Option to implement GoStringer instead of Stringer, to allow using the %x verb

[jonathangjertsen]

Problem

Go makes an IMO bizarre decision when using the %x verb on an integer Stringer: golang/go#21535

Consider the following (Go playground link: https://go.dev/play/p/6SXwSSmZAHW)

package main

import "fmt"

type HasNone uint16

type HasStringer uint16

func (v HasStringer) String() string { return "String" }

type HasGoStringer uint16

func (v HasGoStringer) GoString() string { return "GoString" }

type HasBoth uint16

func (v HasBoth) String() string   { return "String" }
func (v HasBoth) GoString() string { return "GoString" }

func main() {
	hasNone := HasNone(0x1234)
	hasStringer := HasStringer(0x1234)
	hasGoStringer := HasGoStringer(0x1234)
	hasBoth := HasBoth(0x1234)

	fmt.Printf("None        %%v: %v\t %%#v: %#v\t %%#x: %#x\t\t%%s: %s\n", hasNone, hasNone, hasNone, hasNone)
	fmt.Printf("Stringer    %%v: %v\t %%#v: %#v\t %%#x: %#x\t%%s: %s\n", hasStringer, hasStringer, hasStringer, hasStringer)
	fmt.Printf("GoStringer  %%v: %v\t %%#v: %#v\t %%#x: %#x\t\t%%s: %s\n", hasGoStringer, hasGoStringer, hasGoStringer, hasGoStringer)
	fmt.Printf("Both        %%v: %v\t %%#v: %#v\t %%#x: %#x\t%%s: %s\n", hasBoth, hasBoth, hasBoth, hasBoth)
}

output:

None        %v: 4660	 %#v: 0x1234	 %#x: 0x1234		%s: %!s(main.HasNone=4660)
Stringer    %v: String	 %#v: 0x1234	 %#x: 0x537472696e67	%s: String
GoStringer  %v: 4660	 %#v: GoString	 %#x: 0x1234		%s: %!s(main.HasGoStringer=4660)
Both        %v: String	 %#v: GoString	 %#x: 0x537472696e67	%s: String

None of these are great, but at least GoStringer allows you to select between printing the name (%#v) or the hex value (%x) without doing any type conversions. So it would be nice to be able to generate GoStringer instead of Stringer. It's conceivable that someone might want to generate none or both of the methods, so I guess you should write --gostring --no-string if you want only GoString.