[PATCH] D76320: [clang] Fix crash on visiting null nestedNameSpecifier.

[Haojian Wu via Phabricator via cfe-commits]

hokein created this revision.
hokein added a reviewer: sammccall.
Herald added subscribers: usaxena95, kadircet, ilya-biryukov.
Herald added a project: clang.

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


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D76320

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


Index: clang/test/Parser/cxx-template-decl.cpp
===================================================================
--- clang/test/Parser/cxx-template-decl.cpp
+++ clang/test/Parser/cxx-template-decl.cpp
@@ -273,3 +273,9 @@
 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) {}
+}
Index: clang/lib/Sema/SemaTemplate.cpp
===================================================================
--- clang/lib/Sema/SemaTemplate.cpp
+++ clang/lib/Sema/SemaTemplate.cpp
@@ -5923,12 +5923,16 @@
 
 bool UnnamedLocalNoLinkageFinder::VisitDependentNameType(
                                                    const DependentNameType* T) {
-  return VisitNestedNameSpecifier(T->getQualifier());
+  if (auto *Q = T->getQualifier())
+    return VisitNestedNameSpecifier(Q);
+  return false;
 }
 
 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 +5986,7 @@
 
 bool UnnamedLocalNoLinkageFinder::VisitNestedNameSpecifier(
                                                     NestedNameSpecifier *NNS) {
+  assert(NNS && "NNS must not be null!");
   if (NNS->getPrefix() && VisitNestedNameSpecifier(NNS->getPrefix()))
     return true;
 


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