How to map a parametrized enum from a generic type to another?

Question

If I have a type like MyEnum, how can I map it in cases where not every variant is parameterized?

For example, I\'d like to convert from

Answer 1

Some languages (like C++), use Duck Typing: if it quacks like a duck, it must be a duck, and therefore names matter. Rust does not.

In Rust, names are just some display utility for us mere humans, the B in MyEnum and MyEnum may happen to have the same visual representation, but they are completely different syntactic entities as far as the language is concerned.

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There are multiple ways to alleviate your pain, though:

• a code generation plugin or build.rs script can be used as well
• a macro can be used to automate the mapping
• a manual mapping can be done, it's a one shot effort after all
• the code can be restructured to separate type-dependent from type-independent variants

I'll show-case the latter:

enum MyEnumImpl {
    A,
    B,
    C,
}

enum MyEnum {
    Independent(MyEnumImpl),
    Dependent(T),
}

Obviously, the latter makes it much easier to manually map things.