add Expression.asA (#210)

CHANGELOG.md

@@ -1,3 +1,18 @@
+## 3.0.4
+
+* Added `Expression.asA` for creating explicit casts:
+
+```dart
+void main() {
+  test('should emit an explicit cast', () {
+    expect(
+      refer('foo').asA(refer('String')),
+      equalsDart('foo as String'),
+    );
+  });
+}
+```
+
 ## 3.0.3
 
 * Fix a bug that caused all downstream users of `code_builder` to crash due to
@@ -314,7 +329,7 @@ are welcome!
   * `const Code.scope((allocate) => '')`
 
 * Removed `SimpleSpecVisitor` (it was unused).
-* Removed `implements Reference` from `Method` and `Field`; not a lot of value. 
+* Removed `implements Reference` from `Method` and `Field`; not a lot of value.
 
 * `SpecVisitor<T>`'s methods all have an optional `[T context]` parameter now.
   * This makes it much easier to avoid allocating extra `StringBuffer`s.
@@ -353,7 +368,7 @@ final animal = new Class((b) => b
 
 ```dart
 expect(
-  reference('foo').isInstanceOf(_barType), 
+  reference('foo').isInstanceOf(_barType),
   equalsSource('foo is Bar'),
 );
 ```
@@ -403,7 +418,7 @@ that the entire Dart language is buildable with our API, though.
 - Added `ConstructorBuilder.redirectTo` for a redirecting factory constructor.
 - Added a `name` getter to `ReferenceBuilder`.
 - Supplying an empty constructor name (`''`) is equivalent to `null` (default).
-- Automatically encodes string literals with multiple lines as `'''`. 
+- Automatically encodes string literals with multiple lines as `'''`.
 - Added `asThrow` to `ExpressionBuilder`.
 - Fixed a bug that prevented `FieldBuilder` from being used at the top-level.
 

lib/src/specs/expression.dart

@@ -44,6 +44,15 @@ abstract class Expression implements Spec {
     return new BinaryExpression._(expression, other, '&&');
   }
 
+  /// Returns the result of `this` `as` [other].
+  Expression asA(Expression other) {
+    return new BinaryExpression._(
+      expression,
+      other,
+      'as',
+    );
+  }
+
   /// Returns accessing the index operator (`[]`) on `this`.
   Expression index(Expression index) {
     return new BinaryExpression._(

pubspec.yaml

@@ -1,5 +1,5 @@
 name: code_builder
-version: 3.0.4-dev
+version: 3.0.4
 description: A fluent API for generating Dart code
 author: Dart Team <[email protected]>
 homepage: https://github.com/dart-lang/code_builder

test/specs/code/expression_test.dart

@@ -343,6 +343,13 @@ void main() {
     );
   });
 
+  test('should emit an explicit cast', () {
+    expect(
+      refer('foo').asA(refer('String')),
+      equalsDart('foo as String'),
+    );
+  });
+
   test('should emit an is check', () {
     expect(
       refer('foo').isA(refer('String')),