regexp: use slices to simplify the code

Replace reflect.DeepEqual with slices.Equal which is much faster.

Remove unnecessary "runeSlice" and redundant helper functions.

src/regexp/all_test.go

@@ -7,6 +7,7 @@ package regexp
 import (
 	"reflect"
 	"regexp/syntax"
+	"slices"
 	"strings"
 	"testing"
 	"unicode/utf8"
@@ -519,13 +520,13 @@ func TestSplit(t *testing.T) {
 		}
 
 		split := re.Split(test.s, test.n)
-		if !reflect.DeepEqual(split, test.out) {
+		if !slices.Equal(split, test.out) {
 			t.Errorf("#%d: %q: got %q; want %q", i, test.r, split, test.out)
 		}
 
 		if QuoteMeta(test.r) == test.r {
 			strsplit := strings.SplitN(test.s, test.r, test.n)
-			if !reflect.DeepEqual(split, strsplit) {
+			if !slices.Equal(split, strsplit) {
 				t.Errorf("#%d: Split(%q, %q, %d): regexp vs strings mismatch\nregexp=%q\nstrings=%q", i, test.s, test.r, test.n, split, strsplit)
 			}
 		}

src/regexp/exec_test.go

@@ -13,6 +13,7 @@ import (
 	"os"
 	"path/filepath"
 	"regexp/syntax"
+	"slices"
 	"strconv"
 	"strings"
 	"testing"
@@ -167,7 +168,7 @@ func testRE2(t *testing.T, file string) {
 			for i := range res {
 				have, suffix := run[i](re, refull, text)
 				want := parseResult(t, file, lineno, res[i])
-				if !same(have, want) {
+				if !slices.Equal(have, want) {
 					t.Errorf("%s:%d: %#q%s.FindSubmatchIndex(%#q) = %v, want %v", file, lineno, re, suffix, text, have, want)
 					if nfail++; nfail >= 100 {
 						t.Fatalf("stopping after %d errors", nfail)
@@ -309,18 +310,6 @@ func parseResult(t *testing.T, file string, lineno int, res string) []int {
 	return out
 }
 
-func same(x, y []int) bool {
-	if len(x) != len(y) {
-		return false
-	}
-	for i, xi := range x {
-		if xi != y[i] {
-			return false
-		}
-	}
-	return true
-}
-
 // TestFowler runs this package's regexp API against the
 // POSIX regular expression tests collected by Glenn Fowler
 // at http://www2.research.att.com/~astopen/testregex/testregex.html.
@@ -547,7 +536,7 @@ Reading:
 			if len(have) > len(pos) {
 				have = have[:len(pos)]
 			}
-			if !same(have, pos) {
+			if !slices.Equal(have, pos) {
 				t.Errorf("%s:%d: %#q.FindSubmatchIndex(%#q) = %v, want %v", file, lineno, pattern, text, have, pos)
 			}
 		}

src/regexp/onepass.go

@@ -6,7 +6,7 @@ package regexp
 
 import (
 	"regexp/syntax"
-	"sort"
+	"slices"
 	"strings"
 	"unicode"
 	"unicode/utf8"
@@ -282,13 +282,6 @@ func onePassCopy(prog *syntax.Prog) *onePassProg {
 	return p
 }
 
-// runeSlice exists to permit sorting the case-folded rune sets.
-type runeSlice []rune
-
-func (p runeSlice) Len() int           { return len(p) }
-func (p runeSlice) Less(i, j int) bool { return p[i] < p[j] }
-func (p runeSlice) Swap(i, j int)      { p[i], p[j] = p[j], p[i] }
-
 var anyRuneNotNL = []rune{0, '\n' - 1, '\n' + 1, unicode.MaxRune}
 var anyRune = []rune{0, unicode.MaxRune}
 
@@ -383,7 +376,7 @@ func makeOnePass(p *onePassProg) *onePassProg {
 				for r1 := unicode.SimpleFold(r0); r1 != r0; r1 = unicode.SimpleFold(r1) {
 					runes = append(runes, r1, r1)
 				}
-				sort.Sort(runeSlice(runes))
+				slices.Sort(runes)
 			} else {
 				runes = append(runes, inst.Rune...)
 			}
@@ -407,7 +400,7 @@ func makeOnePass(p *onePassProg) *onePassProg {
 				for r1 := unicode.SimpleFold(r0); r1 != r0; r1 = unicode.SimpleFold(r1) {
 					runes = append(runes, r1, r1)
 				}
-				sort.Sort(runeSlice(runes))
+				slices.Sort(runes)
 			} else {
 				runes = append(runes, inst.Rune[0], inst.Rune[0])
 			}

src/regexp/onepass_test.go

@@ -5,8 +5,8 @@
 package regexp
 
 import (
-	"reflect"
 	"regexp/syntax"
+	"slices"
 	"strings"
 	"testing"
 )
@@ -125,10 +125,10 @@ var runeMergeTests = []struct {
 func TestMergeRuneSet(t *testing.T) {
 	for ix, test := range runeMergeTests {
 		merged, next := mergeRuneSets(&test.left, &test.right, test.leftPC, test.rightPC)
-		if !reflect.DeepEqual(merged, test.merged) {
+		if !slices.Equal(merged, test.merged) {
 			t.Errorf("mergeRuneSet :%d (%v, %v) merged\n have\n%v\nwant\n%v", ix, test.left, test.right, merged, test.merged)
 		}
-		if !reflect.DeepEqual(next, test.next) {
+		if !slices.Equal(next, test.next) {
 			t.Errorf("mergeRuneSet :%d(%v, %v) next\n have\n%v\nwant\n%v", ix, test.left, test.right, next, test.next)
 		}
 	}