[clang-tools-extra] [clang-tidy] Avoid readability-use-anyofallof diagnostics on temporary ranges before C++20 (PR #185791)

[Zeyi Xu via cfe-commits]

================
@@ -35,6 +35,13 @@ AST_MATCHER_P(Stmt, nextStmt, ast_matchers::internal::Matcher<Stmt>,
 
   return InnerMatcher.matches(**I, Finder, Builder);
 }
+
+AST_MATCHER(Expr, isUnsupportedRangeInit) {
+  const Expr *E = Node.IgnoreParenImpCasts();
+  if (Finder->getASTContext().getLangOpts().CPlusPlus20)
+    return isa<CXXStdInitializerListExpr>(E);
----------------
zeyi2 wrote:

> we don't want the check to warn on a for-range loop over a raw initializer list in _any_ language mode

Yes! To clarify (and make review easier), my original intention is: 

- suppress diagnostics for all prvalue range initializers in pre-C++20 mode (rewriting them might not be safe). 

- In c++20-or-later, I want to allow diagnostics again for *ordinary* range expressions (`any_of` and `all_of` can consume the range directly).

The special case for `CXXStdInitializerListExpr` (`{a, b, c}`), we still should not diagnose in any language mode, since they cannot be directly reused in the replacement.

> But here the exclusion is limited to C++20 and up, as if we did want the check to warn in pre-C++20.

No, `return E->isPRValue();` already filters that for cases below C++ 20.

> So is this condition doing anything? 🤔

Yes! It re-enable diagnostics for ordinary temporary range expressions in C++20, while still keeping raw braced-init-lists excluded.

https://github.com/llvm/llvm-project/pull/185791