If the pointer for a reference is constexpr-unknown, use the pointer
itself instead, instead of dereferencing it. Unfortunately, that means
constexpr-unknown pointers to reach a lot more places than before.
When revisiting `const T& range = f(T());`, we do mark the variable for
`range` as constexpr-unknown, but not the temporary variable we create
for `T()`. Change that.
Then we also need to ignore constexpr-unknown pointers in
`CheckInvoke()`.
Fixes https://github.com/llvm/llvm-project/issues/187775
Don't pass a combination of `-std=c++26` and `-fcxx-exceptions` to tests
and then try to use `throw` as an invalid statement. C++26 actually has
working exceptions at compile time, even if that is currently not
implemented.
In void*-to-ptr casts, the type of the pointed-to object in the source
operand needs to be compared to the target pointee type.
If a block was created for a `new`/`new[]`/`std::allocator` expression,
then a pointer needs to be stripped from the type of the expression
(which points to the single-object allocation or first element of the
allocation) to get the former.
`Descriptor::getType` did not do this and `Descriptor::getDataType`
returns an array type for array allocations. Therefore this introduces a
new function `Descriptor::getDataElemType` with the same behavior as
`Descriptor::getDataType`, except that it always produces the element
type in the array case and avoids the need for an `ASTContext`
reference. Make `Pointer::getType` use this function instead.
Fixes#174131
Don't return true here in InvalidNewDeleteExpr just because we are in
C++26 mode. This invalid there as well.
Testcase reduced from
libcxx/test/std/utilities/smartptr/unique.ptr/unique.ptr.create/make_unique_for_overwrite.pass.cpp
