cmd/compile: cannot use _ as value

[zigo101]

Please answer these questions before submitting your issue. Thanks!

What version of Go are you using (go version)?

go version go1.7.3 linux/amd64

What did you do?

package main

func main() {
	var _ = struct{}{} // ok
	
	_ = struct{
		a int
	}{
		a: 1, // ok
	}
	
	var _ = struct{
		a int
	}{
		a: 1, // cannot use _ as value
	}
}

What did you expect to see?

compile ok

What did you see instead?

compile error

[zigo101]

I just googled this problem and found a similar issue: #15481

A summary:

package main

func main() {
    var _ = struct{a int}{}
    var _ = [5]int{}
    var _ = map[string]int{}

    _ = struct{a int}{1}
    _ = [5]int{1}
    _ = map[string]int{"a": 1}
    _ = struct {a int}{a: 1}

    var _ = struct {}{}
    var _ = []int{1}

    // aboves are all ok
    // belows are all errors

    var _ = struct{a int}{1}
    var _ = map[string]int{"a": 1}
    var _ = [5]int{1}
    var _ = struct {a int}{a: 1}
}

[griesemer]

Duplicate of #15481.