[PATCH] D72282: [clang-tidy] Add `bugprone-unintended-adl`

[Logan Smith via Phabricator via cfe-commits]

logan-5 marked an inline comment as done.
logan-5 added inline comments.


================
Comment at: clang-tools-extra/clang-tidy/bugprone/UnintendedADLCheck.cpp:43
+      Whitelist(
+          utils::options::parseStringList(Options.get("Whitelist", "swap"))) {}
+
----------------
JonasToth wrote:
> do you mean `std::swap`? If you it should be fully qualified.
> Doesn't `std::error_code` rely on adl, too? I think `std::cout <<` and other streams of the STL rely on it too, and probably many more code-constructs that are commonly used.
> 
> That means, the list should be extended to at least all standard-library facilities that basically required ADL to work. And then we need data on different code bases (e.g. LLVM is a good start) how much noise gets generated.
I distinctly //don't// mean `std::swap` -- I want to whitelist any unqualified function call spelled simply `swap`.

Overloaded operators are the poster child for ADL's usefulness, so that's why this check has a special default-on `IgnoreOverloadedOperators` option. That whitelists a whole ton of legitimate stuff including `std::cout << x` and friends.

I don't see a ton of discussion online about `error_code`/`make_error_code` and ADL being very much intertwined. I'm not particularly familiar with those constructs myself though, and I could just be out of the loop. I do see a fair number of unqualified calls to `make_error_code` within LLVM, though most of those resolve to `llvm::make_error_code`, the documentation for which says it exists because `std::make_error_code` can't be reliably/portably used with ADL. That makes me think `make_error_code` would belong in LLVM's project-specific whitelist configuration, not the check's default.

Speaking of which, I did run this check over LLVM while developing and found it not particularly noisy as written. That is, it generated a fair number of warnings, but only on constructs that, when examined closely, //were// a little suspicious or non-obvious.


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  https://reviews.llvm.org/D72282/new/

https://reviews.llvm.org/D72282