[clang-tools-extra] [clang-tidy] Avoid expensive AST traversal in RedundantTypenameCheck (PR #170540)

[Julian Schmidt via cfe-commits]

================
@@ -18,9 +18,13 @@ using namespace clang::ast_matchers;
 namespace clang::tidy::readability {
 
 void RedundantTypenameCheck::registerMatchers(MatchFinder *Finder) {
-  Finder->addMatcher(typeLoc(unless(hasAncestor(decl(isInstantiated()))))
-                         .bind("nonDependentTypeLoc"),
-                     this);
+  Finder->addMatcher(
+      typeLoc(loc(TypeMatcher(anyOf(typedefType(), tagType(),
+                                    deducedTemplateSpecializationType(),
+                                    templateSpecializationType()))),
+              unless(hasAncestor(decl(isInstantiated()))))
+          .bind("nonDependentTypeLoc"),
+      this);
----------------
5chmidti wrote:

Can't we skip the `hasAncestor` part (I'd keep the anyOf you added anyways since we are producing less matches that way, which also improves perf)

```c++
typeLoc(loc(qualType(unless(dependentNameType())))
```
?

Then we are not checking a type that is dependent, which eliminates the need for the `hasAncestor` and also the
```c++
      if (NonDependentTypeLoc->getType()->isDependentType())
        return SourceLocation();
```
later

https://github.com/llvm/llvm-project/pull/170540