3 files changed, 41 insertions, 1 deletions
diff --git a/src/compiler/scala/tools/nsc/typechecker/Typers.scala b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
index f82786da35..8e06588ed8 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Typers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
@@ -2590,7 +2590,15 @@ trait Typers extends Modes with Adaptations with Tags {
 
       def translated =
         if (members.head eq EmptyTree) setError(tree)
-        else typed(atPos(tree.pos)(Block(List(ClassDef(anonClass, NoMods, ListOfNil, ListOfNil, members, tree.pos.focus)), atPos(tree.pos.focus)(New(anonClass.tpe)))), mode, pt)
+        else {
+          val typedBlock = typed(atPos(tree.pos)(
+            Block(ClassDef(anonClass, NoMods, ListOfNil, ListOfNil, members, tree.pos.focus), atPos(tree.pos.focus)(New(anonClass.tpe)))
+          ), mode, pt)
+          // Don't leak implementation details into the type, see SI-6575
+          if (isPartial && !typedBlock.isErrorTyped)
+            typedBlock modifyType (_ baseType PartialFunctionClass)
+          else typedBlock
+        }
     }
 
     // Function(params, Match(sel, cases)) ==> new <Partial>Function { def apply<OrElse>(params) = `translateMatch('sel match { cases }')` }
diff --git a/test/files/pos/t6575a.scala b/test/files/pos/t6575a.scala
new file mode 100644
index 0000000000..f128714dab
--- /dev/null
+++ b/test/files/pos/t6575a.scala
@@ -0,0 +1,15 @@
+trait X { def foo: PartialFunction[Int, Int] }
+
+trait Y extends X {
+  // Inferred type was AbstractPartialFunction[Int, Int] with Serializable
+  abstract override def foo = { case i => super.foo(i) * 2 }
+}
+trait Z extends X {
+  // ditto
+  abstract override def foo = { case i => super.foo(i) + 3 }
+}
+
+trait Comb extends Y with Z {
+  // ... which led to a type error here.
+  abstract override def foo: PartialFunction[Int, Int] = { case i => super.foo(i) - 2 }
+}
diff --git a/test/files/pos/t6575b.scala b/test/files/pos/t6575b.scala
new file mode 100644
index 0000000000..d3e58b2a16
--- /dev/null
+++ b/test/files/pos/t6575b.scala
@@ -0,0 +1,17 @@
+// inferred types were okay here as Function nodes aren't
+// translated into anoymous subclasses of AbstractFunctionN
+// until after the typer.
+//
+// So this test is just confirmation.
+trait X { def foo: Function1[Int, Int] }
+
+trait Y extends X {
+  abstract override def foo = { case i => super.foo(i) * 2 }
+}
+trait Z extends X {
+  abstract override def foo = { case i => super.foo(i) + 3 }
+}
+
+trait Comb extends Y with Z {
+  abstract override def foo: Function1[Int, Int] = { case i => super.foo(i) - 2 }
+}