Give to @odersky.

compiler/src/dotty/tools/backend/jvm/LabelDefs.scala

@@ -75,8 +75,11 @@ import StdNames.nme
  * Unreachable jumps will be eliminated by local dead code analysis.
  * After JVM is smart enough to remove next-line jumps
  *
- * Note that Label DefDefs can be only nested in Block, otherwise no one would
- * be able to call them Other DefDefs are eliminated
+ * Note that his phase Ychecking this phase required softening scoping rules
+ * as it intentionally allowed to break scoping rules inside methods for labels.
+ * This is modified by setting `labelsReordered` flag in Phases.
+ *
+ * @author Dmitry Petrashko
  */
 class LabelDefs extends MiniPhaseTransform {
   def phaseName: String = "labelDef"
@@ -90,76 +93,24 @@ class LabelDefs extends MiniPhaseTransform {
     else {
       collectLabelDefs.clear
       val newRhs = collectLabelDefs.transform(tree.rhs)
-      val labelCalls = collectLabelDefs.labelCalls
-      var entryPoints = collectLabelDefs.parentLabelCalls
       var labelDefs = collectLabelDefs.labelDefs
-      var callCounts = collectLabelDefs.callCounts
-
-      // make sure that for every label there's a single location it should return and single entry point
-      // if theres already a location that it returns to that's a failure
-      val disallowed = new mutable.HashMap[Symbol, Tree]()
-      queue.sizeHint(labelCalls.size + entryPoints.size)
 
       def putLabelDefsNearCallees = new TreeMap() {
 
         override def transform(tree: tpd.Tree)(implicit ctx: Context): tpd.Tree = {
           tree match {
-            case t: Apply if (entryPoints.contains(t)) =>
-              entryPoints = entryPoints - t
-              labelLevel = labelLevel + 1
-              val r = Block(moveLabels(t), t)
-              labelLevel = labelLevel - 1
-              if (labelLevel == 0) beingAppended.clear()
-              r
-            case _ => if (entryPoints.nonEmpty && labelDefs.nonEmpty) super.transform(tree) else tree
-          }
+            case t: Apply if labelDefs.contains(t.symbol) =>
+              val labelDef = labelDefs(t.symbol)
+              labelDefs -= t.symbol
 
-        }
-      }
+              val labelDef2 = transform(labelDef)
+              Block(labelDef2:: Nil, t)
 
-      def moveLabels(entryPoint: Apply): List[Tree] = {
-        val entrySym = entryPoint.symbol
-        if ((entrySym is Flags.Label) && labelDefs.contains(entrySym)) {
-          val visitedNow = new mutable.HashMap[Symbol, Tree]()
-          val treesToAppend = new ArrayBuffer[Tree]() // order matters. parents should go first
-          treesToAppend += labelDefs(entrySym)
-          queue.clear()
-
-          var visited = 0
-          queue += entryPoint
-          while (visited < queue.size) {
-            val owningLabelDefSym = queue(visited).symbol
-            for (call <- labelCalls(owningLabelDefSym)) {
-              val callSym = call.symbol
-              if (!beingAppended.contains(callSym)) {
-                if (disallowed.contains(callSym)) {
-                  val oldCall = disallowed(callSym)
-                  ctx.error(s"Multiple return locations for Label $oldCall and $call", callSym.pos)
-                } else {
-                  if ((!visitedNow.contains(callSym)) && labelDefs.contains(callSym)) {
-                    val defTree = labelDefs(callSym)
-                    visitedNow.put(callSym, defTree)
-                    val callCount = callCounts(callSym)
-                    if (callCount > 1) {
-                      if (!treesToAppend.contains(defTree)) {
-                        treesToAppend += defTree
-                        queue += call
-
-                      }
-                    } else if (entryPoint.symbol ne callSym) entryPoints += call
-                  }
-                }
-              }
-            }
-
-            visited += 1
+            case _ => if (labelDefs.nonEmpty) super.transform(tree) else tree
           }
-          beingAppended ++= treesToAppend.map(_.symbol)
-          treesToAppend.toList.map(putLabelDefsNearCallees.transform)
-        } else Nil
+        }
       }
 
