Add scala.Dynamic support.

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

@@ -424,8 +424,10 @@ class Definitions {
     def Product_productArity(implicit ctx: Context) = Product_productArityR.symbol
     lazy val Product_productPrefixR = ProductClass.requiredMethodRef(nme.productPrefix)
     def Product_productPrefix(implicit ctx: Context) = Product_productPrefixR.symbol
-  lazy val LanguageModuleRef          = ctx.requiredModule("dotty.language")
+  lazy val LanguageModuleRef = ctx.requiredModule("dotty.language")
   def LanguageModuleClass(implicit ctx: Context) = LanguageModuleRef.symbol.moduleClass.asClass
+  lazy val Scala2LanguageModuleRef = ctx.requiredModule("scala.language")
+  def Scala2LanguageModuleClass(implicit ctx: Context) = Scala2LanguageModuleRef.symbol.moduleClass.asClass
   lazy val NonLocalReturnControlType: TypeRef   = ctx.requiredClassRef("scala.runtime.NonLocalReturnControl")
 
   lazy val ClassTagType = ctx.requiredClassRef("scala.reflect.ClassTag")

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

@@ -383,6 +383,7 @@ object StdNames {
     val delayedInit: N          = "delayedInit"
     val delayedInitArg: N       = "delayedInit$body"
     val drop: N                 = "drop"
+    val dynamics: N             = "dynamics"
     val dummyApply: N           = "<dummy-apply>"
     val elem: N                 = "elem"
     val emptyValDef: N          = "emptyValDef"

src/dotty/tools/dotc/core/TypeOps.scala

@@ -455,17 +455,19 @@ trait TypeOps { this: Context => // TODO: Make standalone object.
    */
   def featureEnabled(owner: ClassSymbol, feature: TermName): Boolean = {
     def toPrefix(sym: Symbol): String =
-      if (sym eq defn.LanguageModuleClass) "" else toPrefix(sym.owner) + sym.name + "."
+      if (!sym.exists || (sym eq defn.LanguageModuleClass) || (sym eq defn.Scala2LanguageModuleRef)) ""
+      else toPrefix(sym.owner) + sym.name + "."
     def featureName = toPrefix(owner) + feature
-    def hasImport(implicit ctx: Context): Boolean = (
-         ctx.importInfo != null
-      && (   (ctx.importInfo.site.widen.typeSymbol eq owner)
-          && ctx.importInfo.originals.contains(feature)
-          ||
-          { var c = ctx.outer
-            while (c.importInfo eq ctx.importInfo) c = c.outer
-            hasImport(c)
-          }))
+    def hasImport(implicit ctx: Context): Boolean = {
+      if (ctx.importInfo == null || (ctx.importInfo.site.widen.typeSymbol ne owner)) false
+      else if (ctx.importInfo.excluded.contains(feature)) false
+      else if (ctx.importInfo.originals.contains(feature)) true
+      else {
+        var c = ctx.outer
+        while (c.importInfo eq ctx.importInfo) c = c.outer
+        hasImport(c)
+      }
+    }
     def hasOption = ctx.base.settings.language.value exists (s => s == featureName || s == "_")
     hasImport(ctx.withPhase(ctx.typerPhase)) || hasOption
   }
@@ -477,6 +479,9 @@ trait TypeOps { this: Context => // TODO: Make standalone object.
   def scala2Mode =
     featureEnabled(defn.LanguageModuleClass, nme.Scala2)
 
+  def dynamicsEnabled =
+    featureEnabled(defn.Scala2LanguageModuleClass, nme.dynamics)
+
   def testScala2Mode(msg: String, pos: Position) = {
     if (scala2Mode) migrationWarning(msg, pos)
     scala2Mode

