IRGen: Correctly register conformances for generic ObjC classes.

They aren't really generic at runtime, so register them as conformances on the nongeneric class. Fixes rdar://problem/27869089.

Author: jckarter

lib/IRGen/GenDecl.cpp

@@ -2000,7 +2000,7 @@ getTypeEntityInfo(IRGenModule &IGM, CanType conformingType) {
 
   auto nom = conformingType->getAnyNominal();
   auto clas = dyn_cast<ClassDecl>(nom);
-  if (nom->isGenericContext() ||
+  if ((nom->isGenericContext() && (!clas || !clas->usesObjCGenericsModel())) ||
       (clas && doesClassMetadataRequireDynamicInitialization(IGM, clas))) {
     // Conformances for generics and concrete subclasses of generics
     // are represented by referencing the nominal type descriptor.
@@ -2152,7 +2152,7 @@ llvm::Constant *IRGenModule::emitProtocolConformances() {
                   LinkEntity::forProtocolDescriptor(conformance->getProtocol()),
                   getPointerAlignment(), ProtocolDescriptorStructTy);
     auto typeEntity = getTypeEntityInfo(*this,
-                                        conformance->getType()->getCanonicalType());
+                                    conformance->getType()->getCanonicalType());
     auto flags = typeEntity.flags
         .withConformanceKind(ProtocolConformanceReferenceKind::WitnessTable);
 

test/IRGen/Inputs/objc_bridged_generic_conformance.h

@@ -0,0 +1,5 @@
+@import Foundation;
+
+@interface Thingy<T>: NSObject
+
+@end

test/IRGen/objc_bridged_generic_conformance.swift

@@ -0,0 +1,14 @@
+// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -emit-ir %s -import-objc-header %S/Inputs/objc_bridged_generic_conformance.h | %FileCheck %s
+// REQUIRES: objc_interop
+
+// CHECK-NOT: _TMnCSo
+
+// CHECK: @"\01l_protocol_conformances" = {{.*}} @"got.OBJC_CLASS_$_Thingy"
+
+// CHECK-NOT: _TMnCSo
+
+protocol P { func test() }
+
+extension Thingy: P {
+  func test() {}
+}