[Clang] Fix crash instantiating functions defaulted outside class templates (#240376)
A function that is defaulted outside its class template is not defaulted
when its declaration is instantiated, so the instantiation of its
definition reuses the info recorded at its definition (#229560).
However, `SetDeclDefaulted` returned for such a pattern before recording
the floating-point features in effect there, so the pattern usually had
no info, and the transfer set the info bit with a null pointer. If
non-default floating-point features were in effect at the point of
instantiation, `SetDeclDefaulted` then tried to store them and asserted
that the function already had the info. Even without the crash, the
instantiation took the floating-point features in effect at its point of
instantiation rather than at its definition, which also crashed codegen
when those were strict but the function was not.
Fixes #240351
llvm-project
c0005dfe - [Clang] Fix crash instantiating functions defaulted outside class templates (#240376)
