[clang-tidy] Fix crash in modernize-use-constraints (#92019)

Improved modernize-use-constraints check by fixing a crash that occurred
in some scenarios and excluded system headers from analysis.

Problem were with DependentNameTypeLoc having null type location as
getQualifierLoc().getTypeLoc().

Fixes #91872

1 files changed, 4 insertions, 0 deletions

diff --git a/clang-tools-extra/clang-tidy/modernize/UseConstraintsCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseConstraintsCheck.cpp
index 1585925e..7a021fe 100644
--- a/clang-tools-extra/clang-tidy/modernize/UseConstraintsCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseConstraintsCheck.cpp
@@ -41,6 +41,8 @@ AST_MATCHER(FunctionDecl, hasOtherDeclarations) {
 void UseConstraintsCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(
       functionTemplateDecl(
+          // Skip external libraries included as system headers
+          unless(isExpansionInSystemHeader()),
           has(functionDecl(unless(hasOtherDeclarations()), isDefinition(),
                            hasReturnTypeLoc(typeLoc().bind("return")))
                   .bind("function")))
@@ -57,6 +59,8 @@ matchEnableIfSpecializationImplTypename(TypeLoc TheType) {
       return std::nullopt;
     }
     TheType = Dep.getQualifierLoc().getTypeLoc();
+    if (TheType.isNull())
+      return std::nullopt;
   }
 
   if (const auto SpecializationLoc =