-
       val res = cpy.DefDef(tree)(rhs = putLabelDefsNearCallees.transform(newRhs))
 
       res
@@ -168,22 +119,11 @@ class LabelDefs extends MiniPhaseTransform {
 
   object collectLabelDefs extends TreeMap() {
 
-    // label calls from this DefDef
-    var parentLabelCalls: mutable.Set[Tree] = new mutable.HashSet[Tree]()
-    var callCounts: mutable.Map[Symbol, Int] = new mutable.HashMap[Symbol, Int]().withDefaultValue(0)
-
-    def shouldMoveLabel = true
-
     // labelSymbol -> Defining tree
     val labelDefs = new mutable.HashMap[Symbol, Tree]()
-    // owner -> all calls by this owner
-    val labelCalls = new mutable.HashMap[Symbol, mutable.Set[Tree]]()
-    var owner: Symbol = null
 
     def clear = {
-      parentLabelCalls.clear()
       labelDefs.clear()
-      labelCalls.clear()
     }
 
     override def transform(tree: tpd.Tree)(implicit ctx: Context): tpd.Tree = tree match {
@@ -196,30 +136,14 @@ class LabelDefs extends MiniPhaseTransform {
         }
       case t: DefDef =>
         assert(t.symbol is Flags.Label)
-
-        val st = parentLabelCalls
-        parentLabelCalls = new mutable.HashSet[Tree]()
-        val symt = owner
-        owner = t.symbol
-
         val r = super.transform(tree)
-
-        owner = symt
-        labelCalls(r.symbol) = parentLabelCalls
-        parentLabelCalls = st
-
-        if (shouldMoveLabel) {
-          labelDefs(r.symbol) = r
-          EmptyTree
-        } else r
+        labelDefs(r.symbol) = r
+        EmptyTree
       case t: Apply if t.symbol is Flags.Label =>
         val sym = t.symbol
-        parentLabelCalls = parentLabelCalls + t
-        if (owner != sym) callCounts(sym) = callCounts(sym) + 1
         super.transform(tree)
       case _ =>
         super.transform(tree)
-
     }
   }
 }

compiler/src/dotty/tools/dotc/Compiler.scala

@@ -17,6 +17,7 @@ import core.DenotTransformers.DenotTransformer
 import core.Denotations.SingleDenotation
 
 import dotty.tools.backend.jvm.{LabelDefs, GenBCode, CollectSuperCalls}
+import dotty.tools.dotc.transform.linker.Simplify
 
 /** The central class of the dotc compiler. The job of a compiler is to create
  *  runs, which process given `phases` in a given `rootContext`.
@@ -74,6 +75,7 @@ class Compiler {
            new ElimByName,          // Expand by-name parameter references
            new AugmentScala2Traits, // Expand traits defined in Scala 2.11 to simulate old-style rewritings
            new ResolveSuper,        // Implement super accessors and add forwarders to trait methods
+           new Simplify,            // Perform local optimizations, simplified versions of what linker does.
            new PrimitiveForwarders, // Add forwarders to trait methods that have a mismatch between generic and primitives
            new ArrayConstructors),  // Intercept creation of (non-generic) arrays and intrinsify.
       List(new Erasure),            // Rewrite types to JVM model, erasing all type parameters, abstract types and refinements.
@@ -86,9 +88,10 @@ class Compiler {
            new NonLocalReturns,     // Expand non-local returns
            new CapturedVars,        // Represent vars captured by closures as heap objects
            new Constructors,        // Collect initialization code in primary constructors
-                                       // Note: constructors changes decls in transformTemplate, no InfoTransformers should be added after it
+                                    // Note: constructors changes decls in transformTemplate, no InfoTransformers should be added after it
            new FunctionalInterfaces, // Rewrites closures to implement @specialized types of Functions.
-           new GetClass),           // Rewrites getClass calls on primitive types.
+           new GetClass,            // Rewrites getClass calls on primitive types.
+           new Simplify),           // Perform local optimizations, simplified versions of what linker does.
       List(new LambdaLift,          // Lifts out nested functions to class scope, storing free variables in environments
                                        // Note: in this mini-phase block scopes are incorrect. No phases that rely on scopes should be here
            new ElimStaticThis,      // Replace `this` references to static objects by global identifiers

compiler/src/dotty/tools/dotc/ast/tpd.scala

@@ -472,15 +472,27 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
       }
     }
 
-    override def Apply(tree: Tree)(fun: Tree, args: List[Tree])(implicit ctx: Context): Apply =
-      ta.assignType(untpd.cpy.Apply(tree)(fun, args), fun, args)
-      // Note: Reassigning the original type if `fun` and `args` have the same types as before
+    override def Apply(tree: Tree)(fun: Tree, args: List[Tree])(implicit ctx: Context): Apply = {
+      val untyped = untpd.cpy.Apply(tree)(fun, args)
+      if (untyped.ne(tree))
+        ta.assignType(untyped, fun, args)
+      else
+        tree.asInstanceOf[Apply]
+    }
+
+    // Note: Reassigning the original type if `fun` and `args` have the same types as before
       // does not work here: The computed type depends on the widened function type, not
       // the function type itself. A treetransform may keep the function type the
       // same but its widened type might change.
 
