- /dev/null
+++ b/tests/patmat/t4408.scala
@@ -0,0 +1,16 @@
+object Test {
+  def printList(in: List[String]): Unit = in match {
+    case Nil => Unit
+
+    case (s: String) :: Nil =>
+      println(s)
+
+    case head :: (s: String) :: Nil =>
+      printList(head :: Nil)
+      for(i <- head){
+        print(i)
+      }
+      println
+      println(s)
+  }
+}
diff --git a/tests/patmat/t4526.check b/tests/patmat/t4526.check
new file mode 100644
index 000000000000..b577cbc0c121
--- /dev/null
+++ b/tests/patmat/t4526.check
@@ -0,0 +1,13 @@
+./tests/patmat/t4526.scala:2: warning: match may not be exhaustive.
+It would fail on the following input: _: Int
+  def foo(a: Int) = a match {
+                      ^
+./tests/patmat/t4526.scala:7: warning: match may not be exhaustive.
+It would fail on the following input: (_, _)
+  def bar(a: (Int, Int)) = a match {
+                             ^
+./tests/patmat/t4526.scala:12: warning: match may not be exhaustive.
+It would fail on the following input: (false, false), (true, true)
+  def baz(a: (Boolean, Boolean)) = a match {
+                                     ^
+three warnings found
\ No newline at end of file
diff --git a/tests/patmat/t4526.scala b/tests/patmat/t4526.scala
new file mode 100644
index 000000000000..d531c6b34304
--- /dev/null
+++ b/tests/patmat/t4526.scala
@@ -0,0 +1,16 @@
+object Test{
+  def foo(a: Int) = a match {
+    case 5  => "Five!"
+    case 42 => "The answer."
+  }
+
+  def bar(a: (Int, Int)) = a match {
+    case (5, 5)  => "Two fives!"
+    case (42, 21) => "The answer and a half."
+  }
+
+  def baz(a: (Boolean, Boolean)) = a match {
+    case (true, false)  => "tf"
+    case (false, true) =>  "ft"
+  }
+}
\ No newline at end of file
diff --git a/tests/patmat/t4691.check b/tests/patmat/t4691.check
new file mode 100644
index 000000000000..4d2c24506810
--- /dev/null
+++ b/tests/patmat/t4691.check
@@ -0,0 +1,5 @@
+./tests/patmat/t4691.scala:15: warning: match may not be exhaustive.
+It would fail on the following input: NodeType2(_)
+  def test (x: Node) = x match {
+                         ^
+one warning found
\ No newline at end of file
diff --git a/tests/patmat/t4691.scala b/tests/patmat/t4691.scala
new file mode 100644
index 000000000000..bfaa61670057
--- /dev/null
+++ b/tests/patmat/t4691.scala
@@ -0,0 +1,18 @@
+sealed trait Node
+
+class NodeType1 (val a:Int) extends Node
+class NodeType2 (val b:Int) extends Node
+
+object NodeType1 {
+  def unapply (x : NodeType1) : Some[Int] = Some(x.a)
+}
+
+object NodeType2 {
+  def unapply (x : NodeType2) : Some[Int] = Some(x.b)
+}
+
+object Test {
+  def test (x: Node) = x match {
+    case NodeType1(a) => "got node type 1 " + a
+  }
+}
\ No newline at end of file
diff --git a/tests/patmat/t5440.check b/tests/patmat/t5440.check
new file mode 100644
index 000000000000..f7d97eef78f3
--- /dev/null
+++ b/tests/patmat/t5440.check
@@ -0,0 +1,5 @@
+./tests/patmat/t5440.scala:3: warning: match may not be exhaustive.
+It would fail on the following input: { (Nil, List(_)), (List(_), Nil) }
+    (list1, list2) match  {
+    ^
+one warning found
diff --git a/tests/patmat/t5968.scala b/tests/patmat/t5968.scala
new file mode 100644
index 000000000000..14cc903c8033
--- /dev/null
+++ b/tests/patmat/t5968.scala
@@ -0,0 +1,7 @@
+object Test {
+  object X
+  def f(e: Either[Int, X.type]) = e match {
+    case Left(i) => i
+    case Right(X) => 0
+  }
+}
\ No newline at end of file
diff --git a/tests/patmat/t6008.scala b/tests/patmat/t6008.scala
new file mode 100644
index 000000000000..c42e9c5a5991
--- /dev/null
+++ b/tests/patmat/t6008.scala
@@ -0,0 +1,5 @@
+object Test {
+  def x(in: (Int, Boolean)) = in match {
+    case (i: Int, b: Boolean) => 3
+  }
+}
\ No newline at end of file
diff --git a/tests/patmat/t6420.check b/tests/patmat/t6420.check
new file mode 100644
index 000000000000..c62b33d181a5
--- /dev/null
+++ b/tests/patmat/t6420.check
@@ -0,0 +1,5 @@
+./tests/patmat/t6420.scala:5: warning: match may not be exhaustive.
+It would fail on the following input: (Nil, _), (List(_, _), _), (Nil, Nil), (Nil, List(_, _)), (List(_, _), Nil), (List(_, _), List(_, _)), (_, Nil), (_, List(_, _))
+  def foo(x: List[Boolean], y: List[Boolean]) = (x,y) match {
+                                                      ^
+one warning found
\ No newline at end of file
diff --git a/tests/patmat/t6420.scala b/tests/patmat/t6420.scala
new file mode 100644
index 000000000000..80c0f90f694b
--- /dev/null
+++ b/tests/patmat/t6420.scala
@@ -0,0 +1,11 @@
+object Test {
+  val c0 = false
+  val c1 = true
+
+  def foo(x: List[Boolean], y: List[Boolean]) = (x,y) match {
+    case (`c0`::x, `c0`::y) => x
+    case (`c0`::x, `c1`::y) => y
+    case (`c1`::x, `c0`::y) => y
+    case (`c1`::x, `c1`::y) => x
+  }
+}
diff --git a/tests/patmat/t6450.scala b/tests/patmat/t6450.scala
new file mode 100644
index 000000000000..157f1ce8124e
--- /dev/null
+++ b/tests/patmat/t6450.scala
@@ -0,0 +1,9 @@
+sealed abstract class FoundNode[T]
+// case class A[T](x: T) extends FoundNode[T]
+
+object Foo {
+  val v: (Some[_], FoundNode[_]) = (???, ???)
+  v match {
+    case (x: Some[t], _) =>
+  }
+}
diff --git a/tests/patmat/t6818.scala b/tests/patmat/t6818.scala
new file mode 100644
index 000000000000..2334095c46d8
--- /dev/null
+++ b/tests/patmat/t6818.scala
@@ -0,0 +1,11 @@
+object Test {
+  type Id[X] = X
+
+  def foo(x:Id[Option[Int]]) = x match {
+    case Some(n) => "foo"
+    case None => "bar"
+  }
+
+  foo(Some(3)) // "foo"
+  foo(None) // "bar"
+}
\ No newline at end of file
diff --git a/tests/patmat/t7206.scala.ignore b/tests/patmat/t7206.scala.ignore
new file mode 100644
index 000000000000..0133f1808e7a
--- /dev/null
+++ b/tests/patmat/t7206.scala.ignore
@@ -0,0 +1,19 @@
+object E extends Enumeration {
+  val V = Value
+}
+
+sealed case class C(e: E.Value)
+
+class Test {
+  def foo(c: C) = {
+    c match {
+      case C(E.V) => {}
+    }
+  }
+
+  def foo2(e: E.Value) = {
+    e match {
+      case E.V => {}
+    }
+  }
+}
diff --git a/tests/patmat/t7285.check b/tests/patmat/t7285.check
new file mode 100644
index 000000000000..703706cdc532
--- /dev/null
+++ b/tests/patmat/t7285.check
@@ -0,0 +1,13 @@
+./tests/patmat/t7285.scala:15: warning: match may not be exhaustive.
+It would fail on the following input: (Up, Down)
+      (d1, d2) match {
+               ^
+./tests/patmat/t7285.scala:33: warning: match may not be exhaustive.
+It would fail on the following input: Down
+      (d1) match {
+           ^
+./tests/patmat/t7285.scala:51: warning: match may not be exhaustive.
+It would fail on the following input: (Base.Up, Base.Down)
+    (d1, d2) match {
+             ^
+three warnings found
\ No newline at end of file
diff --git a/tests/patmat/t7285.scala b/tests/patmat/t7285.scala
new file mode 100644
index 000000000000..d40df7fe8919
--- /dev/null
+++ b/tests/patmat/t7285.scala
@@ -0,0 +1,55 @@
+sealed abstract class Base
+
+
+object Test1 {
+  sealed abstract class Base
+
+  object Base {
+    case object Down extends Base {
+    }
+
+    case object Up extends Base {
+    }
+
+    def foo(d1: Base, d2: Base) =
+      (d1, d2) match {
+        case (Up, Up) | (Down, Down) => false
+        case (Down, Up)              => true
+      }
+  }
+}
+
+object Test2 {
+  sealed abstract class Base
+
+  object Base {
+    case object Down extends Base {
+    }
+
+    case object Up extends Base {
+    }
+
+    def foo(d1: Base, d2: Base) =
+      (d1) match {
+        case Test2.Base.Up => false
+      }
+  }
+}
+
+
+object Test4 {
+  sealed abstract class Base
+
+  object Base {
+    case object Down extends Base
+
+    case object Up extends Base
+  }
+
+  import Test4.Base._
+  def foo(d1: Base, d2: Base) =
+    (d1, d2) match {
+      case (Up, Up) | (Down, Down) => false
+      case (Down, Test4.Base.Up)   => true
+    }
+}
diff --git a/tests/patmat/t7285a.scala b/tests/patmat/t7285a.scala
new file mode 100644
index 000000000000..49f6b663b28c
--- /dev/null
+++ b/tests/patmat/t7285a.scala
@@ -0,0 +1,83 @@
+sealed abstract class Base
+
+object Test {
+  case object Up extends Base
+
+  def foo(d1: Base) =
+    d1 match {
+      case Up  =>
+    }
+
+    // Sealed subtype: ModuleTypeRef   <empty>.this.Test.Up.type
+    // Pattern:        UniqueThisType  Test.this.type
+}
+
+
+object Test1 {
+  sealed abstract class Base
+
+  object Base {
+    case object Down extends Base {
+    }
+
+    case object Up extends Base {
+    }
+
+    def foo(d1: Base, d2: Base) =
+      (d1, d2) match {
+        case (Up, Up) | (Down, Down) => false
+        case (Down, Up)              => true
+        case (Up, Down)              => false
+      }
+  }
+}
+
+object Test2 {
+  sealed abstract class Base
+
+  object Base {
+    case object Down extends Base {
+    }
+
+    case object Up extends Base {
+    }
+
+    def foo(d1: Base, d2: Base) =
+      (d1) match {
+        case Up | Down => false
+      }
+  }
+}
+
+object Test3 {
+  sealed abstract class Base
+
+  object Base {
+    case object Down extends Base
+
+    def foo(d1: Base, d2: Base) =
+      (d1, d2) match {
+        case (Down, Down) => false
+      }
+  }
+}
+
+object Test4 {
+  sealed abstract class Base
+
+  object Base {
+    case object Down extends Base {
+    }
+
+    case object Up extends Base {
+    }
+
+  }
+  import Test4.Base._
+  def foo(d1: Base, d2: Base) =
+    (d1, d2) match {
+      case (Up, Up) | (Down, Down) => false
+      case (Down, Test4.Base.Up)   => true
+      case (Up, Down)              => false
+    }
+}
diff --git a/tests/patmat/t7298.scala b/tests/patmat/t7298.scala
new file mode 100644
index 000000000000..6fba5e120ca3
--- /dev/null
+++ b/tests/patmat/t7298.scala
@@ -0,0 +1,11 @@
+sealed trait Bool
+
+object Bool {
+  case object FALSE extends Bool
+  case object TRUE extends Bool
+
+  def show(b: Bool) = b match {
+    case FALSE => "1"
+    case TRUE  => "2"
+  }
+}
diff --git a/tests/patmat/t7353.scala b/tests/patmat/t7353.scala
new file mode 100644
index 000000000000..7a8fea115fc4
--- /dev/null
+++ b/tests/patmat/t7353.scala
@@ -0,0 +1,11 @@
+sealed trait EthernetType
+
+object EthernetType {
+  final case object Gigabit extends EthernetType
+  final case object FastEthernet extends EthernetType
+
+  final def toInt(t: EthernetType) = t match {
+    case Gigabit => 1
+    case FastEthernet => 2
+  }
+}
\ No newline at end of file
diff --git a/tests/patmat/t7437.scala b/tests/patmat/t7437.scala
new file mode 100644
index 000000000000..b0c5dff7cbbc
--- /dev/null
+++ b/tests/patmat/t7437.scala
@@ -0,0 +1,17 @@
+sealed trait IntegralNumber
+sealed trait FiniteNumber extends IntegralNumber
+
+object IntegralNumber {
+
+  sealed abstract class BaseNumber extends IntegralNumber
+  sealed abstract class NonFinite extends BaseNumber
+  object NaN extends NonFinite
+  sealed abstract class FiniteNumberImpl[N](val value: N) extends BaseNumber with FiniteNumber
+  sealed class IntNumber(value: Int) extends FiniteNumberImpl[Int](value)
+
+  def test(t: IntNumber, o: IntegralNumber) = o match {
+    case NaN => -1
+    case o: IntNumber => t.value.compare(o.value)
+  }
+
+}
\ No newline at end of file
diff --git a/tests/patmat/t7466.check b/tests/patmat/t7466.check
new file mode 100644
index 000000000000..93f7fd62a072
--- /dev/null
+++ b/tests/patmat/t7466.check
@@ -0,0 +1,5 @@
+./tests/patmat/t7466.scala:8: warning: match may not be exhaustive.
+It would fail on the following input: (true, _), (false, _), (_, true), (_, false)
+    (b1, b2) match {
+             ^
+one warning found
\ No newline at end of file
diff --git a/tests/patmat/t7466.scala b/tests/patmat/t7466.scala
new file mode 100644
index 000000000000..a74bf4ee210f
--- /dev/null
+++ b/tests/patmat/t7466.scala
@@ -0,0 +1,17 @@
+object Test extends App {
+  val Yes1 = true
+  val Yes2 = true
+  val No1 = false
+  val No2 = false
+
+  def test(b1: Boolean, b2: Boolean) = {
+    (b1, b2) match {
+      case (No1, No2) => println("1")
+      case (No1, Yes2) => println("2")
+      case (Yes1, No2) => println("3")
+      case (Yes1, Yes2) => println("4")
+    }
+  }
+
+  test(No1, Yes2)
+}
\ No newline at end of file
diff --git a/tests/patmat/t7631.check b/tests/patmat/t7631.check
new file mode 100644
index 000000000000..ede3703e2a60
--- /dev/null
+++ b/tests/patmat/t7631.check
@@ -0,0 +1,5 @@
+./tests/patmat/t7631.scala:8: warning: match may not be exhaustive.
+It would fail on the following input: TestB()
+  val x = input match {
+                ^
+one warning found
\ No newline at end of file
diff --git a/tests/patmat/t7631.scala b/tests/patmat/t7631.scala
new file mode 100644
index 000000000000..13e74183f084
--- /dev/null
+++ b/tests/patmat/t7631.scala
@@ -0,0 +1,11 @@
+sealed trait Test
+case class TestA() extends Test
+case class TestB() extends Test
+
+object Tester {
+  val input : Test = TestA()
+  val num = 3
+  val x = input match {
+    case TestA() if num == 3 => 2
+  }
+}
\ No newline at end of file
diff --git a/tests/patmat/t7669.check b/tests/patmat/t7669.check
new file mode 100644
index 000000000000..2804dbf5c3ac
--- /dev/null
+++ b/tests/patmat/t7669.check
@@ -0,0 +1,5 @@
+./tests/patmat/t7669.scala:10: warning: match may not be exhaustive.
+It would fail on the following input: NotHandled(_)
+  def exhausto(expr: Expr): Unit = expr match {
+                                        ^
+one warning found
\ No newline at end of file
diff --git a/tests/patmat/t7669.scala b/tests/patmat/t7669.scala
new file mode 100644
index 000000000000..3aa74129ed9b
--- /dev/null
+++ b/tests/patmat/t7669.scala
@@ -0,0 +1,14 @@
+object Test {
+
+  sealed abstract class Expr
+  // Change type of `arg` to `Any` and the exhaustiveness warning
+  // is issued below
+  case class Op(arg: Expr) extends Expr
+  case class NotHandled(num: Double) extends Expr
+
+
+  def exhausto(expr: Expr): Unit = expr match {
+    case Op(Op(_)) =>
+    case Op(_) =>
+  }
+}
diff --git a/tests/patmat/t7746.check b/tests/patmat/t7746.check
new file mode 100644
index 000000000000..be4c53570c68
--- /dev/null
+++ b/tests/patmat/t7746.check
@@ -0,0 +1,5 @@
+./tests/patmat/t7746.scala:2: warning: match may not be exhaustive.
+It would fail on the following input: Some(_), None
+  def f[T](x: Option[T]) = x match {
+                             ^
+one warning found
\ No newline at end of file
diff --git a/tests/patmat/t7746.scala b/tests/patmat/t7746.scala
new file mode 100644
index 000000000000..91f3823a47e9
--- /dev/null
+++ b/tests/patmat/t7746.scala
@@ -0,0 +1,5 @@
+object Test {
+  def f[T](x: Option[T]) = x match {
+    case Some(Some(5)) => true
+  }
+}
\ No newline at end of file
diff --git a/tests/patmat/t8068.scala b/tests/patmat/t8068.scala
new file mode 100644
index 000000000000..9837b7381413
--- /dev/null
+++ b/tests/patmat/t8068.scala
@@ -0,0 +1,14 @@
+trait K[A] {
+  sealed trait T
+  case class  C(x: Int) extends T
+  case object O         extends T
+}
+
+object Hello {
+  def f[A](k: K[A])(t: k.T) = {
+    t match {
+      case k.C(x) => ???
+      case k.O    => ???
+    }
+  }
+}
diff --git a/tests/patmat/t8178.check b/tests/patmat/t8178.check
new file mode 100644
index 000000000000..963845f5310c
--- /dev/null
+++ b/tests/patmat/t8178.check
@@ -0,0 +1,13 @@
+./tests/patmat/t8178.scala:6: warning: match may not be exhaustive.
+It would fail on the following input: FailsChild2(_)
+    f match {
+      ^
+./tests/patmat/t8178.scala:14: warning: match may not be exhaustive.
+It would fail on the following input: VarArgs1(_)
+    f match {
+      ^
+./tests/patmat/t8178.scala:27: warning: match may not be exhaustive.
+It would fail on the following input: SeqArgs2(_)
+    f match {
+      ^
+three warnings found
\ No newline at end of file
diff --git a/tests/patmat/t8178.scala b/tests/patmat/t8178.scala
new file mode 100644
index 000000000000..4fb39955bc0e
--- /dev/null
+++ b/tests/patmat/t8178.scala
@@ -0,0 +1,33 @@
+sealed trait Fails
+case class VarArgs1(a: String*) extends Fails
+case class FailsChild2(a: Seq[String]) extends Fails
+object FailsTest {
+  def matchOnVarArgsFirstFails(f: Fails) = {
+    f match {
+      case VarArgs1(_) => ???
+      // BUG: Without this line we should get a non-exhaustive match compiler error.
+      //case FailsChild2(_) => ???
+    }
+  }
+
+  def matchOnSeqArgsFirstWorks(f: Fails) = {
+    f match {
+      case FailsChild2(_) => ???
+      // Without this line, the compiler reports a "match may not be exhaustive" error as expected.
+      // case VarArgs1(_) => ???
+    }
+  }
