go/parser: bad gofmt error message on extra comma in struct type

[evmar]

On some bad code, gofmt gives a confusing error while the compiler gives a nice one.

Online demo at http://play.golang.org/p/htmZpN6HcY (click "format"), also inlined here to keep the bug self-contained.

package main

import "fmt"

func main() {
    x := struct {
        foo string,
    }{3}
}

The issue is the comma.

Format says 6:7: expected expression (and 3 more errors), which points at the "struct" keyword.

Run says prog.go:7: syntax error: unexpected comma, expecting }, which is a good error message.

[gopherbot]

CL https://golang.org/cl/14564 mentions this issue.