New phase: ExplicitSelf

Makes self types explicit, if this is needed to identify
a member in a select. Fixes #789.

5 files changed, 63 insertions, 1 deletions

diff --git a/src/dotty/tools/dotc/Compiler.scala b/src/dotty/tools/dotc/Compiler.scala
index c537d8885..a36743b59 100644
--- a/src/dotty/tools/dotc/Compiler.scala
+++ b/src/dotty/tools/dotc/Compiler.scala
@@ -52,6 +52,7 @@ class Compiler {
            new ClassOf),
       List(new PatternMatcher,
            new ExplicitOuter,
+           new ExplicitSelf,
            new Splitter),
       List(new VCInlineMethods,
            new SeqLiterals,
diff --git a/src/dotty/tools/dotc/core/Types.scala b/src/dotty/tools/dotc/core/Types.scala
index d04da30c0..358720836 100644
--- a/src/dotty/tools/dotc/core/Types.scala
+++ b/src/dotty/tools/dotc/core/Types.scala
@@ -2530,7 +2530,7 @@ object Types {
     def selfType(implicit ctx: Context): Type = {
       if (selfTypeCache == null)
         selfTypeCache = {
-          def fullRef = fullyAppliedRef(cls.typeRef, cls.typeParams)
+          def fullRef = fullyAppliedRef
           val given = givenSelfType
           val raw =
             if (!given.exists) fullRef
@@ -2561,6 +2561,9 @@ object Types {
         base
     }
 
+    /** The class type with all type parameters */
+    def fullyAppliedRef(implicit ctx: Context): Type = fullyAppliedRef(cls.typeRef, cls.typeParams)
+
     def rebase(tp: Type)(implicit ctx: Context): Type =
       if ((prefix eq cls.owner.thisType) || !cls.owner.isClass || ctx.erasedTypes) tp
       else tp.substThis(cls.owner.asClass, prefix)
diff --git a/src/dotty/tools/dotc/transform/ExplicitSelf.scala b/src/dotty/tools/dotc/transform/ExplicitSelf.scala
new file mode 100644
index 000000000..c6a218157
--- /dev/null
+++ b/src/dotty/tools/dotc/transform/ExplicitSelf.scala
@@ -0,0 +1,37 @@
+package dotty.tools.dotc
+package transform
+
+import core._
+import Contexts.Context
+import Types._
+import TreeTransforms._
+import Decorators._
+import ast.Trees._
+import Flags._
+
+/** Transform references of the form
+ *
+ *     C.this.m
+ *
+ *  where `C` is a class with explicit self type and `C` is not a
+ *  subclass of the owner of `m` to
+ *
+ *     C.this.asInstanceOf[S].m
+ *
+ *  where `S` is the self type of `C`.
+ */
+class ExplicitSelf extends MiniPhaseTransform { thisTransform =>
+  import ast.tpd._
+
+  override def phaseName = "explicitSelf"
+
+  override def transformSelect(tree: Select)(implicit ctx: Context, info: TransformerInfo): Tree = tree match {
+    case Select(thiz: This, name) if name.isTermName =>
+      val cls = thiz.symbol.asClass
+      val cinfo = cls.classInfo
+      if (cinfo.givenSelfType.exists && !cls.derivesFrom(tree.symbol.owner))
+        cpy.Select(tree)(thiz.asInstance(cinfo.selfType), name)
+      else tree
+    case _ => tree
+  }
+}
diff --git a/tests/run/i789.check b/tests/run/i789.check
new file mode 100644
index 000000000..d41f69423
--- /dev/null
+++ b/tests/run/i789.check
@@ -0,0 +1 @@
+atPhase: 2
diff --git a/tests/run/i789.scala b/tests/run/i789.scala
new file mode 100644
index 000000000..99b081f0a
--- /dev/null
+++ b/tests/run/i789.scala
@@ -0,0 +1,20 @@
+    trait Periods { self: Context =>
+
+      def atPhase(id: Int): Unit = println(s"atPhase: $id")
+
+    }
+
+    class Phase(val id: Int)
+
+    trait Phases { self: Context =>
+      def atPhase(phase: Phase): Unit = self.atPhase(phase.id)
+    }
+
+    trait Context extends Phases with Periods
+
+    object Test extends Context {
+
+      def main(args: Array[String]) = atPhase(new Phase(2))
+
+    }
+