SemaCXX: Support templates in availability attributes

If the availability context is `FunctionTemplateDecl`, we should look
through it to the `FunctionDecl`.  This prevents a diagnostic in the
following case:

    class C __attribute__((unavailable));
    template <class T> void foo(C&) __attribute__((unavailable));

This adds tests for availability in templates in many other cases, but
that was the only case that failed before this patch.

I added a feature `__has_feature(attribute_availability_in_templates)`
so users can test for this.

rdar://problem/24561029

llvm-svn: 262050

2 files changed, 4 insertions, 0 deletions

diff --git a/clang/lib/AST/DeclBase.cpp b/clang/lib/AST/DeclBase.cpp
index 58c3cc3369f..d41d25f7a44 100644
--- a/clang/lib/AST/DeclBase.cpp
+++ b/clang/lib/AST/DeclBase.cpp
@@ -467,6 +467,9 @@ static AvailabilityResult CheckAvailability(ASTContext &Context,
 }
 
 AvailabilityResult Decl::getAvailability(std::string *Message) const {
+  if (auto *FTD = dyn_cast<FunctionTemplateDecl>(this))
+    return FTD->getTemplatedDecl()->getAvailability(Message);
+
   AvailabilityResult Result = AR_Available;
   std::string ResultMessage;
 
diff --git a/clang/lib/Lex/PPMacroExpansion.cpp b/clang/lib/Lex/PPMacroExpansion.cpp
index 50f07bd82bb..2c9a37525db 100644
--- a/clang/lib/Lex/PPMacroExpansion.cpp
+++ b/clang/lib/Lex/PPMacroExpansion.cpp
@@ -1074,6 +1074,7 @@ static bool HasFeature(const Preprocessor &PP, const IdentifierInfo *II) {
       .Case("attribute_availability_tvos", true)
       .Case("attribute_availability_watchos", true)
       .Case("attribute_availability_with_strict", true)
+      .Case("attribute_availability_in_templates", true)
       .Case("attribute_cf_returns_not_retained", true)
       .Case("attribute_cf_returns_retained", true)
       .Case("attribute_cf_returns_on_parameters", true)