WIP widen 5

Author: odersky

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

@@ -2086,7 +2086,7 @@ class Typer extends Namer
     /** Checks if one of the decls is a type with the same name as class type member in selfType */
     def classExistsOnSelf(decls: Scope, self: tpd.ValDef): Boolean = {
       val selfType = self.tpt.tpe
-      if (!selfType.exists || (selfType.classSymbol eq cls)) false
+      if (!selfType.exists || (selfType.widen.classSymbol eq cls)) false
       else {
         def memberInSelfButNotThis(decl: Symbol) =
           selfType.member(decl.name).symbol.filter(other => other.isClass && other.owner != cls)

tests/neg/i6226.scala

@@ -7,6 +7,6 @@ object O2 {
 }
 
 object O3 { // error
-  opaque type R[X] = T[X]
+  opaque type R[X] = T[X] // error
   opaque type T[X] = R[X] // error
 }

tests/neg/i8337.scala

@@ -2,5 +2,5 @@ trait Foo[F <: Foo[F]]
 class Bar extends Foo[Bar]
 
 object Q {    // error: recursion limit exceeded
-  opaque type X <: Foo[X] = Bar // error: out of bounds
+  opaque type X <: Foo[X] = Bar // error: out of bounds // error
 }