[CodeComplete] Only complete attributes that match the current LangOpts

[aaron.ballman]

LGTM!

clang/lib/Sema/SemaCodeComplete.cpp

void Sema::CodeCompleteAttribute(AttributeCommonInfo::Syntax Syntax,
   bool SyntaxSupportsGuards = Syntax == AttributeCommonInfo::AS_GNU ||
                               Syntax == AttributeCommonInfo::AS_CXX11 ||
                               Syntax == AttributeCommonInfo::AS_C2x;
 
   llvm::DenseSet<llvm::StringRef> FoundScopes;
   auto AddCompletions = [&](const ParsedAttrInfo &A) {
     if (A.IsTargetSpecific && !A.existsInTarget(Context.getTargetInfo()))
       return;
-    // FIXME: filter by langopts (diagLangOpts method requires a ParsedAttr)
+    if (!A.acceptsLangOpts(getLangOpts()))
+      return;
     for (const auto &S : A.Spellings) {
       if (S.Syntax != Syntax)
         continue;
       llvm::StringRef Name = S.NormalizedFullName;
       llvm::StringRef Scope;
       if ((Syntax == AttributeCommonInfo::AS_CXX11 ||
            Syntax == AttributeCommonInfo::AS_C2x)) {
         std::tie(Scope, Name) = Name.split("::");

clang/test/CodeCompletion/attr.cpp

 int a [[gnu::used]];
 // RUN: %clang_cc1 -code-completion-at=%s:1:9 %s | FileCheck --check-prefix=STD %s
 // STD:     COMPLETION: __carries_dependency__
 // STD-NOT: COMPLETION: __convergent__
 // STD:     COMPLETION: __gnu__::__used__
 // STD-NOT: COMPLETION: __gnu__::used
 // STD-NOT: COMPLETION: __used__
 // STD:     COMPLETION: _Clang::__convergent__
 // STD:     COMPLETION: carries_dependency
+// STD-NOT: COMPLETION: clang::called_once
 // STD:     COMPLETION: clang::convergent
 // STD-NOT: COMPLETION: convergent
 // STD-NOT:     COMPLETION: gnu::__used__
 // STD:     COMPLETION: gnu::used
 // STD-NOT: COMPLETION: used
+// RUN: %clang_cc1 -code-completion-at=%s:1:9 -xobjective-c++ %s | FileCheck --check-prefix=STD-OBJC %s
+// STD-OBJC: COMPLETION: clang::called_once
 // RUN: %clang_cc1 -code-completion-at=%s:1:14 %s | FileCheck --check-prefix=STD-NS %s
 // STD-NS-NOT: COMPLETION: __used__
 // STD-NS-NOT: COMPLETION: carries_dependency
 // STD-NS-NOT: COMPLETION: clang::convergent
 // STD-NS-NOT: COMPLETION: convergent
 // STD-NS-NOT: COMPLETION: gnu::used
 // STD-NS:     COMPLETION: used
 int b [[__gnu__::used]];
-// RUN: %clang_cc1 -code-completion-at=%s:22:18 %s | FileCheck --check-prefix=STD-NSU %s
+// RUN: %clang_cc1 -code-completion-at=%s:25:18 %s | FileCheck --check-prefix=STD-NSU %s
 // STD-NSU:     COMPLETION: __used__
 // STD-NSU-NOT: COMPLETION: used
 
 int c [[using gnu: used]];
-// RUN: %clang_cc1 -code-completion-at=%s:27:15 %s | FileCheck --check-prefix=STD-USING %s
+// RUN: %clang_cc1 -code-completion-at=%s:30:15 %s | FileCheck --check-prefix=STD-USING %s
 // STD-USING:     COMPLETION: __gnu__
 // STD-USING:     COMPLETION: _Clang
 // STD-USING-NOT: COMPLETION: carries_dependency
 // STD-USING:     COMPLETION: clang
 // STD-USING-NOT: COMPLETION: clang::
 // STD-USING-NOT: COMPLETION: gnu::
 // STD-USING:     COMPLETION: gnu
-// RUN: %clang_cc1 -code-completion-at=%s:27:20 %s | FileCheck --check-prefix=STD-NS %s
+// RUN: %clang_cc1 -code-completion-at=%s:30:20 %s | FileCheck --check-prefix=STD-NS %s
 