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

@@ -3021,6 +3021,9 @@ object Types {
 
   object ErrorType extends ErrorType
 
+  /* Type used to track Select nodes that could not resolve a member and their qualifier is a scala.Dynamic. */
+  object TryDynamicCallType extends ErrorType
+
   /** Wildcard type, possibly with bounds */
   abstract case class WildcardType(optBounds: Type) extends CachedGroundType with TermType {
     def derivedWildcardType(optBounds: Type)(implicit ctx: Context) =

src/dotty/tools/dotc/reporting/Reporter.scala

@@ -12,6 +12,7 @@ import config.Printers
 import java.lang.System.currentTimeMillis
 import core.Mode
 import interfaces.Diagnostic.{ERROR, WARNING, INFO}
+import dotty.tools.dotc.core.Symbols.Symbol
 
 object Reporter {
   class Error(msgFn: => String, pos: SourcePosition) extends Diagnostic(msgFn, pos, ERROR)
@@ -68,6 +69,29 @@ trait Reporting { this: Context =>
   def featureWarning(msg: => String, pos: SourcePosition = NoSourcePosition): Unit =
     reporter.report(new FeatureWarning(msg, pos))
 
+  def featureWarning(feature: String, featureDescription: String, isScala2Feature: Boolean,
+      featureUseSite: Symbol, required: Boolean, pos: SourcePosition): Unit = {
+    val req = if (required) "needs to" else "should"
+    val prefix = if (isScala2Feature) "scala." else "dotty."
+    val fqname = prefix + "language." + feature
+
+    val explain = {
+      if (reporter.isReportedFeatureUseSite(featureUseSite)) ""
+      else {
+        reporter.reportNewFeatureUseSite(featureUseSite)
+        s"""|
+            |This can be achieved by adding the import clause 'import $fqname'
+            |or by setting the compiler option -language:$feature.
+            |See the Scala docs for value $fqname for a discussion
+            |why the feature $req be explicitly enabled.""".stripMargin
+      }
+    }
+
+    val msg = s"$featureDescription $req be enabled\nby making the implicit value $fqname visible.$explain"
+    if (required) error(msg, pos)
+    else reporter.report(new FeatureWarning(msg, pos))
+  }
+
   def warning(msg: => String, pos: SourcePosition = NoSourcePosition): Unit =
     reporter.report(new Warning(msg, pos))
 
@@ -172,7 +196,7 @@ abstract class Reporter extends interfaces.ReporterResult {
   /** Report a diagnostic */
   def doReport(d: Diagnostic)(implicit ctx: Context): Unit
 
- /** Whether very long lines can be truncated.  This exists so important
+  /** Whether very long lines can be truncated.  This exists so important
    *  debugging information (like printing the classpath) is not rendered
    *  invisible due to the max message length.
    */
@@ -206,6 +230,10 @@ abstract class Reporter extends interfaces.ReporterResult {
    */
   def errorsReported = hasErrors
 
+  private[this] var reportedFeaturesUseSites = Set[Symbol]()
+  def isReportedFeatureUseSite(featureTrait: Symbol): Boolean = reportedFeaturesUseSites.contains(featureTrait)
+  def reportNewFeatureUseSite(featureTrait: Symbol): Unit = reportedFeaturesUseSites += featureTrait
+
   val unreportedWarnings = new mutable.HashMap[String, Int] {
     override def default(key: String) = 0
   }

src/dotty/tools/dotc/typer/Applications.scala

@@ -86,11 +86,12 @@ object Applications {
 
 import Applications._
 
-trait Applications extends Compatibility { self: Typer =>
+trait Applications extends Compatibility { self: Typer with Dynamic =>
 
   import Applications._
   import tpd.{ cpy => _, _ }
   import untpd.cpy
+  import Dynamic.isDynamicMethod
 
