Don't mangle inverse protocols within reabstraction thunks

(cherry picked from commit cab88d1)

Author: DougGregor

lib/AST/ASTMangler.cpp

@@ -453,6 +453,9 @@ std::string ASTMangler::mangleReabstractionThunkHelper(
   assert(ThunkType->getPatternSubstitutions().empty() && "not implemented");
   GenericSignature GenSig = ThunkType->getInvocationGenericSignature();
 
+  // Reabstraction thunks never reference inverse conformances.
+  llvm::SaveAndRestore X(AllowInverses, false);
+
   beginMangling();
   appendType(FromType, GenSig);
   appendType(ToType, GenSig);

lib/IRGen/IRGenMangler.cpp

@@ -499,8 +499,9 @@ IRGenMangler::appendExtendedExistentialTypeShape(CanGenericSignature genSig,
                                                  CanType shapeType) {
   // Append the generalization signature.
   if (genSig) {
-    // Generalization signature never reference inverses.
+    // Generalization signature never references inverses.
     llvm::SaveAndRestore X(AllowInverses, false);
+
     appendGenericSignature(genSig);
   }
 

test/SILGen/existential_member_accesses_self_assoctype.swift

@@ -1,7 +1,5 @@
 // RUN: %target-swift-frontend -emit-silgen %s | %FileCheck %s
 
-// XFAIL: noncopyable_generics
-
 protocol P {
   associatedtype A
 

test/SILGen/tuple_attribute_reabstraction.swift

@@ -1,7 +1,5 @@
 // RUN: %target-swift-emit-silgen %s | %FileCheck %s
 
-// XFAIL: noncopyable_generics
-
 public struct G<T> {
   var t: T
 

test/SILGen/variadic-generic-reabstract-tuple-result.swift

@@ -1,7 +1,5 @@
 // RUN: %target-swift-emit-silgen -disable-availability-checking %s | %FileCheck %s
 
-// XFAIL: noncopyable_generics
-
 // rdar://110391963
 
 struct Use<each T> {}