+}
+
+sealed trait Works
+case class SeqArgs1(a: Seq[String]) extends Works
+case class SeqArgs2(a: Seq[String]) extends Works
+object WorksTest {
+  def matcher(f: Works) = {
+    f match {
+      case SeqArgs1(_) => ???
+      // Without this line, the compiler reports a "match may not be exhaustive" error as expected.
+      // case SeqArgs2(_) => ???
+    }
+  }
+}
\ No newline at end of file
diff --git a/tests/patmat/t8412.check b/tests/patmat/t8412.check
new file mode 100644
index 000000000000..b82b33999613
--- /dev/null
+++ b/tests/patmat/t8412.check
@@ -0,0 +1,5 @@
+./tests/patmat/t8412.scala:7: warning: match may not be exhaustive.
+It would fail on the following input: Lit(_)
+    tree match {
+         ^
+one warning found
\ No newline at end of file
diff --git a/tests/patmat/t8412.scala b/tests/patmat/t8412.scala
new file mode 100644
index 000000000000..f4b2b60907ff
--- /dev/null
+++ b/tests/patmat/t8412.scala
@@ -0,0 +1,14 @@
+sealed trait Tree
+case class Let(sth: List[Any]) extends Tree
+case class Lit(sth: Any) extends Tree
+
+object Test {
+  def wroong(tree: Tree) =
+    tree match {
+      case Let(_ :: rest) =>
+        ???
+      case Let(Nil) =>
+        ???
+      // no warning for missing Lit(_) in 2.10
+    }
+}
diff --git a/tests/patmat/t8430.check b/tests/patmat/t8430.check
new file mode 100644
index 000000000000..4493062bfceb
--- /dev/null
+++ b/tests/patmat/t8430.check
@@ -0,0 +1,5 @@
+./tests/patmat/t8430.scala:15: warning: match may not be exhaustive.
+It would fail on the following input: LetF, LetC, LetP, LetL(UnitLit), LetL(BooleanLit), LetL(IntLit)
+  def transform(tree: Tree) : Any = tree match {
+                                         ^
+one warning found
\ No newline at end of file
diff --git a/tests/patmat/t8430.scala b/tests/patmat/t8430.scala
new file mode 100644
index 000000000000..ccd4585d94b0
--- /dev/null
+++ b/tests/patmat/t8430.scala
@@ -0,0 +1,19 @@
+sealed trait CL3Literal
+case object IntLit extends CL3Literal
+case object CharLit extends CL3Literal
+case object BooleanLit extends CL3Literal
+case object UnitLit extends CL3Literal
+
+
+sealed trait Tree
+case class LetL(value: CL3Literal) extends Tree
+case object LetP extends Tree
+case object LetC extends Tree
+case object LetF extends Tree
+
+object Test {
+  def transform(tree: Tree) : Any = tree match {
+    case LetL(CharLit) =>
+      ???
+  }
+}
diff --git a/tests/patmat/t8511.check b/tests/patmat/t8511.check
new file mode 100644
index 000000000000..df07d019aa33
--- /dev/null
+++ b/tests/patmat/t8511.check
@@ -0,0 +1,5 @@
+./tests/patmat/t8511.scala:18: warning: match may not be exhaustive.
+It would fail on the following input: Baz(), Bar(_)
+  private def logic(head: Expr): String = head match {
+                                               ^
+one warning found
\ No newline at end of file
diff --git a/tests/patmat/t8511.scala b/tests/patmat/t8511.scala
new file mode 100644
index 000000000000..bc7f64713441
--- /dev/null
+++ b/tests/patmat/t8511.scala
@@ -0,0 +1,25 @@
+sealed trait Expr
+final case class Foo(other: Option[String]) extends Expr
+final case class Bar(someConstant: String) extends Expr
+final case class Baz() extends Expr
+final case class EatsExhaustiveWarning(other: Reference) extends Expr
+
+sealed trait Reference {
+  val value: String
+}
+
+object Reference {
+  def unapply(reference: Reference): Option[(String)] = {
+    Some(reference.value)
+  }
+}
+
+object EntryPoint {
+  private def logic(head: Expr): String = head match {
+    case Foo(_) =>
+      ???
+    // Commenting this line only causes the exhaustive search warning to be emitted
+    case EatsExhaustiveWarning(Reference(text)) =>
+      ???
+  }
+}
\ No newline at end of file
diff --git a/tests/patmat/t8546.scala b/tests/patmat/t8546.scala
new file mode 100644
index 000000000000..c39d749b4c45
--- /dev/null
+++ b/tests/patmat/t8546.scala
@@ -0,0 +1,49 @@
+package test
+
+class F1() {
+  private sealed abstract class T
+  private case class A(m: Int) extends T
+  private case class B() extends T
+  private case object C extends T
+
+  // No warnings here
+  private def foo(t: T) = t match {
+    case A(m) => println("A:" + m)
+    case B() => println("B")
+    case C => println("C")
+  }
+
+  def test(m: Int): Unit = {
+    foo(A(m))
+    foo(B())
+    foo(C)
+  }
+}
+
+class F2[M]() {
+  private sealed abstract class T
+  private case class A(m: M) extends T
+  private case class B() extends T
+  private case object C extends T
+
+  // match may not be exhaustive. It would fail on the following input: C
+  private def foo(t: T) = t match {
+    case A(m) => println("A:" + m)
+    case B() => println("B")
+    case C => println("C")
+  }
+
+  def test(m: M): Unit = {
+    foo(A(m))
+    foo(B())
+    foo(C)
+  }
+
+}
+
+object Test {
+  def main(args: Array[String]): Unit = {
+    new F1().test(1)
+    new F2[Int]().test(1)
+  }
+}
\ No newline at end of file
diff --git a/tests/patmat/t8606.scala b/tests/patmat/t8606.scala
new file mode 100644
index 000000000000..9388c9f02bd0
--- /dev/null
+++ b/tests/patmat/t8606.scala
@@ -0,0 +1,18 @@
+class Cl[T] {
+
+  sealed trait A {
+    def foo = this match {
+      case AObj => 0
+      case BObj => 0
+      case ACls(x) => 0
+      case BCls(x) => 0
+    }
+  }
+
+  case object AObj extends A
+  case class ACls(x: Int) extends A
+
+  sealed trait B extends A
+  case object BObj extends B
+  case class BCls(x: Int) extends B
+}
diff --git a/tests/patmat/t9129.check b/tests/patmat/t9129.check
new file mode 100644
index 000000000000..aa722a61acad
--- /dev/null
+++ b/tests/patmat/t9129.check
@@ -0,0 +1,5 @@
+./tests/patmat/t9129.scala:21: warning: match may not be exhaustive.
+It would fail on the following input: Two(B2, A2), Two(_, A2)
+  def foo(c: C): Unit = c match {
+                          ^
+one warning found
\ No newline at end of file
diff --git a/tests/patmat/t9129.scala b/tests/patmat/t9129.scala
new file mode 100644
index 000000000000..89f08f0ac2db
--- /dev/null
+++ b/tests/patmat/t9129.scala
@@ -0,0 +1,29 @@
+object Test {
+
+  sealed abstract class A
+
+  case object A1 extends A
+
+  case object A2 extends A
+
+  sealed abstract class B
+
+  case object B1 extends B
+
+  case object B2 extends B
+
+  sealed abstract class C
+
+  final case class One(a: A, b: B) extends C
+
+  final case class Two(b: B, a: A) extends C
+
+  def foo(c: C): Unit = c match {
+    case One(A1, B1) =>
+    case One(A2, B1) =>
+    case One(A1, B2) =>
+    case One(A2, B2) =>
+    case Two(B1, A1) =>
+    case Two(B2, A1) =>
+  }
+}
\ No newline at end of file
diff --git a/tests/patmat/t9232.check b/tests/patmat/t9232.check
new file mode 100644
index 000000000000..c3957c0ffa1d
--- /dev/null
+++ b/tests/patmat/t9232.check
@@ -0,0 +1,5 @@
+./tests/patmat/t9232.scala:13: warning: match may not be exhaustive.
+It would fail on the following input: Node2()
+  def transformTree(tree: Tree): Any = tree match {
+                                            ^
+one warning found
diff --git a/tests/patmat/t9232.scala b/tests/patmat/t9232.scala
new file mode 100644
index 000000000000..975ec58db823
--- /dev/null
+++ b/tests/patmat/t9232.scala
@@ -0,0 +1,16 @@
+final class Foo(val value: Int)
+
+object Foo {
+  def unapplySeq(foo: Foo): Some[Seq[Int]] = Some(List(foo.value))
+  // def unapply(foo: Foo): Some[Int] = Some(foo.value)
+}
+
+sealed trait Tree
+case class Node1(foo: Foo) extends Tree
+case class Node2() extends Tree
+
+object Test {
+  def transformTree(tree: Tree): Any = tree match {
+    case Node1(Foo(1)) => ???
+  }
+}
diff --git a/tests/patmat/t9289.check b/tests/patmat/t9289.check
new file mode 100644
index 000000000000..5240988e2606
--- /dev/null
+++ b/tests/patmat/t9289.check
@@ -0,0 +1,9 @@
+./tests/patmat/t9289.scala:9: warning: match may not be exhaustive.
+It would fail on the following input: module.LetR()
+  def patmat(tree: module.Tree) = tree match {
+                                       ^
+./tests/patmat/t9289.scala:20: warning: match may not be exhaustive.
+It would fail on the following input: module.LetR()
+  def patmat(tree: module.Tree) = tree match {
+                                       ^
+two warnings found
\ No newline at end of file
diff --git a/tests/patmat/t9289.scala b/tests/patmat/t9289.scala
new file mode 100644
index 000000000000..714a4a0e3928
--- /dev/null
+++ b/tests/patmat/t9289.scala
@@ -0,0 +1,28 @@
+trait Module {
+  sealed trait Tree
+
+  case class LetL() extends Tree
+  case class LetR() extends Tree
+}
+
+class Patmat[T <: Module](val module: T) {
+  def patmat(tree: module.Tree) = tree match {
+    case module.LetL() => ???
+  }
+
+  def exhaust(tree: module.Tree) = tree match {
+    case module.LetL() => ???
+    case module.LetR() => ???
+  }
+}
+
+class Patmat2(val module: Module) {
+  def patmat(tree: module.Tree) = tree match {
+    case module.LetL() => ???
+  }
+
+  def exhaust(tree: module.Tree) = tree match {
+    case module.LetL() => ???
+    case module.LetR() => ???
+  }
+}
diff --git a/tests/patmat/t9351.check b/tests/patmat/t9351.check
new file mode 100644
index 000000000000..03b94c2c001b
--- /dev/null
+++ b/tests/patmat/t9351.check
@@ -0,0 +1,13 @@
+./tests/patmat/t9351.scala:8: warning: match may not be exhaustive.
+It would fail on the following input: _: A
+    a match {
+      ^
+./tests/patmat/t9351.scala:17: warning: match may not be exhaustive.
+It would fail on the following input: (_, _), (_, None), (_, Some(_))
+    (a, o) match {
+           ^
+./tests/patmat/t9351.scala:28: warning: match may not be exhaustive.
+It would fail on the following input: (_, _)
+    (a, b) match {
+           ^
+three warnings found
\ No newline at end of file
diff --git a/tests/patmat/t9351.scala b/tests/patmat/t9351.scala
new file mode 100644
index 000000000000..9b9bd4312ae7
--- /dev/null
+++ b/tests/patmat/t9351.scala
@@ -0,0 +1,35 @@
+trait A {}
+case object B extends A {}
+case object C extends A {}
+
+class X {
+  def good = {
+    val a: A = B
+    a match {
+      case B =>
+      case C =>
+    }
+  }
+
+  def bad = {
+    val a: A = B
+    val o: Option[Int] = None
+    (a, o) match {
+      case (B, None) =>
+      case (B, Some(_)) =>
+      case (C, None) =>
+      case (C, Some(_)) =>
+    }
+  }
+
+  def alsoGood = {
+    val a: A = B
+    val b: A = C
+    (a, b) match {
+      case (B, B) =>
+      case (B, C) =>
+      case (C, B) =>
+      case (C, C) =>
+    }
+  }
+}
diff --git a/tests/patmat/t9398.check b/tests/patmat/t9398.check
new file mode 100644
index 000000000000..0efbf231d6c5
--- /dev/null
+++ b/tests/patmat/t9398.check
@@ -0,0 +1,5 @@
+./tests/patmat/t9398.scala:11: warning: match may not be exhaustive.
+It would fail on the following input: CC(_, B2)
+    case CC(_, B) => ()
+    ^
+one warning found
diff --git a/tests/patmat/t9398.scala b/tests/patmat/t9398.scala
new file mode 100644
index 000000000000..6d4d6bd3b111
--- /dev/null
+++ b/tests/patmat/t9398.scala
@@ -0,0 +1,13 @@
+sealed abstract class TA
+sealed abstract class TB extends TA
+case object B extends TB
+case object B2 extends TB
+
+case class CC(i: Int, tb: TB)
+
+object Test {
+  // Should warn that CC(_, B2) isn't matched
+  def foo: CC => Unit = {
+    case CC(_, B) => ()
+  }
+}
\ No newline at end of file
diff --git a/tests/patmat/t9399.scala b/tests/patmat/t9399.scala
new file mode 100644
index 000000000000..89dbedd9672f
--- /dev/null
+++ b/tests/patmat/t9399.scala
@@ -0,0 +1,16 @@
+sealed abstract class TA
+sealed abstract class TB extends TA
+case object A extends TA
+case object B extends TB
+
+sealed trait C
+case class CTA(id: Int, da: TA) extends C
+case class CTB(id: Int, da: TB) extends C
+
+object Test {
+  val test: C => Unit = {
+    case CTA(_, A) =>
+    case CTA(_, B) =>
+    case CTB(_, B) =>
+  }
+}
diff --git a/tests/patmat/t9573.check b/tests/patmat/t9573.check
new file mode 100644
index 000000000000..4ec379161422
--- /dev/null
+++ b/tests/patmat/t9573.check
@@ -0,0 +1,5 @@
+./tests/patmat/t9573.scala:9: warning: match may not be exhaustive.
+It would fail on the following input: Horse(_)
+    x match {
+      ^
+one warning found
\ No newline at end of file
diff --git a/tests/patmat/t9573.scala b/tests/patmat/t9573.scala
new file mode 100644
index 000000000000..2a32c2599f23
--- /dev/null
+++ b/tests/patmat/t9573.scala
@@ -0,0 +1,13 @@
+class Foo {
+
+  def foo = {
+    abstract sealed class Animal
+    case class Goat(age: Int) extends Animal
+    case class Horse(age: Int) extends Animal
+
+    val x: Animal = Goat(1)
+    x match {
+      case Goat(_) => println("a goat")
+    }
+  }
+}
\ No newline at end of file
diff --git a/tests/patmat/t9630.scala b/tests/patmat/t9630.scala
new file mode 100644
index 000000000000..c846faa99350
--- /dev/null
+++ b/tests/patmat/t9630.scala
@@ -0,0 +1,21 @@
+sealed trait OpError
+sealed trait RequestErrorType
+sealed trait ProcessingErrorType
+
+final case class InvalidEndpoint(reason: String) extends RequestErrorType
+final case class InvalidParameters(reason: String) extends RequestErrorType
+
+final case class InvalidFormat(response: String) extends ProcessingErrorType
+final case class EntityNotFound(id: Long) extends ProcessingErrorType
+
+final case class RequestError(errorType: RequestErrorType) extends OpError
+final case class ProcessingError(errorType: ProcessingErrorType) extends OpError
+
+object Test{
+  def printMatches(error: OpError): Unit = error match {
+    case RequestError(InvalidEndpoint(reason)) => //print something
+    case RequestError(InvalidParameters(reason)) => //print something
+    case ProcessingError(InvalidFormat(format)) => //print something
+    case ProcessingError(EntityNotFound(entityId)) => //print something
+  }
+}
\ No newline at end of file
diff --git a/tests/patmat/t9657.scala.ignore b/tests/patmat/t9657.scala.ignore
new file mode 100644
index 000000000000..d15a441e3237
--- /dev/null
+++ b/tests/patmat/t9657.scala.ignore
@@ -0,0 +1,28 @@
+sealed trait PowerSource
+
+case object Petrol extends PowerSource
+
+case object Pedal extends PowerSource
+
+sealed abstract class Vehicle {
+  type A <: PowerSource
+}
+
+case object Bicycle extends Vehicle {
+  type A = Pedal.type
+}
+
+case class Bus(fuel: Int) extends Vehicle {
+  type A = Petrol.type
+}
+
+case class Car(fuel: Int) extends Vehicle {
+  type A = Petrol.type
+}
+
+object Test {
+  def refuel[P <: Petrol.type](vehicle: Vehicle {type A = P} ): Vehicle = vehicle match {
+    case Car(_) => Car(100)
+    case Bus(_) => Bus(100)
+  }
+}
\ No newline at end of file
diff --git a/tests/patmat/t9672.check b/tests/patmat/t9672.check
new file mode 100644
index 000000000000..3284d1df1e8d
--- /dev/null
+++ b/tests/patmat/t9672.check
@@ -0,0 +1,5 @@
+./tests/patmat/t9672.scala:22: warning: match may not be exhaustive.
+It would fail on the following input: SimpleExpr.IntExpr(_)
+  def func(expr: Expr) = expr match {
+                              ^
+one warning found
\ No newline at end of file
diff --git a/tests/patmat/t9672.scala b/tests/patmat/t9672.scala
new file mode 100644
index 000000000000..fe068f3d5e78
--- /dev/null
+++ b/tests/patmat/t9672.scala
@@ -0,0 +1,28 @@
+trait Hierarchy {
+  sealed trait Expr
+}
+trait If {
+  this: Hierarchy =>
+  case class If(cond: Expr, yes: Expr, no: Expr) extends Expr
+}
+trait Word {
+  this: Hierarchy =>
+  case class Word(name: String) extends Expr
+}
+trait IntExpr {
+  this: Hierarchy =>
+  case class IntExpr(value : Int) extends Expr
+}
+
+object SimpleExpr extends Hierarchy with If with Word with IntExpr
+//object OtherExpr extends Hierarchy with If with IntExpr
+
+object Demo extends App {
+  import SimpleExpr._
+  def func(expr: Expr) = expr match {
+    case If(cond, yes, no) => cond
+    case Word(name) => name
+    // compiler should emit warning "missing case statement"
+    // emits the wrong warning "unreachable code"
+  }
+}
\ No newline at end of file
diff --git a/tests/patmat/t9677.scala b/tests/patmat/t9677.scala
new file mode 100644
index 000000000000..1e9b1df5e891
--- /dev/null
+++ b/tests/patmat/t9677.scala
@@ -0,0 +1,23 @@
+sealed abstract class Base
+
+sealed trait A extends Base
+
+object A {
+
+  case object Root extends Base
+
+  def apply(param: String): A = {
+      new A {}
+  }
+}
+
+object ExhaustiveMatchWarning {
+
+  def test: Unit = {
+    val b: Base = A("blabla")
+    b match {
+      case A.Root => println("Root")
+      case path: A => println("Not root")
+    }
+  }
+}
\ No newline at end of file

