Support named type parameters

Changes needed to support simple named type parameters.
Not yet implemented: named arguments.

1 files changed, 7 insertions, 1 deletions

diff --git a/src/dotty/tools/dotc/core/Types.scala b/src/dotty/tools/dotc/core/Types.scala
index 8595da640..27828c588 100644
--- a/src/dotty/tools/dotc/core/Types.scala
+++ b/src/dotty/tools/dotc/core/Types.scala
@@ -485,7 +485,13 @@ object Types {
       }
       def goThis(tp: ThisType) = {
         val d = go(tp.underlying)
-        if (d.exists) d
+        if (d.exists)
+          if ((pre eq tp) && d.symbol.is(NamedTypeParam) && (d.symbol.owner eq tp.cls))
+            // If we look for a named type parameter `P` in `C.this.P`, looking up
+            // the fully applied self type of `C` will give as an info the alias type
+            // `P = this.P`. We need to return a denotation with the underlying bounds instead.
+            d.symbol.denot
+          else d
         else
           // There is a special case to handle:
           //   trait Super { this: Sub => private class Inner {} println(this.Inner) }