Fix PR19169 [Crash on invalid attempting to specialize a template method as a template variable].

A template declaration of a template name can be null in case we have a dependent name or a set of function templates.
Hence use dyn_cast_or_null instead of dyn_cast. Also improve the diagnostic emitted in this case.

llvm-svn: 208313

1 files changed, 11 insertions, 2 deletions

diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index e21d1eef46d..8c0261381c1 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -2420,10 +2420,19 @@ DeclResult Sema::ActOnVarTemplateSpecialization(
 
   // The template-id must name a variable template.
   VarTemplateDecl *VarTemplate =
-      dyn_cast<VarTemplateDecl>(Name.getAsTemplateDecl());
-  if (!VarTemplate)
+      dyn_cast_or_null<VarTemplateDecl>(Name.getAsTemplateDecl());
+  if (!VarTemplate) {
+    NamedDecl *FnTemplate;
+    if (auto *OTS = Name.getAsOverloadedTemplate())
+      FnTemplate = *OTS->begin();
+    else
+      FnTemplate = dyn_cast_or_null<FunctionTemplateDecl>(Name.getAsTemplateDecl());
+    if (FnTemplate)
+      return Diag(D.getIdentifierLoc(), diag::err_var_spec_no_template_but_method)
+               << FnTemplate->getDeclName();
     return Diag(D.getIdentifierLoc(), diag::err_var_spec_no_template)
              << IsPartialSpecialization;
+  }
 
   // Check for unexpanded parameter packs in any of the template arguments.
   for (unsigned I = 0, N = TemplateArgs.size(); I != N; ++I)