Homogenize #Apply projections.

Simplify fully applied #Apply projections before comparing trees.
Such projections are now (correctly) simplified on unpickling
but persist in the original tree before pickling.

The discrepancy was uncovered by the last commit.

2 files changed, 14 insertions, 1 deletions

diff --git a/src/dotty/tools/dotc/core/TypeApplications.scala b/src/dotty/tools/dotc/core/TypeApplications.scala
index 02526a30b..6c3fef1a9 100644
--- a/src/dotty/tools/dotc/core/TypeApplications.scala
+++ b/src/dotty/tools/dotc/core/TypeApplications.scala
@@ -191,6 +191,17 @@ class TypeApplications(val self: Type) extends AnyVal {
       if (res.isInstantiatedLambda) res.select(tpnme.Apply) else res
     }
   }
+  
+  /** Simplify a fully instantiated type of the form `LambdaX{... type Apply = T } # Apply` to `T`. 
+   */
+  def simplifyApply(implicit ctx: Context): Type = self match {
+    case self @ TypeRef(prefix, tpnme.Apply) if prefix.isInstantiatedLambda =>
+      prefix.member(tpnme.Apply).info match {
+        case TypeAlias(alias) => alias
+        case _ => self
+      }
+    case _ => self
+  }
 
   final def appliedTo(arg: Type)(implicit ctx: Context): Type = appliedTo(arg :: Nil)
   final def appliedTo(arg1: Type, arg2: Type)(implicit ctx: Context): Type = appliedTo(arg1 :: arg2 :: Nil)
diff --git a/src/dotty/tools/dotc/printing/PlainPrinter.scala b/src/dotty/tools/dotc/printing/PlainPrinter.scala
index 8669db9a0..ce33132ab 100644
--- a/src/dotty/tools/dotc/printing/PlainPrinter.scala
+++ b/src/dotty/tools/dotc/printing/PlainPrinter.scala
@@ -43,7 +43,9 @@ class PlainPrinter(_ctx: Context) extends Printer {
         case tp: TypeVar if tp.isInstantiated => homogenize(tp.instanceOpt)
         case AndType(tp1, tp2) => homogenize(tp1) & homogenize(tp2)
         case OrType(tp1, tp2) => homogenize(tp1) | homogenize(tp2)
-        case _ => tp
+        case _ => 
+          val tp1 = tp.simplifyApply
+          if (tp1 eq tp) tp else homogenize(tp1)
       }
     else tp