From 9a0952cdd0c2bc7a5ed0fdb4bf1cff968d1ab874 Mon Sep 17 00:00:00 2001
From: liu fengyun <liufengyunchina@gmail.com>
Date: Wed, 25 May 2016 01:25:48 +0200
Subject: [PATCH 02/11] support check java enum from classfile and source file

---
 src/dotty/tools/dotc/Compiler.scala           |   4 -
 src/dotty/tools/dotc/core/Phases.scala        |   8 +-
 src/dotty/tools/dotc/core/Types.scala         |   7 +
 .../dotc/core/classfile/ClassfileParser.scala |  10 ++
 .../tools/dotc/transform/PatternMatcher.scala |   9 +-
 .../dotc/transform/{ => patmat}/Space.scala   | 152 +++++++++---------
 src/dotty/tools/dotc/typer/Namer.scala        |  30 ++++
 .../transform/PatmatExhaustivityTest.scala    |  42 ++++-
 tests/patmat/enum/Day.java                    |   4 +
 tests/patmat/enum/expected.check              |   5 +
 tests/patmat/enum/patmat-enum.scala           |   9 ++
 11 files changed, 189 insertions(+), 91 deletions(-)
 rename src/dotty/tools/dotc/transform/{ => patmat}/Space.scala (80%)
 create mode 100644 tests/patmat/enum/Day.java
 create mode 100644 tests/patmat/enum/expected.check
 create mode 100644 tests/patmat/enum/patmat-enum.scala

diff --git a/src/dotty/tools/dotc/Compiler.scala b/src/dotty/tools/dotc/Compiler.scala
index ce9280d827b8..6442d2feec22 100644
--- a/src/dotty/tools/dotc/Compiler.scala
+++ b/src/dotty/tools/dotc/Compiler.scala
@@ -8,12 +8,8 @@ import Symbols._
 import Types._
 import Scopes._
 import typer.{FrontEnd, Typer, ImportInfo, RefChecks}
-import reporting.{Reporter, ConsoleReporter}
 import Phases.Phase
 import transform._
-import transform.TreeTransforms.{TreeTransform, TreeTransformer}
-import core.DenotTransformers.DenotTransformer
-import core.Denotations.SingleDenotation
 
 import dotty.tools.backend.jvm.{LabelDefs, GenBCode}
 import dotty.tools.backend.sjs.GenSJSIR
diff --git a/src/dotty/tools/dotc/core/Phases.scala b/src/dotty/tools/dotc/core/Phases.scala
index 4b2861452d0c..fc7623f94ebc 100644
--- a/src/dotty/tools/dotc/core/Phases.scala
+++ b/src/dotty/tools/dotc/core/Phases.scala
@@ -1,17 +1,17 @@
 package dotty.tools.dotc
 package core
 
-import Periods._
 import Contexts._
-import dotty.tools.backend.jvm.{LabelDefs, GenBCode}
+import dotty.tools.backend.jvm.{GenBCode, LabelDefs}
 import dotty.tools.dotc.core.Symbols.ClassSymbol
 import util.DotClass
 import DenotTransformers._
 import Denotations._
 import Decorators._
 import config.Printers._
-import scala.collection.mutable.{ListBuffer, ArrayBuffer}
-import dotty.tools.dotc.transform.TreeTransforms.{TreeTransformer, MiniPhase, TreeTransform}
+
+import scala.collection.mutable.ListBuffer
+import dotty.tools.dotc.transform.TreeTransforms.{MiniPhase, TreeTransformer}
 import dotty.tools.dotc.transform._
 import Periods._
 import typer.{FrontEnd, RefChecks}
diff --git a/src/dotty/tools/dotc/core/Types.scala b/src/dotty/tools/dotc/core/Types.scala
index f514a329e1b9..83998303dc27 100644
--- a/src/dotty/tools/dotc/core/Types.scala
+++ b/src/dotty/tools/dotc/core/Types.scala
@@ -810,6 +810,13 @@ object Types {
       case _ => this
     }
 
+    /** Eliminate anonymous classes */
+    final def elimAnonymousClass(implicit ctx: Context): Type = this match {
+      case tp:TypeRef if tp.symbol.isAnonymousClass =>
+        tp.symbol.asClass.typeRef.asSeenFrom(tp.prefix, tp.symbol.owner)
+      case tp => tp
+    }
+
     /** Follow aliases and dereferences LazyRefs and instantiated TypeVars until type
      *  is no longer alias type, LazyRef, or instantiated type variable.
      */
diff --git a/src/dotty/tools/dotc/core/classfile/ClassfileParser.scala b/src/dotty/tools/dotc/core/classfile/ClassfileParser.scala
index f7a69aa53f28..e159162ccdcc 100644
--- a/src/dotty/tools/dotc/core/classfile/ClassfileParser.scala
+++ b/src/dotty/tools/dotc/core/classfile/ClassfileParser.scala
@@ -90,6 +90,7 @@ class ClassfileParser(
     val jflags       = in.nextChar
     val isAnnotation = hasAnnotation(jflags)
     val sflags       = classTranslation.flags(jflags)
+    val isEnum       = (jflags & JAVA_ACC_ENUM) != 0
     val nameIdx      = in.nextChar
     currentClassName = pool.getClassName(nameIdx)
 
@@ -145,6 +146,15 @@ class ClassfileParser(
       setClassInfo(classRoot, classInfo)
       setClassInfo(moduleRoot, staticInfo)
     }
+
+    // eager load java enum definitions for exhaustivity check of pattern match
+    if (isEnum) {
+      instanceScope.toList.map(_.ensureCompleted())
+      staticScope.toList.map(_.ensureCompleted())
+      classRoot.setFlag(Flags.Enum)
+      moduleRoot.setFlag(Flags.Enum)
+    }
+
     result
   }
 
diff --git a/src/dotty/tools/dotc/transform/PatternMatcher.scala b/src/dotty/tools/dotc/transform/PatternMatcher.scala
index 9e3047645a34..da417b5cb60f 100644
--- a/src/dotty/tools/dotc/transform/PatternMatcher.scala
+++ b/src/dotty/tools/dotc/transform/PatternMatcher.scala
@@ -24,6 +24,7 @@ import Applications._
 import TypeApplications._
 import SymUtils._, core.NameOps._
 import core.Mode
+import patmat._
 
 import dotty.tools.dotc.util.Positions.Position
 import dotty.tools.dotc.core.Decorators._
@@ -56,9 +57,9 @@ class PatternMatcher extends MiniPhaseTransform with DenotTransformer {thisTrans
 
     // check exhaustivity and unreachability
     val engine = new SpaceEngine
-    if (!engine.skipCheck(sel.tpe)) {
-      engine.exhaustivity(tree)
-      engine.redundancy(tree)
+    if (engine.checkable(sel.tpe.widen.elimAnonymousClass)) {
+      engine.checkExhaustivity(tree)
+      engine.checkRedundancy(tree)
     }
 
     translated.ensureConforms(tree.tpe)
@@ -1275,7 +1276,7 @@ class PatternMatcher extends MiniPhaseTransform with DenotTransformer {thisTrans
     def translateMatch(match_ : Match): Tree = {
       val Match(sel, cases) = match_
 
-      val selectorTp = elimAnonymousClass(sel.tpe.widen/*withoutAnnotations*/)
+      val selectorTp = sel.tpe.widen.elimAnonymousClass/*withoutAnnotations*/
 
       val selectorSym = freshSym(sel.pos, selectorTp, "selector")
 
diff --git a/src/dotty/tools/dotc/transform/Space.scala b/src/dotty/tools/dotc/transform/patmat/Space.scala
similarity index 80%
rename from src/dotty/tools/dotc/transform/Space.scala
rename to src/dotty/tools/dotc/transform/patmat/Space.scala
index 30a297d0c6bc..c7ddd82d839e 100644
--- a/src/dotty/tools/dotc/transform/Space.scala
+++ b/src/dotty/tools/dotc/transform/patmat/Space.scala
@@ -1,5 +1,6 @@
 package dotty.tools.dotc
 package transform
+package patmat
 
 import core.Types._
 import core.Contexts._
@@ -12,8 +13,26 @@ import core.Symbols._
 import core.NameOps._
 import core.Constants._
 
-/** Space logic for checking exhaustivity and unreachability of
- *  pattern matching.
+/** Space logic for checking exhaustivity and unreachability of pattern matching.
+ *
+ *  The core idea of the algorithm is that patterns and types are value
+ *  spaces, which is recursively defined as follows:
+ *
+ *      1. `Empty` is a space
+ *      2. For a type T, `Typ(T)` is a space
+ *      3. A union of spaces `S1 | S2 | ...` is a space
+ *      4. For a case class Kon(x1: T1, x2: T2, .., xn: Tn), if S1, S2, ..., Sn
+ *          are spaces, then `Kon(S1, S2, ..., Sn)` is a space.
+ *      5. A constant `Const(value, T)` is a point in space
+ *      6. A stable identifier `Var(sym, T)` is a space
+ *
+ *  For the problem of exhaustivity check, its formulation in terms of space is as follows:
+ *
+ *      Is the space Typ(T) a subspace of the union of space covered by all the patterns?
+ *
+ *  The problem of unreachable patterns can be formulated as follows:
+ *
+ *      Is the space covered by a pattern a subspace of the space covered by previous patterns?
  */
 
 
@@ -41,7 +60,7 @@ trait SpaceLogic {
   /** Is the type `tp` decomposable? i.e. all values of the type can be covered
    *  by its decomposed types.
    *
-   * Abstract sealed class, OrType and Boolean can be decomposed.
+   * Abstract sealed class, OrType, Boolean and Java enums can be decomposed.
    */
   def canDecompose(tp: Type): Boolean
 
@@ -197,7 +216,7 @@ trait SpaceLogic {
     case (Const(_, tp1), Typ(tp2, _)) =>
       if (isSubType(tp1, tp2)) Empty else a
     case (Const(_, _), _) => a
-    case (Typ(tp1, _), Const(_, tp2)) =>  // Boolean
+    case (Typ(tp1, _), Const(_, tp2)) =>  // Boolean & Java enum
       if (isSubType(tp2, tp1) && canDecompose(tp1))
         minus(Or(partitions(tp1)), b)
       else a
@@ -215,10 +234,6 @@ trait SpaceLogic {
 class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
   import tpd._
 
-  def debug(s: String): Unit = {
-    if (ctx.debug) println(s)
-  }
-
   /** Return the space that represents the pattern `pat`
    *
    *  If roundUp is true, approximate extractors to its type,
@@ -227,10 +242,13 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
   def project(pat: Tree, roundUp: Boolean = true)(implicit ctx: Context): Space = pat match {
     case Literal(c) => Const(c, c.tpe)
     case _: BackquotedIdent => Var(pat.symbol, pat.tpe)
-    case Ident(_) => Typ(pat.tpe.stripAnnots, false)
-    case Select(_, _) =>
+    case Ident(_) =>
+      Typ(pat.tpe.stripAnnots, false)
+    case Select(_, _)  =>
       if (pat.symbol.is(Module))
         Typ(pat.tpe.stripAnnots, false)
+      else if (pat.symbol.is(Enum))
+        Const(Constant(pat.symbol), pat.tpe)
       else
         Var(pat.symbol, pat.tpe)
     case Alternative(trees) => Or(trees.map(project(_, roundUp)))
@@ -243,7 +261,6 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
     case Typed(pat @ UnApply(_, _, _), _) => project(pat)
     case Typed(expr, _) => Typ(expr.tpe.stripAnnots, true)
     case _ =>
-      debug(s"========unkown tree: $pat========")
       Empty
   }
 
@@ -255,71 +272,61 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
     case (tp1: RefinedType, tp2: RefinedType) => isSubType(tp1.parent, tp2.parent)
     case (tp1: RefinedType, _) => isSubType(tp1.parent, tp2)
     case (_, tp2: RefinedType) => isSubType(tp1, tp2.parent)
-    case (_, _) =>
-      val res = tp1 <:< tp2
-      debug(s"$tp1 <: $tp2 ? $res")
-      res
+    case (_, _) => tp1 <:< tp2
   }
 
-  def isEqualType(tp1: Type, tp2: Type): Boolean = {
-    val res = tp1 =:= tp2
-    debug(s"$tp1 == $tp2 ? $res")
-    res
-  }
+  def isEqualType(tp1: Type, tp2: Type): Boolean = tp1 =:= tp2
 
   def signature(tp: Type): List[Type] = {
     val ktor = tp.classSymbol.primaryConstructor.info
 
-    debug(s"=======ktor: $ktor")
-
     val meth =
       if (ktor.isInstanceOf[MethodType]) ktor
       else
       tp match {
         case AppliedType(_, params) =>
-          debug(s"=======params: $params")
           val refined = params.map {
             // TypeBounds would generate an exception
             case tp: TypeBounds => tp.underlying
             case tp => tp
           }
-          debug(s"=======refined params: $refined")
           ktor.appliedTo(refined)
         case _ =>
           ktor
       }
 
-    val sign = meth.firstParamTypes.map(_.stripTypeVar).map(paramTp => refine(tp, paramTp))
-
-    debug(s"====signature of $tp: $sign")
-    sign
+    meth.firstParamTypes.map(_.stripTypeVar).map(refine(tp, _))
   }
 
-  def partitions(tp: Type): List[Space] = tp match {
-    case OrType(tp1, tp2) => List(Typ(tp1, true), Typ(tp2, true))
-    case _ if tp =:= ctx.definitions.BooleanType =>
-      List(
-        Const(Constant(true), ctx.definitions.BooleanType),
-        Const(Constant(false), ctx.definitions.BooleanType)
-      )
-    case _ =>
-      val children = tp.classSymbol.annotations.filter(_.symbol == ctx.definitions.ChildAnnot).map { annot =>
-        // refer to definition of Annotation.makeChild
-        val sym = annot.tree match {
-          case Apply(TypeApply(_, List(tpTree)), _) => tpTree.symbol.asClass
-        }
-
-        if (sym.is(ModuleClass))
-          sym.classInfo.selfType
-        else if (sym.info.typeParams.length > 0 || tp.isInstanceOf[TypeRef])
-          refine(tp, sym.classInfo.symbolicTypeRef)
-        else
-          sym.info
-      } filter(_ <:< tp) // child may not always be subtype of parent: SI-4020
-
-      debug(s"=========child of ${tp.show}: ${children.map(_.show).mkString(", ")}")
+  def partitions(tp: Type): List[Space] = {
+    val children = tp.classSymbol.annotations.filter(_.symbol == ctx.definitions.ChildAnnot).map { annot =>
+      // refer to definition of Annotation.makeChild
+      annot.tree match {
+        case Apply(TypeApply(_, List(tpTree)), _) => tpTree.symbol
+      }
+    }
 
-      children.map(tp => Typ(tp, true))
+    tp match {
+      case OrType(tp1, tp2) => List(Typ(tp1, true), Typ(tp2, true))
+      case _ if tp =:= ctx.definitions.BooleanType =>
+        List(
+          Const(Constant(true), ctx.definitions.BooleanType),
+          Const(Constant(false), ctx.definitions.BooleanType)
+        )
+      case _ if tp.classSymbol.is(Enum) =>
+        children.map(sym => Const(Constant(sym), tp))
+      case _ =>
+        val parts = children.map { sym =>
+          if (sym.is(ModuleClass))
+            sym.asClass.classInfo.selfType
+          else if (sym.info.typeParams.length > 0 || tp.isInstanceOf[TypeRef])
+            refine(tp, sym.asClass.classInfo.symbolicTypeRef)
+          else
+            sym.info
+        } filter(_ <:< tp) // child may not always be subtype of parent: SI-4020
+
+        parts.map(tp => Typ(tp, true))
+    }
   }
 
   /** Refine tp2 based on tp1
@@ -337,13 +344,13 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
     case _ => tp2
   }
 
