diff --git a/pkg/analyzer/lib/src/generated/error_verifier.dart b/pkg/analyzer/lib/src/generated/error_verifier.dart
index caff028..e82fa74 100644
--- a/pkg/analyzer/lib/src/generated/error_verifier.dart
+++ b/pkg/analyzer/lib/src/generated/error_verifier.dart
@@ -398,7 +398,6 @@
       _errorReporter.reportErrorForToken(
           CompileTimeErrorCode.AWAIT_IN_WRONG_CONTEXT, node.awaitKeyword);
     }
-    _checkForUseOfVoidResult(node.expression);
     return super.visitAwaitExpression(node);
   }
 
diff --git a/pkg/analyzer/test/generated/static_warning_code_kernel_test.dart b/pkg/analyzer/test/generated/static_warning_code_kernel_test.dart
index f3c148e..92bc27e 100644
--- a/pkg/analyzer/test/generated/static_warning_code_kernel_test.dart
+++ b/pkg/analyzer/test/generated/static_warning_code_kernel_test.dart
@@ -1636,9 +1636,4 @@
   test_useOfVoidResult_variableDeclaration_method_ok() async {
     return super.test_useOfVoidResult_variableDeclaration_method_ok();
   }
-
-  @override
-  test_useOfVoidResult_await() async {
-    return super.test_useOfVoidResult_await();
-  }
 }
diff --git a/pkg/analyzer/test/generated/static_warning_code_test.dart b/pkg/analyzer/test/generated/static_warning_code_test.dart
index 1417d23..222f88e 100644
--- a/pkg/analyzer/test/generated/static_warning_code_test.dart
+++ b/pkg/analyzer/test/generated/static_warning_code_test.dart
@@ -4489,15 +4489,4 @@
     await computeAnalysisResult(source);
     assertNoErrors(source);
   }
-
-  test_useOfVoidResult_await() async {
-    Source source = addSource(r'''
-main() async {
-  void x;
-  await x;
-}''');
-    await computeAnalysisResult(source);
-    assertErrors(source, [StaticWarningCode.USE_OF_VOID_RESULT]);
-    verify([source]);
-  }
 }
diff --git a/pkg/async_helper/lib/async_helper.dart b/pkg/async_helper/lib/async_helper.dart
index 961d1d6..46360f9 100644
--- a/pkg/async_helper/lib/async_helper.dart
+++ b/pkg/async_helper/lib/async_helper.dart
@@ -23,8 +23,6 @@
 
 library async_helper;
 
-import 'dart:async';
-
 bool _initialized = false;
 int _asyncLevel = 0;
 
@@ -83,7 +81,7 @@
  *
  * [f] must return a [:Future:] for the test computation.
  */
-Future<void> asyncTest(f()) {
+void asyncTest(f()) {
   asyncStart();
-  return f().then(asyncSuccess);
+  f().then(asyncSuccess);
 }
diff --git a/pkg/dev_compiler/lib/src/compiler/js_names.dart b/pkg/dev_compiler/lib/src/compiler/js_names.dart
index 7de9cf9..8c02846 100644
--- a/pkg/dev_compiler/lib/src/compiler/js_names.dart
+++ b/pkg/dev_compiler/lib/src/compiler/js_names.dart
@@ -15,6 +15,23 @@
 /// generation without needing global knowledge. See [TemporaryNamer].
 // TODO(jmesserly): move into js_ast? add a boolean to Identifier?
 class TemporaryId extends Identifier {
+  // TODO(jmesserly): by design, temporary identifier nodes are shared
+  // throughout the AST, so any source information we attach in one location
+  // be incorrect for another location (and overwrites previous data).
+  //
+  // If we want to track source information for temporary variables, we'll
+  // need to separate the identity of the variable from its Identifier.
+  //
+  // In practice that makes temporaries more difficult to use: they're no longer
+  // JS AST nodes, so `toIdentifier()` is required to put them in the JS AST.
+  // And anywhere we currently use type `Identifier` to hold Identifier or
+  // TemporaryId, those types would need to change to `Identifier Function()`.
+  //
+  // However we may need to fix this if we want hover to work well for things
+  // like library prefixes and field-initializing formals.
+  get sourceInformation => null;
+  set sourceInformation(Object obj) {}
+
   TemporaryId(String name) : super(name);
 }
 
diff --git a/pkg/front_end/test/incremental_dart2js_load_from_dill_test.dart b/pkg/front_end/test/incremental_dart2js_load_from_dill_test.dart
index ea0190d..d9a9cad 100644
--- a/pkg/front_end/test/incremental_dart2js_load_from_dill_test.dart
+++ b/pkg/front_end/test/incremental_dart2js_load_from_dill_test.dart
@@ -2,7 +2,6 @@
 // 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.
 
