[PATCH] D106302: Implement P1937 consteval in unevaluated contexts

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman added inline comments.


================
Comment at: clang/test/SemaCXX/cxx2a-consteval.cpp:603
+
+long f(); //expected-note {{declared here}}
+auto consteval g(auto a) {
----------------



================
Comment at: clang/test/SemaCXX/cxx2a-consteval.cpp:608
+
+auto e = g(f()); // expected-error{{is not a constant expression}} expected-note {{non-constexpr function 'f' cannot be used in a constant expression}}
+
----------------



================
Comment at: clang/test/SemaCXX/cxx2a-consteval.cpp:612
+static_assert(is_same<long, T>::value);
+
+} // namespace unevaluated
----------------
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?


Repository:
  rG LLVM Github Monorepo

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

https://reviews.llvm.org/D106302