Replace the two-level implementation with a simpler one that directly subclasses
the predicates, avoiding the instantiation of the template to get the `type`
member in a situation where we should short-circuit. This prevents incorrect
diagnostics when the instantiated predicate contains a static assertion.
Add a test case that reproduced the previous problem. The existing test case
involving `HasNoValue` didn't catch the problem because `HasNoValue` was in the
final position. The bug comes up when the predicate that shouldn't be
instantiated is after the short-circuit position but there is more to follow,
because then `__conjunction_impl<False, BadPredicate, ...>` instantiates
`__conjunction_impl<BadPredicate, ...>` (in order to obtain its `type` member),
which in turn instantiates `BadPredicate` in order to obtain its `value` member.
In contrast the new implementation doesn't recurse in instantiation any further
than it needs to, because it doesn't require particular members of the recursive
case.
I've also updated the test cases for `std::disjunction` to match,
although it doesn't have the same particular bug (its implementation is
quite different).
Fixes#58490.
Reviewed By: #libc, ldionne, philnik
Spies: philnik, ldionne, libcxx-commits
Differential Revision: https://reviews.llvm.org/D136318
a0549ee2a3