Targeted fix for pulling in Hashable conformance for Set and Dictionary when a nil literal is bridged

When bridging values via the ObjectiveCBridgeable protocol,
SILGen has to look up conformances directly, behind the
type checker's back.

To make sure the ObjectiveCBridgeable conformance is forced,
Sema calls useObjectiveCBridgeableConformances() in the right
places.

However, another conformance we may also need when bridging
is the Hashable conformance for a Set or Dictionary's key type.

Make sure we force these too, because otherwise when bridging
a nil literal nothing needs them in Sema.

Fixes <rdar://problem/27470505>.

Author: slavapestov

lib/Sema/TypeCheckProtocol.cpp

@@ -4246,13 +4246,25 @@ void TypeChecker::useObjectiveCBridgeableConformances(DeclContext *dc,
       : TC(tc), DC(dc), Proto(proto) { }
 
     virtual Action walkToTypePre(Type ty) {
+      ConformanceCheckOptions options = ConformanceCheckFlags::InExpression
+          | ConformanceCheckFlags::Used
+          | ConformanceCheckFlags::SuppressDependencyTracking;
+
       // If we have a nominal type, "use" its conformance to
       // _ObjectiveCBridgeable if it has one.
-      if (ty->getAnyNominal()) {
-        ConformanceCheckOptions options = ConformanceCheckFlags::InExpression
-            | ConformanceCheckFlags::Used
-            | ConformanceCheckFlags::SuppressDependencyTracking;
+      if (auto *nominalDecl = ty->getAnyNominal()) {
         (void)TC.conformsToProtocol(ty, Proto, DC, options);
+
+        if (nominalDecl == TC.Context.getSetDecl() ||
+            nominalDecl == TC.Context.getDictionaryDecl()) {
+          auto args = ty->castTo<BoundGenericType>()->getGenericArgs();
+          if (!args.empty()) {
+            auto keyType = args[0];
+            auto *hashableProto =
+              TC.Context.getProtocol(KnownProtocolKind::Hashable);
+            (void)TC.conformsToProtocol(keyType, hashableProto, DC, options);
+          }
+        }
       }
 
       return Action::Continue;

test/IRGen/objc_generic_class_metadata.sil

@@ -71,6 +71,11 @@ entry(%0: $Subclass):
   unreachable
 }
 
+sil @_TToFC27objc_generic_class_metadata8SubclasscfT7optionsGSqGVs10DictionaryVSC13GenericOptionP____GSQS0__ : $@convention(objc_method) (@owned Subclass, @owned NSDictionary) -> @owned Subclass {
+entry(%0: $Subclass, %1: $NSDictionary):
+  unreachable
+}
+
 // CHECK-LABEL: define linkonce_odr hidden %swift.type* @_TMaCSo12GenericClass()
 // CHECK:         [[T0:%.*]] = load %objc_class*, %objc_class** @"OBJC_CLASS_REF_$_GenericClass",
 // CHECK:         call %objc_class* @rt_swift_getInitializedObjCClass(%objc_class* [[T0]])

test/Inputs/clang-importer-sdk/usr/include/objc_generics.h

@@ -1,8 +1,18 @@
 #import <Foundation.h>
 
+#define _CF_TYPED_ENUM __attribute__((swift_wrapper(enum)))
+#define NS_STRING_ENUM _CF_TYPED_ENUM
+#define NS_SWIFT_NAME(Name) __attribute__((swift_name(#Name)))
+
+typedef NSString * GenericOption NS_STRING_ENUM;
+
+GenericOption const GenericOptionMultithreaded NS_SWIFT_NAME(multithreaded);
+
+
 @interface GenericClass<T> : NSObject
 - (id)initWithThing:(T)thing;
 - (id)initWithArrayOfThings:(NSArray<T> *__nonnull)things;
+- (id)initWithOptions:(nullable NSDictionary<GenericOption, id> *)options;
 - (void)dealloc;
 - (__nullable T)thing;
 - (int)count;

test/SILGen/objc_imported_generic.swift

@@ -103,5 +103,29 @@ func genericFunc<V: AnyObject>(_ v: V.Type) {
   }
 }
 
+// CHECK-LABEL: sil hidden @_TF21objc_imported_generic23configureWithoutOptionsFT_T_ : $@convention(thin) () -> ()
+// CHECK: [[NIL_FN:%.*]] = function_ref @_TFSqCfT10nilLiteralT__GSqx_ : $@convention(method) <τ_0_0> (@thin Optional<τ_0_0>.Type) -> @out Optional<τ_0_0>
+// CHECK: apply [[NIL_FN]]<[GenericOption : Any]>({{.*}})
+// CHECK: return
+func configureWithoutOptions() {
+  _ = GenericClass<NSObject>(options: nil)
+}
+
+// foreign to native thunk for init(options:), uses GenericOption : Hashable
+// conformance
+
+// CHECK-LABEL: sil shared [thunk] @_TTOFCSo12GenericClasscfT7optionsGSqGVs10DictionaryVSC13GenericOptionP____GSQGS_x__ : $@convention(method) <T where T : AnyObject> (@owned Optional<Dictionary<GenericOption, Any>>, @owned GenericClass<T>) -> @owned ImplicitlyUnwrappedOptional<GenericClass<T>>
+// CHECK: [[FN:%.*]] = function_ref @_TFE10FoundationVs10Dictionary19_bridgeToObjectiveCfT_CSo12NSDictionary : $@convention(method) <τ_0_0, τ_0_1 where τ_0_0 : Hashable> (@guaranteed Dictionary<τ_0_0, τ_0_1>) -> @owned NSDictionary
+// CHECK: apply [[FN]]<GenericOption, Any>({{.*}}) : $@convention(method) <τ_0_0, τ_0_1 where τ_0_0 : Hashable> (@guaranteed Dictionary<τ_0_0, τ_0_1>) -> @owned NSDictionary
+// CHECK: return
+
+// This gets emitted down here for some reason
+
 // CHECK-LABEL: sil shared [thunk] @_TTOFCSo12GenericClasscfT13arrayOfThings
 // CHECK:         class_method [volatile] {{%.*}} : $GenericClass<T>, #GenericClass.init!initializer.1.foreign {{.*}}, $@convention(objc_method) @pseudogeneric <τ_0_0 where τ_0_0 : AnyObject> (NSArray, @owned GenericClass<τ_0_0>) -> @owned ImplicitlyUnwrappedOptional<GenericClass<τ_0_0>>
+
+// Make sure we emitted the witness table for the above conformance
+
+// CHECK-LABEL: sil_witness_table shared [fragile] GenericOption: Hashable module objc_generics {
+// CHECK: method #Hashable.hashValue!getter.1: @_TTWVSC13GenericOptions8Hashable13objc_genericsFS0_g9hashValueSi
+// CHECK: }

validation-test/stdlib/SceneKit.swift

@@ -346,7 +346,7 @@ if #available(iOS 8.0, *) {
     let sceneData = sceneDescription.data(
       using: .utf8,
       allowLossyConversion: true)!
-    let sceneSource = SCNSceneSource(data: sceneData as Data, options: [:])!
+    let sceneSource = SCNSceneSource(data: sceneData as Data, options: nil)!
 
     do {
       var unarchivedPlaneGeometry =