Stop panicking when trying to parse numbers bigger than 2^64.

Before: panic: mixedNumberPattern yielded an unparseable int: strconv.ParseInt: parsing "99999999999999999999999999999999999999999999999": value out of range

.gitignore

@@ -1 +1,4 @@
 keep-sorted
+
+.idea/
+*.iml

goldens/numeric.in

@@ -6,6 +6,7 @@ FOO_3
 BAR_1
 BAR_2
 BAR_10
+BAR_99999999999999999999999999999999999999999999999
 // keep-sorted-test end
 
 

goldens/numeric.out

@@ -3,6 +3,7 @@ Numeric sorting:
 BAR_1
 BAR_2
 BAR_10
+BAR_99999999999999999999999999999999999999999999999
 FOO_2
 FOO_3
 FOO_100

keepsorted/keep_sorted.go

@@ -52,7 +52,7 @@ func (f *Fixer) errorMissingEnd() string {
 	return fmt.Sprintf("This instruction doesn't have matching '%s' line", f.endDirective)
 }
 
-// Fix all of the findings on contents to make go/keep-sorted happy.
+// Fix all of the findings on contents to make keep-sorted happy.
 func (f *Fixer) Fix(contents string, modifiedLines []LineRange) (fixed string, alreadyCorrect bool) {
 	lines := strings.Split(contents, "\n")
 	fs := f.findings("unused-filename", lines, modifiedLines, false)
@@ -78,7 +78,7 @@ func (f *Fixer) Fix(contents string, modifiedLines []LineRange) (fixed string, a
 }
 
 // Findings returns a slice of things that need to be addressed in the file to
-// make go/keep-sorted happy.
+// make keep-sorted happy.
 //
 // If modifiedLines is non-nil, we only report findings for issues within the
 // modified lines. Otherwise, we report all findings.

keepsorted/options.go

@@ -18,12 +18,12 @@ import (
 	"fmt"
 	"reflect"
 	"regexp"
-	"strconv"
 	"strings"
 	"unicode"
 
 	"go.uber.org/multierr"
 	"golang.org/x/exp/slices"
+	"math/big"
 )
 
 var (
@@ -83,7 +83,7 @@ type blockOptions struct {
 
 	// LINT.ThenChange(//depot/google3/devtools/keep_sorted/README.md)
 
-	// Syntax used to start a comment for go/keep-sorted annotation, e.g. "//".
+	// Syntax used to start a comment for keep-sorted annotation, e.g. "//".
 	commentMarker string
 }
 
@@ -242,8 +242,8 @@ func (opts blockOptions) maybeParseNumeric(s string) numericTokens {
 				// See the comment on numericTokens for more details.
 				t.s = append(t.s, "")
 			}
-			i, err := strconv.ParseInt(sm[1], 10, 64)
-			if err != nil {
+			i := new(big.Int)
+			if err := i.UnmarshalText([]byte(sm[1])); err != nil {
 				panic(fmt.Errorf("mixedNumberPattern yielded an unparseable int: %w", err))
 			}
 			t.i = append(t.i, i)
@@ -269,7 +269,7 @@ func (opts blockOptions) maybeParseNumeric(s string) numericTokens {
 //	i: []int64{123},
 type numericTokens struct {
 	s []string
-	i []int64
+	i []*big.Int
 }
 
 func (t numericTokens) len() int {
@@ -287,10 +287,8 @@ func (t numericTokens) compare(o numericTokens) int {
 				return c
 			}
 		} else { // Alternate by comparing with numbers.
-			if c := t.i[i/2] - o.i[i/2]; c < 0 {
-				return -1
-			} else if c > 0 {
-				return 1
+			if c := t.i[i/2].Cmp(o.i[i/2]); c != 0 {
+				return c
 			}
 		}
 	}