https://wg21.link/p1937 proposes that in unevaluated contexts, consteval
functions should not be immediately evaluated.
Clang implemented p1937 a while ago, its behavior is correct and the
test needs an update.
Reviewed By: aaron.ballman, shafik
Differential Revision: https://reviews.llvm.org/D145362
During Clang 15, 3d2629dd3aab17098813c68b5b76bb864bc5e285 claimed we
achieved full support for consteval in C++20. However, further testing
shows that Clang doesn't correctly handle all of the examples from
https://wg21.link/P1073R3 and has several other known issues that are
preventing us from defining the `__cpp_consteval` macro.
I think we should only claim Partial support for the moment. Once we
correct the major outstanding issues, then I think we should change the
status back to full support and define __cpp_consteval at the same time
(even if it's only to the 201811L value instead of the latest value
from C++2b). This helps users understand the support situation more
clearly.
Differential Revision: https://reviews.llvm.org/D144572
