[Frontend] Handle skipped bodies in template instantiations

Summary:
- Fixed an assert in Sema::InstantiateFunctionDefinition and added
  support for instantiating a function template with skipped body.
- Properly call setHasSkippedBody for FunctionTemplateDecl passed to
  Sema::ActOnSkippedFunctionBody.

Reviewers: sepavloff, bkramer

Reviewed By: sepavloff

Subscribers: klimek, cfe-commits

Differential Revision: https://reviews.llvm.org/D41237

llvm-svn: 321174

1 files changed, 4 insertions, 2 deletions

diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index c60cc52f415..a1fc725f8df 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -12179,9 +12179,11 @@ bool Sema::canSkipFunctionBody(Decl *D) {
 }
 
 Decl *Sema::ActOnSkippedFunctionBody(Decl *Decl) {
-  if (FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(Decl))
+  if (!Decl)
+    return nullptr;
+  if (FunctionDecl *FD = Decl->getAsFunction())
     FD->setHasSkippedBody();
-  else if (ObjCMethodDecl *MD = dyn_cast_or_null<ObjCMethodDecl>(Decl))
+  else if (ObjCMethodDecl *MD = dyn_cast<ObjCMethodDecl>(Decl))
     MD->setHasSkippedBody();
   return Decl;
 }