regexp: add ErrLarge error

For #56041

Change-Id: I6c98458b5c0d3b3636a53ee04fc97221f3fd8bbc
Reviewed-on: https://go-review.googlesource.com/c/go/+/444817
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: Bryan Mills <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>
Run-TryBot: Ian Lance Taylor <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>
Auto-Submit: Ian Lance Taylor <[email protected]>
Run-TryBot: xie cui <[email protected]>

Author: cuiweixie

api/next/56041.txt

@@ -0,0 +1,2 @@
+pkg regexp/syntax, const ErrLarge = "expression too large" #56041
+pkg regexp/syntax, const ErrLarge ErrorCode #56041

src/regexp/all_test.go

@@ -49,6 +49,7 @@ var badRe = []stringError{
 	{`a**`, "invalid nested repetition operator: `**`"},
 	{`a*+`, "invalid nested repetition operator: `*+`"},
 	{`\x`, "invalid escape sequence: `\\x`"},
+	{strings.Repeat(`\pL`, 27000), "expression too large"},
 }
 
 func compileTest(t *testing.T, expr string, error string) *Regexp {

src/regexp/syntax/parse.go

@@ -44,6 +44,7 @@ const (
 	ErrTrailingBackslash     ErrorCode = "trailing backslash at end of expression"
 	ErrUnexpectedParen       ErrorCode = "unexpected )"
 	ErrNestingDepth          ErrorCode = "expression nests too deeply"
+	ErrLarge                 ErrorCode = "expression too large"
 )
 
 func (e ErrorCode) String() string {
@@ -159,7 +160,7 @@ func (p *parser) reuse(re *Regexp) {
 
 func (p *parser) checkLimits(re *Regexp) {
 	if p.numRunes > maxRunes {
-		panic(ErrInternalError)
+		panic(ErrLarge)
 	}
 	p.checkSize(re)
 	p.checkHeight(re)
@@ -203,7 +204,7 @@ func (p *parser) checkSize(re *Regexp) {
 	}
 
 	if p.calcSize(re, true) > maxSize {
-		panic(ErrInternalError)
+		panic(ErrLarge)
 	}
 }
 
@@ -897,8 +898,8 @@ func parse(s string, flags Flags) (_ *Regexp, err error) {
 			panic(r)
 		case nil:
 			// ok
-		case ErrInternalError: // too big
-			err = &Error{Code: ErrInternalError, Expr: s}
+		case ErrLarge: // too big
+			err = &Error{Code: ErrLarge, Expr: s}
 		case ErrNestingDepth:
 			err = &Error{Code: ErrNestingDepth, Expr: s}
 		}