Compare two generic types in go2go. https://go2goplay.golang.org/p/WWTcvX9lDWH

same_type.go

package main

import (
	"bytes"
	"fmt"
	"io"
)

type wrap[T any] struct{}

func (wrap[T]) t() (zero T) {
	return
}

type wrapI[T any] interface {
	t() T
}

func SameType[A, B any]() bool {
	var a A

	switch (interface{})(a).(type) {
	case nil:
		var w wrap[B]
		switch (interface{})(w).(type) {
		case wrapI[A]:
		default:
			return false
		}

	case B:
	default:
		return false
	}

	var b B
	switch (interface{})(b).(type) {
	case nil:
		var w wrap[B]
		switch (interface{})(w).(type) {
		case wrapI[A]:
		default:
			return false
		}

	case A:
	default:
		return false
	}

	return true
}

type writer[T any] interface {
    Write(T) (int, error)
}

func main() {
	fmt.Println(SameType[io.Writer, io.Writer]())
	fmt.Println(SameType[*bytes.Buffer, *bytes.Buffer]())
    	fmt.Println(SameType[writer[int], writer[int]]())
    	fmt.Println(SameType[writer[io.Writer], writer[io.Writer]]())
	fmt.Println()
    	fmt.Println(SameType[writer[int], writer[string]]())
	fmt.Println(SameType[io.Writer, *bytes.Buffer]())
	fmt.Println(SameType[io.Writer, bytes.Buffer]())
	fmt.Println(SameType[*bytes.Buffer, io.Writer]())
	fmt.Println(SameType[bytes.Buffer, io.Writer]())
	fmt.Println(SameType[io.Writer, io.Reader]())

}