Warn if function or variable cannot be implicitly instantiated

With this patch compiler emits warning if it tries to make implicit instantiation
of a template but cannot find the template definition. The warning can be suppressed
by explicit instantiation declaration or by command line options
-Wundefined-var-template and -Wundefined-func-template. The implementation follows
the discussion of http://reviews.llvm.org/D12326.

Differential Revision: http://reviews.llvm.org/D16396


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@266719 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 11 insertions, 0 deletions

diff --git a/lib/AST/DeclBase.cpp b/lib/AST/DeclBase.cpp
index 57149af3c1..aec3b7cd3b 100644
--- a/lib/AST/DeclBase.cpp
+++ b/lib/AST/DeclBase.cpp
@@ -196,6 +196,17 @@ bool Decl::isTemplateDecl() const {
   return isa<TemplateDecl>(this);
 }
 
+TemplateDecl *Decl::getDescribedTemplate() const {
+  if (auto *FD = dyn_cast<FunctionDecl>(this))
+    return FD->getDescribedFunctionTemplate();
+  else if (auto *RD = dyn_cast<CXXRecordDecl>(this))
+    return RD->getDescribedClassTemplate();
+  else if (auto *VD = dyn_cast<VarDecl>(this))
+    return VD->getDescribedVarTemplate();
+
+  return nullptr;
+}
+
 const DeclContext *Decl::getParentFunctionOrMethod() const {
   for (const DeclContext *DC = getDeclContext();
        DC && !DC->isTranslationUnit() && !DC->isNamespace();