[cxx-interop] Add basic support for using UFOs as members, etc.

This does not add support for using UFOs in generic contexts, this just emits their struct/field metadata as opaque pointers.

Author: zoecarver

lib/IRGen/GenMeta.cpp

@@ -2515,6 +2515,15 @@ void irgen::emitLazyTypeContextDescriptor(IRGenModule &IGM,
 void irgen::emitLazyTypeMetadata(IRGenModule &IGM, NominalTypeDecl *type) {
   eraseExistingTypeContextDescriptor(IGM, type);
 
+  // Special case, UFOs are opaque pointers for now.
+  if (auto cd = dyn_cast<ClassDecl>(type)) {
+    if (cd->isForeignReferenceType()) {
+      auto sd = cast<StructDecl>(type->getASTContext().getOpaquePointerDecl());
+      emitStructMetadata(IGM, sd);
+      return;
+    }
+  }
+
   if (requiresForeignTypeMetadata(type)) {
     emitForeignTypeMetadata(IGM, type);
   } else if (auto sd = dyn_cast<StructDecl>(type)) {

lib/IRGen/GenReflection.cpp

@@ -717,21 +717,21 @@ class FieldTypeMetadataBuilder : public ReflectionMetadataBuilder {
     if (!type) {
       B.addInt32(0);
     } else {
-      if (type->isForeignReferenceType()) {
-        type->getASTContext().Diags.diagnose(
-            type->lookThroughAllOptionalTypes()
-                ->getClassOrBoundGenericClass()
-                ->getLoc(),
-            diag::foreign_reference_types_unsupported.ID, {});
-        exit(1);
-      }
-
       auto genericSig = NTD->getGenericSignature();
 
-      // The standard library's Mirror demangles metadata from field
-      // descriptors, so use MangledTypeRefRole::Metadata to ensure
-      // runtime metadata is available.
-      addTypeRef(type, genericSig, MangledTypeRefRole::Metadata);
+      // Special case, UFOs are opaque pointers for now.
+      if (type->isForeignReferenceType()) {
+        auto opaqueType = type->getASTContext().getOpaquePointerType();
+        // The standard library's Mirror demangles metadata from field
+        // descriptors, so use MangledTypeRefRole::Metadata to ensure
+        // runtime metadata is available.
+        addTypeRef(opaqueType, genericSig, MangledTypeRefRole::Metadata);
+      } else {
+        // The standard library's Mirror demangles metadata from field
+        // descriptors, so use MangledTypeRefRole::Metadata to ensure
+        // runtime metadata is available.
+        addTypeRef(type, genericSig, MangledTypeRefRole::Metadata);
+      }
     }
 
     if (IGM.IRGen.Opts.EnableReflectionNames) {

test/Interop/Cxx/foreign-reference/error-as-class-member.swift

@@ -1,21 +1,20 @@
 // RUN: %target-run-simple-swift(-I %S/Inputs/ -Xfrontend -enable-experimental-cxx-interop -Xfrontend -validate-tbd-against-ir=none -Xfrontend -disable-llvm-verify -g)
 //
 // REQUIRES: executable_test
+// XFAIL: OS=windows-msvc
 
 import StdlibUnittest
 import POD
 
-//  TODO: Waiting on foreign reference type metadata implementation.
-//
-//  struct StructHoldingPair {
-//    var pair: IntPair
-//  };
-//
-//  class ClassHoldingPair {
-//    var pair: IntPair
-//
-//    init(pair: IntPair) { self.pair = pair }
-//  };
+struct StructHoldingPair {
+  var pair: IntPair
+};
+
+class ClassHoldingPair {
+  var pair: IntPair
+
+  init(pair: IntPair) { self.pair = pair }
+};
 
 var globalPair: IntPair? = nil
 
@@ -106,33 +105,31 @@ PODTestSuite.test("RefHoldingPairPtr") {
   expectEqual(x.test(), 41)
 }
 
-//  TODO: Waiting on foreign reference types metadata implementation.
-//
-//  PODTestSuite.test("StructHoldingPair") {
-//   var x = StructHoldingPair(pair: IntPair.create())
-//   expectEqual(x.pair.test(), 1)
-//   expectEqual(x.pair.testMutable(), 1)
-//
-//   mutateIt(x.pair)
-//   expectEqual(x.pair.test(), 2)
-//   expectEqual(x.pair.testMutable(), 2)
-//
-//   x.pair = IntPair.create()
-//   expectEqual(x.pair.test(), 1)
-//  }
-//
-//  PODTestSuite.test("ClassHoldingPair") {
-//    var x = ClassHoldingPair(pair: IntPair.create())
-//    expectEqual(x.pair.test(), 1)
-//    expectEqual(x.pair.testMutable(), 1)
-//
-//    mutateIt(x.pair)
-//    expectEqual(x.pair.test(), 2)
-//    expectEqual(x.pair.testMutable(), 2)
-//
-//    x.pair = IntPair.create()
-//    expectEqual(x.pair.test(), 1)
-//  }
+PODTestSuite.test("StructHoldingPair") {
+  var x = StructHoldingPair(pair: IntPair.create())
+  expectEqual(x.pair.test(), 1)
+  expectEqual(x.pair.testMutable(), 1)
+
+  mutateIt(x.pair)
+  expectEqual(x.pair.test(), 2)
+  expectEqual(x.pair.testMutable(), 2)
+
+  x.pair = IntPair.create()
+  expectEqual(x.pair.test(), 1)
+}
+
+PODTestSuite.test("ClassHoldingPair") {
+  var x = ClassHoldingPair(pair: IntPair.create())
+  expectEqual(x.pair.test(), 1)
+  expectEqual(x.pair.testMutable(), 1)
+
+  mutateIt(x.pair)
+  expectEqual(x.pair.test(), 2)
+  expectEqual(x.pair.testMutable(), 2)
+
+  x.pair = IntPair.create()
+  expectEqual(x.pair.test(), 1)
+}
 
 PODTestSuite.test("BigType") {
   var x = BigType.create()