`custom_type!()` not support path as a custom type

[lexoliu]

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I'm trying to define a custom type for a type in my crate

uniffi::custom_type!(crate::Environment, Arc<crate::ffi::Environment>);

However, compiler complain that

rustc: Custom types must only have one component

This problem can be simply triggered by a minimum case:

uniffi::custom_type!(A::B, C);

Custom types must only have one component error would spawn instantly, so seem that it is a limitation from macro...I don't know why the limiation is here...

And there is also a similar case:

// ...

uniffi::custom_type!(Computed<Str>, Arc<ComputedStr>); // not work

rustc: Custom types must only have one component

---

// ...
type CS=Computed<Str>;
uniffi::custom_type!(CS, Arc<ComputedStr>); // it works