We had an llvm_unreachable following a switch on the WasmAddress's type.
However, the type is encoded in a larger 64 bit address, and therefore
it's possible to create an invalid value that doesn't map back on one of
the enum types.
We could try to diagnose that in the wrapper, or treat all invalid types
the same. I took the latter approach because it makes it easier to show
the invalid type after the fact in an error message.
rdar://168314695
074653aa53