Yeah, I tried to fix even that case but is not so simple so not worth any extra time/complexivity.
> Dňa 8. 10. 2019 o 19:09 užívateľ Arthur O'Dwyer <arthur.j.odw...@gmail.com> > napísal: > > > On Mon, Oct 7, 2019 at 6:58 PM Dávid Bolvanský <david.bolvan...@gmail.com> > wrote: > >> FWIW I found the "always evaluates to 'true'" bit important to > >> understand the warning. > > > > Yeah. I moved this check somewhere else, so we can print precise message: > > r373973 should emit "bitwise negation of a boolean expression always > > evaluates to 'true'; did you mean logical negation?" where possible. > > In the suspicious case like int i = ~b there is a general message > > "bitwise negation of a boolean expression; did you mean logical > > negation?". > > > > I like it now. What do you think? fine for you? > > I see. Yes, all the cases I tried produce appropriate diagnostics. I like it! > >> Hm, there is no "bitwise negation of a boolean expression always >> evaluates to 'true'; did you mean logical negation?" for chromium >> case [ https://bugs.chromium.org/p/chromium/issues/detail?id=1011810 ]. I >> will try to fix it. > > The important part there seems to be that the result of `~b` (which must be > either -1 or -2) is used as the operand to `!=` or `==`. > My opinion is that it is not worth the extra complication just to improve the > error message for this case. > It would be interesting to do some kind of general-purpose dataflow before > emitting diagnostics... > I notice that Clang's optimizer is smart enough to optimize > bool foo(bool a, bool b) { > return a == ~b; > } > bool bar(int x) { > return x + 1 < -INT_MAX; > } > into `return 0`. If it could propagate that information up and produce a > diagnostic, users might appreciate that. But the challenge as always is that > we can never tell if the user might sometimes be doing that sort of thing on > purpose (in inlined code, in macros, in generated code, etc). > > my $.02, > –Arthur
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