Generics: Self Referencing Constraint Types

[jfcg...@gmail.com]

Hi, please take a look.

The aim is to write a HaveLess constraint that will work with any type like Large, without any reflection / traditional interfaces / dictionaries etc., just plain method calls.

How would you write this? Keep in mind that type Large is large :)

[Axel Wagner]

At its core, this is this restriction of the current generics design:

https://go.googlesource.com/proposal/+/refs/heads/master/design/43651-type-parameters.md#no-way-to-require-pointer-methods

That is, there is no real "nice" way to do it.

If you are willing to require a pointer receiver, you can do constraint type inference:

https://go.dev/play/p/L2NiAAM8qE4

Alternatively, it might be appropriate to do away with methods and pass a comparison function:

https://go.dev/play/p/XRoD70UFbzi

This has the advantage of being able to use types which you don't control as well.

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[jfcg...@gmail.com]

If you are willing to require a pointer receiver, you can do constraint type inference:

https://go.dev/play/p/L2NiAAM8qE4

A single cast worked nicely, thank you.