[clang] [Clang] Diagnose defaulted assignment operator with incompatible object parameter (PR #70176)

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

> Per https://eel.is/c++draft/dcl.fct.def.default#2.2, the explicit object parameter of a defaulted special member function must be of the same type as the one of an equivalent implicitly defaulted function, ignoring references.

I could use an explanation as to how they must be the same type when 2.2 says "...may be an explicit object member function whose explicit object parameter is of (possibly different) type “reference to C”, in which case..."

https://github.com/llvm/llvm-project/pull/70176