Compile time check if two Types are Equal

1

Note, all this is happening compile time. True, False being types is intended. It is not a mistake.

Suppose we have:

pub struct True {};
pub struct False {};

is it possible to design a "IsEqual" so that "A IsEqual A => True", "A IsEqual B => False" for A != B

One possible approach is:

pub trait IsEqualT<Target> {
  type BoolOutput;
}

(A as IsEqualT<B>)::BoolOutput

This technique can be made to work, but all the structs, 'A', and 'B' must be declared via a procedural macro which injects a Uid field containing a typenum number: lhlist/lib.rs at master · agnes-rs/lhlist · GitHub

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Question: is there a simpler way to do this?

2

Probably requires specialization.

3

Yeah, with specialization this wouldn't be terribly difficult to accomplish. Without it I don't believe it's possible.