-    override def TypeApply(tree: Tree)(fun: Tree, args: List[Tree])(implicit ctx: Context): TypeApply =
-      ta.assignType(untpd.cpy.TypeApply(tree)(fun, args), fun, args)
+    override def TypeApply(tree: Tree)(fun: Tree, args: List[Tree])(implicit ctx: Context): TypeApply = {
+      val untyped = untpd.cpy.TypeApply(tree)(fun, args)
+      if (untyped.ne(tree))
+        ta.assignType(untyped, fun, args)
+      else
+        tree.asInstanceOf[TypeApply]
+
+    }
       // Same remark as for Apply
 
     override def Literal(tree: Tree)(const: Constant)(implicit ctx: Context): Literal =
@@ -514,8 +526,14 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
       }
     }
 
-    override def Closure(tree: Tree)(env: List[Tree], meth: Tree, tpt: Tree)(implicit ctx: Context): Closure =
-      ta.assignType(untpd.cpy.Closure(tree)(env, meth, tpt), meth, tpt)
+    override def Closure(tree: Tree)(env: List[Tree], meth: Tree, tpt: Tree)(implicit ctx: Context): Closure = {
+      val untyped = untpd.cpy.Closure(tree)(env, meth, tpt)
+      val typed = ta.assignType(untyped, meth, tpt)
+      if (untyped.ne(tree))
+        typed
+      else
+        tree.asInstanceOf[Closure]
+    }
       // Same remark as for Apply
 
     override def Match(tree: Tree)(selector: Tree, cases: List[CaseDef])(implicit ctx: Context): Match = {

compiler/src/dotty/tools/dotc/config/Printers.scala

@@ -32,4 +32,5 @@ object Printers {
   val pickling: Printer = noPrinter
   val inlining: Printer = noPrinter
   val exhaustivity: Printer = noPrinter
+  val simplify: Printer = noPrinter
 }

compiler/src/dotty/tools/dotc/core/Definitions.scala

@@ -392,6 +392,16 @@ class Definitions {
     def Boolean_&& = Boolean_andR.symbol
     lazy val Boolean_orR  = BooleanClass.requiredMethodRef(nme.ZOR)
     def Boolean_|| = Boolean_orR.symbol
+    lazy val Boolean_eqeqR = BooleanClass.info.member(nme.EQ).suchThat(_.info.firstParamTypes match {
+      case List(pt) => (pt isRef BooleanClass)
+      case _ => false
+    })
+    def Boolean_== = Boolean_eqeqR.symbol
+    lazy val Boolean_neqeqR = BooleanClass.info.member(nme.NE).suchThat(_.info.firstParamTypes match {
+      case List(pt) => (pt isRef BooleanClass)
+      case _ => false
+    })
+    def Boolean_!= = Boolean_neqeqR.symbol
 
