provide MISSING_RETURN on factory constructors

pkg/analyzer/lib/src/generated/resolver.dart

 // Copyright (c) 2014, 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 analyzer.src.generated.resolver;
 
 import 'dart:collection';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
@@ skipping 149 matching lines @@
     return super.visitExportDirective(node);
   }
 
   @override
   Object visitForStatement(ForStatement node) {
     _checkForPossibleNullCondition(node.condition);
     return super.visitForStatement(node);
   }
 
   @override
+  Object visitConstructorDeclaration(ConstructorDeclaration node) {
+    if (node.element.isFactory) {
+      if (node.body is BlockFunctionBody) {
+        // Check the block for a return statement, if not, create the hint.
+        if (!ExitDetector.exits(node.body)) {
+          _errorReporter.reportErrorForNode(
+              HintCode.MISSING_RETURN, node, [node.returnType.name]);
+        }
+      }
+    }
+    return super.visitFunctionDeclaration(node);
+  }
+
+  @override
   Object visitFunctionDeclaration(FunctionDeclaration node) {
     bool wasInDeprecatedMember = inDeprecatedMember;
     ExecutableElement element = node.element;
     if (element != null && element.isDeprecated) {
       inDeprecatedMember = true;
     }
     try {
       _checkForMissingReturn(node.returnType, node.functionExpression.body);
       return super.visitFunctionDeclaration(node);
     } finally {
@@ skipping 10646 matching lines @@
       return null;
     }
     if (identical(node.staticElement, variable)) {
       if (node.inSetterContext()) {
         result = true;
       }
     }
     return null;
   }
 }