test: add test case for concat-expr

Author: link-duan

ast.go

@@ -44,7 +44,7 @@ const (
 	Plus               // +
 	Colon              // :
 	Minus              // -
-	Connect            // &
+	Concat             // &
 	Equal              // =
 	NotEqual           // <>
 	LessThan           // <

lexer.go

@@ -84,6 +84,9 @@ func (l *lexer) next() (*Token, error) {
 		return newToken(l.pos, l.pos, Divide, "/"), nil
 	case '$':
 		return l.absoluteReference()
+	case '&':
+		l.nextch()
+		return newToken(l.pos, l.pos, Concat, "&"), nil
 	case '%':
 		l.nextch()
 		return newToken(l.pos, l.pos, Percent, "%"), nil

parser.go

@@ -81,7 +81,7 @@ func (p *Parser) connection() (Node, error) {
 	if p.token == nil {
 		return left, nil // No more tokens, return the left node
 	}
-	for p.token != nil && p.token.Type == Connect {
+	for p.token != nil && p.token.Type == Concat {
 		var op = p.token
 		if err := p.advance(); err != nil { // consume the operator token
 			return nil, err

parser_test.go

@@ -7,6 +7,7 @@ func TestParse(t *testing.T) {
 		src      string
 		expected string
 	}{
+		{"=A1&B1", "BinaryExpr(Left: CellExpr(A1), Operator: &, Right: CellExpr(B1))"},
 		{"=1<>2", "BinaryExpr(Left: LiteralExpr(Value: 1), Operator: <>, Right: LiteralExpr(Value: 2))"},
 		{"=$A:$A", "RangeExpr(CellExpr($A):CellExpr($A))"},
 		{"=$1:1", "RangeExpr(CellExpr($1):CellExpr(1))"},