If an if or do statement always exits, following statements are dead.

pkg/analyzer/test/generated/hint_code_test.dart

 // 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 analyzer.test.generated.hint_code_test;
 
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/error.dart';
 import 'package:analyzer/src/generated/source_io.dart';
 import 'package:unittest/unittest.dart';
 
 import '../reflective_tests.dart';
 import '../utils.dart';
 import 'analysis_context_factory.dart';
 import 'resolver_test_case.dart';
 
 main() {
   initializeTestEnvironment();
   runReflectiveTests(HintCodeTest);
 }
 
 @reflectiveTest
 class HintCodeTest extends ResolverTestCase {
-  void fail_deadCode_statementAfterRehrow() {
+  void test_deadCode_statementAfterRethrow() {
     Source source = addSource(r'''
 f() {
   try {
     var one = 1;
   } catch (e) {
     rethrow;
     var two = 2;
   }
 }''');
     computeLibrarySourceErrors(source);
     assertErrors(source, [HintCode.DEAD_CODE]);
     verify([source]);
   }
 
-  void fail_deadCode_statementAfterThrow() {
+  void test_deadCode_statementAfterThrow() {
     Source source = addSource(r'''
 f() {
   var one = 1;
   throw 'Stop here';
   var two = 2;
 }''');
     computeLibrarySourceErrors(source);
     assertErrors(source, [HintCode.DEAD_CODE]);
     verify([source]);
   }
@@ skipping 562 matching lines @@
   return;
   var two = 2;
   return;
   var three = 3;
 }''');
     computeLibrarySourceErrors(source);
     assertErrors(source, [HintCode.DEAD_CODE]);
     verify([source]);
   }
 
+  void test_deadCode_statementAfterExitingIf_returns() {
+    Source source = addSource(r'''
+f() {
+  if (1 > 2) {
+    return;
+  } else {
+    return;
+  }
+  var one = 1;
+}''');
+    computeLibrarySourceErrors(source);
+    assertErrors(source, [HintCode.DEAD_CODE]);
+    verify([source]);
+  }
+
   void test_deprecatedAnnotationUse_assignment() {
     Source source = addSource(r'''
 class A {
   @deprecated
   A operator+(A a) { return a; }
 }
 f(A a) {
   A b;
   a += b;
 }''');
@@ skipping 2723 matching lines @@
   n() {
     var a = m(), b = m();
   }
 }''');
     computeLibrarySourceErrors(source);
     assertErrors(
         source, [HintCode.USE_OF_VOID_RESULT, HintCode.USE_OF_VOID_RESULT]);
     verify([source]);
   }
 }