[clang] bd763e2 - [clang] Fix crash on visiting null nestedNameSpecifier.

[Haojian Wu via cfe-commits]

Author: Haojian Wu
Date: 2020-03-18T09:15:02+01:00
New Revision: bd763e2cf7c1d84bab95064cc5cbe542b227b025

URL: https://github.com/llvm/llvm-project/commit/bd763e2cf7c1d84bab95064cc5cbe542b227b025
DIFF: https://github.com/llvm/llvm-project/commit/bd763e2cf7c1d84bab95064cc5cbe542b227b025.diff

LOG: [clang] Fix crash on visiting null nestedNameSpecifier.

Summary: Fix https://github.com/clangd/clangd/issues/293

Reviewers: sammccall

Subscribers: ilya-biryukov, kadircet, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D76320

Added: 
    

Modified: 
    clang/lib/Sema/SemaTemplate.cpp
    clang/test/Parser/cxx-template-decl.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index 1ba66d4a976a..f95b16c1cbae 100755
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -5928,7 +5928,9 @@ bool UnnamedLocalNoLinkageFinder::VisitDependentNameType(
 
 bool UnnamedLocalNoLinkageFinder::VisitDependentTemplateSpecializationType(
                                  const DependentTemplateSpecializationType* T) {
-  return VisitNestedNameSpecifier(T->getQualifier());
+  if (auto *Q = T->getQualifier())
+    return VisitNestedNameSpecifier(Q);
+  return false;
 }
 
 bool UnnamedLocalNoLinkageFinder::VisitPackExpansionType(
@@ -5982,6 +5984,7 @@ bool UnnamedLocalNoLinkageFinder::VisitTagDecl(const TagDecl *Tag) {
 
 bool UnnamedLocalNoLinkageFinder::VisitNestedNameSpecifier(
                                                     NestedNameSpecifier *NNS) {
+  assert(NNS);
   if (NNS->getPrefix() && VisitNestedNameSpecifier(NNS->getPrefix()))
     return true;
 

diff  --git a/clang/test/Parser/cxx-template-decl.cpp b/clang/test/Parser/cxx-template-decl.cpp
index 3d7a3dc14f4c..0d52ad8fb50f 100644
--- a/clang/test/Parser/cxx-template-decl.cpp
+++ b/clang/test/Parser/cxx-template-decl.cpp
@@ -273,3 +273,9 @@ namespace AnnotateAfterInvalidTemplateId {
 namespace PR45063 {
   template<class=class a::template b<>> struct X {}; // expected-error {{undeclared identifier 'a'}}
 }
+
+namespace NoCrashOnEmptyNestedNameSpecifier {
+  template <typename FnT,
+            typename T = typename ABC<FnT>::template arg_t<0>> // expected-error {{no template named 'ABC'}}
+  void foo(FnT) {}
+}