fix scanner initialization, add test

R=r
DELTA=27  (25 added, 0 deleted, 2 changed)
OCL=26798
CL=26798

src/lib/go/scanner.go

@@ -76,10 +76,12 @@ func (S *Scanner) next() {
 // white space and ignored.
 //
 func (S *Scanner) Init(src []byte, err ErrorHandler, scan_comments bool) {
+	// Explicitly initialize all fields since a scanner may be reused.
 	S.src = src;
 	S.err = err;
 	S.scan_comments = scan_comments;
-	S.pos.Line = 1;
+	S.pos = token.Position{0, 1, 0};
+	S.offset = 0;
 	S.next();
 }
 

src/lib/go/scanner_test.go

@@ -176,7 +176,8 @@ func NewlineCount(s string) int {
 }
 
 
-func Test(t *testing.T) {
+// Verify that calling Scan() provides the correct results.
+func TestScan(t *testing.T) {
 	// make source
 	var src string;
 	for i, e := range tokens {
@@ -223,3 +224,25 @@ func Test(t *testing.T) {
 		}
 	);
 }
+
+
+// Verify that initializing the same scanner more then once works correctly.
+func TestInit(t *testing.T) {
+	var s scanner.Scanner;
+
+	// 1st init
+	s.Init(io.StringBytes("if true { }"), &TestErrorHandler{t}, false);
+	s.Scan();  // if
+	s.Scan();  // true
+	pos, tok, lit := s.Scan();  // {
+	if tok != token.LBRACE {
+		t.Errorf("bad token: got %s, expected %s", tok.String(), token.LBRACE);
+	}
+
+	// 2nd init
+	s.Init(io.StringBytes("go true { ]"), &TestErrorHandler{t}, false);
+	pos, tok, lit = s.Scan();  // go
+	if tok != token.GO {
+		t.Errorf("bad token: got %s, expected %s", tok.String(), token.GO);
+	}
+}