regexp: LiteralPrefix returns complete=true incorrectly

[dvyukov]

The following program fails:

package main

import "regexp"

func main() {
    re := regexp.MustCompile("^0^000000$")
    prefix, complete := re.LiteralPrefix()
    if complete && !re.MatchString(prefix) {
        panic("prefix:" + prefix)
    }
}

panic: prefix:0

If LiteralPrefix return complete==true, the re must match the prefix.

go version devel +b0532a9 Mon Jun 8 05:13:15 2015 +0000 linux/amd64

[rsc]

This one is a real problem.

[gopherbot]

CL https://golang.org/cl/16200 mentions this issue.