   /** @tparam Arg       the type of arguments, could be tpd.Tree, untpd.Tree, or Type
    *  @param methRef    the reference to the method of the application
@@ -553,6 +554,13 @@ trait Applications extends Compatibility { self: Typer =>
 
       fun1.tpe match {
         case ErrorType => tree.withType(ErrorType)
+        case TryDynamicCallType =>
+          tree match {
+            case tree @ Apply(Select(qual, name), args) if !isDynamicMethod(name) =>
+              typedDynamicApply(qual, name, args, pt)(tree)
+            case _ =>
+              handleUnexpectedFunType(tree, fun1)
+          }
         case _ => methPart(fun1).tpe match {
           case funRef: TermRef =>
             tryEither { implicit ctx =>

src/dotty/tools/dotc/typer/Dynamic.scala

@@ -0,0 +1,71 @@
+package dotty.tools
+package dotc
+package typer
+
+import dotty.tools.dotc.ast.Trees.NamedArg
+import dotty.tools.dotc.ast.tpd._
+import dotty.tools.dotc.ast.untpd
+import dotty.tools.dotc.core.Constants.Constant
+import dotty.tools.dotc.core.Contexts.Context
+import dotty.tools.dotc.core.Names.Name
+import dotty.tools.dotc.core.StdNames._
+import dotty.tools.dotc.core.Types._
+import dotty.tools.dotc.core.Mode
+import dotty.tools.dotc.core.Decorators._
+
+object Dynamic {
+  def isDynamicMethod(name: Name): Boolean =
+    name == nme.applyDynamic || name == nme.selectDynamic || name == nme.updateDynamic || name == nme.applyDynamicNamed
+}
+
+/** Translates selection that does not typecheck according to the scala.Dynamic rules:
+ *    foo.bar(baz) = quux                   ~~> foo.selectDynamic(bar).update(baz, quux)
+ *    foo.bar = baz                         ~~> foo.updateDynamic("bar")(baz)
+ *    foo.bar(x = bazX, y = bazY, baz, ...) ~~> foo.applyDynamicNamed("bar")(("x", bazX), ("y", bazY), ("", baz), ...)
+ *    foo.bar(baz0, baz1, ...)              ~~> foo.applyDynamic(bar)(baz0, baz1, ...)
+ *    foo.bar                               ~~> foo.selectDynamic(bar)
+ *
+ *  The first matching rule of is applied.
+ */
+trait Dynamic { self: Typer with Applications =>
+
+  /** Translate selection that does not typecheck according to the normal rules into a applyDynamic/applyDynamicNamed.
+   *    foo.bar(baz0, baz1, ...)              ~~> foo.applyDynamic(bar)(baz0, baz1, ...)
+   *    foo.bar(x = bazX, y = bazY, baz, ...) ~~> foo.applyDynamicNamed("bar")(("x", bazX), ("y", bazY), ("", baz), ...)
+   */
+  def typedDynamicApply(qual: untpd.Tree, name: Name, args: List[untpd.Tree], pt: Type)(original: untpd.Apply)(
+      implicit ctx: Context): Tree = {
+    def isNamedArg(arg: untpd.Tree): Boolean = arg match { case NamedArg(_, _) => true; case _ => false }
+    val dynName = if (args.exists(isNamedArg)) nme.applyDynamicNamed else nme.applyDynamic
+    if (dynName == nme.applyDynamicNamed && untpd.isWildcardStarArgList(args)) {
+      ctx.error("applyDynamicNamed does not support passing a vararg parameter", original.pos)
+      original.withType(ErrorType)
+    } else {
+      def namedArgTuple(name: String, arg: untpd.Tree) = untpd.Tuple(List(Literal(Constant(name)), arg))
+      def namedArgs = args.map {
+        case NamedArg(argName, arg) => namedArgTuple(argName.toString, arg)
+        case arg => namedArgTuple("", arg)
+      }
+      val args1 = if (dynName == nme.applyDynamic) args else namedArgs
+      typedApply(untpd.Apply(coreDynamic(qual, dynName, name), args1), pt)
+    }
+  }
+
+  /** Translate selection that does not typecheck according to the normal rules into a selectDynamic.
+   *    foo.bar ~~> foo.selectDynamic(bar)
+   *
+   *  Note: inner part of translation foo.bar(baz) = quux ~~> foo.selectDynamic(bar).update(baz, quux) is achieved
+   *  through an existing transformation of in typedAssign [foo.bar(baz) = quux ~~> foo.bar.update(baz, quux)].
+   */
+  def typedDynamicSelect(tree: untpd.Select, pt: Type)(implicit ctx: Context): Tree =
+    typedApply(coreDynamic(tree.qualifier, nme.selectDynamic, tree.name), pt)
+
+  /** Translate selection that does not typecheck according to the normal rules into a updateDynamic.
+   *    foo.bar = baz ~~> foo.updateDynamic(bar)(baz)
+   */
+  def typedDynamicAssign(qual: untpd.Tree, name: Name, rhs: untpd.Tree, pt: Type)(implicit ctx: Context): Tree =
+    typedApply(untpd.Apply(coreDynamic(qual, nme.updateDynamic, name), rhs), pt)
+
+  private def coreDynamic(qual: untpd.Tree, dynName: Name, name: Name)(implicit ctx: Context): untpd.Apply =
+    untpd.Apply(untpd.Select(qual, dynName), Literal(Constant(name.toString)))
+}

