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reflect.DeepEqual error for empty slice and variadic #1147

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visualfc opened this issue Sep 12, 2022 · 1 comment · Fixed by #1150
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reflect.DeepEqual error for empty slice and variadic #1147

visualfc opened this issue Sep 12, 2022 · 1 comment · Fixed by #1150
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bug
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Go spec compliance

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@visualfc
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visualfc commented Sep 12, 2022 •
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demo

package main

import (
	"reflect"
)

func test1(v ...string) {
	var names []string
	ret := reflect.DeepEqual(names, v)
	println(ret)
}

func test2(opt int, v ...string) {
	var names []string
	ret := reflect.DeepEqual(names, v)
	println(ret)
}

func main() {
	test1()
	test2(100)
}

gopherjs run main.go

output error

true
false
@visualfc visualfc mentioned this issue Sep 12, 2022
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@nevkontakte nevkontakte added this to the Go spec compliance milestone Sep 18, 2022
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Thanks for the report.

Looking at the generated code, for some reason the compiler initializes the variadic argument differently depending on whether it's the only argument or not:

$r = test1(sliceType.nil); /* */ $s = 1; case 1: if($c) { $c = false; $r = $r.$blk(); } if ($r && $r.$blk !== undefined) { break s; }
$r = test2(100, new sliceType([])); /* */ $s = 2; case 2: if($c) { $c = false; $r = $r.$blk(); } if ($r && $r.$blk !== undefined) { break s; }

According to the Go spec, this is a bug:

If f is invoked with no actual arguments for p, the value passed to p is nil.

nevkontakte added a commit to nevkontakte/gopherjs that referenced this issue Sep 18, 2022
@nevkontakte
Pass nil slice when variadic arguments are omitted after regular args.
4e9568a 
Previously we would pass an empty slice, which is against the Go spec:

> If f is invoked with no actual arguments for p, the value passed to p
> is nil.

Source: https://go.dev/ref/spec#Passing_arguments_to_..._parameters

Fixes gopherjs#1147
nevkontakte added a commit to nevkontakte/gopherjs that referenced this issue Sep 18, 2022
@nevkontakte
Pass nil slice when variadic arguments are omitted after regular args.
29337c9 
Previously we would pass an empty slice, which is against the Go spec:

> If f is invoked with no actual arguments for p, the value passed to p
> is nil.

Source: https://go.dev/ref/spec#Passing_arguments_to_..._parameters

Fixes gopherjs#1147
@nevkontakte nevkontakte mentioned this issue Sep 18, 2022
Merged
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Pass nil slice when variadic arguments are omitted after regular args. nevkontakte/gopherjs
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@nevkontakte @visualfc