Add a note that points to the linkage specifier for the C++ linkage errors

This commit improves the "must have C++ linkage" error diagnostics that are
emitted for C++ declarations like templates and literal operators by adding an
additional note that points to the appropriate extern "C" linkage specifier.

rdar://19021120

Differential Revision: https://reviews.llvm.org/D26189

llvm-svn: 285823

3 files changed, 7 insertions, 5 deletions

diff --git a/clang/test/CXX/over/over.oper/over.literal/p6.cpp b/clang/test/CXX/over/over.oper/over.literal/p6.cpp
index 6bfb8560d68..9ecf9ccccb1 100644
--- a/clang/test/CXX/over/over.oper/over.literal/p6.cpp
+++ b/clang/test/CXX/over/over.oper/over.literal/p6.cpp
@@ -1,9 +1,11 @@
 // RUN: %clang_cc1 -std=c++11 %s -verify
 
+// expected-note@+1 {{extern "C" language linkage specification begins here}}
 extern "C" void operator "" _a(const char *); // expected-error {{must have C++ linkage}}
 extern "C" template<char...> void operator "" _b(); // expected-error {{must have C++ linkage}}
+// expected-note@-1 {{extern "C" language linkage specification begins here}}
 
-extern "C" {
+extern "C" { // expected-note 4 {{extern "C" language linkage specification begins here}}
   void operator "" _c(const char *); // expected-error {{must have C++ linkage}}
   template<char...> void operator "" _d(); // expected-error {{must have C++ linkage}}
   namespace N {
diff --git a/clang/test/SemaCXX/cxx0x-defaulted-functions.cpp b/clang/test/SemaCXX/cxx0x-defaulted-functions.cpp
index f4bbce818d9..f623dc765f8 100644
--- a/clang/test/SemaCXX/cxx0x-defaulted-functions.cpp
+++ b/clang/test/SemaCXX/cxx0x-defaulted-functions.cpp
@@ -180,7 +180,7 @@ namespace PR14577 {
   Outer<T>::Inner2<T>::~Inner2() = default; // expected-error {{nested name specifier 'Outer<T>::Inner2<T>::' for declaration does not refer into a class, class template or class template partial specialization}}  expected-error {{only special member functions may be defaulted}}
 }
 
-extern "C" {
+extern "C" { // expected-note {{extern "C" language linkage specification begins here}}
  template<typename _Tp> // expected-error {{templates must have C++ linkage}}
  void PR13573(const _Tp&) = delete;
 }
diff --git a/clang/test/SemaTemplate/class-template-decl.cpp b/clang/test/SemaTemplate/class-template-decl.cpp
index 63482d84df0..2e36cae14f6 100644
--- a/clang/test/SemaTemplate/class-template-decl.cpp
+++ b/clang/test/SemaTemplate/class-template-decl.cpp
@@ -10,11 +10,11 @@ namespace N {
   template<typename T> class C;
 }
 
-extern "C" {
+extern "C" { // expected-note {{extern "C" language linkage specification begins here}}
   template<typename T> class D; // expected-error{{templates must have C++ linkage}}
 }
 
-extern "C" {
+extern "C" { // expected-note 2 {{extern "C" language linkage specification begins here}}
   class PR17968 {
     template<typename T> class D; // expected-error{{templates must have C++ linkage}}
     template<typename T> void f(); // expected-error{{templates must have C++ linkage}}
@@ -148,7 +148,7 @@ namespace redecl {
 }
 
 extern "C" template <typename T> // expected-error{{templates must have C++ linkage}}
-void DontCrashOnThis() {
+void DontCrashOnThis() { // expected-note@-1 {{extern "C" language linkage specification begins here}}
   T &pT = T();
   pT;
 }