-  /** Abstract sealed types,  or-types and Boolean can be decomposed */
-  def canDecompose(tp: Type): Boolean = {
+  /** Abstract sealed types,  or-types, Boolean and Java enums can be decomposed */
+  def canDecompose(tp: Type): Boolean =
     tp.typeSymbol.is(allOf(Abstract, Sealed)) ||
       tp.typeSymbol.is(allOf(Trait, Sealed)) ||
       tp.isInstanceOf[OrType] ||
-      tp =:= ctx.definitions.BooleanType
-  }
+      tp =:= ctx.definitions.BooleanType ||
+      tp.typeSymbol.is(Enum)
 
   def isCaseClass(tp: Type): Boolean = tp.classSymbol.isClass && tp.classSymbol.is(CaseClass)
 
@@ -428,27 +435,24 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
     flatten(s).map(doShow(_, false)).distinct.mkString(", ")
   }
 
-  /** Does the type t have @unchecked annotation? */
-  def skipCheck(tp: Type): Boolean = tp match {
-    case AnnotatedType(tp, annot) => ctx.definitions.UncheckedAnnot == annot.symbol
-    case _ => false
-  }
-
-  /** Widen a type and eliminate anonymous classes */
-  private def widen(tp: Type): Type = tp.widen match {
-    case tp:TypeRef if tp.symbol.isAnonymousClass =>
-      tp.symbol.asClass.typeRef.asSeenFrom(tp.prefix, tp.symbol.owner)
-    case tp => tp
+  def checkable(tp: Type): Boolean = tp match {
+    case AnnotatedType(tp, annot) =>
+      (ctx.definitions.UncheckedAnnot != annot.symbol) && checkable(tp)
+    case _ => true  // actually everything is checkable unless @unchecked
+
+      // tp.classSymbol.is(Sealed) ||
+      //   tp.isInstanceOf[OrType] ||
+      //   tp.classSymbol.is(Enum) ||
+      //   Boolean
+      //   Int
+      //   ...
   }
 
-  def exhaustivity(_match: Match): Unit = {
+  def checkExhaustivity(_match: Match): Unit = {
     val Match(sel, cases) = _match
-    val selTyp = widen(sel.tpe)
+    val selTyp = sel.tpe.widen.elimAnonymousClass
 
-    debug(s"====patterns:\n${cases.map(_.pat).mkString("\n")}")
     val patternSpace = cases.map(x => project(x.pat)).reduce((a, b) => Or(List(a, b)))
-    debug(s"====selector:\n" + selTyp)
-    debug("====pattern space:\n" + show(patternSpace))
     val uncovered = simplify(minus(Typ(selTyp, true), patternSpace))
 
     if (uncovered != Empty) {
@@ -460,9 +464,9 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
     }
   }
 
-  def redundancy(_match: Match): Unit = {
+  def checkRedundancy(_match: Match): Unit = {
     val Match(sel, cases) = _match
-    val selTyp = widen(sel.tpe)
+    val selTyp = sel.tpe.widen.elimAnonymousClass
 
     // starts from the second, the first can't be redundant
     (1 until cases.length).foreach { i =>
diff --git a/src/dotty/tools/dotc/typer/Namer.scala b/src/dotty/tools/dotc/typer/Namer.scala
index a8f3b89183cf..2b0e360a0c2e 100644
--- a/src/dotty/tools/dotc/typer/Namer.scala
+++ b/src/dotty/tools/dotc/typer/Namer.scala
@@ -408,6 +408,16 @@ class Namer { typer: Typer =>
     case mdef: DefTree =>
       val sym = enterSymbol(createSymbol(mdef))
       setDocstring(sym, stat)
+
+      // add java enum constants
+      mdef match {
+        case vdef: ValDef if (isEnumConstant(vdef)) =>
+          val enumClass = sym.owner.linkedClass
+          if (!(enumClass is Flags.Sealed)) enumClass.setFlag(Flags.AbstractSealed)
+          enumClass.addAnnotation(Annotation.makeChild(sym))
+        case _ =>
+      }
+
       ctx
     case stats: Thicket =>
       for (tree <- stats.toList) {
@@ -419,6 +429,24 @@ class Namer { typer: Typer =>
       ctx
   }
 
+  /** Determines whether this field holds an enum constant.
+    * To qualify, the following conditions must be met:
+    *  - The field's class has the ENUM flag set
+    *  - The field's class extends java.lang.Enum
+    *  - The field has the ENUM flag set
+    *  - The field is static
+    *  - The field is stable
+    */
+  def isEnumConstant(vd: ValDef)(implicit ctx: Context) = {
+    // val ownerHasEnumFlag =
+    // Necessary to check because scalac puts Java's static members into the companion object
+    // while Scala's enum constants live directly in the class.
+    // We don't check for clazz.superClass == JavaEnumClass, because this causes a illegal
+    // cyclic reference error. See the commit message for details.
+    //  if (ctx.compilationUnit.isJava) ctx.owner.companionClass.is(Enum) else ctx.owner.is(Enum)
+    vd.mods.is(allOf(Enum,  Stable, JavaStatic, JavaDefined)) // && ownerHasEnumFlag
+  }
+
   def setDocstring(sym: Symbol, tree: Tree)(implicit ctx: Context) = tree match {
     case t: MemberDef => ctx.base.addDocstring(sym, t.rawComment)
     case _ => ()
@@ -996,4 +1024,6 @@ class Namer { typer: Typer =>
       case _ => mapOver(tp)
     }
   }
+
+
 }
diff --git a/test/test/transform/PatmatExhaustivityTest.scala b/test/test/transform/PatmatExhaustivityTest.scala
index 1ecaa2b1d14d..37e29fabc268 100644
--- a/test/test/transform/PatmatExhaustivityTest.scala
+++ b/test/test/transform/PatmatExhaustivityTest.scala
@@ -1,10 +1,10 @@
 package test.transform
 
 import java.io._
+
 import scala.io.Source._
 import scala.reflect.io.Directory
 import org.junit.Test
-
 import dotty.tools.dotc.Main
 import dotty.tools.dotc.reporting.ConsoleReporter
 
@@ -35,13 +35,45 @@ class PatmatExhaustivityTest {
     (file, checkContent, actual)
   }
 
-  @Test def patmatExhaustivity: Unit = {
-    val res = Directory(testsDir).deepFiles.toList.filter(_.extension == "scala").map { f =>
-      compileFile(f.jfile)
+  /** A single test with multiple files grouped in a folder */
+  private def compileDir(file: File) = {
+    val stringBuffer = new StringWriter()
+    val reporter = new ConsoleReporter(writer = new PrintWriter(stringBuffer))
+
+    val files = Directory(file.getPath).list.toList
+      .filter(f => f.extension == "scala" || f.extension == "java" )
+      .map(_.jfile.getPath)
+
+    try {
+      Main.process((options::files).toArray, reporter, null)
+    } catch {
+      case e: Throwable =>
+        println(s"Compile $file exception:")
+        e.printStackTrace()
     }
 
+    val actual = stringBuffer.toString.trim
+    val checkFilePath = file.getPath + File.separator + "expected.check"
+    val checkContent =
+      if (new File(checkFilePath).exists)
+        fromFile(checkFilePath).getLines.mkString("\n").trim
+      else ""
+
+    (file, checkContent, actual)
+  }
+
+  @Test def patmatExhaustivity: Unit = {
+    val res = Directory(testsDir).list.toList
+      .filter(f => f.extension == "scala" || f.isDirectory)
+      .map { f =>
+        if (f.isDirectory)
+          compileDir(f.jfile)
+        else
+          compileFile(f.jfile)
+      }
+
     val failed = res.filter { case (_, expected, actual) => expected != actual }
-    val ignored = Directory(testsDir).deepFiles.toList.filter(_.extension == "ignore")
+    val ignored = Directory(testsDir).list.toList.filter(_.extension == "ignore")
 
     failed.foreach { case (file, expected, actual) =>
       println(s"\n----------------- incorrect output for $file --------------\n" +
diff --git a/tests/patmat/enum/Day.java b/tests/patmat/enum/Day.java
new file mode 100644
index 000000000000..eedb9a72b541
--- /dev/null
+++ b/tests/patmat/enum/Day.java
@@ -0,0 +1,4 @@
+public enum Day {
+  SUNDAY, MONDAY, TUESDAY, WEDNESDAY,
+  THURSDAY, FRIDAY, SATURDAY
+}
\ No newline at end of file
diff --git a/tests/patmat/enum/expected.check b/tests/patmat/enum/expected.check
new file mode 100644
index 000000000000..d957e08e104e
--- /dev/null
+++ b/tests/patmat/enum/expected.check
@@ -0,0 +1,5 @@
+./tests/patmat/enum/patmat-enum.scala:4: warning: match may not be exhaustive.
+It would fail on the following input: SATURDAY, FRIDAY, THURSDAY, SUNDAY
+  day match {
+      ^
+one warning found
\ No newline at end of file
diff --git a/tests/patmat/enum/patmat-enum.scala b/tests/patmat/enum/patmat-enum.scala
new file mode 100644
index 000000000000..e7786b1e28f6
--- /dev/null
+++ b/tests/patmat/enum/patmat-enum.scala
@@ -0,0 +1,9 @@
+object Test {
+  val day: Day = ???
+
+  day match {
+    case Day.MONDAY => true
+    case Day.TUESDAY => true
+    case Day.WEDNESDAY => true
+  }
+}
\ No newline at end of file

From fd1b28689b14e6ec3627324c1247184841f47e98 Mon Sep 17 00:00:00 2001
From: liu fengyun <liufengyunchina@gmail.com>
Date: Thu, 2 Jun 2016 20:37:04 +0200
Subject: [PATCH 03/11] fix false warning about Nil

scala.Nil refines scala.collection.immutable.Nil, this commit
follows redefinition of case objects.
---
 .../tools/dotc/transform/PatternMatcher.scala |  4 +-
 .../tools/dotc/transform/patmat/Space.scala   | 50 +++++++++++--------
 tests/patmat/enum/expected.check              |  6 ++-
 tests/patmat/enum/patmat-enum.scala           | 14 +++++-
 tests/patmat/patmat-adt.scala                 |  5 ++
 tests/patmat/patmat-indent.check              | 13 +++++
 tests/patmat/patmat-indent.scala              | 30 +++++++++++
 tests/patmat/t7466.check                      |  2 +-
 tests/patmat/t9411a.scala                     | 27 ++++++++++
 tests/patmat/t9411b.scala                     | 36 +++++++++++++
 tests/patmat/virtpatmat_apply.check           |  5 ++
 tests/patmat/virtpatmat_apply.scala           |  7 +++
 12 files changed, 172 insertions(+), 27 deletions(-)
 create mode 100644 tests/patmat/patmat-indent.check
 create mode 100644 tests/patmat/patmat-indent.scala
 create mode 100644 tests/patmat/t9411a.scala
 create mode 100644 tests/patmat/t9411b.scala
 create mode 100644 tests/patmat/virtpatmat_apply.check
 create mode 100644 tests/patmat/virtpatmat_apply.scala

diff --git a/src/dotty/tools/dotc/transform/PatternMatcher.scala b/src/dotty/tools/dotc/transform/PatternMatcher.scala
index da417b5cb60f..af742420c4cb 100644
--- a/src/dotty/tools/dotc/transform/PatternMatcher.scala
+++ b/src/dotty/tools/dotc/transform/PatternMatcher.scala
@@ -51,13 +51,11 @@ class PatternMatcher extends MiniPhaseTransform with DenotTransformer {thisTrans
   private var _id = 0 // left for debuging
 
   override def transformMatch(tree: Match)(implicit ctx: Context, info: TransformerInfo): Tree = {
-    val Match(sel, cases) = tree
-
     val translated = new Translator()(ctx).translator.translateMatch(tree)
 
     // check exhaustivity and unreachability
     val engine = new SpaceEngine
-    if (engine.checkable(sel.tpe.widen.elimAnonymousClass)) {
+    if (engine.checkable(tree)) {
       engine.checkExhaustivity(tree)
       engine.checkRedundancy(tree)
     }
diff --git a/src/dotty/tools/dotc/transform/patmat/Space.scala b/src/dotty/tools/dotc/transform/patmat/Space.scala
index c7ddd82d839e..0d22e957bc6d 100644
--- a/src/dotty/tools/dotc/transform/patmat/Space.scala
+++ b/src/dotty/tools/dotc/transform/patmat/Space.scala
@@ -116,7 +116,7 @@ trait SpaceLogic {
       ss.exists(subspace(a, _)) ||
       (canDecompose(tp1) && subspace(Or(partitions(tp1)), b))
     case (Typ(tp1, _), Kon(tp2, ss)) =>
-      isSubType(tp1, tp2) && subspace(Kon(tp2, signature(tp2).map(tp => Typ(tp, false))), b)
+      isSubType(tp1, tp2) && subspace(Kon(tp2, signature(tp2).map(Typ(_, false))), b)
     case (Kon(tp1, ss), Typ(tp2, _)) =>
       isSubType(tp1, tp2) ||
       simplify(a) == Empty ||
@@ -188,7 +188,7 @@ trait SpaceLogic {
         minus(Or(partitions(tp1)), b)
       else a
     case (Typ(tp1, _), Kon(tp2, ss)) =>
-      if (isSubType(tp1, tp2)) minus(Kon(tp2, signature(tp2).map(tp => Typ(tp, false))), b)
+      if (isSubType(tp1, tp2)) minus(Kon(tp2, signature(tp2).map(Typ(_, false))), b)
       else if (isSubType(tp2, tp1) && canDecompose(tp1))
         minus(Or(partitions(tp1)), b)
       else a
@@ -242,15 +242,17 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
   def project(pat: Tree, roundUp: Boolean = true)(implicit ctx: Context): Space = pat match {
     case Literal(c) => Const(c, c.tpe)
     case _: BackquotedIdent => Var(pat.symbol, pat.tpe)
-    case Ident(_) =>
-      Typ(pat.tpe.stripAnnots, false)
-    case Select(_, _)  =>
-      if (pat.symbol.is(Module))
-        Typ(pat.tpe.stripAnnots, false)
-      else if (pat.symbol.is(Enum))
-        Const(Constant(pat.symbol), pat.tpe)
-      else
-        Var(pat.symbol, pat.tpe)
+    case Ident(_) | Select(_, _) =>
+      pat.tpe.stripAnnots match {
+        case tp: TermRef =>
+          if (pat.symbol.is(Enum))
+            Const(Constant(pat.symbol), tp)
+          else if (tp.underlyingIterator.exists(_.classSymbol.is(Module)))
+            Typ(tp.widenTermRefExpr.stripAnnots, false)
+          else
+            Var(pat.symbol, tp)
+        case tp => Typ(tp, false)
+      }
     case Alternative(trees) => Or(trees.map(project(_, roundUp)))
     case Bind(_, pat) => project(pat)
     case UnApply(_, _, pats) =>
@@ -295,6 +297,7 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
           ktor
       }
 
+    // refine path-dependent type in params. refer to t9672
     meth.firstParamTypes.map(_.stripTypeVar).map(refine(tp, _))
   }
 
@@ -415,19 +418,19 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
           if (mergeList) "_" else "List(_)"
         else if (tp.classSymbol.is(CaseClass))
         // use constructor syntax for case class
-          showType(tp) + signature(tp).map(_ => "_").mkString("(", ",", ")")
+          showType(tp) + signature(tp).map(_ => "_").mkString("(", ", ", ")")
         else if (signature(tp).nonEmpty)
-          tp.classSymbol.name + signature(tp).map(_ => "_").mkString("(", ",", ")")
+          tp.classSymbol.name + signature(tp).map(_ => "_").mkString("(", ", ", ")")
         else if (decomposed) "_: " + showType(tp)
         else "_"
       case Kon(tp, params) =>
         if (ctx.definitions.isTupleType(tp))
-          "(" + params.map(p => doShow(p)).mkString(", ") + ")"
+          "(" + params.map(doShow(_)).mkString(", ") + ")"
         else if (tp.widen.classSymbol.showFullName == "scala.collection.immutable.::")
-          if (mergeList) params.map(p => doShow(p, mergeList)).mkString(", ")
-          else params.map(p => doShow(p, true)).mkString("List(", ", ", ")")
+          if (mergeList) params.map(doShow(_, mergeList)).mkString(", ")
+          else params.map(doShow(_, true)).filter(_ != "Nil").mkString("List(", ", ", ")")
         else
-          showType(tp) + params.map(p => doShow(p)).mkString("(", ", ", ")")
+          showType(tp) + params.map(doShow(_)).mkString("(", ", ", ")")
       case Or(_) =>
         throw new Exception("incorrect flatten result " + s)
     }
@@ -435,10 +438,11 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
     flatten(s).map(doShow(_, false)).distinct.mkString(", ")
   }
 
-  def checkable(tp: Type): Boolean = tp match {
-    case AnnotatedType(tp, annot) =>
-      (ctx.definitions.UncheckedAnnot != annot.symbol) && checkable(tp)
-    case _ => true  // actually everything is checkable unless @unchecked
+  def checkable(tree: Match): Boolean = {
+    def isCheckable(tp: Type): Boolean = tp match {
+      case AnnotatedType(tp, annot) =>
+        (ctx.definitions.UncheckedAnnot != annot.symbol) && isCheckable(tp)
+      case _ => true // actually everything is checkable unless @unchecked
 
       // tp.classSymbol.is(Sealed) ||
       //   tp.isInstanceOf[OrType] ||
@@ -446,6 +450,10 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
       //   Boolean
       //   Int
       //   ...
+    }
+
+    val Match(sel, cases) = tree
+    isCheckable(sel.tpe.widen.elimAnonymousClass)
   }
 
   def checkExhaustivity(_match: Match): Unit = {
diff --git a/tests/patmat/enum/expected.check b/tests/patmat/enum/expected.check
index d957e08e104e..b3dafa8bdd02 100644
--- a/tests/patmat/enum/expected.check
+++ b/tests/patmat/enum/expected.check
@@ -2,4 +2,8 @@
 It would fail on the following input: SATURDAY, FRIDAY, THURSDAY, SUNDAY
   day match {
       ^
-one warning found
\ No newline at end of file
+./tests/patmat/enum/patmat-enum.scala:15: warning: match may not be exhaustive.
+It would fail on the following input: SATURDAY, FRIDAY, THURSDAY
+  day match {
+      ^
+two warnings found
\ No newline at end of file
diff --git a/tests/patmat/enum/patmat-enum.scala b/tests/patmat/enum/patmat-enum.scala
index e7786b1e28f6..ec5c90255f7a 100644
--- a/tests/patmat/enum/patmat-enum.scala
+++ b/tests/patmat/enum/patmat-enum.scala
@@ -1,4 +1,4 @@
-object Test {
+object Test1 {
   val day: Day = ???
 
