Check for return types on setters (#122).

lib/src/rules/avoid_return_types_on_setters.dart

Index: lib/src/rules/avoid_return_types_on_setters.dart
diff --git a/lib/src/rules/avoid_return_types_on_setters.dart b/lib/src/rules/avoid_return_types_on_setters.dart
new file mode 100644
index 0000000000000000000000000000000000000000..d17122b82b2497d49546c59d1a94f53d062dbb03
--- /dev/null
+++ b/lib/src/rules/avoid_return_types_on_setters.dart
@@ -0,0 +1,60 @@
+// 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.
+
+library linter.src.rules.avoid_return_types_on_setters;
+
+import 'package:analyzer/src/generated/ast.dart';
+import 'package:analyzer/src/generated/scanner.dart';
+import 'package:linter/src/linter.dart';
+
+const desc = r'Avoid return types on setters.';
+
+const details = r'''
+**AVOID** return types on setters.
+
+**GOOD:**
+```
+set speed(int ms);
+```
+
+**BAD:**
+```
+void set speed(int ms);
+```
+''';
+
+class AvoidReturnTypesOnSetters extends LintRule {
+  AvoidReturnTypesOnSetters()
+      : super(
+            name: 'avoid_return_types_on_setters',
+            description: desc,
+            details: details,
+            group: Group.style);
+
+  @override
+  AstVisitor getVisitor() => new Visitor(this);
+}
+
+class Visitor extends SimpleAstVisitor {
+  final LintRule rule;
+  Visitor(this.rule);
+
+  @override
+  visitFunctionDeclaration(FunctionDeclaration node) {
+    if (node.isSetter) {
+      if (node.returnType != null) {
+        rule.reportLint(node.returnType);
+      }
+    }
+  }
+
+  @override
+  visitMethodDeclaration(MethodDeclaration node) {
+    if (node.isSetter) {
+      if (node.returnType != null) {
+        rule.reportLint(node.returnType);
+      }
+    }
+  }
+}