Merge pull request #7397 from dotty-staging/fix-#7383

Fix #7383: Don't include nested classes in class bounds

Author: smarter

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

@@ -53,17 +53,19 @@ trait TypeAssigner {
     def addRefinement(parent: Type, decl: Symbol) = {
       val inherited =
         parentType.findMember(decl.name, cls.thisType,
-          required = EmptyFlags, excluded = Private)
-          .suchThat(decl.matches(_))
+          required = EmptyFlags, excluded = Private
+        ).suchThat(decl.matches(_))
       val inheritedInfo = inherited.info
       val isPolyFunctionApply = decl.name == nme.apply && (parent <:< defn.PolyFunctionType)
-      if (isPolyFunctionApply || inheritedInfo.exists &&
-          decl.info.widenExpr <:< inheritedInfo.widenExpr &&
-          !(inheritedInfo.widenExpr <:< decl.info.widenExpr)) {
+      if isPolyFunctionApply
+         || inheritedInfo.exists
+            && !decl.isClass
+            && decl.info.widenExpr <:< inheritedInfo.widenExpr
+            && !(inheritedInfo.widenExpr <:< decl.info.widenExpr)
+      then
         val r = RefinedType(parent, decl.name, decl.info)
         typr.println(i"add ref $parent $decl --> " + r)
         r
-      }
       else
         parent
     }

tests/pos/i7383.scala

@@ -0,0 +1,15 @@
+trait ZSink {
+
+  type State
+
+  def foo: ZSink =
+    class Anon extends ZSink {
+      case class State(x: Int)
+    }
+    new Anon
+
+  def foo2: ZSink =
+    new ZSink {
+      case class State(x: Int)
+    }
+}