[PATCH] D86176: [clang-tidy] readability-simplify-boolean-expr detects negated literals

Thu Aug 20 23:19:20 PDT 2020

njames93 added inline comments.

================
Comment at: clang-tools-extra/clang-tidy/readability/SimplifyBooleanExprCheck.cpp:66
+  if (const auto *Negated = Result.Nodes.getNodeAs<UnaryOperator>(Id)) {
+    if (Negated->getOpcode() == UO_LNot &&
+        isa<CXXBoolLiteralExpr>(Negated->getSubExpr()))
----------------
aaron.ballman wrote:
> njames93 wrote:
> > aaron.ballman wrote:
> > > I'd like to see this handled recursively instead so that we properly handle more esoteric logic (but it still shows up from time to time) like `!!foo`: https://codesearch.isocpp.org/cgi-bin/cgi_ppsearch?q=%21%21&search=Search
> > > 
> > > This is a case where I don't think the simplification should happen -- e.g., the code is usually subtly incorrect when converted to remove the `!!`. It's less clear to me whether the same is true for something like `!!!` being converted to `!`, but that's not a case I'm really worried about either.
> > As this is only looking for boolean literals that shouldn't matter
> > `!!true` is identical to `true`.
> > I get putting `!!` in front of expressions that aren't boolean has an effect, but we aren't looking for that in this case.
> Oh, derp, I saw "SimplifyBooleanExprCheck" and assumed it was simplifying arbitrary boolean expressions, not just literals. I am now far less worried about supporting this case, it's up to you if you want to do the extra work. Thank you for clarifying and sorry for my think-o!
Personally I don't think the extra complexity is worth it. Usages of `!true`, I expect are rather low but likely show up in a few places, however I doubt anyone would use `!!true`. 

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CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D86176/new/

https://reviews.llvm.org/D86176