   lazy val ByteType: TypeRef = valueTypeRef("scala.Byte", BoxedByteType, java.lang.Byte.TYPE, ByteEnc)
   def ByteClass(implicit ctx: Context) = ByteType.symbol.asClass
@@ -423,6 +433,13 @@ class Definitions {
     lazy val Long_LSR_Int = LongType.member(nme.LSR).requiredSymbol(
       x => (x is Method) && (x.info.firstParamTypes.head isRef defn.IntClass)
     )
+    lazy val Long_plusR   = LongClass.requiredMethodRef(nme.PLUS, List(LongType))
+    def Long_+ = Long_plusR.symbol
+    lazy val Long_mulR   = LongClass.requiredMethodRef(nme.MUL, List(LongType))
+    def Long_* = Long_mulR.symbol
+    lazy val Long_divR   = LongClass.requiredMethodRef(nme.DIV, List(LongType))
+    def Long_/ = Long_divR.symbol
+
   lazy val FloatType: TypeRef = valueTypeRef("scala.Float", BoxedFloatType, java.lang.Float.TYPE, FloatEnc)
   def FloatClass(implicit ctx: Context) = FloatType.symbol.asClass
   lazy val DoubleType: TypeRef = valueTypeRef("scala.Double", BoxedDoubleType, java.lang.Double.TYPE, DoubleEnc)
@@ -483,6 +500,11 @@ class Definitions {
   lazy val BoxedNumberClass          = ctx.requiredClass("java.lang.Number")
   lazy val ThrowableClass            = ctx.requiredClass("java.lang.Throwable")
   lazy val ClassCastExceptionClass   = ctx.requiredClass("java.lang.ClassCastException")
+  lazy val ArithmeticExceptionClass  = ctx.requiredClass("java.lang.ArithmeticException")
+    lazy val ArithmeticExceptionClass_stringConstructor  = ArithmeticExceptionClass.info.member(nme.CONSTRUCTOR).suchThat(_.info.firstParamTypes match {
+      case List(pt) => (pt isRef StringClass)
+      case _ => false
+    }).symbol.asTerm
   lazy val JavaSerializableClass     = ctx.requiredClass("java.io.Serializable")
   lazy val ComparableClass           = ctx.requiredClass("java.lang.Comparable")
 
@@ -514,6 +536,10 @@ class Definitions {
   def DynamicClass(implicit ctx: Context) = DynamicType.symbol.asClass
   lazy val OptionType: TypeRef                  = ctx.requiredClassRef("scala.Option")
   def OptionClass(implicit ctx: Context) = OptionType.symbol.asClass
+  lazy val SomeType: TypeRef                  = ctx.requiredClassRef("scala.Some")
+  def SomeClass(implicit ctx: Context) = SomeType.symbol.asClass
+  lazy val NoneModuleRef: TermRef                  = ctx.requiredModuleRef("scala.None")
+  def NoneClass(implicit ctx: Context) = NoneModuleRef.symbol.moduleClass.asClass
   lazy val EnumType: TypeRef                    = ctx.requiredClassRef("scala.Enum")
   def EnumClass(implicit ctx: Context) = EnumType.symbol.asClass
   lazy val EnumValuesType: TypeRef              = ctx.requiredClassRef("scala.runtime.EnumValues")

compiler/src/dotty/tools/dotc/core/NameKinds.scala

@@ -308,6 +308,9 @@ object NameKinds {
   val PatMatCaseName          = new UniqueNameKind("case")
   val PatMatMatchFailName     = new UniqueNameKind("matchFail")
   val PatMatSelectorName      = new UniqueNameKind("selector")
+  val LocalOptFact            = new UniqueNameKind("fact")
+  val LocalOptSelector        = new UniqueNameKind("selector")
+  val LocalOptFallback        = new UniqueNameKind("fallback")
 
   /** The kind of names of default argument getters */
   val DefaultGetterName = new NumberedNameKind(DEFAULTGETTER, "DefaultGetter") {
@@ -384,4 +387,4 @@ object NameKinds {
   def qualifiedNameKindOfTag   : collection.Map[Int, QualifiedNameKind]  = qualifiedNameKinds
   def numberedNameKindOfTag    : collection.Map[Int, NumberedNameKind]   = numberedNameKinds
   def uniqueNameKindOfSeparator: collection.Map[String, UniqueNameKind]  = uniqueNameKinds
-}
+}

compiler/src/dotty/tools/dotc/core/Scopes.scala

@@ -85,8 +85,10 @@ object Scopes {
     /** Is the scope empty? */
     def isEmpty: Boolean = lastEntry eq null
 
-    def foreach[U](p: Symbol => U)(implicit ctx: Context): Unit = toList foreach p
+    /** Applies a function f to all Symbols of this Scope. */
+    def foreach[U](f: Symbol => U)(implicit ctx: Context): Unit = toList.foreach(f)
 
+    /** Selects all Symbols of this Scope which satisfy a predicate. */
     def filter(p: Symbol => Boolean)(implicit ctx: Context): List[Symbol] = {
       ensureComplete()
       var syms: List[Symbol] = Nil
@@ -99,6 +101,10 @@ object Scopes {
       syms
     }
 