   day match {
@@ -6,4 +6,16 @@ object Test {
     case Day.TUESDAY => true
     case Day.WEDNESDAY => true
   }
+}
+
+object Test2 {
+  import Day._
+  val day: Day = ???
+
+  day match {
+    case MONDAY => true
+    case TUESDAY => true
+    case WEDNESDAY => true
+    case SUNDAY => true
+  }
 }
\ No newline at end of file
diff --git a/tests/patmat/patmat-adt.scala b/tests/patmat/patmat-adt.scala
index acb4d3465ee6..e7eac4e4a662 100644
--- a/tests/patmat/patmat-adt.scala
+++ b/tests/patmat/patmat-adt.scala
@@ -50,4 +50,9 @@ object PatmatADT {
   def foo5(tree: Tree) : Any = tree match {
     case LetL(CharLit) =>
   }
+
+  def foo6[T](l: List[T]): Boolean = l match {
+    case x::xs => true
+    case Nil => false
+  }
 }
\ No newline at end of file
diff --git a/tests/patmat/patmat-indent.check b/tests/patmat/patmat-indent.check
new file mode 100644
index 000000000000..3a76e0a9581b
--- /dev/null
+++ b/tests/patmat/patmat-indent.check
@@ -0,0 +1,13 @@
+./tests/patmat/patmat-indent.scala:9: warning: match may not be exhaustive.
+It would fail on the following input: Nil
+  def foo1a[T](l: List[T]) = l match {
+                               ^
+./tests/patmat/patmat-indent.scala:23: warning: match may not be exhaustive.
+It would fail on the following input: _: Boolean
+  def foo2(b: Boolean) = b match {
+                           ^
+./tests/patmat/patmat-indent.scala:27: warning: match may not be exhaustive.
+It would fail on the following input: _: Int
+  def foo3(x: Int) = x match {
+                       ^
+three warnings found
\ No newline at end of file
diff --git a/tests/patmat/patmat-indent.scala b/tests/patmat/patmat-indent.scala
new file mode 100644
index 000000000000..ef25bb2c7ccf
--- /dev/null
+++ b/tests/patmat/patmat-indent.scala
@@ -0,0 +1,30 @@
+object Test {
+  val Nil = scala.Nil
+  val X = 5
+
+  object Inner {
+    val Y = false
+  }
+
+  def foo1a[T](l: List[T]) = l match {
+    case x::xs => false
+  }
+
+  def foo1b[T](l: List[T]) = l match {
+    case Nil => true
+    case x::xs => false
+  }
+
+  def foo1c[T](l: List[T]) = l match {
+    case Test.Nil => true
+    case x::xs => false
+  }
+
+  def foo2(b: Boolean) = b match {
+    case Inner.Y => false
+  }
+
+  def foo3(x: Int) = x match {
+    case X => 0
+  }
+}
\ No newline at end of file
diff --git a/tests/patmat/t7466.check b/tests/patmat/t7466.check
index 93f7fd62a072..8e575f6a213f 100644
--- a/tests/patmat/t7466.check
+++ b/tests/patmat/t7466.check
@@ -1,5 +1,5 @@
 ./tests/patmat/t7466.scala:8: warning: match may not be exhaustive.
-It would fail on the following input: (true, _), (false, _), (_, true), (_, false)
+It would fail on the following input: (_, _)
     (b1, b2) match {
              ^
 one warning found
\ No newline at end of file
diff --git a/tests/patmat/t9411a.scala b/tests/patmat/t9411a.scala
new file mode 100644
index 000000000000..d5264663ece9
--- /dev/null
+++ b/tests/patmat/t9411a.scala
@@ -0,0 +1,27 @@
+object OhNoes {
+
+  sealed trait F
+  sealed abstract class FA extends F
+  sealed abstract class FB extends F
+
+  case object FA1 extends FA
+  case object FB1 extends FB
+  case object FB2 extends FB
+
+  sealed trait G
+  case object G1 extends G
+  case object G2 extends G
+
+  sealed trait H
+  case class H1(a: FB, b: G) extends H
+  case class H2(a: F)        extends H
+
+  val demo: H => Unit = {
+    case H1(FB1, G1) =>
+    case H1(FB2, G2) =>
+    case H2(_: FB) =>
+    case H2(_: FA) =>
+    case H1(FB1, G2) =>
+    case H1(FB2, G1) =>
+  }
+}
diff --git a/tests/patmat/t9411b.scala b/tests/patmat/t9411b.scala
new file mode 100644
index 000000000000..6888ba9382c8
--- /dev/null
+++ b/tests/patmat/t9411b.scala
@@ -0,0 +1,36 @@
+object OhNoes {
+
+  sealed trait F
+  sealed abstract class FA extends F
+  sealed abstract class FB extends F
+
+  case object FA1 extends FA
+  case object FB1 extends FB
+  case object FB2 extends FB
+
+  sealed trait G
+  case object G1 extends G
+  case object G2 extends G
+
+  sealed trait H
+  case class H1(a: FB, b: G) extends H
+  case class H2(b: F)        extends H
+
+  val demo: H => Unit = {
+    case H1(FB1, G1) =>
+    case H1(FB2, G2) =>
+    case H2(_: FB) =>
+    case H2(_: FA) =>
+    case H1(FB1, G2) =>
+    case H1(FB2, G1) =>
+  }
+
+  val demo2: H => Unit = {
+    case H2(_: FA) =>
+    case H2(_: FB) =>
+    case H1(FB1, G1) =>
+    case H1(FB2, G1) =>
+    case H1(FB1, G2) =>
+    case H1(FB2, G2) =>
+  }
+}
diff --git a/tests/patmat/virtpatmat_apply.check b/tests/patmat/virtpatmat_apply.check
new file mode 100644
index 000000000000..d10d82165a3e
--- /dev/null
+++ b/tests/patmat/virtpatmat_apply.check
@@ -0,0 +1,5 @@
+./tests/patmat/virtpatmat_apply.scala:2: warning: match may not be exhaustive.
+It would fail on the following input: List(_)
+  List(1, 2, 3) match {
+                ^
+one warning found
\ No newline at end of file
diff --git a/tests/patmat/virtpatmat_apply.scala b/tests/patmat/virtpatmat_apply.scala
new file mode 100644
index 000000000000..646d15f902ac
--- /dev/null
+++ b/tests/patmat/virtpatmat_apply.scala
@@ -0,0 +1,7 @@
+object Test {
+  List(1, 2, 3) match {
+    case Nil => println("FAIL")
+    case x :: y :: xs if xs.length == 2 => println("FAIL")
+    case x :: y :: xs if xs.length == 1 => println("OK "+ y)
+  }
+}

From d681a78c554709f6893f6ff3512434534bbcbb41 Mon Sep 17 00:00:00 2001
From: liu fengyun <liufengyunchina@gmail.com>
Date: Fri, 3 Jun 2016 12:02:46 +0200
Subject: [PATCH 04/11] suppress checking of for, try and partial functions

---
 src/dotty/tools/dotc/ast/Desugar.scala           | 16 ++++++++++------
 src/dotty/tools/dotc/transform/ExpandSAMs.scala  |  3 ++-
 .../tools/dotc/transform/patmat/Space.scala      |  6 +++---
 src/dotty/tools/dotc/typer/TypeAssigner.scala    |  2 +-
 src/dotty/tools/dotc/typer/Typer.scala           |  3 ++-
 test/test/transform/PatmatExhaustivityTest.scala |  8 ++++----
 tests/patmat/for.scala                           |  5 +++++
 tests/patmat/i947.check                          |  4 ++++
 tests/patmat/i947.scala                          | 16 ++++++++++++++++
 tests/patmat/partial-function.scala              | 12 ++++++++++++
 tests/patmat/t1056.scala                         |  5 +++++
 tests/patmat/try.scala                           |  5 +++++
 12 files changed, 69 insertions(+), 16 deletions(-)
 create mode 100644 tests/patmat/for.scala
 create mode 100644 tests/patmat/i947.check
 create mode 100644 tests/patmat/i947.scala
 create mode 100644 tests/patmat/partial-function.scala
 create mode 100644 tests/patmat/t1056.scala
 create mode 100644 tests/patmat/try.scala

diff --git a/src/dotty/tools/dotc/ast/Desugar.scala b/src/dotty/tools/dotc/ast/Desugar.scala
index f603f68178a3..12ca8c14cea4 100644
--- a/src/dotty/tools/dotc/ast/Desugar.scala
+++ b/src/dotty/tools/dotc/ast/Desugar.scala
@@ -616,16 +616,20 @@ object desugar {
    *
    *       { cases }
    *  ==>
-   *       x$1 => x$1 match { cases }
+   *       x$1 => (x$1 @unchecked) match { cases }
    *
    *  If `nparams` != 1, expand instead to
    *
-   *       (x$1, ..., x$n) => (x$0, ..., x${n-1}) match { cases }
+   *       (x$1, ..., x$n) => (x$0, ..., x${n-1} @unchecked) match { cases }
    */
-  def makeCaseLambda(cases: List[CaseDef], nparams: Int = 1)(implicit ctx: Context) = {
+  def makeCaseLambda(cases: List[CaseDef], nparams: Int = 1, unchecked: Boolean = true)(implicit ctx: Context) = {
     val params = (1 to nparams).toList.map(makeSyntheticParameter(_))
     val selector = makeTuple(params.map(p => Ident(p.name)))
-    Function(params, Match(selector, cases))
+
+    if (unchecked)
+      Function(params, Match(Annotated(New(ref(defn.UncheckedAnnotType)), selector), cases))
+    else
+      Function(params, Match(selector, cases))
   }
 
   /** Map n-ary function `(p1, ..., pn) => body` where n != 1 to unary function as follows:
@@ -753,7 +757,7 @@ object desugar {
         case VarPattern(named, tpt) =>
           Function(derivedValDef(named, tpt, EmptyTree, Modifiers(Param)) :: Nil, body)
         case _ =>
-          makeCaseLambda(CaseDef(pat, EmptyTree, body) :: Nil)
+          makeCaseLambda(CaseDef(pat, EmptyTree, body) :: Nil, unchecked = false)
       }
 
       /** If `pat` is not an Identifier, a Typed(Ident, _), or a Bind, wrap
@@ -799,7 +803,7 @@ object desugar {
         val cases = List(
           CaseDef(pat, EmptyTree, Literal(Constant(true))),
           CaseDef(Ident(nme.WILDCARD), EmptyTree, Literal(Constant(false))))
-        Apply(Select(rhs, nme.withFilter), Match(EmptyTree, cases))
+        Apply(Select(rhs, nme.withFilter), makeCaseLambda(cases))
       }
 
       /** Is pattern `pat` irrefutable when matched against `rhs`?
diff --git a/src/dotty/tools/dotc/transform/ExpandSAMs.scala b/src/dotty/tools/dotc/transform/ExpandSAMs.scala
index d9445d04673e..04c6864b1cd2 100644
--- a/src/dotty/tools/dotc/transform/ExpandSAMs.scala
+++ b/src/dotty/tools/dotc/transform/ExpandSAMs.scala
@@ -74,7 +74,8 @@ class ExpandSAMs extends MiniPhaseTransform { thisTransformer =>
             Bind(defaultSym, Underscore(selector.tpe.widen)),
             EmptyTree,
             Literal(Constant(false)))
-        cpy.Match(applyRhs)(paramRef, cases.map(translateCase) :+ defaultCase)
+        val annotated = Annotated(New(ref(defn.UncheckedAnnotType)), paramRef)
+        cpy.Match(applyRhs)(annotated, cases.map(translateCase) :+ defaultCase)
       case _ =>
         tru
     }
diff --git a/src/dotty/tools/dotc/transform/patmat/Space.scala b/src/dotty/tools/dotc/transform/patmat/Space.scala
index 0d22e957bc6d..08896fb3364c 100644
--- a/src/dotty/tools/dotc/transform/patmat/Space.scala
+++ b/src/dotty/tools/dotc/transform/patmat/Space.scala
@@ -258,7 +258,7 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
     case UnApply(_, _, pats) =>
       if (pat.tpe.classSymbol.is(CaseClass))
         Kon(pat.tpe.stripAnnots, pats.map(pat => project(pat, roundUp)))
-      else if (roundUp) Typ(pat.tpe, false)
+      else if (roundUp) Typ(pat.tpe.stripAnnots, false)
       else Empty
     case Typed(pat @ UnApply(_, _, _), _) => project(pat)
     case Typed(expr, _) => Typ(expr.tpe.stripAnnots, true)
@@ -392,9 +392,9 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
       case _ => tp.show.stripSuffix("$")
     }
 
-    val text = tp match {
+    val text = tp.stripAnnots match {
       case tp: OrType => showType(tp.tp1) + " | " + showType(tp.tp2)
-      case _ => refine(tp)
+      case tp => refine(tp)
     }
 
     if (text.isEmpty) enclosingCls.show.stripSuffix("$")
diff --git a/src/dotty/tools/dotc/typer/TypeAssigner.scala b/src/dotty/tools/dotc/typer/TypeAssigner.scala
index 995fa43ca7b1..b2abe3b36f49 100644
--- a/src/dotty/tools/dotc/typer/TypeAssigner.scala
+++ b/src/dotty/tools/dotc/typer/TypeAssigner.scala
@@ -470,7 +470,7 @@ trait TypeAssigner {
     tree.withType(sym.nonMemberTermRef)
 
   def assignType(tree: untpd.Annotated, annot: Tree, arg: Tree)(implicit ctx: Context) =
-    tree.withType(AnnotatedType(arg.tpe, Annotation(annot)))
+    tree.withType(AnnotatedType(arg.tpe.widen, Annotation(annot)))
 
   def assignType(tree: untpd.PackageDef, pid: Tree)(implicit ctx: Context) =
     tree.withType(pid.symbol.valRef)
diff --git a/src/dotty/tools/dotc/typer/Typer.scala b/src/dotty/tools/dotc/typer/Typer.scala
index 268020ec51d3..3834a57c2599 100644
--- a/src/dotty/tools/dotc/typer/Typer.scala
+++ b/src/dotty/tools/dotc/typer/Typer.scala
@@ -719,7 +719,8 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
     tree.selector match {
       case EmptyTree =>
         val (protoFormals, _) = decomposeProtoFunction(pt, 1)
-        typed(desugar.makeCaseLambda(tree.cases, protoFormals.length) withPos tree.pos, pt)
+        val unchecked = pt <:< defn.PartialFunctionType
+        typed(desugar.makeCaseLambda(tree.cases, protoFormals.length, unchecked) withPos tree.pos, pt)
       case _ =>
         val sel1 = typedExpr(tree.selector)
         val selType = widenForMatchSelector(
diff --git a/test/test/transform/PatmatExhaustivityTest.scala b/test/test/transform/PatmatExhaustivityTest.scala
index 37e29fabc268..935085480f5e 100644
--- a/test/test/transform/PatmatExhaustivityTest.scala
+++ b/test/test/transform/PatmatExhaustivityTest.scala
@@ -10,15 +10,15 @@ import dotty.tools.dotc.reporting.ConsoleReporter
 
 class PatmatExhaustivityTest {
   val testsDir = "./tests/patmat"
-  val options = "-Ystop-after:splitter"  // no need for code generation
-                                         // patmatexhaust-huge.scala crash compiler
+  // stop-after: patmatexhaust-huge.scala crash compiler
+  val options = List("-Ystop-after:splitter")
 
   private def compileFile(file: File) = {
     val stringBuffer = new StringWriter()
     val reporter = new ConsoleReporter(writer = new PrintWriter(stringBuffer))
 
     try {
-      Main.process(Array(file.getPath, options), reporter, null)
+      Main.process((file.getPath::options).toArray, reporter, null)
     } catch {
       case e: Throwable =>
         println(s"Compile $file exception:")
@@ -45,7 +45,7 @@ class PatmatExhaustivityTest {
       .map(_.jfile.getPath)
 
     try {
-      Main.process((options::files).toArray, reporter, null)
+      Main.process((options ++ files).toArray, reporter, null)
     } catch {
       case e: Throwable =>
         println(s"Compile $file exception:")
diff --git a/tests/patmat/for.scala b/tests/patmat/for.scala
new file mode 100644
index 000000000000..ae9dcf65e9f1
--- /dev/null
+++ b/tests/patmat/for.scala
@@ -0,0 +1,5 @@
+object Test {
+  def foo[A, B](l: List[(A, B)]): List[A] = {
+    for ((a, b) <- l) yield a
+  }
+}
\ No newline at end of file
diff --git a/tests/patmat/i947.check b/tests/patmat/i947.check
new file mode 100644
index 000000000000..5cce559c4834
--- /dev/null
+++ b/tests/patmat/i947.check
@@ -0,0 +1,4 @@
+./tests/patmat/i947.scala:10: warning: unreachable code
+      case ys: List[d18383] => false
+                           ^
+one warning found
\ No newline at end of file
diff --git a/tests/patmat/i947.scala b/tests/patmat/i947.scala
new file mode 100644
index 000000000000..0f2d9e77583a
--- /dev/null
+++ b/tests/patmat/i947.scala
@@ -0,0 +1,16 @@
+object Test {
+
+  class c {
+
+    private var x: Int = 0
+
+    override def equals(other: Any) = other match {
+      case o: c => x == o.x
+      case xs: List[c] => false
+      case ys: List[d18383] => false
+      case _ => false
+    }
+
+
+  }
+}
diff --git a/tests/patmat/partial-function.scala b/tests/patmat/partial-function.scala
new file mode 100644
index 000000000000..f168489dad74
--- /dev/null
+++ b/tests/patmat/partial-function.scala
@@ -0,0 +1,12 @@
+sealed abstract class TA
+sealed abstract class TB extends TA
+case object B extends TB
+case object B2 extends TB
+
+case class CC(i: Int, tb: TB)
+
+object Test {
+  def foo: PartialFunction[CC, Unit] = {
+    case CC(_, B) => ()
+  }
+}
\ No newline at end of file
diff --git a/tests/patmat/t1056.scala b/tests/patmat/t1056.scala
new file mode 100644
index 000000000000..68f1ff27310c
--- /dev/null
+++ b/tests/patmat/t1056.scala
@@ -0,0 +1,5 @@
+object Test {
+  type T = PartialFunction[String,String]
+  def g(h: T) = ()
+  g({case s: String => s})
+}
diff --git a/tests/patmat/try.scala b/tests/patmat/try.scala
new file mode 100644
index 000000000000..d7df24ee0184
--- /dev/null
+++ b/tests/patmat/try.scala
@@ -0,0 +1,5 @@
+object Test {
+  try 2/0 catch {
+    case e: Exception =>
+  }
+}
\ No newline at end of file

