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

1 files changed, 12 insertions, 0 deletions

diff --git a/clang/lib/AST/DeclBase.cpp b/clang/lib/AST/DeclBase.cpp
index 7e790cec68a..5d130acfbed 100644
--- a/clang/lib/AST/DeclBase.cpp
+++ b/clang/lib/AST/DeclBase.cpp
@@ -992,6 +992,18 @@ bool DeclContext::isExternCContext() const {
   return isLinkageSpecContext(this, clang::LinkageSpecDecl::lang_c);
 }
 
+const LinkageSpecDecl *DeclContext::getExternCContext() const {
+  const DeclContext *DC = this;
+  while (DC->getDeclKind() != Decl::TranslationUnit) {
+    if (DC->getDeclKind() == Decl::LinkageSpec &&
+        cast<LinkageSpecDecl>(DC)->getLanguage() ==
+            clang::LinkageSpecDecl::lang_c)
+      return cast<LinkageSpecDecl>(DC);
+    DC = DC->getLexicalParent();
+  }
+  return nullptr;
+}
+
 bool DeclContext::isExternCXXContext() const {
   return isLinkageSpecContext(this, clang::LinkageSpecDecl::lang_cxx);
 }