Add Expression.operators (add/substract/divide/multiply/euclidean modulo) (#218)

Closes #216

Author: eredo

lib/src/specs/expression.dart

@@ -142,6 +142,51 @@ abstract class Expression implements Spec {
     );
   }
 
+  /// Returns the result of `this` `+` [other].
+  Expression operatorAdd(Expression other) {
+    return new BinaryExpression._(
+      expression,
+      other,
+      '+',
+    );
+  }
+
+  /// Returns the result of `this` `-` [other].
+  Expression operatorSubstract(Expression other) {
+    return new BinaryExpression._(
+      expression,
+      other,
+      '-',
+    );
+  }
+
+  /// Returns the result of `this` `/` [other].
+  Expression operatorDivide(Expression other) {
+    return new BinaryExpression._(
+      expression,
+      other,
+      '/',
+    );
+  }
+
+  /// Returns the result of `this` `*` [other].
+  Expression operatorMultiply(Expression other) {
+    return new BinaryExpression._(
+      expression,
+      other,
+      '*',
+    );
+  }
+
+  /// Returns the result of `this` `%` [other].
+  Expression operatorEuclideanModulo(Expression other) {
+    return new BinaryExpression._(
+      expression,
+      other,
+      '%',
+    );
+  }
+
   Expression conditional(Expression whenTrue, Expression whenFalse) {
     return new BinaryExpression._(
       expression,

test/specs/code/expression_test.dart

@@ -412,4 +412,28 @@ void main() {
       equalsDart('foo ? 1 : 2'),
     );
   });
+
+  test('should emit an operator add call', () {
+    expect(refer('foo').operatorAdd(refer('foo2')), equalsDart('foo + foo2'));
+  });
+
+  test('should emit an operator substract call', () {
+    expect(refer('foo').operatorSubstract(refer('foo2')),
+        equalsDart('foo - foo2'));
+  });
+
+  test('should emit an operator divide call', () {
+    expect(
+        refer('foo').operatorDivide(refer('foo2')), equalsDart('foo / foo2'));
+  });
+
+  test('should emit an operator multiply call', () {
+    expect(
+        refer('foo').operatorMultiply(refer('foo2')), equalsDart('foo * foo2'));
+  });
+
+  test('should emit an euclidean modulo operator call', () {
+    expect(refer('foo').operatorEuclideanModulo(refer('foo2')),
+        equalsDart('foo % foo2'));
+  });
 }