[Proposal]: never/bottom type

[333fred]

never/bottom type

• Discussion: Proposal: never/bottom type #8603

Summary

A new type that has no instances and is a subtype of every other type can be introduced, called never or bottom. It will be the official return type of the throw expression and will allow transforming return, break, continue and goto into expressions (see #176). This will allow them in all expression contexts where never is combined with another type (&&, ||, ??, ?:) or discarded (expression statements). Instantiating variables/fields of type never should be impossible.

It can either be implemented as a real CLR type (well, as real as void) or as a compiler trick (never-returning methods are actually void with a NeverReturnsAttribute).

Design meetings