From da9511d599cd1b110de159aa2204062d3e1b59a4 Mon Sep 17 00:00:00 2001
From: liu fengyun <liufengyunchina@gmail.com>
Date: Sun, 12 Jun 2016 00:02:05 +0200
Subject: [PATCH 05/11] add GADT test

---
 .../tools/dotc/transform/patmat/Space.scala   | 25 +++++-----
 tests/patmat/gadt.check                       | 13 +++++
 tests/patmat/gadt.scala                       | 49 +++++++++++++++++++
 3 files changed, 73 insertions(+), 14 deletions(-)
 create mode 100644 tests/patmat/gadt.check
 create mode 100644 tests/patmat/gadt.scala

diff --git a/src/dotty/tools/dotc/transform/patmat/Space.scala b/src/dotty/tools/dotc/transform/patmat/Space.scala
index 08896fb3364c..5c4e2fd370b7 100644
--- a/src/dotty/tools/dotc/transform/patmat/Space.scala
+++ b/src/dotty/tools/dotc/transform/patmat/Space.scala
@@ -266,19 +266,12 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
       Empty
   }
 
-  /** Is `tp1` a subtype of `tp2`?
-   *
-   *  Ignore type parameters in comparison due to erasure, i.e., Some[Int] <: Some[T]
-   */
-  def isSubType(tp1: Type, tp2: Type): Boolean = (tp1, tp2) match {
-    case (tp1: RefinedType, tp2: RefinedType) => isSubType(tp1.parent, tp2.parent)
-    case (tp1: RefinedType, _) => isSubType(tp1.parent, tp2)
-    case (_, tp2: RefinedType) => isSubType(tp1, tp2.parent)
-    case (_, _) => tp1 <:< tp2
-  }
+  /** Is `tp1` a subtype of `tp2`?  */
+  def isSubType(tp1: Type, tp2: Type): Boolean = tp1 <:< tp2
 
   def isEqualType(tp1: Type, tp2: Type): Boolean = tp1 =:= tp2
 
+  /** Parameter types of the case class type `tp`  */
   def signature(tp: Type): List[Type] = {
     val ktor = tp.classSymbol.primaryConstructor.info
 
@@ -325,10 +318,14 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
           else if (sym.info.typeParams.length > 0 || tp.isInstanceOf[TypeRef])
             refine(tp, sym.asClass.classInfo.symbolicTypeRef)
           else
-            sym.info
-        } filter(_ <:< tp) // child may not always be subtype of parent: SI-4020
-
-        parts.map(tp => Typ(tp, true))
+            sym.typeRef
+        } filter { tpe =>
+          // Child class may not always be subtype of parent:
+          // GADT & path-dependent types
+          isSubType(tpe, tp)
+        }
+
+        parts.map(Typ(_, true))
     }
   }
 
diff --git a/tests/patmat/gadt.check b/tests/patmat/gadt.check
new file mode 100644
index 000000000000..caeb0c4eb39e
--- /dev/null
+++ b/tests/patmat/gadt.check
@@ -0,0 +1,13 @@
+./tests/patmat/gadt.scala:13: warning: match may not be exhaustive.
+It would fail on the following input: IntLit(_)
+  def foo1b(x: Expr[Int]) = x match {
+                              ^
+./tests/patmat/gadt.scala:22: warning: match may not be exhaustive.
+It would fail on the following input: Or(_, _)
+  def foo2b(x: Expr[Boolean]) = x match {
+                                  ^
+./tests/patmat/gadt.scala:45: warning: match may not be exhaustive.
+It would fail on the following input: BooleanLit(_), IntLit(_)
+  def foo4b(x: Expr) = x match {
+                         ^
+three warnings found
\ No newline at end of file
diff --git a/tests/patmat/gadt.scala b/tests/patmat/gadt.scala
new file mode 100644
index 000000000000..54751d5d8800
--- /dev/null
+++ b/tests/patmat/gadt.scala
@@ -0,0 +1,49 @@
+object Test {
+  sealed trait Expr[T]
+  case class IntLit(i: Int) extends Expr[Int]
+  case class BooleanLit(b: Boolean) extends Expr[Boolean]
+  case class Sum(l: Expr[Int], r: Expr[Int]) extends Expr[Int]
+  case class Or(l: Expr[Boolean], r: Expr[Boolean]) extends Expr[Boolean]
+
+  def foo1a(x: Expr[Int]) = x match {
+    case _: IntLit => true
+    case _: Sum => true
+  }
+
+  def foo1b(x: Expr[Int]) = x match {
+    case _: Sum => true
+  }
+
+  def foo2a(x: Expr[Boolean]) = x match {
+    case _: BooleanLit => true
+    case _: Or => true
+  }
+
+  def foo2b(x: Expr[Boolean]) = x match {
+    case _: BooleanLit => true
+  }
+
+  def foo3a(x: Expr[Boolean]) = x match {
+    case _: BooleanLit => true
+    case _: Or => true
+    // case _: Sum => true
+  }
+
+  def foo3b(x: Expr[Int]) = x match {
+    case _: IntLit => true
+    case _: Sum => true
+    // case _: Or => true
+  }
+
+  def foo4a(x: Expr) = x match {
+    case _: IntLit => true
+    case _: Sum => true
+    case _: BooleanLit => true
+    case _: Or => true
+  }
+
+  def foo4b(x: Expr) = x match {
+    case _: Sum => true
+    case _: Or => true
+  }
+}
\ No newline at end of file

From 89e8ff917826529890b10aa157634cbe4c15e4ef Mon Sep 17 00:00:00 2001
From: liu fengyun <liufengyunchina@gmail.com>
Date: Sun, 12 Jun 2016 00:34:58 +0200
Subject: [PATCH 06/11] refine patmat check for type erasure

---
 src/dotty/tools/dotc/transform/patmat/Space.scala | 15 +++++++++++++--
 tests/patmat/t2425.scala                          | 15 +++++++++++++++
 2 files changed, 28 insertions(+), 2 deletions(-)
 create mode 100644 tests/patmat/t2425.scala

diff --git a/src/dotty/tools/dotc/transform/patmat/Space.scala b/src/dotty/tools/dotc/transform/patmat/Space.scala
index 5c4e2fd370b7..4c57416c631d 100644
--- a/src/dotty/tools/dotc/transform/patmat/Space.scala
+++ b/src/dotty/tools/dotc/transform/patmat/Space.scala
@@ -251,7 +251,7 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
             Typ(tp.widenTermRefExpr.stripAnnots, false)
           else
             Var(pat.symbol, tp)
-        case tp => Typ(tp, false)
+        case tp => Typ(erase(tp), false)
       }
     case Alternative(trees) => Or(trees.map(project(_, roundUp)))
     case Bind(_, pat) => project(pat)
@@ -261,11 +261,22 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
       else if (roundUp) Typ(pat.tpe.stripAnnots, false)
       else Empty
     case Typed(pat @ UnApply(_, _, _), _) => project(pat)
-    case Typed(expr, _) => Typ(expr.tpe.stripAnnots, true)
+    case Typed(expr, _) => Typ(erase(expr.tpe.stripAnnots), true)
     case _ =>
       Empty
   }
 
+  /* Erase a type binding according to erasure rule */
+  def erase(tp: Type): Type = {
+    def doErase(tp: Type): Type = tp match {
+      case tp: RefinedType => erase(tp.parent)
+      case _ => tp
+    }
+
+    val origin = doErase(tp)
+    if (origin =:= defn.ArrayType) tp else origin
+  }
+
   /** Is `tp1` a subtype of `tp2`?  */
   def isSubType(tp1: Type, tp2: Type): Boolean = tp1 <:< tp2
 
diff --git a/tests/patmat/t2425.scala b/tests/patmat/t2425.scala
new file mode 100644
index 000000000000..477d5467aab3
--- /dev/null
+++ b/tests/patmat/t2425.scala
@@ -0,0 +1,15 @@
+trait B
+class D extends B
+object Test extends App {
+  def foo[T](bar: T) = {
+    bar match {
+      case _: Array[Array[_]] => println("array 2d")
+      case _: Array[_] => println("array 1d")
+      case _ => println("something else")
+    }
+  }
+  foo(Array.fill(10)(2))
+  foo(Array.fill(10, 10)(2))
+  foo(Array.fill(10, 10, 10)(2))
+  foo(List(1, 2, 3))
+}

From b25e9526cbc43e5a5d7c5c07715d157a5bc0ac82 Mon Sep 17 00:00:00 2001
From: liu fengyun <liufengyunchina@gmail.com>
Date: Sun, 12 Jun 2016 02:07:06 +0200
Subject: [PATCH 07/11] add tuple test to patmat check

---
 src/dotty/tools/dotc/transform/patmat/Space.scala | 8 +++++++-
 tests/patmat/tuple.scala                          | 5 +++++
 2 files changed, 12 insertions(+), 1 deletion(-)
 create mode 100644 tests/patmat/tuple.scala

diff --git a/src/dotty/tools/dotc/transform/patmat/Space.scala b/src/dotty/tools/dotc/transform/patmat/Space.scala
index 4c57416c631d..031f3518c5bf 100644
--- a/src/dotty/tools/dotc/transform/patmat/Space.scala
+++ b/src/dotty/tools/dotc/transform/patmat/Space.scala
@@ -302,7 +302,13 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
       }
 
     // refine path-dependent type in params. refer to t9672
-    meth.firstParamTypes.map(_.stripTypeVar).map(refine(tp, _))
+    meth.firstParamTypes.map(_.stripTypeVar).map { ptp =>
+      (tp, ptp) match {
+        case (TypeRef(ref1: TypeProxy, _), TypeRef(ref2: TypeProxy, name)) =>
+          if (ref1.underlying <:< ref2.underlying) TypeRef(ref1, name) else ptp
+        case _ => ptp
+      }
+    }
   }
 
   def partitions(tp: Type): List[Space] = {
diff --git a/tests/patmat/tuple.scala b/tests/patmat/tuple.scala
new file mode 100644
index 000000000000..f33a5cfec38f
--- /dev/null
+++ b/tests/patmat/tuple.scala
@@ -0,0 +1,5 @@
+object Test {
+  (4, (4, 6)) match {
+    case (x, (y, z)) => true
+  }
+}
\ No newline at end of file

From e2db834f2e7a472da119629a509ca4433fccd3d2 Mon Sep 17 00:00:00 2001
From: liu fengyun <liufengyunchina@gmail.com>
Date: Mon, 13 Jun 2016 15:42:44 +0200
Subject: [PATCH 08/11] add test t5440 for patmat check

---
 tests/patmat/t5440.check | 8 ++++----
 tests/patmat/t5440.scala | 6 ++++++
 2 files changed, 10 insertions(+), 4 deletions(-)
 create mode 100644 tests/patmat/t5440.scala

diff --git a/tests/patmat/t5440.check b/tests/patmat/t5440.check
index f7d97eef78f3..0780d652945e 100644
--- a/tests/patmat/t5440.check
+++ b/tests/patmat/t5440.check
@@ -1,5 +1,5 @@
-./tests/patmat/t5440.scala:3: warning: match may not be exhaustive.
-It would fail on the following input: { (Nil, List(_)), (List(_), Nil) }
-    (list1, list2) match  {
-    ^
+./tests/patmat/t5440.scala:2: warning: match may not be exhaustive.
+It would fail on the following input: (Nil, List(_)), (List(_), Nil)
+  def merge(list1: List[Long], list2: List[Long]): Boolean = (list1, list2) match {
+                                                                            ^
 one warning found
diff --git a/tests/patmat/t5440.scala b/tests/patmat/t5440.scala
new file mode 100644
index 000000000000..6721b0562466
--- /dev/null
+++ b/tests/patmat/t5440.scala
@@ -0,0 +1,6 @@
+object Test {
+  def merge(list1: List[Long], list2: List[Long]): Boolean = (list1, list2) match {
+    case (hd1::_, hd2::_) => true
+    case (Nil, Nil) => true
+  }
+}
\ No newline at end of file

From 2d6e80348ad06a3bb60e9b314e5a257f74f36186 Mon Sep 17 00:00:00 2001
From: liu fengyun <liufengyunchina@gmail.com>
Date: Wed, 15 Jun 2016 14:18:05 +0200
Subject: [PATCH 09/11] better warning for higher-kinded types and alias types

---
 src/dotty/tools/dotc/transform/patmat/Space.scala | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/dotty/tools/dotc/transform/patmat/Space.scala b/src/dotty/tools/dotc/transform/patmat/Space.scala
index 031f3518c5bf..7c5fc3df7af1 100644
--- a/src/dotty/tools/dotc/transform/patmat/Space.scala
+++ b/src/dotty/tools/dotc/transform/patmat/Space.scala
@@ -10,6 +10,7 @@ import ast.tpd
 import core.Decorators._
 import core.TypeApplications._
 import core.Symbols._
+import core.StdNames._
 import core.NameOps._
 import core.Constants._
 
@@ -401,7 +402,8 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
       case tp: ThisType => refine(tp.tref)
       case tp: NamedType =>
         val pre = refinePrefix(tp.prefix)
-        if (pre.isEmpty) tp.name.show.stripSuffix("$")
+        if (tp.name == tpnme.hkApply) pre
+        else if (pre.isEmpty) tp.name.show.stripSuffix("$")
         else pre + "." + tp.name.show.stripSuffix("$")
       case _ => tp.show.stripSuffix("$")
     }
@@ -472,7 +474,8 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
 
   def checkExhaustivity(_match: Match): Unit = {
     val Match(sel, cases) = _match
-    val selTyp = sel.tpe.widen.elimAnonymousClass
+    val selTyp = sel.tpe.widen.elimAnonymousClass.dealias
+
 
     val patternSpace = cases.map(x => project(x.pat)).reduce((a, b) => Or(List(a, b)))
     val uncovered = simplify(minus(Typ(selTyp, true), patternSpace))

From f69b305e56cac0836baaed88982660fe40070aed Mon Sep 17 00:00:00 2001
From: liu fengyun <liufengyunchina@gmail.com>
Date: Thu, 23 Jun 2016 10:12:22 +0200
Subject: [PATCH 10/11] fix SI-9657 about type bounds

---
 .../tools/dotc/transform/patmat/Space.scala   | 72 +++++++++++++++++--
 tests/patmat/gadt.check                       |  6 +-
 tests/patmat/gadt.scala                       | 11 ++-
 tests/patmat/t9657.check                      | 17 +++++
 tests/patmat/t9657.scala                      | 62 ++++++++++++++++
 tests/patmat/t9657.scala.ignore               | 28 --------
 6 files changed, 161 insertions(+), 35 deletions(-)
 create mode 100644 tests/patmat/t9657.check
 create mode 100644 tests/patmat/t9657.scala
 delete mode 100644 tests/patmat/t9657.scala.ignore

diff --git a/src/dotty/tools/dotc/transform/patmat/Space.scala b/src/dotty/tools/dotc/transform/patmat/Space.scala
index 7c5fc3df7af1..6d5323d08373 100644
--- a/src/dotty/tools/dotc/transform/patmat/Space.scala
+++ b/src/dotty/tools/dotc/transform/patmat/Space.scala
@@ -14,10 +14,14 @@ import core.StdNames._
 import core.NameOps._
 import core.Constants._
 
-/** Space logic for checking exhaustivity and unreachability of pattern matching.
+/** Space logic for checking exhaustivity and unreachability of pattern matching
  *
- *  The core idea of the algorithm is that patterns and types are value
- *  spaces, which is recursively defined as follows:
+ *  Space can be thought of as a set of possible values. A type or a pattern
+ *  both refer to spaces. The space of a type is the values that inhabit the
+ *  type. The space of a pattern is the values that can be covered by the
+ *  pattern.
+ *
+ *  Space is recursively defined as follows:
  *
  *      1. `Empty` is a space
  *      2. For a type T, `Typ(T)` is a space
@@ -279,7 +283,11 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
   }
 
   /** Is `tp1` a subtype of `tp2`?  */
-  def isSubType(tp1: Type, tp2: Type): Boolean = tp1 <:< tp2
+  def isSubType(tp1: Type, tp2: Type): Boolean = {
+    // expose is important due to type bounds
+    // check SI-9657 and tests/patmat/gadt.scala
+    tp1 <:< expose(tp2)
+  }
 
   def isEqualType(tp1: Type, tp2: Type): Boolean = tp1 =:= tp2
 
@@ -472,6 +480,59 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
     isCheckable(sel.tpe.widen.elimAnonymousClass)
   }
 