+    /** Tests whether a predicate holds for at least one Symbol of this Scope. */
+    def exists(p: Symbol => Boolean)(implicit ctx: Context): Boolean = filter(p).isEmpty
+
+    /** Finds the first Symbol of this Scope satisfying a predicate, if any. */
     def find(p: Symbol => Boolean)(implicit ctx: Context): Symbol = filter(p) match {
       case sym :: _ => sym
       case _ => NoSymbol

compiler/src/dotty/tools/dotc/core/StdNames.scala

@@ -434,6 +434,7 @@ object StdNames {
     val isArray: N              = "isArray"
     val isDefinedAt: N          = "isDefinedAt"
     val isDefinedAtImpl: N      = "$isDefinedAt"
+    val isDefined: N            = "isDefined"
     val isEmpty: N              = "isEmpty"
     val isInstanceOf_ : N       = "isInstanceOf"
     val java: N                 = "java"

compiler/src/dotty/tools/dotc/core/TypeComparer.scala

@@ -624,7 +624,7 @@ class TypeComparer(initctx: Context) extends DotClass with ConstraintHandling {
    */
   def compareHkApply2(tp1: Type, tp2: HKApply, tycon2: Type, args2: List[Type]): Boolean = {
     val tparams = tycon2.typeParams
-    if (tparams.isEmpty) return false // can happen for ill-typed programs, e.g. neg/tcpoly_overloaded.scala
+    if (tparams.isEmpty) return tp1.isRef(NothingClass) // can happen for ill-typed programs, e.g. neg/tcpoly_overloaded.scala
 
     /** True if `tp1` and `tp2` have compatible type constructors and their
      *  corresponding arguments are subtypes relative to their variance (see `isSubArgs`).

compiler/src/dotty/tools/dotc/core/TypeErasure.scala

@@ -440,7 +440,7 @@ class TypeErasure(isJava: Boolean, semiEraseVCs: Boolean, isConstructor: Boolean
         // but potentially re-introduced by ResolveSuper, when we add
         // forwarders to mixin methods.
         // See doc comment for ElimByName for speculation how we could improve this.
-      else MethodType(Nil, Nil, eraseResult(rt))
+      else MethodType(Nil, Nil, eraseResult(sym.info.finalResultType))
     case tp: PolyType =>
       eraseResult(tp.resultType) match {
         case rt: MethodType => rt

compiler/src/dotty/tools/dotc/core/Types.scala

@@ -3080,7 +3080,7 @@ object Types {
       myRepr
     }
 
-    override def toString = s"Skolem($hashCode)"
+    override def toString = s"Skolem()"
   }
 
   // ------------ Type variables ----------------------------------------

compiler/src/dotty/tools/dotc/core/classfile/ClassfileParser.scala

@@ -174,7 +174,7 @@ class ClassfileParser(
       if (method) Flags.Method | methodTranslation.flags(jflags)
       else fieldTranslation.flags(jflags)
     val name = pool.getName(in.nextChar)
-    if (!(sflags is Flags.Private) || name == nme.CONSTRUCTOR || ctx.settings.optimise.value) {
+    if (!(sflags is Flags.Private) || name == nme.CONSTRUCTOR) {
       val member = ctx.newSymbol(
         getOwner(jflags), name, sflags, memberCompleter, coord = start)
       getScope(jflags).enter(member)

compiler/src/dotty/tools/dotc/printing/PlainPrinter.scala

@@ -53,7 +53,9 @@ class PlainPrinter(_ctx: Context) extends Printer {
         case AndType(tp1, tp2) =>
           homogenize(tp1) & homogenize(tp2)
         case OrType(tp1, tp2) =>
-          homogenize(tp1) | homogenize(tp2)
+          if (tp1.classSymbol.id > tp2.classSymbol.id)
+            homogenize(tp1) | homogenize(tp2)
+          else homogenize(tp2) | homogenize(tp1)
         case tp: SkolemType =>
           homogenize(tp.info)
         case tp: LazyRef =>

compiler/src/dotty/tools/dotc/printing/RefinedPrinter.scala

@@ -124,7 +124,10 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
             toTextTuple(args.init)
         ("implicit " provided isImplicit) ~ argStr ~ " => " ~ argText(args.last)
       }
-    homogenize(tp) match {
+    val htp = homogenize(tp)
+    htp match {
+      case x: ConstantType if homogenizedView =>
+        return toText(x.widen)
       case AppliedType(tycon, args) =>
         val cls = tycon.typeSymbol
         if (tycon.isRepeatedParam) return toTextLocal(args.head) ~ "*"