Infer Null for return type of functions with empty returns.

pkg/dev_compiler/tool/sdk_expected_errors.txt

Index: pkg/dev_compiler/tool/sdk_expected_errors.txt
diff --git a/pkg/dev_compiler/tool/sdk_expected_errors.txt b/pkg/dev_compiler/tool/sdk_expected_errors.txt
index 94a78502c1f4306c3975f9f76cb2fe994a80f8f0..381ac619a0aae5bbb94a4ac5978e6d10eddc5d6d 100644
--- a/pkg/dev_compiler/tool/sdk_expected_errors.txt
+++ b/pkg/dev_compiler/tool/sdk_expected_errors.txt
@@ -75,18 +75,13 @@
 [warning] Unsafe implicit cast from '(T) → void' to '(Event) → dynamic'. This usually indicates that type information was lost and resulted in 'dynamic' and/or a place that will have a failure at runtime. (dart:html, line 40126, col 45)
 [warning] Unsafe implicit cast from 'List<dynamic>' to 'List<int>'. This usually indicates that type information was lost and resulted in 'dynamic' and/or a place that will have a failure at runtime. (dart:io/data_transformer.dart, line 492, col 23)
 [warning] Unsafe implicit cast from 'Stream<dynamic>' to 'Stream<FileSystemEntity>'. This usually indicates that type information was lost and resulted in 'dynamic' and/or a place that will have a failure at runtime. (dart:io/directory_impl.dart, line 239, col 12)
-[warning] Missing return value after 'return'. (dart:io/directory_impl.dart, line 394, col 15)
-[warning] Missing return value after 'return'. (dart:io/file_impl.dart, line 101, col 11)
 [warning] Unsafe implicit cast from 'Future<dynamic>' to 'Future<List<int>>'. This usually indicates that type information was lost and resulted in 'dynamic' and/or a place that will have a failure at runtime. (dart:io/file_impl.dart, line 484, col 14)
 [warning] Unsafe implicit cast from 'List<dynamic>' to 'List<int>'. This usually indicates that type information was lost and resulted in 'dynamic' and/or a place that will have a failure at runtime. (dart:io/file_impl.dart, line 831, col 33)
 [warning] Unsafe implicit cast from 'StreamSubscription<dynamic>' to 'StreamSubscription<List<int>>'. This usually indicates that type information was lost and resulted in 'dynamic' and/or a place that will have a failure at runtime. (dart:io/http_impl.dart, line 269, col 14)
 [warning] Unsafe implicit cast from 'Stream<dynamic>' to 'Stream<List<int>>'. This usually indicates that type information was lost and resulted in 'dynamic' and/or a place that will have a failure at runtime. (dart:io/http_impl.dart, line 1056, col 29)
 [warning] Unsafe implicit cast from 'Function' to '(List<int>) → void'. This usually indicates that type information was lost and resulted in 'dynamic' and/or a place that will have a failure at runtime. (dart:io/http_impl.dart, line 1173, col 54)
 [warning] Unsafe implicit cast from 'Function' to '(List<int>) → void'. This usually indicates that type information was lost and resulted in 'dynamic' and/or a place that will have a failure at runtime. (dart:io/http_impl.dart, line 1175, col 33)
-[warning] Missing return value after 'return'. (dart:io/http_impl.dart, line 1401, col 21)
-[warning] Missing return value after 'return'. (dart:io/http_impl.dart, line 1403, col 31)
 [warning] Unsafe implicit cast from 'Future<dynamic>' to 'Future<_ConnectionInfo>'. This usually indicates that type information was lost and resulted in 'dynamic' and/or a place that will have a failure at runtime. (dart:io/http_impl.dart, line 1635, col 14)
-[warning] Missing return value after 'return'. (dart:io/http_impl.dart, line 2111, col 42)
 [warning] Unsafe implicit cast from 'StreamSubscription<dynamic>' to 'StreamSubscription<List<int>>'. This usually indicates that type information was lost and resulted in 'dynamic' and/or a place that will have a failure at runtime. (dart:io/http_parser.dart, line 201, col 16)
 [warning] Unsafe implicit cast from 'StreamSubscription<dynamic>' to 'StreamSubscription<List<int>>'. This usually indicates that type information was lost and resulted in 'dynamic' and/or a place that will have a failure at runtime. (dart:io/http_parser.dart, line 203, col 50)
 [warning] Unsafe implicit cast from 'Map<dynamic, dynamic>' to 'Map<String, String>'. This usually indicates that type information was lost and resulted in 'dynamic' and/or a place that will have a failure at runtime. (dart:io/platform_impl.dart, line 100, col 69)
@@ -94,9 +89,6 @@
 [warning] Unsafe implicit cast from 'Future<dynamic>' to 'Future<SecureSocket>'. This usually indicates that type information was lost and resulted in 'dynamic' and/or a place that will have a failure at runtime. (dart:io/secure_socket.dart, line 138, col 12)
 [warning] Unsafe implicit cast from 'StreamSubscription<dynamic>' to 'StreamSubscription<RawSocketEvent>'. This usually indicates that type information was lost and resulted in 'dynamic' and/or a place that will have a failure at runtime. (dart:io/secure_socket.dart, line 446, col 33)
 [warning] Unsafe implicit cast from 'Future<dynamic>' to 'Future<RawSecureSocket>'. This usually indicates that type information was lost and resulted in 'dynamic' and/or a place that will have a failure at runtime. (dart:io/secure_socket.dart, line 580, col 12)
-[warning] Missing return value after 'return'. (dart:io/secure_socket.dart, line 861, col 11)
-[warning] Missing return value after 'return'. (dart:io/secure_socket.dart, line 868, col 13)
-[warning] Missing return value after 'return'. (dart:io/secure_socket.dart, line 882, col 11)
 [warning] Unsafe implicit cast from 'List<dynamic>' to 'List<int>'. This usually indicates that type information was lost and resulted in 'dynamic' and/or a place that will have a failure at runtime. (dart:io/secure_socket.dart, line 1176, col 32)
 [warning] Unsafe implicit cast from 'List<dynamic>' to 'List<int>'. This usually indicates that type information was lost and resulted in 'dynamic' and/or a place that will have a failure at runtime. (dart:io/stdio.dart, line 109, col 28)
 [warning] Unsafe implicit cast from 'Future<dynamic>' to 'Future<WebSocket>'. This usually indicates that type information was lost and resulted in 'dynamic' and/or a place that will have a failure at runtime. (dart:io/websocket_impl.dart, line 471, col 14)