regexp/syntax: panic: unhandled case in compile - x{2}

[bogdan-deac]

Go version

go version go1.22.2 darwin/arm64

Output of go env in your module/workspace:

GO111MODULE=''
GOARCH='arm64'
GOBIN=''
GOCACHE='/Users/bdeac/Library/Caches/go-build'
GOENV='/Users/bdeac/Library/Application Support/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='arm64'
GOHOSTOS='darwin'
GOINSECURE=''
GOMODCACHE='/Users/bdeac/go/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='darwin'
GOPATH='/Users/bdeac/go'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/opt/homebrew/Cellar/go/1.22.2/libexec'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/opt/homebrew/Cellar/go/1.22.2/libexec/pkg/tool/darwin_arm64'
GOVCS=''
GOVERSION='go1.22.2'
GCCGO='gccgo'
AR='ar'
CC='cc'
CXX='c++'
CGO_ENABLED='1'
GOMOD='/Users/bdeac/Documents/learning/regex/go.mod'
GOWORK=''
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
PKG_CONFIG='pkg-config'
GOGCCFLAGS='-fPIC -arch arm64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -ffile-prefix-map=/var/folders/fd/pkkd278j26g5q23_wwwj38bh0000gq/T/go-build4036665068=/tmp/go-build -gno-record-gcc-switches -fno-common

What did you do?

import (
	"errors"
	"fmt"
	"regexp/syntax"
)

func main() {
        regex := "x{2}"
        regParse, err := syntax.Parse(regex, 0)
	if err != nil {
		return errors.New(fmt.Sprintf("issue parsing regex %s: %s ", regex, err.Error()))
	}

	regParse.Simplify()

	prog, err := syntax.Compile(regParse)
	if err != nil {
		return errors.New(fmt.Sprintf("issue compiling regex %s: %s ", regex, err.Error()))
	}

        fmt.Println(len(prog.Inst))
}

What did you see happen?

panic: regexp: unhandled case in compile

This appears to be because OpRepeat (17) is not handled here. I based my implementation on this suggestion.

Furthermore, using something like regexp.MustCompile causes no issue for x{2} .

What did you expect to see?

Successful Compilation

I'm not sure if this is intended behaviour and there's an alternative way to accomplish this, but I would think at the very least the documentation of syntax.Compile should include a possible panic.

[gabyhelp]

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