"Why isn't there an LSP for Crystal?"

[nobodywasishere]

Proposal: Interfaces for more generic code

This is a great idea, and I’d like this to happen. The problem is that interfaces are typed, but in the rest of the language it’s not mandatory to type your methods. So a user will create a type with def to_i without an explicit return type, and the compiler won’t consider that type. For example BigDecimal has to_i without a return type. Same goes for BigFloat, Complex and maybe others. The problem is that when you create an interface expecting to “capture” existing types with it, that might…