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cmd/go2go: generic type receiver cannot have type parameters in the method declaration? #39704

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ycalansy opened this issue Jun 19, 2020 · 1 comment

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@ycalansy
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@ycalansy ycalansy commented Jun 19, 2020

package main

import (
	"fmt"
)

func main() {
	vec := Vector(string){"abc", "xyz"}

	vec.ForEach(PrintString)
	
	fmt.Println(Reduce(int, string)(0, vec, CountCharacters))

	fmt.Println(vec.Reduce(int)(0, CountCharacters))
}

func PrintString(s string) { fmt.Println(s) }

func CountCharacters(acc int, s string) int { return acc + len(s) }

type Vector(type E) []E

func (v Vector(E)) ForEach(fn func(E)) {
	for _, ele := range v {
		fn(ele)
	}
}

func (v Vector(E)) Reduce(type A)(acc A, fn func(A, E) A) A {
	for _, ele := range v {
		acc = fn(acc, ele)
	}
	return acc
}

func Reduce(type A, E)(acc A, vec Vector(E), fn func(A, E) A) A {
	for _, ele := range vec {
		acc = fn(acc, ele)
	}
	return acc
}

What did you expect to see?

abc
xyz
6
6

What did you see instead?

type checking failed for main
prog.go2:29:26: methods cannot have type parameters

@ycalansy ycalansy changed the title cmd/go2go: Generic type receiver cannot have type parameters method? cmd/go2go: generic type receiver cannot have type parameters method? Jun 19, 2020
@ycalansy ycalansy changed the title cmd/go2go: generic type receiver cannot have type parameters method? cmd/go2go: generic type receiver cannot have type parameters in the method declaration? Jun 19, 2020
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