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

[Dmitri Gribenko via Phabricator via cfe-commits]

gribozavr added a comment.

In D62845#1529149 <https://reviews.llvm.org/D62845#1529149>, @hokein wrote:

> > 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?


Fair enough.

>> 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.

Indeed, this is complicated.  Could you add tests for `new NoCopyMoveCtor{1, 2}` with TODOs (the message suggests the user to do the impossible).



================
Comment at: clang-tools-extra/test/clang-tidy/modernize-make-unique-cxx14.cpp:1
-// RUN: %check_clang_tidy -std=c++14-or-later %s modernize-make-unique %t -- -- -I %S/Inputs/modernize-smart-ptr
+// RUN: %check_clang_tidy -std=c++14 %s modernize-make-unique %t -- -- -I %S/Inputs/modernize-smart-ptr
 
----------------
WDYT about merging two tests and adding run lines like this:

```
// RUN: %check_clang_tidy -std=c++14,c++17 -check-suffix=CXX_14_17 %s modernize-make-unique %t -- -- -I %S/Inputs/modernize-smart-ptr -D CXX_14_17=1
// RUN: %check_clang_tidy -std=c++2a -check-suffix=CXX_2A %s modernize-make-unique %t -- -- -I %S/Inputs/modernize-smart-ptr -DCXX_2A=1
```


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