+
+  /** Expose refined type to eliminate reference to type variables
+   *
+   *  A = B                      M { type T = A }        ~~>  M { type T = B }
+   *
+   *  A <: X :> Y                M { type T = A }        ~~>  M { type T <: X :> Y }
+   *
+   *  A <: X :> Y  B <: U :> V   M { type T <: A :> B }  ~~>  M { type T <: X :> B }
+   *
+   *  A = X  B = Y               M { type T <: A :> B }  ~~>  M { type T <: X :> Y }
+   */
+  def expose(tp: Type): Type = {
+    def follow(tp: Type, up: Boolean): Type = tp match {
+      case tp: TypeProxy =>
+        tp.underlying match {
+          case TypeBounds(lo, hi) =>
+            follow(if (up) hi else lo, up)
+          case _ =>
+            tp
+        }
+      case OrType(tp1, tp2) =>
+        OrType(follow(tp1, up), follow(tp2, up))
+      case AndType(tp1, tp2) =>
+        AndType(follow(tp1, up), follow(tp2, up))
+    }
+
+    tp match {
+      case tp: RefinedType =>
+        tp.refinedInfo match {
+          case tpa : TypeAlias =>
+            val hi = follow(tpa.alias, true)
+            val lo = follow(tpa.alias, false)
+            val refined = if (hi =:= lo)
+              tpa.derivedTypeAlias(hi)
+            else
+              tpa.derivedTypeBounds(lo, hi)
+
+            tp.derivedRefinedType(
+              expose(tp.parent),
+              tp.refinedName,
+              refined
+            )
+          case tpb @ TypeBounds(lo, hi) =>
+            tp.derivedRefinedType(
+              expose(tp.parent),
+              tp.refinedName,
+              tpb.derivedTypeBounds(follow(lo, false), follow(hi, true))
+            )
+        }
+      case _ => tp
+    }
+  }
+
   def checkExhaustivity(_match: Match): Unit = {
     val Match(sel, cases) = _match
     val selTyp = sel.tpe.widen.elimAnonymousClass.dealias
@@ -491,7 +552,8 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
 
   def checkRedundancy(_match: Match): Unit = {
     val Match(sel, cases) = _match
-    val selTyp = sel.tpe.widen.elimAnonymousClass
+    // ignore selector type for now
+    // val selTyp = sel.tpe.widen.elimAnonymousClass.dealias
 
     // starts from the second, the first can't be redundant
     (1 until cases.length).foreach { i =>
diff --git a/tests/patmat/gadt.check b/tests/patmat/gadt.check
index caeb0c4eb39e..79b3494e08cf 100644
--- a/tests/patmat/gadt.check
+++ b/tests/patmat/gadt.check
@@ -10,4 +10,8 @@ It would fail on the following input: Or(_, _)
 It would fail on the following input: BooleanLit(_), IntLit(_)
   def foo4b(x: Expr) = x match {
                          ^
-three warnings found
\ No newline at end of file
+./tests/patmat/gadt.scala:55: warning: match may not be exhaustive.
+It would fail on the following input: Sum(_, _)
+  def foo5b[T <: Int](x: Expr[T]) = x match {
+                                      ^
+four warnings found
\ No newline at end of file
diff --git a/tests/patmat/gadt.scala b/tests/patmat/gadt.scala
index 54751d5d8800..9f3e7696f75d 100644
--- a/tests/patmat/gadt.scala
+++ b/tests/patmat/gadt.scala
@@ -46,4 +46,13 @@ object Test {
     case _: Sum => true
     case _: Or => true
   }
-}
\ No newline at end of file
+
+  def foo5a[T <: Int](x: Expr[T]) = x match {
+    case _: IntLit => true
+    case _: Sum => true
+  }
+
+  def foo5b[T <: Int](x: Expr[T]) = x match {
+    case _: IntLit => true
+  }
+}
diff --git a/tests/patmat/t9657.check b/tests/patmat/t9657.check
new file mode 100644
index 000000000000..d3e2ec73f494
--- /dev/null
+++ b/tests/patmat/t9657.check
@@ -0,0 +1,17 @@
+./tests/patmat/t9657.scala:29: warning: match may not be exhaustive.
+It would fail on the following input: Bus(_)
+  def refuel2[P <: Petrol.type](vehicle: Vehicle {type A = P} ): Vehicle = vehicle match {
+                                                                                   ^
+./tests/patmat/t9657.scala:38: warning: match may not be exhaustive.
+It would fail on the following input: Bus(_)
+  def foo2(vehicle: Vehicle {type A <: Petrol.type} ): Vehicle = vehicle match {
+                                                                         ^
+./tests/patmat/t9657.scala:49: warning: match may not be exhaustive.
+It would fail on the following input: Bus(_)
+  def bar2(vehicle: Vehicle {type A <: P} ): Vehicle = vehicle match {
+                                                               ^
+./tests/patmat/t9657.scala:58: warning: match may not be exhaustive.
+It would fail on the following input: Bus(_)
+  def qux2[P <: Petrol.type](vehicle: Vehicle {type A <: P} ): Vehicle = vehicle match {
+                                                                                 ^
+four warnings found
\ No newline at end of file
diff --git a/tests/patmat/t9657.scala b/tests/patmat/t9657.scala
new file mode 100644
index 000000000000..f9769574ed35
--- /dev/null
+++ b/tests/patmat/t9657.scala
@@ -0,0 +1,62 @@
+sealed trait PowerSource
+
+case object Petrol extends PowerSource
+
+case object Pedal extends PowerSource
+
+sealed abstract class Vehicle {
+  type A <: PowerSource
+}
+
+case object Bicycle extends Vehicle {
+  type A = Pedal.type
+}
+
+case class Bus(fuel: Int) extends Vehicle {
+  type A = Petrol.type
+}
+
+case class Car(fuel: Int) extends Vehicle {
+  type A = Petrol.type
+}
+
+class Test {
+  def refuel[P <: Petrol.type](vehicle: Vehicle {type A = P} ): Vehicle = vehicle match {
+    case Car(_) => Car(100)
+    case Bus(_) => Bus(100)
+  }
+
+  def refuel2[P <: Petrol.type](vehicle: Vehicle {type A = P} ): Vehicle = vehicle match {
+    case Car(_) => Car(100)
+  }
+
+  def foo1(vehicle: Vehicle {type A <: Petrol.type} ): Vehicle = vehicle match {
+    case Car(_) => Car(100)
+    case Bus(_) => Bus(100)
+  }
+
+  def foo2(vehicle: Vehicle {type A <: Petrol.type} ): Vehicle = vehicle match {
+    case Car(_) => Car(100)
+  }
+
+  type P = Petrol.type
+
+  def bar1(vehicle: Vehicle {type A <: P} ): Vehicle = vehicle match {
+    case Car(_) => Car(100)
+    case Bus(_) => Bus(100)
+  }
+
+  def bar2(vehicle: Vehicle {type A <: P} ): Vehicle = vehicle match {
+    case Car(_) => Car(100)
+  }
+
+  def qux1[P <: Petrol.type](vehicle: Vehicle {type A <: P} ): Vehicle = vehicle match {
+    case Car(_) => Car(100)
+    case Bus(_) => Bus(100)
+  }
+
+  def qux2[P <: Petrol.type](vehicle: Vehicle {type A <: P} ): Vehicle = vehicle match {
+    case Car(_) => Car(100)
+  }
+
+}
diff --git a/tests/patmat/t9657.scala.ignore b/tests/patmat/t9657.scala.ignore
deleted file mode 100644
index d15a441e3237..000000000000
--- a/tests/patmat/t9657.scala.ignore
+++ /dev/null
@@ -1,28 +0,0 @@
-sealed trait PowerSource
-
-case object Petrol extends PowerSource
-
-case object Pedal extends PowerSource
-
-sealed abstract class Vehicle {
-  type A <: PowerSource
-}
-
-case object Bicycle extends Vehicle {
-  type A = Pedal.type
-}
-
-case class Bus(fuel: Int) extends Vehicle {
-  type A = Petrol.type
-}
-
-case class Car(fuel: Int) extends Vehicle {
-  type A = Petrol.type
-}
-
-object Test {
-  def refuel[P <: Petrol.type](vehicle: Vehicle {type A = P} ): Vehicle = vehicle match {
-    case Car(_) => Car(100)
-    case Bus(_) => Bus(100)
-  }
-}
\ No newline at end of file

From c79181d08230b5387fb74e0c9fa3de8a6c56830d Mon Sep 17 00:00:00 2001
From: liu fengyun <liufengyunchina@gmail.com>
Date: Mon, 4 Jul 2016 00:59:51 +0200
Subject: [PATCH 11/11] address counter-example of two unrelated traits

---
 src/dotty/tools/dotc/core/Types.scala         |   2 +-
 .../tools/dotc/transform/PatternMatcher.scala |   9 +-
 .../tools/dotc/transform/patmat/Space.scala   | 358 ++++++++++--------
 tests/patmat/NonAbstractSealed.check          |   5 +
 tests/patmat/NonAbstractSealed.scala          |  10 +
 tests/patmat/TwoTrait.scala                   |  12 +
 tests/patmat/patmatexhaust.check              |   2 +-
 tests/patmat/t9677.check                      |   4 +
 8 files changed, 239 insertions(+), 163 deletions(-)
 create mode 100644 tests/patmat/NonAbstractSealed.check
 create mode 100644 tests/patmat/NonAbstractSealed.scala
 create mode 100644 tests/patmat/TwoTrait.scala
 create mode 100644 tests/patmat/t9677.check

diff --git a/src/dotty/tools/dotc/core/Types.scala b/src/dotty/tools/dotc/core/Types.scala
index 83998303dc27..3c051b952c45 100644
--- a/src/dotty/tools/dotc/core/Types.scala
+++ b/src/dotty/tools/dotc/core/Types.scala
@@ -811,7 +811,7 @@ object Types {
     }
 
     /** Eliminate anonymous classes */
-    final def elimAnonymousClass(implicit ctx: Context): Type = this match {
+    final def deAnonymize(implicit ctx: Context): Type = this match {
       case tp:TypeRef if tp.symbol.isAnonymousClass =>
         tp.symbol.asClass.typeRef.asSeenFrom(tp.prefix, tp.symbol.owner)
       case tp => tp
diff --git a/src/dotty/tools/dotc/transform/PatternMatcher.scala b/src/dotty/tools/dotc/transform/PatternMatcher.scala
index af742420c4cb..accdc762f66d 100644
--- a/src/dotty/tools/dotc/transform/PatternMatcher.scala
+++ b/src/dotty/tools/dotc/transform/PatternMatcher.scala
@@ -1254,13 +1254,6 @@ class PatternMatcher extends MiniPhaseTransform with DenotTransformer {thisTrans
       case _                                                => false
     }
 
-    def elimAnonymousClass(t: Type) = t match {
-      case t:TypeRef if t.symbol.isAnonymousClass =>
-        t.symbol.asClass.typeRef.asSeenFrom(t.prefix, t.symbol.owner)
-      case _ =>
-        t
-    }
-
     /** Implement a pattern match by turning its cases (including the implicit failure case)
       * into the corresponding (monadic) extractors, and combining them with the `orElse` combinator.
       *
@@ -1274,7 +1267,7 @@ class PatternMatcher extends MiniPhaseTransform with DenotTransformer {thisTrans
     def translateMatch(match_ : Match): Tree = {
       val Match(sel, cases) = match_
 
-      val selectorTp = sel.tpe.widen.elimAnonymousClass/*withoutAnnotations*/
+      val selectorTp = sel.tpe.widen.deAnonymize/*withoutAnnotations*/
 
       val selectorSym = freshSym(sel.pos, selectorTp, "selector")
 
diff --git a/src/dotty/tools/dotc/transform/patmat/Space.scala b/src/dotty/tools/dotc/transform/patmat/Space.scala
index 6d5323d08373..0829e6c34161 100644
--- a/src/dotty/tools/dotc/transform/patmat/Space.scala
+++ b/src/dotty/tools/dotc/transform/patmat/Space.scala
@@ -8,7 +8,6 @@ import core.Flags._
 import ast.Trees._
 import ast.tpd
 import core.Decorators._
-import core.TypeApplications._
 import core.Symbols._
 import core.StdNames._
 import core.NameOps._
@@ -43,13 +42,37 @@ import core.Constants._
 
 /** space definition */
 sealed trait Space
+
+/** Empty space */
 case object Empty extends Space
+
+/** Space representing the set of all values of a type
+ *
+ * @param tp: the type this space represents
+ * @param decomposed: does the space result from decomposition? Used for pretty print
+ *
+ * Note:  When transform patterns like `_: List[T]` into space, the type parameter is
+ *        erased. E.g., `_: List[Int]` will be erased to `Typ(List, _)`.
+ *
+ *        However, the scrutinee of pattern matching is not erased in order to make
+ *        pattern matching for GADT more precise.
+ */
 case class Typ(tp: Type, decomposed: Boolean) extends Space
+
+/** Space representing a constructor pattern */
 case class Kon(tp: Type, params: List[Space]) extends Space
+
+/** Union of spaces */
+case class Or(spaces: List[Space]) extends Space
+
+/** Point in space */
 sealed trait Point extends Space
+
+/** Point representing variables(stable identifier) in patterns */
 case class Var(sym: Symbol, tp: Type) extends Point
+
+/** Point representing literal constants in patterns */
 case class Const(value: Constant, tp: Type) extends Point
-case class Or(spaces: List[Space]) extends Space
 
 /** abstract space logic */
 trait SpaceLogic {
@@ -59,7 +82,13 @@ trait SpaceLogic {
   /** Is `tp1` the same type as `tp2`? */
   def isEqualType(tp1: Type, tp2: Type): Boolean
 
-  /** Is `tp` a case class? */
+  /** Is `tp` a case class?
+   *
+   *  Assumption:
+   *    (1) One case class cannot be inherited directly or indirectly by another
+   *        case class.
+   *    (2) Inheritance of a case class cannot be well handled by the algorithm.
+   */
   def isCaseClass(tp: Type): Boolean
 
   /** Is the type `tp` decomposable? i.e. all values of the type can be covered
@@ -69,17 +98,17 @@ trait SpaceLogic {
    */
   def canDecompose(tp: Type): Boolean
 
-  /** Return parameters types of the case class `tp` */
+  /** Return term parameter types of the case class `tp` */
   def signature(tp: Type): List[Type]
 
   /** Get components of decomposable types */
-  def partitions(tp: Type): List[Space]
+  def decompose(tp: Type): List[Space]
 
   /** Simplify space using the laws, there's no nested union after simplify */
   def simplify(space: Space): Space = space match {
     case Kon(tp, spaces) =>
       val sp = Kon(tp, spaces.map(simplify _))
-      if (sp.params.exists(_ == Empty)) Empty
+      if (sp.params.contains(Empty)) Empty
       else sp
     case Or(spaces) =>
       val set = spaces.map(simplify _).flatMap {
@@ -91,7 +120,7 @@ trait SpaceLogic {
       else if (set.size == 1) set.toList(0)
       else Or(set)
     case Typ(tp, _) =>
-      if (canDecompose(tp) && partitions(tp).isEmpty) Empty
+      if (canDecompose(tp) && decompose(tp).isEmpty) Empty
       else space
     case _ => space
   }
@@ -111,127 +140,157 @@ trait SpaceLogic {
   }
 
   /** Is `a` a subspace of `b`? Equivalent to `a - b == Empty`, but faster */
-  def subspace(a: Space, b: Space): Boolean = (a, b) match {
-    case (Empty, _) => true
-    case (_, Empty) => false
-    case (Or(ss), _) => ss.forall(subspace(_, b))
-    case (Typ(tp1, _), Typ(tp2, _)) =>
-      isSubType(tp1, tp2)
-    case (Typ(tp1, _), Or(ss)) =>
-      ss.exists(subspace(a, _)) ||
-      (canDecompose(tp1) && subspace(Or(partitions(tp1)), b))
-    case (Typ(tp1, _), Kon(tp2, ss)) =>
-      isSubType(tp1, tp2) && subspace(Kon(tp2, signature(tp2).map(Typ(_, false))), b)
-    case (Kon(tp1, ss), Typ(tp2, _)) =>
-      isSubType(tp1, tp2) ||
-      simplify(a) == Empty ||
-      (isSubType(tp2, tp1) &&
-        canDecompose(tp1) &&
-        subspace(Or(partitions(tp1)), b))
-    case (Kon(_, _), Or(_)) =>
-      simplify(minus(a, b)) == Empty
-    case (Kon(tp1, ss1), Kon(tp2, ss2)) =>
-      isEqualType(tp1, tp2) && ss1.zip(ss2).forall((subspace _).tupled)
-    case (Const(v1, _), Const(v2, _)) => v1 == v2
-    case (Const(_, tp1), Typ(tp2, _)) => isSubType(tp1, tp2)
-    case (Const(_, _), Or(ss)) => ss.exists(subspace(a, _))
-    case (Const(_, _), _) => false
-    case (_, Const(_, _)) => false
-    case (Var(x, _), Var(y, _)) => x == y
-    case (Var(_, tp1), Typ(tp2, _)) => isSubType(tp1, tp2)
-    case (Var(_, _), Or(ss)) => ss.exists(subspace(a, _))
-    case (Var(_, _), _) => false
-    case (_, Var(_, _)) => false
+  def isSubspace(a: Space, b: Space): Boolean = {
+    def tryDecompose1(tp: Type) = canDecompose(tp) && isSubspace(Or(decompose(tp)), b)
+    def tryDecompose2(tp: Type) = canDecompose(tp) && isSubspace(a, Or(decompose(tp)))
+
+    (a, b) match {
+      case (Empty, _) => true
+      case (_, Empty) => false
+      case (Or(ss), _) => ss.forall(isSubspace(_, b))
+      case (Typ(tp1, _), Typ(tp2, _)) =>
+        isSubType(tp1, tp2) || tryDecompose1(tp1) || tryDecompose2(tp2)
+      case (Typ(tp1, _), Or(ss)) =>
+        ss.exists(isSubspace(a, _)) || tryDecompose1(tp1)
+      case (Typ(tp1, _), Kon(tp2, ss)) =>
+        isSubType(tp1, tp2) && isSubspace(Kon(tp2, signature(tp2).map(Typ(_, false))), b) ||
+        tryDecompose1(tp1)
+      case (Kon(tp1, ss), Typ(tp2, _)) =>
+        isSubType(tp1, tp2) ||
+          simplify(a) == Empty ||
+          (isSubType(tp2, tp1) && tryDecompose1(tp1)) ||
+          tryDecompose2(tp2)
+      case (Kon(_, _), Or(_)) =>
+        simplify(minus(a, b)) == Empty
+      case (Kon(tp1, ss1), Kon(tp2, ss2)) =>
+        isEqualType(tp1, tp2) && ss1.zip(ss2).forall((isSubspace _).tupled)
+      case (Const(v1, _), Const(v2, _)) => v1 == v2
+      case (Const(_, tp1), Typ(tp2, _)) => isSubType(tp1, tp2) || tryDecompose2(tp2)
+      case (Const(_, _), Or(ss)) => ss.exists(isSubspace(a, _))
+      case (Const(_, _), _) => false
+      case (_, Const(_, _)) => false
+      case (Var(x, _), Var(y, _)) => x == y
+      case (Var(_, tp1), Typ(tp2, _)) => isSubType(tp1, tp2) || tryDecompose2(tp2)
+      case (Var(_, _), Or(ss)) => ss.exists(isSubspace(a, _))
+      case (Var(_, _), _) => false
+      case (_, Var(_, _)) => false
+    }
   }
 
