Error while trying to match a string with a specific unicode against a RegExp that contains a space and a group

[beatzzz]

When trying to match (phrase.MatchString(X)) messages like gg 󠀀 󠀀 (notice that these are not the regular spaces) against a phrase like regexp2.MustCompile("\\bcool (house)\\b", 0), the following error will be thrown:

panic: runtime error: index out of range [917504] with length 128

goroutine 1 [running]:
github.com/dlclark/regexp2/syntax.(*BmPrefix).Scan(0xc000180540, {0xc000b70948, 0x6, 0x0?}, 0x0?, 0x0, 0x6)
        C:/Users/X/go/pkg/mod/github.com/dlclark/regexp2@v1.4.0/syntax/prefix.go:716 +0x3bb
github.com/dlclark/regexp2.(*runner).findFirstChar(0xc000623a00)
        C:/Users/X/go/pkg/mod/github.com/dlclark/regexp2@v1.4.0/runner.go:1305 +0x366
github.com/dlclark/regexp2.(*runner).scan(0xc000623a00, {0xc000b70948?, 0x6, 0xc000b70948?}, 0x6?, 0x1, 0xc00008f8e8?)
        C:/Users/X/go/pkg/mod/github.com/dlclark/regexp2@v1.4.0/runner.go:130 +0x1e5
github.com/dlclark/regexp2.(*Regexp).run(0xc0000f6200, 0xf4?, 0xffffffffffffffff, {0xc000b70948, 0x6, 0x6})
        C:/Users/X/go/pkg/mod/github.com/dlclark/regexp2@v1.4.0/runner.go:91 +0xfa
github.com/dlclark/regexp2.(*Regexp).MatchString(0x10f9c40?, {0x108f0f4?, 0xc00008fb48?})
        C:/Users/X/go/pkg/mod/github.com/dlclark/regexp2@v1.4.0/regexp.go:213 +0x45
main.main()
        C:/Users/X/Desktop/GoRegExTests/test.go:127 +0xbdc

The error is only being thrown when:
a. The message contains those unicode characters
b. The RegExp contains a space and a group like (house)

The RegExp above is just a very basic example to demonstrate this problem.

[dlclark]

Unfortunately I'm not able to reproduce this via copy-paste. I suspect GitHub isn't preserving the exact unicode characters of your input. Can you give me the exact runes in question via the unicode escape sequences (e.g. \uabcd)?

[beatzzz]

Yes, you are right. GitHub modified one of the characters.

This is the original one: https://apps.timwhitlock.info/unicode/inspect?s=gg+%F3%A0%80%80+%F3%A0%80%80
(and this is the one copied from GitHub: https://apps.timwhitlock.info/unicode/inspect?s=gg+%F3%A0%80%80+)

[dlclark]

I've confirmed this is fixed with #36 so you just need to upgrade to v1.5 or v1.6 to get the fix.