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

[Arthur O'Dwyer via Phabricator via cfe-commits]

Quuxplusone added subscribers: zoecarver, CaseyCarter, ldionne, EricWF, mclow.lists.
Quuxplusone added a comment.

Re which libc++ folks could give feedback on this ADL-diagnosing patch: I don't know precisely, but the candidates are few! @mclow.lists @ericwf @ldionne @zoecarver @CaseyCarter.



================
Comment at: clang-tools-extra/test/clang-tidy/checkers/bugprone-unintended-adl.cpp:61
+void templateFunction(T t) {
+  swap(t, t);
+
----------------
logan-5 wrote:
> Quuxplusone wrote:
> > This is not the idiomatic way of calling `swap`: there is no ADL swap for `int`, for example (so `templateFunction<int>` will hard-error during instantiation). It would probably be scope-creep to try to handle the "std::swap two-step", but can you leave a TODO comment somewhere to revisit this issue?
> > 
> I believe this addressed by my juggling the tests around a bit.
Juggling the tests around doesn't address the fact that any code that does `swap(a,b)` without doing `using std::swap;` first (or `begin(a)` without `using std::begin;`) is almost certainly broken for primitive types.

My naive thought is that you would //not// do `using std::make_error_code;` because `make_error_code` is definitely never going to be used with primitive types. So "functions okay to call via ADL" and "functions that require the std::swap two-step" actually are slightly different whitelists.

I was saying that although this issue is probably out-of-scope for what you're doing in this patch, still, it would be nice to leave a TODO somewhere. ...Or maybe you say "nah, that's so far out of scope I don't want to think about it, and it may never get done, so even leaving a TODO is inappropriate."


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

https://reviews.llvm.org/D72282