[libcxx-commits] [clang] [clang-tools-extra] [libcxx] [clang] improved preservation of template keyword (PR #133610)

[Amy Huang via libcxx-commits]

amykhuang wrote:

Hi we're seeing some msan failures after this patch in tests such as clang-tools-extra/test/clang-tidy/checkers/modernize/use-using.cpp

Here's the top of the stack trace
```
==6262==WARNING: MemorySanitizer: use-of-uninitialized-value
    #0 0x560847d4ff8a in clang::DependentTemplateSpecializationTypeLoc::getQualifierLoc() const [third_party/llvm/llvm-project/clang/include/clang/AST/TypeLoc.h:2502](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang/include/clang/AST/TypeLoc.h?l=2502&ws=akhuang/7402&snapshot=28):9
    #1 0x56084edfb6ff in clang::DependentTemplateSpecializationTypeLoc::getLocalSourceRange() const [third_party/llvm/llvm-project/clang/include/clang/AST/TypeLoc.h:2578](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang/include/clang/AST/TypeLoc.h?l=2578&ws=akhuang/7402&snapshot=28):14
    #2 0x56084edfb1d0 in (anonymous namespace)::TypeLocRanger::VisitDependentTemplateSpecializationTypeLoc(clang::DependentTemplateSpecializationTypeLoc) blaze-out/k8-fastbuild-msan/bin/third_party/llvm/llvm-project/clang/include/clang/AST/TypeNodes.inc:47:1
    #3 0x56084edf0bcd in Visit blaze-out/k8-fastbuild-msan/bin/third_party/llvm/llvm-project/clang/include/clang/AST/TypeNodes.inc:47:1
    #4 0x56084edf0bcd in clang::TypeLoc::getLocalSourceRangeImpl(clang::TypeLoc) [third_party/llvm/llvm-project/clang/lib/AST/TypeLoc.cpp:56](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang/lib/AST/TypeLoc.cpp?l=56&ws=akhuang/7402&snapshot=28):26
    #5 0x56084edf82a5 in getLocalSourceRange [third_party/llvm/llvm-project/clang/include/clang/AST/TypeLoc.h:161](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang/include/clang/AST/TypeLoc.h?l=161&ws=akhuang/7402&snapshot=28):12
    #6 0x56084edf82a5 in clang::TypeLoc::getBeginLoc() const [third_party/llvm/llvm-project/clang/lib/AST/TypeLoc.cpp:223](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang/lib/AST/TypeLoc.cpp?l=223&ws=akhuang/7402&snapshot=28):15
    #7 0x56084ebf05c5 in clang::NestedNameSpecifierLoc::getLocalSourceRange() const [third_party/llvm/llvm-project/clang/lib/AST/NestedNameSpecifier.cpp:443](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang/lib/AST/NestedNameSpecifier.cpp?l=443&ws=akhuang/7402&snapshot=28):27
    #8 0x56084ebf02f9 in clang::NestedNameSpecifierLoc::getSourceRange() const [third_party/llvm/llvm-project/clang/lib/AST/NestedNameSpecifier.cpp:418](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang/lib/AST/NestedNameSpecifier.cpp?l=418&ws=akhuang/7402&snapshot=28):22
    #9 0x56084c6582a3 in getSourceRange [third_party/llvm/llvm-project/clang/include/clang/AST/NestedNameSpecifier.h:480](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang/include/clang/AST/NestedNameSpecifier.h?l=480&ws=akhuang/7402&snapshot=28):59
    #10 0x56084c6582a3 in clang::CXXScopeSpec::Extend(clang::ASTContext&, clang::TypeLoc, clang::SourceLocation) [third_party/llvm/llvm-project/clang/lib/Sema/DeclSpec.cpp:58](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang/lib/Sema/DeclSpec.cpp?l=58&ws=akhuang/7402&snapshot=28):3
    #11 0x56084c7b25ea in clang::Sema::ActOnCXXNestedNameSpecifier(clang::Scope*, clang::CXXScopeSpec&, clang::SourceLocation, clang::OpaquePtr<clang::TemplateName>, clang::SourceLocation, clang::SourceLocation, llvm::MutableArrayRef<clang::ParsedTemplateArgument>, clang::SourceLocation, clang::SourceLocation, bool) [third_party/llvm/llvm-project/clang/lib/Sema/SemaCXXScopeSpec.cpp:883](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang/lib/Sema/SemaCXXScopeSpec.cpp?l=883&ws=akhuang/7402&snapshot=28):8
```



https://github.com/llvm/llvm-project/pull/133610