alexeyr marked an inline comment as done.
alexeyr added inline comments.

================
Comment at: 
clang-tools-extra/test/clang-tidy/checkers/misc-redundant-expression.cpp:114
   if (P.a[X++] != P.a[X++]) return 1;
+  if (X && X++ && X) return 1;
 
----------------
aaron.ballman wrote:
> What do you think about the following?
> ```
> bool foo(int&);
> bool bar();
> 
> int i;
> if (foo(i) && bar() && foo(i)) return 1;
> ```
> I think that this should not be warned on (under the assumption that the 
> reference variable can be modified by the call and thus may or may not be 
> duplicate), but didn't see a test covering it.
> 
> It also brings up an interesting question about what to do if those were 
> non-const pointers rather than references, because the data being pointed to 
> could be modified as well.
> 
> (If you think this should be done separately from this review, that's totally 
> fine by me, it looks like it would be an issue with the original code as 
> well.)
> 
> One thing that is missing from this review are tests for the overloaded 
> operator functionality.
This is actually handled correctly, by the same logic as `(X && X++ && X)`, so 
I don't think it needs a separate test. The drawback is that:

1. it's too conservative, `X && bar() && X` isn't warned on either, because I 
don't know a way to check that `bar()` doesn't have side effects //on `X`// and 
so just test `HasSideEffects` 
(https://stackoverflow.com/questions/60035219/check-which-variables-can-be-side-effected-by-expression-evaluation-in-clang-ast).

2. the original code does have the same issue and I didn't fix it, so `foo(X) 
&& foo(X)` and `X++ && X++` do get a warning. 

I'll add overloaded operator tests.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D73775/new/

https://reviews.llvm.org/D73775



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