[clang] Resolve FIXME: Look at E, not M (PR #85541)

[Matheus Izvekov via cfe-commits]

mizvekov wrote:

> Hmm. The best solution there is probably to use a consistent representation but introduce some sort of `GLValueThatTheStandardAbsurdlyPretendsIsAnRValue` (definitely the only and best word for this, ship it) that we can use as the value category. IIRC, something similar happens in C where the standard pretends that function l-values don't exist.

IIRC GCC also implements a similar value category as an alternative to the two-phase lookup rules for implicit moves, pre-C++23. This is almost an XValue, except it binds to LValue references as well.

https://github.com/llvm/llvm-project/pull/85541