[clang-tools-extra] [clang-tidy] Add readability-use-rethrow check (PR #190580)

[Victor Chernyakin via cfe-commits]

================
@@ -0,0 +1,43 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "UseRethrowCheck.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::readability {
+
+void UseRethrowCheck::registerMatchers(MatchFinder *Finder) {
+  auto CatchVar = varDecl(isExceptionVariable(), hasType(referenceType()));
+  auto RefToVar = declRefExpr(to(CatchVar));
+
+  Finder->addMatcher(
+      cxxThrowExpr(has(expr(anyOf(
+                       ignoringParenImpCasts(RefToVar),
+                       cxxConstructExpr(
+                           hasDeclaration(cxxConstructorDecl(anyOf(
+                               isCopyConstructor(), isMoveConstructor()))),
+                           hasArgument(0, ignoringParenImpCasts(RefToVar)))))))
+          .bind("throw"),
+      this);
----------------
localspook wrote:

Because this code doesn't verify that the rethrown exception variable is the currently active exception, it looks like it gives a false positive in this snippet?
```cpp
try {
  ...
} catch (const std::exception outer) {
  try {
    ...
  } catch (const std::exception& inner) {
    throw outer; // FP?
  }
}
```


https://github.com/llvm/llvm-project/pull/190580