[PATCH] D106302: Implement P1937 consteval in unevaluated contexts

[Corentin Jabot via Phabricator via cfe-commits]

cor3ntin added inline comments.


================
Comment at: clang/test/SemaCXX/cxx2a-consteval.cpp:612
+static_assert(is_same<long, T>::value);
+
+} // namespace unevaluated
----------------
cor3ntin wrote:
> aaron.ballman wrote:
> > Here's an interesting test case:
> > ```
> > #include <typeinfo>
> > 
> > struct S {
> >   virtual void f();
> > };
> > 
> > struct D : S {
> >   void f() override;
> > };
> > 
> > consteval S *get_s() { return nullptr; }
> > 
> > void func() {
> >   (void)typeid(*get_s());
> > }
> > ```
> > `typeid` still needs to evaluate its operand (due to the polymorphic return type of `*get_s()`), and so you should get a diagnostic about evaluating the side effects by calling `get_s()`. I think this then runs into https://eel.is/c++draft/expr.const#13.sentence-3 and we should diagnose?
> Not sure!
> Also, in the context of this pr, the question is also whether `decltype(typeid(*get_s()))` should be ill-formed I think
Actually, I'm reading the wording again and I really don't know anymore.
`get_s()` is a constant expression, right?
`*get_s()` is not, I think but is that relevant here

I played with a bunch of things in the code but the more I look at it the less I'm convinced an action is needed.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D106302/new/

https://reviews.llvm.org/D106302