[PATCH] D122111: [clang-tidy] Fix false positives in `misc-redundant-expression` check

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman accepted this revision.
aaron.ballman added a comment.
This revision is now accepted and ready to land.

LGTM! Please also add a release note for the fix when you land it.



================
Comment at: clang-tools-extra/clang-tidy/misc/RedundantExpressionCheck.cpp:605
+          unless(isMacro()), unless(isInTemplateInstantiation()),
+          hasRHS(ignoringParenImpCasts(integerLiteral().bind(ConstId))))
           .bind(OverloadId);
----------------
fwolff wrote:
> aaron.ballman wrote:
> > This seems incorrect to me -- the LHS and RHS can be swapped along with which operator is used and still achieve the same semantic results.
> > 
> > While playing around to test the behavior we currently have, I was a bit surprised at the difference in results here: https://godbolt.org/z/hE4qfca1b.
> > 
> > Also, do we need to bind? Nothing seems to look at that binding that I can see.
> > This seems incorrect to me -- the LHS and RHS can be swapped along with which operator is used and still achieve the same semantic results.
> 
> Fixed.
> 
> > While playing around to test the behavior we currently have, I was a bit surprised at the difference in results here: https://godbolt.org/z/hE4qfca1b.
> 
> All four conditions get a warning with my changes. I've added your example to the test file.
> 
> > Also, do we need to bind? Nothing seems to look at that binding that I can see.
> 
> Yes, it is hard to see, but [[ https://github.com/llvm/llvm-project/blob/240e06dfe77feabe38a03cbb1c94875639d0f9ff/clang-tools-extra/clang-tidy/misc/RedundantExpressionCheck.cpp#L498 | here ]] the constant is actually read.
> Yes, it is hard to see, but here the constant is actually read.

Oh, thanks for the info!


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D122111/new/

https://reviews.llvm.org/D122111