[Index] Prevent canonical decl becoming nullptr

Summary:
This patch prevents getCanonicalDecl returning nullptr in case it finds
a canonical TemplateDeclaration with no attached TemplatedDecl.
Found by running the indexer over a version of the standard library deep inside
a template metaprogramming mess.

Reviewers: klimek, vsk

Reviewed By: vsk

Subscribers: vsk, arphaman, cfe-commits

Differential Revision: https://reviews.llvm.org/D35212

llvm-svn: 308269

1 files changed, 4 insertions, 2 deletions

diff --git a/clang/lib/Index/IndexingContext.cpp b/clang/lib/Index/IndexingContext.cpp
index c4aa51d62f0..addee691e80 100644
--- a/clang/lib/Index/IndexingContext.cpp
+++ b/clang/lib/Index/IndexingContext.cpp
@@ -260,8 +260,10 @@ static const Decl *adjustParent(const Decl *Parent) {
 static const Decl *getCanonicalDecl(const Decl *D) {
   D = D->getCanonicalDecl();
   if (auto TD = dyn_cast<TemplateDecl>(D)) {
-    D = TD->getTemplatedDecl();
-    assert(D->isCanonicalDecl());
+    if (auto TTD = TD->getTemplatedDecl()) {
+      D = TTD;
+      assert(D->isCanonicalDecl());
+    }
   }
 
   return D;