[PATCH] D62845: [clang-tidy] Fix make-unique tests on C++2a.

[Haojian Wu via Phabricator via cfe-commits]

hokein added a comment.

> I think we should be looking at the intent of the test rather than its name.
> 
> The intent looks like testing how the check works when `std::make_unique` is available from the standard library (as opposed to some kind of replacement like `absl::make_unique`).  See the patch that introduced it: https://reviews.llvm.org/D43766
> 
> So modernize-make-unique-cxx14 is actually "C++14 or later".  (Probably it should be renamed.)

yeap, it seems to me that "modernize-make-unique-cxx14" is redundant, "modernize-make-unique" should cover what it tests, I believe. We also have "modernize-make-unique-cxx11" which runs on C++11 mode only, maybe we just repurpose the `modernize-make-unique-cxx14`, what do you think?

> I see.  Assuming it is desired behavior, I'd say for these cases we should create separate files that are specifically run in C++14 and 17, and another one for C++2a onward.
> 
> But is it desired behavior?  That is, can we generate a call to `std::make_unique` in C++14 in practice -- would it compile?

The fix is compilable for C++14, but it is tricky to support it:

1. `new NoCopyMoveCtor{}`: the `make_unique` fix is compilable
2. `new NoCopyMoveCtor{1, 2}`: the `make_unique` fix is not compilable

The AST for case 1) and 2)  are the same in C++14,  supporting that would introduce hacky change to the logic here <https://github.com/llvm/llvm-project/blob/master/clang-tools-extra/clang-tidy/modernize/MakeSmartPtrCheck.cpp#L400>. I'd leave it as-is now.


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https://reviews.llvm.org/D62845