 int d __attribute__((used));
-// RUN: %clang_cc1 -code-completion-at=%s:38:22 %s | FileCheck --check-prefix=GNU %s
+// RUN: %clang_cc1 -code-completion-at=%s:41:22 %s | FileCheck --check-prefix=GNU %s
 // GNU:     COMPLETION: __carries_dependency__
 // GNU:     COMPLETION: __convergent__
 // GNU-NOT: COMPLETION: __gnu__::__used__
 // GNU:     COMPLETION: __used__
 // GNU-NOT: COMPLETION: _Clang::__convergent__
 // GNU:     COMPLETION: carries_dependency
 // GNU-NOT: COMPLETION: clang::convergent
 // GNU:     COMPLETION: convergent
 // GNU-NOT: COMPLETION: gnu::used
 // GNU:     COMPLETION: used
 
 #pragma clang attribute push (__attribute__((internal_linkage)), apply_to=variable)
 int e;
 #pragma clang attribute pop
-// RUN: %clang_cc1 -code-completion-at=%s:51:46 %s | FileCheck --check-prefix=PRAGMA %s
+// RUN: %clang_cc1 -code-completion-at=%s:54:46 %s | FileCheck --check-prefix=PRAGMA %s
 // PRAGMA: internal_linkage
 
 #ifdef MS_EXT
 int __declspec(thread) f;
-// RUN: %clang_cc1 -fms-extensions -DMS_EXT -code-completion-at=%s:58:16 %s | FileCheck --check-prefix=DS %s
+// RUN: %clang_cc1 -fms-extensions -DMS_EXT -code-completion-at=%s:61:16 %s | FileCheck --check-prefix=DS %s
 // DS-NOT: COMPLETION: __convergent__
 // DS-NOT: COMPLETION: __used__
 // DS-NOT: COMPLETION: clang::convergent
 // DS-NOT: COMPLETION: convergent
 // DS:     COMPLETION: thread
 // DS-NOT: COMPLETION: used
 // DS:     COMPLETION: uuid
 
 [uuid("123e4567-e89b-12d3-a456-426614174000")] struct g;
-// RUN: %clang_cc1 -fms-extensions -DMS_EXT -code-completion-at=%s:68:2 %s | FileCheck --check-prefix=MS %s
+// RUN: %clang_cc1 -fms-extensions -DMS_EXT -code-completion-at=%s:71:2 %s | FileCheck --check-prefix=MS %s
 // MS-NOT: COMPLETION: __uuid__
 // MS-NOT: COMPLETION: clang::convergent
 // MS-NOT: COMPLETION: convergent
 // MS-NOT: COMPLETION: thread
 // MS-NOT: COMPLETION: used
 // MS:     COMPLETION: uuid
 #endif // MS_EXT
 
 void foo() {
   [[omp::sequence(directive(parallel), directive(critical))]]
   {}
 }
 // FIXME: support for omp attributes would be nice.
-// RUN: %clang_cc1 -fopenmp -code-completion-at=%s:79:5 %s | FileCheck --check-prefix=OMP-NS --allow-empty %s
+// RUN: %clang_cc1 -fopenmp -code-completion-at=%s:82:5 %s | FileCheck --check-prefix=OMP-NS --allow-empty %s
 // OMP-NS-NOT: omp
-// RUN: %clang_cc1 -fopenmp -code-completion-at=%s:79:10 %s | FileCheck --check-prefix=OMP-ATTR --allow-empty %s
+// RUN: %clang_cc1 -fopenmp -code-completion-at=%s:82:10 %s | FileCheck --check-prefix=OMP-ATTR --allow-empty %s
 // OMP-ATTR-NOT: sequence
-// RUN: %clang_cc1 -fopenmp -code-completion-at=%s:79:19 %s | FileCheck --check-prefix=OMP-NESTED --allow-empty %s
+// RUN: %clang_cc1 -fopenmp -code-completion-at=%s:82:19 %s | FileCheck --check-prefix=OMP-NESTED --allow-empty %s
 // OMP-NESTED-NOT: directive