[interop][sourcekit] interface generator should show unavailable C++ declarations

Author: hyp

test/SourceKit/InterfaceGen/gen_clang_cxx_module_with_unavailable.swift

@@ -0,0 +1,38 @@
+// RUN: %empty-directory(%t)
+// RUN: split-file %s %t
+
+// RUN: %sourcekitd-test -req=interface-gen -module CxxModule -- -Xfrontend -disable-implicit-concurrency-module-import -Xfrontend -disable-implicit-string-processing-module-import -Xfrontend -enable-experimental-cxx-interop -I %t/Inputs -target %target-triple %clang-importer-sdk-nosource | %FileCheck %s
+
+//--- Inputs/module.modulemap
+module CxxModule {
+    header "headerA.h"
+    requires cplusplus
+}
+
+//--- Inputs/headerA.h
+
+template<class T>
+struct X {
+public:
+    int x;
+    X(): x(0) {}
+
+    int *xy();
+};
+
+using XofInt = X<int>;
+
+//--- test.swift
+
+import CxxModule
+
+func testMe() {
+    var v = XofInt();
+    print(v.x);
+}
+
+// CHECK: @available(*, unavailable, message: "Un-specialized class templates are not currently supported. Please use a specialization of this type.")
+// CHECK-NEXT: public struct X<T> {
+// CHECK-NEXT: }
+// CHECK: public struct X<Int32> {
+// CHECK: public typealias XofInt = X<Int32>

tools/SourceKit/lib/SwiftLang/SwiftEditorInterfaceGen.cpp

@@ -290,6 +290,11 @@ static bool getModuleInterfaceInfo(ASTContext &Ctx,
 
   PrintOptions Options = PrintOptions::printModuleInterface(
       Ctx.TypeCheckerOpts.PrintFullConvention);
+  if (Mod->findUnderlyingClangModule()) {
+    // Show unavailable C++ APIs.
+    if (Ctx.LangOpts.EnableCXXInterop)
+      Options.SkipUnavailable = false;
+  }
   ModuleTraversalOptions TraversalOptions = None; // Don't print submodules.
   SmallString<128> Text;
   llvm::raw_svector_ostream OS(Text);