Fix #657: Add scala.Dynamic support.

6 files changed, 109 insertions, 7 deletions

diff --git a/src/dotty/tools/dotc/core/Types.scala b/src/dotty/tools/dotc/core/Types.scala
index f514a329e..8a4bf727b 100644
--- a/src/dotty/tools/dotc/core/Types.scala
+++ b/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) =
diff --git a/src/dotty/tools/dotc/typer/Applications.scala b/src/dotty/tools/dotc/typer/Applications.scala
index a9184c7e5..bab85f2a4 100644
--- a/src/dotty/tools/dotc/typer/Applications.scala
+++ b/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 =>
diff --git a/src/dotty/tools/dotc/typer/Dynamic.scala b/src/dotty/tools/dotc/typer/Dynamic.scala
new file mode 100644
index 000000000..aeb3cca8c
--- /dev/null
+++ b/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)))
+}
diff --git a/src/dotty/tools/dotc/typer/ProtoTypes.scala b/src/dotty/tools/dotc/typer/ProtoTypes.scala
index 740258821..622e3b9d8 100644
--- a/src/dotty/tools/dotc/typer/ProtoTypes.scala
+++ b/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)
   }
diff --git a/src/dotty/tools/dotc/typer/TypeAssigner.scala b/src/dotty/tools/dotc/typer/TypeAssigner.scala
index 995fa43ca..5e65df75e 100644
--- a/src/dotty/tools/dotc/typer/TypeAssigner.scala
+++ b/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
     }
diff --git a/src/dotty/tools/dotc/typer/Typer.scala b/src/dotty/tools/dotc/typer/Typer.scala
index 268020ec5..019c460e8 100644
--- a/src/dotty/tools/dotc/typer/Typer.scala
+++ b/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
             }
@@ -1665,7 +1678,7 @@ 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 {