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

[Paul Kirth via cfe-commits]

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@@ -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);
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ilovepi wrote:

The simpler matcher also seems to cut the overhead at runtime down significantly. I'll need to re-run it again, but --enable-profile shows its under ~3 seconds now. I'm a little concerned that file still takes a couple minutes to finish reporting under C++20 and only 8 seconds under C++17, so it could be that I held something wrong in my last evaluation.

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