Fix order in limit expressions with comma

Fixes #73

moor/lib/src/runtime/components/limit.dart

@@ -14,7 +14,7 @@ class Limit extends Component {
   @override
   void writeInto(GenerationContext context) {
     if (offset != null) {
-      context.buffer.write('LIMIT $amount, $offset');
+      context.buffer.write('LIMIT $amount OFFSET $offset');
     } else {
       context.buffer.write('LIMIT $amount');
     }

moor/test/select_test.dart

@@ -36,9 +36,9 @@ void main() {
     });
 
     test('with limit statements', () {
-      (db.select(db.users)..limit(10)).get();
+      (db.select(db.users)..limit(10, offset: 0)).get();
       verify(executor.runSelect(
-          'SELECT * FROM users LIMIT 10;', argThat(isEmpty)));
+          'SELECT * FROM users LIMIT 10 OFFSET 0;', argThat(isEmpty)));
     });
 
     test('with like expressions', () {

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

@@ -405,16 +405,21 @@ class Parser {
   Limit _limit() {
     if (!_matchOne(TokenType.limit)) return null;
 
-    final count = expression();
-    Token offsetSep;
-    Expression offset;
+    // Unintuitive, it's "$amount OFFSET $offset", but "$offset, $amount"
+    // the order changes between the separator tokens.
+    final first = expression();
 
-    if (_match(const [TokenType.comma, TokenType.offset])) {
-      offsetSep = _previous;
-      offset = expression();
+    if (_matchOne(TokenType.comma)) {
+      final separator = _previous;
+      final count = expression();
+      return Limit(count: count, offsetSeparator: separator, offset: first);
+    } else if (_matchOne(TokenType.offset)) {
+      final separator = _previous;
+      final offset = expression();
+      return Limit(count: first, offsetSeparator: separator, offset: offset);
+    } else {
+      return Limit(count: first);
     }
-
-    return Limit(count: count, offsetSeparator: offsetSep, offset: offset);
   }
 
   DeleteStatement _deleteStmt() {

sqlparser/test/parser/select/limit_test.dart

@@ -40,6 +40,8 @@ void main() {
     });
 
     test('with offset as comma', () {
+      // with the comma notation, the offset comes first.
+      // https://www.sqlite.org/lang_select.html#limitoffset
       final select = SqlEngine()
           .parse('SELECT * FROM test LIMIT 10, 2')
           .rootNode as SelectStatement;
@@ -47,9 +49,9 @@ void main() {
       enforceEqual(
         select.limit,
         Limit(
-          count: NumericLiteral(10, token(TokenType.numberLiteral)),
+          count: NumericLiteral(2, token(TokenType.numberLiteral)),
           offsetSeparator: token(TokenType.comma),
-          offset: NumericLiteral(2, token(TokenType.numberLiteral)),
+          offset: NumericLiteral(10, token(TokenType.numberLiteral)),
         ),
       );
     });