src/dotty/tools/dotc/typer/ProtoTypes.scala

@@ -430,6 +430,8 @@ object ProtoTypes {
       (if (theMap != null) theMap else new WildApproxMap).mapOver(tp)
   }
 
+  @sharable object AssignProto extends UncachedGroundType with MatchAlways
+
   private[ProtoTypes] class WildApproxMap(implicit ctx: Context) extends TypeMap {
     def apply(tp: Type) = wildApprox(tp, this)
   }

src/dotty/tools/dotc/typer/TypeAssigner.scala

@@ -196,11 +196,16 @@ trait TypeAssigner {
   def selectionType(site: Type, name: Name, pos: Position)(implicit ctx: Context): Type = {
     val mbr = site.member(name)
     if (reallyExists(mbr)) site.select(name, mbr)
-    else {
+    else if (site.derivesFrom(defn.DynamicClass) && !Dynamic.isDynamicMethod(name)) {
+      TryDynamicCallType
+    } else {
       if (!site.isErroneous) {
         ctx.error(
           if (name == nme.CONSTRUCTOR) d"$site does not have a constructor"
-          else d"$name is not a member of $site", pos)
+          else if (site.derivesFrom(defn.DynamicClass)) {
+            d"$name is not a member of $site\n" +
+            "possible cause: maybe a wrong Dynamic method signature?"
+          } else d"$name is not a member of $site", pos)
       }
       ErrorType
     }

src/dotty/tools/dotc/typer/Typer.scala

@@ -58,11 +58,12 @@ object Typer {
       assert(tree.pos.exists, s"position not set for $tree # ${tree.uniqueId}")
 }
 
-class Typer extends Namer with TypeAssigner with Applications with Implicits with Checking {
+class Typer extends Namer with TypeAssigner with Applications with Implicits with Dynamic with Checking {
 
   import Typer._
   import tpd.{cpy => _, _}
   import untpd.cpy
+  import Dynamic.isDynamicMethod
 
   /** A temporary data item valid for a single typed ident:
    *  The set of all root import symbols that have been
@@ -316,7 +317,13 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
     def asSelect(implicit ctx: Context): Tree = {
       val qual1 = typedExpr(tree.qualifier, selectionProto(tree.name, pt, this))
       if (tree.name.isTypeName) checkStable(qual1.tpe, qual1.pos)
-      typedSelect(tree, pt, qual1)
+      val select = typedSelect(tree, pt, qual1)
+      pt match {
+        case _: FunProto | AssignProto => select
+        case _ =>
+          if (select.tpe eq TryDynamicCallType) typedDynamicSelect(tree, pt)
+          else select
+      }
    }
 
