How to declare a method of generic pointer interface or slice pointer interface parameters

[wake2012 (gopher)]

0

eg:

type AnyPtr[T any] interface {
    *T
}

type AnyPtrSlice[T any] interface {
    []*T
}

func FuncName[T AnyPtr[E] | AnyPtrSlice[E], E any](data T) (err error) {
}


type ModelAA struct {
    A int
    B int
}

func TestAddV2(t *testing.T) {
    var a = ModelAA{
        A: 1, B: 2,
    }
    _ = FuncName(&a)
}

This approach will be reported by the compiler as being unable to infer E. Is there any other way to write it?

[christophberger]

Hi @wake2012, welcome to the forum.

Maybe you need the two Any* interfaces for some reason that is not apparent from the code snippet, but I have removed them to simplify the code. Within the context of the given code, the following function signature is semantically identical to your definition using the Any* interfaces:

func FuncName[T *E | []*E, E any](data T) (err error)

The error message seems unjustified, as the type of &a is clearly “pointer to ModelAA” and not “slice of pointers to ModelAA”. But you can help the compiler and specify the types to use for T and E when calling the function:

package main

import "testing"

func FuncName[T *E | []*E, E any](data T) (err error) {
	return nil
}

type ModelAA struct {
	A int
	B int
}

func TestAddV2(t *testing.T) {
	var a = ModelAA{
		A: 1, B: 2,
	}
	_ = FuncName[*ModelAA, ModelAA](&a)
}

(Run the code in the Go Playground)

(See also Type inferrence in the langugage specification)