llvm/llvm-project

[clang-tidy] Add `readability-use-rethrow` check

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#189,672 opened on Mar 31, 2026

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Description

It would be useful to have a clang-tidy check that detects cases where code is clearly trying to rethrow the currently handled exception, but spells it as throw e; instead of throw;.

For example, code like this is easy to write:

try {
  f();
} catch (const std::exception &e) {
  log(e.what());
  throw e;
}

but if the intent is to rethrow the active exception, the clearer spelling is:

try {
  f();
} catch (const std::exception &e) {
  log(e.what());
  throw;
}

The latter expresses the intent directly and avoids the impression that the code is deliberately throwing the caught object as a new exception expression.

Contributor guide

Research direction
Study existing clang tidy checks for patterns, especially those using AST matchers, then implement a matcher that detects `throw e;` inside a catch handler where `e` is the caught exception, and suggest replacing with `throw;`.
Tech stack
cpp
Domain
tooling
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
3-5 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
C++Clang AST
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
70