     def asJavaSelectFromTypeTree(implicit ctx: Context): Tree = {
@@ -480,7 +487,7 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
         val appliedUpdate = cpy.Apply(fn)(wrappedUpdate, (args map untpd.TypedSplice) :+ tree.rhs)
         typed(appliedUpdate, pt)
       case lhs =>
-        val lhsCore = typedUnadapted(lhs)
+        val lhsCore = typedUnadapted(lhs, AssignProto)
         def lhs1 = typed(untpd.TypedSplice(lhsCore))
         def canAssign(sym: Symbol) = // allow assignments from the primary constructor to class fields
           sym.is(Mutable, butNot = Accessor) ||
@@ -508,6 +515,12 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
                   case _ =>
                     reassignmentToVal
                 }
+              case TryDynamicCallType =>
+                tree match {
+                  case Assign(Select(qual, name), rhs) if !isDynamicMethod(name) =>
+                    typedDynamicAssign(qual, name, rhs, pt)
+                  case _ => reassignmentToVal
+                }
               case tpe =>
                 reassignmentToVal
             }
@@ -1079,7 +1092,13 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
       .withType(dummy.nonMemberTermRef)
     checkVariance(impl1)
     if (!cls.is(AbstractOrTrait) && !ctx.isAfterTyper) checkRealizableBounds(cls.typeRef, cdef.pos)
-    assignType(cpy.TypeDef(cdef)(name, impl1, Nil), cls)
+    val cdef1 = assignType(cpy.TypeDef(cdef)(name, impl1, Nil), cls)
+    if (ctx.phase.isTyper && cdef1.tpe.derivesFrom(defn.DynamicClass) && !ctx.dynamicsEnabled) {
+      val isRequired = parents1.exists(_.tpe.isRef(defn.DynamicClass))
+      ctx.featureWarning(nme.dynamics.toString, "extension of type scala.Dynamic", isScala2Feature = true,
+          cls, isRequired, cdef.pos)
+    }
+    cdef1
 
     // todo later: check that
     //  1. If class is non-abstract, it is instantiatable:
@@ -1665,7 +1684,7 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
     tree match {
       case _: MemberDef | _: PackageDef | _: Import | _: WithoutTypeOrPos[_] => tree
       case _ => tree.tpe.widen match {
-        case ErrorType =>
+        case _: ErrorType =>
           tree
         case ref: TermRef =>
           pt match {

tests/neg/dynamicApplyDynamicTest1.scala

@@ -0,0 +1,7 @@
+import scala.language.dynamics
+
+class Foo extends scala.Dynamic
+
+object DynamicTest {
+  new Foo().bazApply() // error
+}

tests/neg/dynamicApplyDynamicTest2.scala

@@ -0,0 +1,7 @@
+import scala.language.dynamics
+
+class Foo extends scala.Dynamic
+
+object DynamicTest {
+  new Foo().bazApply("abc", 1)  // error
+}

tests/neg/dynamicApplyDynamicTest3.scala

@@ -0,0 +1,7 @@
+import scala.language.dynamics
+
+class Foo extends scala.Dynamic
+
+object DynamicTest {
+  new Foo().bazApply _  // error // error
+}

tests/neg/dynamicApplyDynamicTest4.scala

@@ -0,0 +1,10 @@
+import scala.language.dynamics
+
+class Foo extends scala.Dynamic {
+  def selectDynamic(name: String): String = ???
+  def applyDynamicNamed(name: String)(args: Any*): String = ???
+}
+
+object DynamicTest {
+  new Foo().bazApply() // error
+}

tests/neg/dynamicApplyDynamicTest5.scala

@@ -0,0 +1,9 @@
+import scala.language.dynamics
+
+class Foo extends scala.Dynamic {
+  def applyDynamic(name: String)(args: String*): String = ???
+}
+
+object DynamicTest {
+  new Foo().bazApply(1, 2, 3) // error // error // error
+}

tests/neg/dynamicApplyDynamicTest6.scala

@@ -0,0 +1,9 @@
+import scala.language.dynamics
+
+class Foo extends scala.Dynamic {
+  def applyDynamic(name: String)(args: String*): String = ???
+}
+
+object DynamicTest {
+  def test: Int = new Foo().bazApply() // error
+}

tests/neg/dynamicApplyDynamicTest7.scala

@@ -0,0 +1,9 @@
+import scala.language.dynamics
+
+class Foo extends scala.Dynamic {
+  def applyDynamic(name: Int)(args: String*): String = ???
+}
+
+object DynamicTest {
+  def test: String = new Foo().bazApply() // error
+}