[Interop] Handle existential types in ClangTypeConverter and

the ClangImporter.

Author: hborla

lib/AST/ClangTypeConverter.cpp

@@ -750,6 +750,11 @@ ClangTypeConverter::visitProtocolCompositionType(ProtocolCompositionType *type)
   return clangCtx.getObjCObjectPointerType(clangType);
 }
 
+clang::QualType
+ClangTypeConverter::visitExistentialType(ExistentialType *type) {
+  return visit(type->getConstraintType());
+}
+
 clang::QualType
 ClangTypeConverter::visitBuiltinRawPointerType(BuiltinRawPointerType *type) {
   return ClangASTContext.VoidPtrTy;
@@ -828,6 +833,9 @@ clang::QualType ClangTypeConverter::convert(Type type) {
     return it->second;
 
   // Try to do this without making cache entries for obvious cases.
+  if (auto existential = type->getAs<ExistentialType>())
+    type = existential->getConstraintType();
+
   if (auto nominal = type->getAs<NominalType>()) {
     auto decl = nominal->getDecl();
     if (auto clangDecl = decl->getClangDecl()) {

lib/AST/ClangTypeConverter.h

@@ -122,6 +122,7 @@ class ClangTypeConverter :
   clang::QualType visitEnumType(EnumType *type);
   clang::QualType visitFunctionType(FunctionType *type);
   clang::QualType visitProtocolCompositionType(ProtocolCompositionType *type);
+  clang::QualType visitExistentialType(ExistentialType *type);
   clang::QualType visitBuiltinRawPointerType(BuiltinRawPointerType *type);
   clang::QualType visitBuiltinIntegerType(BuiltinIntegerType *type);
   clang::QualType visitBuiltinFloatType(BuiltinFloatType *type);

lib/ClangImporter/ImportDecl.cpp

@@ -6244,6 +6244,9 @@ SwiftDeclConverter::importSwiftNewtype(const clang::TypedefNameDecl *decl,
   // Local function to add a known protocol only when the
   // underlying type conforms to it.
   auto computedNominal = computedPropertyUnderlyingType->getAnyNominal();
+  if (auto existential =
+          computedPropertyUnderlyingType->getAs<ExistentialType>())
+    computedNominal = existential->getConstraintType()->getAnyNominal();
   auto transferKnown = [&](KnownProtocolKind kind) {
     if (!computedNominal)
       return false;

lib/ClangImporter/ImportType.cpp

@@ -1183,6 +1183,10 @@ namespace {
             }
           }
 
+          if (bridgedType->isConstraintType() &&
+              Impl.SwiftContext.LangOpts.EnableExplicitExistentialTypes)
+            bridgedType = ExistentialType::get(bridgedType);
+
           return { importedType,
                    ImportHint(ImportHint::ObjCBridged, bridgedType) };
         }
@@ -2505,6 +2509,8 @@ ImportedType ClangImporter::Implementation::importMethodParamsAndReturnType(
     if (kind == SpecialMethodKind::NSDictionarySubscriptGetter &&
         paramTy->isObjCIdType()) {
       swiftParamTy = SwiftContext.getNSCopyingType();
+      if (SwiftContext.LangOpts.EnableExplicitExistentialTypes)
+        swiftParamTy = ExistentialType::get(swiftParamTy);
       if (!swiftParamTy)
         return {Type(), false};
       if (optionalityOfParam != OTK_None)