   /** Intersection of two spaces  */
-  def intersect(a: Space, b: Space): Space = (a, b) match {
-    case (Empty, _) | (_, Empty) => Empty
-    case (_, Or(ss)) => Or(ss.map(intersect(a, _)))
-    case (Or(ss), _) => Or(ss.map(intersect(_, b)))
-    case (Typ(tp1, _), Typ(tp2, _)) =>
-      if (isSubType(tp1, tp2)) a
-      else if (isSubType(tp2, tp1)) b
-      else Empty
-    case (Typ(tp1, _), Kon(tp2, ss)) =>
-      if (isSubType(tp2, tp1)) b
-      else if (isSubType(tp1, tp2)) a
-      else Empty
-    case (Kon(tp1, ss), Typ(tp2, _)) =>
-      if (isSubType(tp1, tp2) || isSubType(tp2, tp1)) a
-      else Empty
-    case (Kon(tp1, ss1), Kon(tp2, ss2)) =>
-      if (!isEqualType(tp1, tp2)) Empty
-      else if (ss1.zip(ss2).exists(p => simplify(intersect(p._1, p._2)) == Empty)) Empty
-      else
-        Kon(tp1, ss1.zip(ss2).map((intersect _).tupled))
-    case (Const(v1, _), Const(v2, _)) =>
-      if (v1 == v2) a else Empty
-    case (Const(_, tp1), Typ(tp2, _)) =>
-      if (isSubType(tp1, tp2)) a else Empty
-    case (Const(_, _), _) => Empty
-    case (Typ(tp1, _), Const(_, tp2)) =>
-      if (isSubType(tp2, tp1)) b else Empty
-    case (_, Const(_, _)) => Empty
-    case (Var(x, _), Var(y, _)) =>
-      if (x == y) a else Empty
-    case (Var(_, tp1), Typ(tp2, _)) =>
-      if (isSubType(tp1, tp2)) a else Empty
-    case (Var(_, _), _) => Empty
-    case (Typ(tp1, _), Var(_, tp2)) =>
-      if (isSubType(tp2, tp1)) b else Empty
-    case (_, Var(_, _)) => Empty
+  def intersect(a: Space, b: Space): Space = {
+    def tryDecompose1(tp: Type) = intersect(Or(decompose(tp)), b)
+    def tryDecompose2(tp: Type) = intersect(a, Or(decompose(tp)))
+
+    (a, b) match {
+      case (Empty, _) | (_, Empty) => Empty
+      case (_, Or(ss)) => Or(ss.map(intersect(a, _)).filterConserve(_ ne Empty))
+      case (Or(ss), _) => Or(ss.map(intersect(_, b)).filterConserve(_ ne Empty))
+      case (Typ(tp1, _), Typ(tp2, _)) =>
+        if (isSubType(tp1, tp2)) a
+        else if (isSubType(tp2, tp1)) b
+        else if (canDecompose(tp1)) tryDecompose1(tp1)
+        else if (canDecompose(tp2)) tryDecompose2(tp2)
+        else Empty
+      case (Typ(tp1, _), Kon(tp2, ss)) =>
+        if (isSubType(tp2, tp1)) b
+        else if (isSubType(tp1, tp2)) a // problematic corner case: inheriting a case class
+        else if (canDecompose(tp1)) tryDecompose1(tp1)
+        else Empty
+      case (Kon(tp1, ss), Typ(tp2, _)) =>
+        if (isSubType(tp1, tp2)) a
+        else if (isSubType(tp2, tp1)) a  // problematic corner case: inheriting a case class
+        else if (canDecompose(tp2)) tryDecompose2(tp2)
+        else Empty
+      case (Kon(tp1, ss1), Kon(tp2, ss2)) =>
+        if (!isEqualType(tp1, tp2)) Empty
+        else if (ss1.zip(ss2).exists(p => simplify(intersect(p._1, p._2)) == Empty)) Empty
+        else Kon(tp1, ss1.zip(ss2).map((intersect _).tupled))
+      case (Const(v1, _), Const(v2, _)) =>
+        if (v1 == v2) a else Empty
+      case (Const(_, tp1), Typ(tp2, _)) =>
+        if (isSubType(tp1, tp2)) a
+        else if (canDecompose(tp2)) tryDecompose2(tp2)
+        else Empty
+      case (Const(_, _), _) => Empty
+      case (Typ(tp1, _), Const(_, tp2)) =>
+        if (isSubType(tp2, tp1)) b
+        else if (canDecompose(tp1)) tryDecompose1(tp1)
+        else Empty
+      case (_, Const(_, _)) => Empty
+      case (Var(x, _), Var(y, _)) =>
+        if (x == y) a else Empty
+      case (Var(_, tp1), Typ(tp2, _)) =>
+        if (isSubType(tp1, tp2)) a
+        else if (canDecompose(tp2)) tryDecompose2(tp2)
+        else Empty
+      case (Var(_, _), _) => Empty
+      case (Typ(tp1, _), Var(_, tp2)) =>
+        if (isSubType(tp2, tp1)) b
+        else if (canDecompose(tp1)) tryDecompose1(tp1)
+        else Empty
+      case (_, Var(_, _)) => Empty
+    }
   }
 
   /** The space of a not covered by b */
-  def minus(a: Space, b: Space): Space = (a, b) match {
-    case (Empty, _) => Empty
-    case (_, Empty) => a
-    case (Typ(tp1, _), Typ(tp2, _)) =>
-      if (isSubType(tp1, tp2)) Empty
-      else if (isSubType(tp2, tp1) && canDecompose(tp1))
-        minus(Or(partitions(tp1)), b)
-      else a
-    case (Typ(tp1, _), Kon(tp2, ss)) =>
-      if (isSubType(tp1, tp2)) minus(Kon(tp2, signature(tp2).map(Typ(_, false))), b)
-      else if (isSubType(tp2, tp1) && canDecompose(tp1))
-        minus(Or(partitions(tp1)), b)
-      else a
-    case (_, Or(ss)) =>
-      ss.foldLeft(a)(minus)
-    case (Or(ss), _) =>
-      Or(ss.map(minus(_, b)))
-    case (Kon(tp1, ss), Typ(tp2, _)) =>
-      if (isSubType(tp1, tp2)) Empty
-      else if (simplify(a) == Empty) Empty
-      else if (isSubType(tp2, tp1) && canDecompose(tp1))
-        minus(Or(partitions(tp1)), b)
-      else a
-    case (Kon(tp1, ss1), Kon(tp2, ss2)) =>
-      if (!isEqualType(tp1, tp2)) a
-      else if (ss1.zip(ss2).exists(p => simplify(intersect(p._1, p._2)) == Empty)) a
-      else if (ss1.zip(ss2).forall((subspace _).tupled)) Empty
-      else
-        Or(
-          ss1.zip(ss2).map((minus _).tupled).zip(0 to ss2.length - 1).map {
-            case (ri, i) => Kon(tp1, ss1.updated(i, ri))
-          })
-    case (Const(v1, _), Const(v2, _)) =>
-      if (v1 == v2) Empty else a
-    case (Const(_, tp1), Typ(tp2, _)) =>
-      if (isSubType(tp1, tp2)) Empty else a
-    case (Const(_, _), _) => a
-    case (Typ(tp1, _), Const(_, tp2)) =>  // Boolean & Java enum
-      if (isSubType(tp2, tp1) && canDecompose(tp1))
-        minus(Or(partitions(tp1)), b)
-      else a
-    case (_, Const(_, _)) => a
-    case (Var(x, _), Var(y, _)) =>
-      if (x == y) Empty else a
-    case (Var(_, tp1), Typ(tp2, _)) =>
-      if (isSubType(tp1, tp2)) Empty else a
-    case (Var(_, _), _) => a
-    case (_, Var(_, _)) => a
+  def minus(a: Space, b: Space): Space = {
+    def tryDecompose1(tp: Type) = minus(Or(decompose(tp)), b)
+    def tryDecompose2(tp: Type) = minus(a, Or(decompose(tp)))
+
+    (a, b) match {
+      case (Empty, _) => Empty
+      case (_, Empty) => a
+      case (Typ(tp1, _), Typ(tp2, _)) =>
+        if (isSubType(tp1, tp2)) Empty
+        else if (canDecompose(tp1)) tryDecompose1(tp1)
+        else if (canDecompose(tp2)) tryDecompose2(tp2)
+        else a
+      case (Typ(tp1, _), Kon(tp2, ss)) =>
+        // corner case: inheriting a case class
+        // rationale: every instance of `tp1` is covered by `tp2(_)`
+        if (isSubType(tp1, tp2)) minus(Kon(tp2, signature(tp2).map(Typ(_, false))), b)
+        else if (canDecompose(tp1)) tryDecompose1(tp1)
+        else a
+      case (_, Or(ss)) =>
+        ss.foldLeft(a)(minus)
+      case (Or(ss), _) =>
+        Or(ss.map(minus(_, b)))
+      case (Kon(tp1, ss), Typ(tp2, _)) =>
+        // uncovered corner case: tp2 :< tp1
+        if (isSubType(tp1, tp2)) Empty
+        else if (simplify(a) == Empty) Empty
+        else if (canDecompose(tp2)) tryDecompose2(tp2)
+        else a
+      case (Kon(tp1, ss1), Kon(tp2, ss2)) =>
+        if (!isEqualType(tp1, tp2)) a
+        else if (ss1.zip(ss2).exists(p => simplify(intersect(p._1, p._2)) == Empty)) a
+        else if (ss1.zip(ss2).forall((isSubspace _).tupled)) Empty
+        else
+          // `(_, _, _) - (Some, None, _)` becomes `(None, _, _) | (_, Some, _) | (_, _, Empty)`
+          Or(ss1.zip(ss2).map((minus _).tupled).zip(0 to ss2.length - 1).map {
+              case (ri, i) => Kon(tp1, ss1.updated(i, ri))
+            })
+      case (Const(v1, _), Const(v2, _)) =>
+        if (v1 == v2) Empty else a
+      case (Const(_, tp1), Typ(tp2, _)) =>
+        if (isSubType(tp1, tp2)) Empty
+        else if (canDecompose(tp2)) tryDecompose2(tp2)
+        else a
+      case (Const(_, _), _) => a
+      case (Typ(tp1, _), Const(_, tp2)) =>  // Boolean & Java enum
+        if (canDecompose(tp1)) tryDecompose1(tp1)
+        else a
+      case (_, Const(_, _)) => a
+      case (Var(x, _), Var(y, _)) =>
+        if (x == y) Empty else a
+      case (Var(_, tp1), Typ(tp2, _)) =>
+        if (isSubType(tp1, tp2)) Empty
+        else if (canDecompose(tp2)) tryDecompose2(tp2)
+        else a
+      case (Var(_, _), _) => a
+      case (_, Var(_, _)) => a
+    }
   }
 }
 
@@ -271,15 +330,22 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
       Empty
   }
 
-  /* Erase a type binding according to erasure rule */
+  /* Erase a type binding according to erasure semantics in pattern matching */
   def erase(tp: Type): Type = {
     def doErase(tp: Type): Type = tp match {
       case tp: RefinedType => erase(tp.parent)
       case _ => tp
     }
 
-    val origin = doErase(tp)
-    if (origin =:= defn.ArrayType) tp else origin
+    tp match {
+      case OrType(tp1, tp2) =>
+        OrType(erase(tp1), erase(tp2))
+      case AndType(tp1, tp2) =>
+        AndType(erase(tp1), erase(tp2))
+      case _ =>
+        val origin = doErase(tp)
+        if (origin =:= defn.ArrayType) tp else origin
+    }
   }
 
   /** Is `tp1` a subtype of `tp2`?  */
@@ -295,32 +361,18 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
   def signature(tp: Type): List[Type] = {
     val ktor = tp.classSymbol.primaryConstructor.info
 
-    val meth =
-      if (ktor.isInstanceOf[MethodType]) ktor
-      else
-      tp match {
-        case AppliedType(_, params) =>
-          val refined = params.map {
-            // TypeBounds would generate an exception
-            case tp: TypeBounds => tp.underlying
-            case tp => tp
-          }
-          ktor.appliedTo(refined)
-        case _ =>
-          ktor
-      }
+    val meth = ktor match {
+      case ktor: PolyType =>
+        ktor.instantiate(tp.classSymbol.typeParams.map(_.typeRef)).asSeenFrom(tp, tp.classSymbol)
+      case _ => ktor
+    }
 
     // refine path-dependent type in params. refer to t9672
-    meth.firstParamTypes.map(_.stripTypeVar).map { ptp =>
-      (tp, ptp) match {
-        case (TypeRef(ref1: TypeProxy, _), TypeRef(ref2: TypeProxy, name)) =>
-          if (ref1.underlying <:< ref2.underlying) TypeRef(ref1, name) else ptp
-        case _ => ptp
-      }
-    }
+    meth.firstParamTypes.map(_.asSeenFrom(tp, tp.classSymbol))
   }
 
-  def partitions(tp: Type): List[Space] = {
+  /** Decompose a type into subspaces -- assume the type can be decomposed */
+  def decompose(tp: Type): List[Space] = {
     val children = tp.classSymbol.annotations.filter(_.symbol == ctx.definitions.ChildAnnot).map { annot =>
       // refer to definition of Annotation.makeChild
       annot.tree match {
@@ -342,7 +394,7 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
           if (sym.is(ModuleClass))
             sym.asClass.classInfo.selfType
           else if (sym.info.typeParams.length > 0 || tp.isInstanceOf[TypeRef])
-            refine(tp, sym.asClass.classInfo.symbolicTypeRef)
+            refine(tp, sym.typeRef)
           else
             sym.typeRef
         } filter { tpe =>
@@ -477,7 +529,7 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
     }
 
     val Match(sel, cases) = tree
-    isCheckable(sel.tpe.widen.elimAnonymousClass)
+    isCheckable(sel.tpe.widen.deAnonymize)
   }
 
 
@@ -487,7 +539,7 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
    *
    *  A <: X :> Y                M { type T = A }        ~~>  M { type T <: X :> Y }
    *
-   *  A <: X :> Y  B <: U :> V   M { type T <: A :> B }  ~~>  M { type T <: X :> B }
+   *  A <: X :> Y  B <: U :> V   M { type T <: A :> B }  ~~>  M { type T <: X :> V }
    *
    *  A = X  B = Y               M { type T <: A :> B }  ~~>  M { type T <: X :> Y }
    */
@@ -535,7 +587,7 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
 
   def checkExhaustivity(_match: Match): Unit = {
     val Match(sel, cases) = _match
-    val selTyp = sel.tpe.widen.elimAnonymousClass.dealias
+    val selTyp = sel.tpe.widen.deAnonymize.dealias
 
 
     val patternSpace = cases.map(x => project(x.pat)).reduce((a, b) => Or(List(a, b)))
@@ -553,7 +605,7 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
   def checkRedundancy(_match: Match): Unit = {
     val Match(sel, cases) = _match
     // ignore selector type for now
-    // val selTyp = sel.tpe.widen.elimAnonymousClass.dealias
+    // val selTyp = sel.tpe.widen.deAnonymize.dealias
 
     // starts from the second, the first can't be redundant
     (1 until cases.length).foreach { i =>
@@ -566,7 +618,7 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
 
       val curr = project(cases(i).pat)
 
-      if (subspace(curr, prevs)) {
+      if (isSubspace(curr, prevs)) {
         ctx.warning("unreachable code", cases(i).body.pos)
       }
     }
diff --git a/tests/patmat/NonAbstractSealed.check b/tests/patmat/NonAbstractSealed.check
new file mode 100644
index 000000000000..9224ee370ce0
--- /dev/null
+++ b/tests/patmat/NonAbstractSealed.check
@@ -0,0 +1,5 @@
+./tests/patmat/NonAbstractSealed.scala:6: warning: match may not be exhaustive.
+It would fail on the following input: _: A
+  (null: A) match {
+            ^
+one warning found
\ No newline at end of file
diff --git a/tests/patmat/NonAbstractSealed.scala b/tests/patmat/NonAbstractSealed.scala
new file mode 100644
index 000000000000..ff2e90aeeb05
--- /dev/null
+++ b/tests/patmat/NonAbstractSealed.scala
@@ -0,0 +1,10 @@
+sealed class A
+class B extends A
+class C extends A
+
+object Test {
+  (null: A) match {
+    case t: B =>
+    case t: C =>
+  }
+}
diff --git a/tests/patmat/TwoTrait.scala b/tests/patmat/TwoTrait.scala
new file mode 100644
index 000000000000..b8e3402c5e8c
--- /dev/null
+++ b/tests/patmat/TwoTrait.scala
@@ -0,0 +1,12 @@
+object Test {
+  sealed trait A
+  sealed trait B
+
+  abstract sealed class Parent
+  class Foo extends Parent with A with B
+  class Bar extends Parent with B with A
+
+  (null: A) match {
+    case _: B =>
+  }
+}
diff --git a/tests/patmat/patmatexhaust.check b/tests/patmat/patmatexhaust.check
index 5121b73638a8..ef2b578d6e3b 100644
--- a/tests/patmat/patmatexhaust.check
+++ b/tests/patmat/patmatexhaust.check
@@ -23,7 +23,7 @@ It would fail on the following input: _: C1
     def ma10(x: C) = x match { // not exhaustive: C1 is not sealed.
                        ^
 ./tests/patmat/patmatexhaust.scala:114: warning: match may not be exhaustive.
-It would fail on the following input: _: C1
+It would fail on the following input: D2(), D1
     def ma10(x: C) = x match {  // not exhaustive: C1 has subclasses.
                        ^
 ./tests/patmat/patmatexhaust.scala:126: warning: match may not be exhaustive.
diff --git a/tests/patmat/t9677.check b/tests/patmat/t9677.check
new file mode 100644
index 000000000000..f1e1817cbbaa
--- /dev/null
+++ b/tests/patmat/t9677.check
@@ -0,0 +1,4 @@
+./tests/patmat/t9677.scala:20: warning: unreachable code
+      case path: A => println("Not root")
+                   ^
+one warning found
\ No newline at end of file