[clang] [Clang] Skip type-aware operator delete resolution for incomplete pointee types (PR #213455)

[Oliver Hunt via cfe-commits]

ojhunt wrote:

> Hey @ojhunt Same issue also happens in C++23, not just C++17 — the error only kicks in at C++26 on current trunk. I tried to cover all three modes and confirm clean codegen (calls @_ZdlPv, no assert). Let me know if there is some improvisation required here.

Hmmmm.

Ok, I think I remember now the reason I thought we could just gate on incomplete types.

I think first pass of this should not be target version gated. We track the existence of type aware allocation functions, so basic defensive level should be:

1. The allocation lookup comes in requesting a type aware allocator
2. If the type is incomplete produce a warning, and drop the type aware request part of the requested IAP.

That's fairly conservative, but we could go a step further: if template deduction can bind a type aware allocation function to the (incomplete) allocation type we upgrade to an error. But I'll need to look into whether that change would still be in the "good first function" family

https://github.com/llvm/llvm-project/pull/213455