Golang Generic Support for methods defined on structs

Getting Help
1

hi Gophers,
I think this could be a valuable feature addition for generics in golang.

type SomeStruct struct {
	genericValue interface{}
}

Now lets use generics to extract a specific value type.
This works perfectly

func GetGenericReturnValue[T any](input SomeStruct) (*T, error) {
	if val, ok := input.genericValue.(T); ok {
		return &val, nil
	}
	return nil, errors.New("invalid")
}
/* Sample code to demonstrate the above use case
	s := SomeStruct{
		genericValue: 42,
	}
	intValue, err := GetGenericReturnValue[int64](s)
	if err != nil {
		fmt.Println("Returned int value:", *intValue)
	}
*/

But now if I want the method to be associated with a struct like below

func (s SomeStruct) GetReturnValue[T any]() (*T,error) {
    if val,ok:=s.genericValue.(T) ;ok{
            return &val,nil
    }
    return &val,errors.New("invalid")
}

It gives a syntax error ==> method must have no type parameters

Is there any reason why this above use case should not be supported?

For people wondering what’s difference between 2 and why I am trying to advocate second style—> Encapsulation Principle is what I wanted to respect

2

Here is the answer why it was not implemented from the start.

https://go.googlesource.com/proposal/+/refs/heads/master/design/43651-type-parameters.md#No-parameterized-methods

And here is the huge discussion ~3 years, how it could/should be done.

Imho, I see no difference between sugar like struct method and generic func which takes a struct pointer as the first argument. With current generics implementation, the only thing you can do, if you want “generic” method, is to move type to the struct, instead of func itself, something like:

package main

import "fmt"

type Test[T any] struct {
	genericValue T
}

func (t *Test[T]) GetValue() T {
	return t.genericValue
}

func main() {
	t := &Test[int]{42}
	fmt.Println(t.GetValue())

	t1 := &Test[string]{"Hello"}
	fmt.Println(t1.GetValue(), "world!")
}