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regexp: LiteralPrefix lies about completeness #11172

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dvyukov opened this issue Jun 11, 2015 · 3 comments
Closed

regexp: LiteralPrefix lies about completeness #11172

dvyukov opened this issue Jun 11, 2015 · 3 comments
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Go1.6

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@dvyukov
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dvyukov commented Jun 11, 2015

The following program fails with the panic:

package main

import "regexp"

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

If complete is false, Match must fail.

go version devel +b0532a9 Mon Jun 8 05:13:15 2015 +0000 linux/amd64
@cespare
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cespare commented Jun 11, 2015

If complete is false, Match must fail.

Why? A match doesn't have to match the entire input.

http://play.golang.org/p/E4iOdS7Av0

@dvyukov
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dvyukov commented Jun 11, 2015

It's the other way around here. In your example, there is leftover in the string. In my example, there is leftover in the regexp (according to LiteralPrefix).

@ianlancetaylor ianlancetaylor added this to the Go1.6 milestone Jun 11, 2015
@rsc
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rsc commented Oct 14, 2015

If complete is false, Match must fail.

Not true. If complete is false it means that there is something to the regexp beyond what has been returned in 'prefix'.

@rsc rsc closed this as completed Oct 14, 2015
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