A constrained GetAwaiter call on a type parameter that is not known to be
a value type wraps its receiver in LdObjIfRef so the reference is read
before any further arguments. ExpressionBuilder has no translation for
LdObjIfRef, so the operand was dropped. GetAwaiter takes no further
arguments, so the operand can be translated from the address, as
CallBuilder already does for call receivers.
When the branches of a conditional have different types, its type falls
back to the IL stack slot type, which is (U)IntPtr. IntroduceNativeIntTypeOnLocals
only retypes variables, so with native integers enabled the branches got
cast to IntPtr. Map (U)IntPtr to n(u)int the same way boxing does; pointer
types are unaffected.
dualfroz
upstream