Imported Upstream version 1.2upstream/1.2

1 files changed, 16 insertions, 13 deletions

diff --git a/src/pkg/regexp/syntax/prog.go b/src/pkg/regexp/syntax/prog.go
index 902d3b3a5..a482a82f2 100644
--- a/src/pkg/regexp/syntax/prog.go
+++ b/src/pkg/regexp/syntax/prog.go
@@ -56,23 +56,26 @@ const (
 // Passing r2 == -1 indicates that the position is
 // at the end of the text.
 func EmptyOpContext(r1, r2 rune) EmptyOp {
-	var op EmptyOp
-	if r1 < 0 {
-		op |= EmptyBeginText | EmptyBeginLine
-	}
-	if r1 == '\n' {
+	var op EmptyOp = EmptyNoWordBoundary
+	var boundary byte
+	switch {
+	case IsWordChar(r1):
+		boundary = 1
+	case r1 == '\n':
 		op |= EmptyBeginLine
+	case r1 < 0:
+		op |= EmptyBeginText | EmptyBeginLine
 	}
-	if r2 < 0 {
-		op |= EmptyEndText | EmptyEndLine
-	}
-	if r2 == '\n' {
+	switch {
+	case IsWordChar(r2):
+		boundary ^= 1
+	case r2 == '\n':
 		op |= EmptyEndLine
+	case r2 < 0:
+		op |= EmptyEndText | EmptyEndLine
 	}
-	if IsWordChar(r1) != IsWordChar(r2) {
-		op |= EmptyWordBoundary
-	} else {
-		op |= EmptyNoWordBoundary
+	if boundary != 0 { // IsWordChar(r1) != IsWordChar(r2)
+		op ^= (EmptyWordBoundary | EmptyNoWordBoundary)
 	}
 	return op
 }