Add support for is, is! expressions (#111)

* FieldBuilders now works to-level

* Ran dartfmt

* asThrow on ExpressionBuilder

* Removed asThrow

* Added isInstanceOf, isNotInstanceOf, and corresponding tests. Also added a .gitignore rule to exclude the `.idea` directory, for convenience's sake.

* Undo .gitignore change

* Undo .gitignore change, remove IntelliJ metadata

* Removed isNotInstanceOf

Author: thosakwe

lib/src/builders/expression.dart

@@ -26,6 +26,7 @@ part 'expression/cascade.dart';
 part 'expression/cast.dart';
 part 'expression/index.dart';
 part 'expression/invocation.dart';
+part 'expression/is_instance_of.dart';
 part 'expression/negate.dart';
 part 'expression/operators.dart';
 part 'expression/return.dart';
@@ -294,6 +295,10 @@ abstract class AbstractExpressionMixin implements ExpressionBuilder {
     return invocation;
   }
 
+  @override
+  ExpressionBuilder isInstanceOf(TypeBuilder type) =>
+      new _IsInstanceOfExpression(this, type);
+
   @override
   ExpressionBuilder negate() => new _NegateExpression(this);
 
@@ -447,6 +452,9 @@ abstract class ExpressionBuilder
     Map<String, ExpressionBuilder> namedArguments,
   });
 
+  /// Returns as an [ExpressionBuilder] indicating whether this expression is an instance of [type], using the `is` operator.
+  ExpressionBuilder isInstanceOf(TypeBuilder type);
+
   /// Returns as an [ExpressionBuilder] negating using the `!` operator.
   ExpressionBuilder negate();
 

lib/src/builders/expression/is_instance_of.dart

@@ -0,0 +1,22 @@
+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+part of code_builder.src.builders.expression;
+
+class _IsInstanceOfExpression extends AbstractExpressionMixin
+    with TopLevelMixin {
+  final ExpressionBuilder _expression;
+  final TypeBuilder _type;
+
+  _IsInstanceOfExpression(this._expression, this._type);
+
+  @override
+  AstNode buildAst([Scope scope]) => buildExpression(scope);
+
+  @override
+  Expression buildExpression([Scope scope]) {
+    return astFactory.isExpression(
+        _expression.buildExpression(scope), $is, null, _type.buildType(scope));
+  }
+}

lib/src/tokens.dart

@@ -118,6 +118,9 @@ final Token $implements = new KeywordToken(Keyword.IMPLEMENTS, 0);
 /// The `in` token.
 final Token $in = new KeywordToken(Keyword.IN, 0);
 
+/// The `is` token.
+final Token $is = new KeywordToken(Keyword.IS, 0);
+
 /// The `library` token.
 final Token $library = new KeywordToken(Keyword.LIBRARY, 0);
 

test/builders/is_instance_of_test.dart

@@ -0,0 +1,20 @@
+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'package:code_builder/code_builder.dart';
+import 'package:code_builder/testing.dart';
+import 'package:test/test.dart';
+
+final TypeBuilder _barType = new TypeBuilder('Bar');
+
+void main() {
+  test('should emit an `is` expression', () {
+    expect(reference('foo').isInstanceOf(_barType), equalsSource('foo is Bar'));
+  });
+
+  test('should emit an `is!` expression', () {
+    expect(reference('foo').isInstanceOf(_barType).negate(),
+        equalsSource('!(foo is Bar)'));
+  });
+}