func charAlt() {
	regexp.MustCompile(`(a|b|c|d)`)
	regexp.MustCompile(`a|b`)
}
a|b|c -> [abc]
package checker_test
import (
	"regexp"
)
func multiPass() {
	regexp.MustCompile(`[a-a]`)
	regexp.MustCompile(`(?:a|b|c)`)
}
func altCommonPrefixSuffix() {
	regexp.MustCompile(`foo|fo`)
	regexp.MustCompile(`(?:http|https): 
	regexp.MustCompile(`xpath|path`)
	regexp.MustCompile(`❤path|path`)
	regexp.MustCompile(`fo|fo❤`)
}
func merge() {
	regexp.MustCompile(`x[abcd][abcd]*y`)
	regexp.MustCompile(`axx*y`)
}
func ungroup() {
	regexp.MustCompile(`(?:x)+`)
	regexp.MustCompile(`(?:[abc])+`)
}
func repeat() {
	regexp.MustCompile(`  `)
	regexp.MustCompile(`   `)
	regexp.MustCompile(`    `)
	regexp.MustCompile(`[a-z][a-z]`)
	regexp.MustCompile(`[abc][abc][abc]`)
	regexp.MustCompile(`(?:foo|bar)(?:foo|bar)`)
	regexp.MustCompile(`aaaaax`)
	regexp.MustCompile(`\d\d\d`)
	regexp.MustCompile(`\.\.\.`)
	regexp.MustCompile(`\.\.\.\.`)
	regexp.MustCompile(`....`)
	regexp.MustCompile(`.....x`)
}
func replaceCharClass() {
	regexp.MustCompile(`foo[0-9]+`)
	regexp.MustCompile(`[0-9]`)
	regexp.MustCompile(`[[:word:]]`)
	regexp.MustCompile(`[[:^word:]]`)
	regexp.MustCompile(`[[:digit:]]`)
	regexp.MustCompile(`[[:^digit:]]`)
	regexp.MustCompile(`[[:space:]]`)
	regexp.MustCompile(`[[:^space:]]`)
	regexp.MustCompile(`[^\D]`)
	regexp.MustCompile(`[^[:^word:]]`)
}
func unwrapCharClass() {
	regexp.MustCompile(`[x]`)
	regexp.MustCompile(`[\d]`)
	regexp.MustCompile(`[]]`)
	regexp.MustCompile(`[][]`)
}
func unescape() {
	regexp.MustCompile(`\#`)
	regexp.MustCompile(`\&`)
	regexp.MustCompile(`\!`)
	regexp.MustCompile(`\@`)
	regexp.MustCompile(`\%`)
	regexp.MustCompile(`\>`)
	regexp.MustCompile(`\<`)
	regexp.MustCompile(`\:`)
	regexp.MustCompile(`\;`)
	regexp.MustCompile(`\/`)
	regexp.MustCompile(`\,`)
	regexp.MustCompile(`\=`)
	regexp.MustCompile(`[x\#]`)
	regexp.MustCompile(`[x\.]`)
}