[PATCH] D114427: [clang-tidy] Warn on functional C-style casts

[Carlos Galvez via Phabricator via cfe-commits]

carlosgalvezp added inline comments.


================
Comment at: clang-tools-extra/test/clang-tidy/checkers/google-readability-casting.cpp:342
+  auto w = new int(x);
+}
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carlosgalvezp wrote:
> Quuxplusone wrote:
> > What about
> > ```
> > template<class T> T foo(int i) { return T(i); }
> > int main() {
> >     foo<std::vector<int>>(); // valid, OK(!)
> >     foo<double>(); // valid, not OK
> > }
> > ```
> > What about
> > ```
> > struct Widget { Widget(int); };
> > using T = Widget;
> > using U = Widget&;
> > int i = 42;
> > Widget t = T(i);  // valid, OK?
> > Widget u = U(i);  // valid C++, should definitely not be OK
> > ```
> > https://quuxplusone.github.io/blog/2020/01/22/expression-list-in-functional-cast/
> Good point, thanks! I've added the first one to the unit test.
> 
> Regarding the second check, I'm not sure if it's the scope of this check. This check does not care whether the constructor of the class is implicit or not - if you use a class type, then you are calling the constructor so it's fine. Same goes when it's a reference - in my opinion this check is not concerned with that.
> 
> I definitely see the problems that can arise from the example that you posted, but maybe it fits better as a separate check in the `bugprone` category? This check (`google-readability-casting`) is focused only about avoiding C-style casting, i.e. it's a readability/style/modernize matter IMO. If cpplint is not diagnosing that, I don't think this check should either.
It seems I should be able to just add the second example as a test and clang-tidy would warn but, what should be the fixit for it? A `static_cast<U>` would lead to compiler error (which I personally would gladly take, but I don't know in general if we want clang-tidy to "fix" code leading to compiler errors"). Adding an ad-hoc message for this particular error seems out of the scope of a "readability" check. 

What do you guys think?


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  https://reviews.llvm.org/D114427/new/

https://reviews.llvm.org/D114427