Option of string not ffi safe

[ZakharEl]

I have a trait that has a method that returns a stabby::option::Optionstabby::string::String. It says that it resturns the type stabby::stabby_abi::End, which is not FFI-safe.

[ZakharEl]

Ah it only gives me trouble with methods returning stabby::option::Option<stabby::string::String> if I use stabby::option::Option::None() in the method body.

[ZakharEl]

if used in stable trait default method body it will not compile but if the method default is left undefined and then the method is implemented for a type using stabby::option::Option::None() in its body it will compile with same messages as a warning instead of an error.

[xuchaoqian]

I have a trait that has a method that returns a stabby::option::Optionstabby::string::String. It says that it resturns the type stabby::stabby_abi::End, which is not FFI-safe.

Met the similar case. It should be a bug.