Parse empty tuples

Closes #54

sqlparser/lib/src/ast/expressions/simple.dart

@@ -128,7 +128,9 @@ class Parentheses extends Expression {
   final Expression expression;
   final Token closingRight;
 
-  Parentheses(this.openingLeft, this.expression, this.closingRight);
+  Parentheses(this.openingLeft, this.expression, this.closingRight) {
+    setSpan(openingLeft, closingRight);
+  }
 
   @override
   T accept<T>(AstVisitor<T> visitor) {

sqlparser/lib/src/reader/parser/parser.dart

@@ -687,6 +687,12 @@ class Parser {
           _consume(TokenType.rightParen, 'Expected a closing bracket');
           return SubQuery(select: stmt);
         } else {
+          // alright, it's either a tuple or just parenthesis. A tuple can be
+          // empty, so if the next statement is the closing bracket we're done
+          if (_matchOne(TokenType.rightParen)) {
+            return TupleExpression(expressions: [])..setSpan(left, _previous);
+          }
+
           final expr = expression();
 
           // Are we witnessing a tuple?

sqlparser/test/parser/select/generic_test.dart

@@ -1,22 +1,8 @@
 import 'package:sqlparser/src/ast/ast.dart';
-import 'package:sqlparser/src/reader/parser/parser.dart';
-import 'package:sqlparser/src/reader/tokenizer/scanner.dart';
-import 'package:sqlparser/src/reader/tokenizer/token.dart';
-import 'package:sqlparser/src/utils/ast_equality.dart';
-import 'package:test/test.dart';
-
 import '../utils.dart';
 
-void main() {
+final Map<String, AstNode> testCases = {
-  test('parses select statements', () {
+  'SELECT table.*, *, 1 as name WHERE 1 ORDER BY name LIMIT 3 OFFSET 5':
-    final scanner = Scanner(
-        'SELECT table.*, *, 1 as name WHERE 1 ORDER BY name LIMIT 3 OFFSET 5');
-    final tokens = scanner.scanTokens();
-    final parser = Parser(tokens);
-
-    final stmt = parser.select();
-    enforceEqual(
-      stmt,
       SelectStatement(
     columns: [
       StarResultColumn('table'),
@@ -36,19 +22,8 @@ void main() {
       offset: NumericLiteral(5, token(TokenType.numberLiteral)),
     ),
   ),
-    );
+  'SELECT table.*, (SELECT * FROM table2) FROM table': SelectStatement(
-  });
+    columns: [
-
-  test('supports subqueries', () {
-    final scanner =
-        Scanner('SELECT table.*, (SELECT * FROM table2) FROM table');
-    final tokens = scanner.scanTokens();
-    final parser = Parser(tokens);
-
-    final stmt = parser.select();
-    enforceEqual(
-      stmt,
-      SelectStatement(columns: [
       StarResultColumn('table'),
       ExpressionResultColumn(
         expression: SubQuery(
@@ -58,9 +33,21 @@ void main() {
           ),
         ),
       ),
-      ], from: [
+    ],
+    from: [
       TableReference('table', null),
-      ]),
+    ],
-    );
+  ),
-  });
+  'SELECT * FROM table WHERE id IN ()': SelectStatement(
+    columns: [StarResultColumn(null)],
+    from: [TableReference('table', null)],
+    where: InExpression(
+      left: Reference(columnName: 'id'),
+      inside: TupleExpression(expressions: []),
+    ),
+  ),
+};
+
+void main() {
+  testAll(testCases);
 }