assert_inhabited intrinsic support
#851
Merged
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The assert_inhabited intrinsic will (possibly) panic if a type in uninhabited (cannot be instantiated). E.g.
Despite being an
assert, panicking is not guaranteed and is dependent on the target and code generation - it is sound to perform a NO OP. Since calling the intrinsic comes from aTerminatorKind::Call, there must be aBasicBlockto go to after the call. However we observe that forassert_inhabited<!>()the execution continues tonoBasicBlockIdx(which would get stuck). The semantics looks for this case and converts to#AssertInhabitedFailure, and otherwise performs aNO OP.