[PATCH] D90042: [clang-tidy] performance-unnecessary-copy-initialization: Check for const reference arguments that are replaced template parameter type.

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman added a comment.

In D90042#2360042 <https://reviews.llvm.org/D90042#2360042>, @flx wrote:

> In D90042#2357078 <https://reviews.llvm.org/D90042#2357078>, @aaron.ballman wrote:
>
>> In D90042#2356265 <https://reviews.llvm.org/D90042#2356265>, @flx wrote:
>>
>>> In D90042#2356180 <https://reviews.llvm.org/D90042#2356180>, @aaron.ballman wrote:
>>>
>>>> In D90042#2350035 <https://reviews.llvm.org/D90042#2350035>, @flx wrote:
>>>>
>>>>> I should note that I was only able to reproduce the false positive with the actual implementation std::function and not our fake version here.
>>>>
>>>> Any reason not to lift enough of the actual definition to be able to reproduce the issue in your test cases? Does the change in definitions break other tests?
>>>
>>> I poured over the actual definition and couldn't find any difference wrt the call operator that would explain it. I would also think that:
>>>
>>>   template <typename T>
>>>   void foo(T&& t) {
>>>     std::forward<T>(t).modify();
>>>   }
>>>
>>> would be a simpler case that should trigger replacement, but it doesn't. Do you have any idea what I could be missing?
>>
>> Perhaps silly question, but are you instantiating `foo()`?
>
> I think I added a full implementation of foo now, reverted the change, but am still not getting the negative case to fail. Can you spot an issue with the code?

I can't, but to be honest, I'm not certain I understand how that false positive could happen in the first place. That's why I was hoping to see the original case -- one thing you could try is with the original code, pass `-E` to preprocess to a file, and then try reducing the test case from that output (either by hand or by using a tool like creduce), or did you already give that a shot?


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