IRGen: Use mangled names to access opaque type associated types in Swift >=5.2.

Author: jckarter

lib/IRGen/MetadataRequest.cpp

@@ -2213,17 +2213,19 @@ static bool shouldAccessByMangledName(IRGenModule &IGM, CanType type) {
   }
 
   // The Swift 5.1 runtime fails to demangle associated types of opaque types.
-  auto hasNestedOpaqueArchetype = type.findIf([](CanType sub) -> bool {
-    if (auto archetype = dyn_cast<NestedArchetypeType>(sub)) {
-      if (isa<OpaqueTypeArchetypeType>(archetype->getRoot())) {
-        return true;
+  if (!IGM.getAvailabilityContext().isContainedIn(IGM.Context.getSwift52Availability())) {
+    auto hasNestedOpaqueArchetype = type.findIf([](CanType sub) -> bool {
+      if (auto archetype = dyn_cast<NestedArchetypeType>(sub)) {
+        if (isa<OpaqueTypeArchetypeType>(archetype->getRoot())) {
+          return true;
+        }
       }
-    }
-    return false;
-  });
-  
-  if (hasNestedOpaqueArchetype)
-    return false;
+      return false;
+    });
+    
+    if (hasNestedOpaqueArchetype)
+      return false;
+  }
 
   return true;
 

test/IRGen/access_type_metadata_by_mangled_name_51.swift

@@ -0,0 +1,20 @@
+// RUN: %target-swift-frontend -target x86_64-apple-macosx10.99 -parse-stdlib -emit-ir %s | %FileCheck %s --check-prefix=CHECK --check-prefix=SWIFT_52
+// RUN: %target-swift-frontend -target x86_64-apple-macosx10.15 -parse-stdlib -emit-ir %s | %FileCheck %s --check-prefix=CHECK --check-prefix=SWIFT_PRE_52
+
+protocol P {
+  associatedtype A
+  var a: A { get }
+}
+
+@_silgen_name("useMetadata") func useMetadata<T>(_: T)
+
+struct X: P { var a: X { return self } }
+
+dynamic func foo() -> some P { return X() }
+
+// CHECK-LABEL: define{{.*}}3bar
+public func bar() {
+  // SWIFT_52: @__swift_instantiateConcreteTypeFromMangledName({{.*}} @"$s39access_type_metadata_by_mangled_name_513fooQryFQOyQo_1AAA1PPQxMD")
+  // SWIFT_PRE_52: @"$s39access_type_metadata_by_mangled_name_513fooQryFQOyQo_1AAA1PPQxMa"(
+  useMetadata(foo().a)
+}