-import 'dart:async' show Future;
 import 'dart:io' show Directory, File;
 
 import 'package:expect/expect.dart' show Expect;
@@ -23,7 +22,7 @@
   }
 }
 
-Future<void> testDart2jsCompile() async {
+void testDart2jsCompile() async {
   final Uri dart2jsUrl = Uri.base.resolve("pkg/compiler/bin/dart2js.dart");
   final Uri invalidateUri = Uri.parse("package:compiler/src/filenames.dart");
   Uri normalDill = outDir.uri.resolve("dart2js.full.dill");
diff --git a/runtime/observatory/tests/service/async_next_regession_18877_test.dart b/runtime/observatory/tests/service/async_next_regession_18877_test.dart
new file mode 100644
index 0000000..bd74274
--- /dev/null
+++ b/runtime/observatory/tests/service/async_next_regession_18877_test.dart
@@ -0,0 +1,51 @@
+// Copyright (c) 2018, 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.
+// VMOptions=--error_on_bad_type --error_on_bad_override  --verbose_debug
+
+import 'dart:developer';
+import 'service_test_common.dart';
+import 'test_helper.dart';
+
+const int LINE_A = 23;
+const int LINE_B = 24;
+const int LINE_C = 25;
+
+foo() async {}
+
+doAsync(stop) async {
+  // Flutter issue 18877:
+  // If a closure is defined in the context of an async method, stepping over
+  // an await causes the implicit breakpoint to be set for that closure instead
+  // of the async_op, resulting in the debugger falling through.
+  final baz = () => print('doAsync($stop) done!');
+  if (stop) debugger();
+  await foo(); // Line A.
+  await foo(); // Line B.
+  await foo(); // Line C.
+  baz();
+  return null;
+}
+
+testMain() {
+  // With two runs of doAsync floating around, async step should only cause
+  // us to stop in the run we started in.
+  doAsync(false);
+  doAsync(true);
+}
+
+var tests = <IsolateTest>[
+  hasStoppedAtBreakpoint,
+  stoppedAtLine(LINE_A),
+  stepOver, // foo()
+  asyncNext,
+  hasStoppedAtBreakpoint,
+  stoppedAtLine(LINE_B),
+  stepOver, // foo()
+  asyncNext,
+  hasStoppedAtBreakpoint,
+  stoppedAtLine(LINE_C),
+  resumeIsolate,
+];
+
+main(args) => runIsolateTests(args, tests, testeeConcurrent: testMain);
diff --git a/runtime/observatory/tests/service/service_kernel.status b/runtime/observatory/tests/service/service_kernel.status
index b65243f..5f6e399 100644
--- a/runtime/observatory/tests/service/service_kernel.status
+++ b/runtime/observatory/tests/service/service_kernel.status
@@ -5,6 +5,7 @@
 [ $compiler == app_jitk ]
 add_breakpoint_rpc_test: RuntimeError
 async_generator_breakpoint_test: RuntimeError
+async_next_regession_18877_test: RuntimeError
 async_next_test: RuntimeError
 async_scope_test: RuntimeError
 async_single_step_exception_test: RuntimeError
diff --git a/runtime/vm/debugger.cc b/runtime/vm/debugger.cc
index bb87152..8db8d44 100644
--- a/runtime/vm/debugger.cc
+++ b/runtime/vm/debugger.cc
@@ -2860,11 +2860,17 @@
                                             TokenPosition token_pos,
                                             TokenPosition last_token_pos,
                                             intptr_t requested_line,
-                                            intptr_t requested_column) {
+                                            intptr_t requested_column,
+                                            const Function& function) {
   Function& func = Function::Handle();
-  if (!FindBestFit(script, token_pos, last_token_pos, &func)) {
-    return NULL;
+  if (function.IsNull()) {
+    if (!FindBestFit(script, token_pos, last_token_pos, &func)) {
+      return NULL;
+    }
+  } else {
+    func = function.raw();
   }
+
   if (!func.IsNull()) {
     // There may be more than one function object for a given function
     // in source code. There may be implicit closure functions, and
@@ -2971,7 +2977,7 @@
   const Script& script = Script::Handle(target_function.script());
   BreakpointLocation* bpt_location = SetBreakpoint(
       script, target_function.token_pos(), target_function.end_token_pos(), -1,
-      -1 /* no requested line/col */);
+      -1 /* no requested line/col */, target_function);
   if (bpt_location == NULL) {
     return NULL;
   }
@@ -2990,8 +2996,9 @@
   }
   const Function& func = Function::Handle(Closure::Cast(closure).function());
   const Script& script = Script::Handle(func.script());
-  BreakpointLocation* bpt_location = SetBreakpoint(
-      script, func.token_pos(), func.end_token_pos(), -1, -1 /* no line/col */);
+  BreakpointLocation* bpt_location =
+      SetBreakpoint(script, func.token_pos(), func.end_token_pos(), -1,
+                    -1 /* no line/col */, func);
   return bpt_location->AddPerClosure(this, closure, for_over_await);
 }
 
@@ -3108,7 +3115,7 @@
   ASSERT(first_token_idx <= last_token_idx);
   while ((bpt == NULL) && (first_token_idx <= last_token_idx)) {
     bpt = SetBreakpoint(script, first_token_idx, last_token_idx, line_number,
-                        column_number);
+                        column_number, Function::Handle());
     first_token_idx.Next();
   }
   if ((bpt == NULL) && FLAG_verbose_debug) {
diff --git a/runtime/vm/debugger.h b/runtime/vm/debugger.h
index fedfed1..2128046 100644
--- a/runtime/vm/debugger.h
+++ b/runtime/vm/debugger.h
@@ -664,7 +664,8 @@
                                     TokenPosition token_pos,
                                     TokenPosition last_token_pos,
                                     intptr_t requested_line,
-                                    intptr_t requested_column);
+                                    intptr_t requested_column,
+                                    const Function& function);
   bool RemoveBreakpointFromTheList(intptr_t bp_id, BreakpointLocation** list);
   Breakpoint* GetBreakpointByIdInTheList(intptr_t id, BreakpointLocation* list);
   void RemoveUnlinkedCodeBreakpoints();
diff --git a/tests/co19_2/co19_2-analyzer.status b/tests/co19_2/co19_2-analyzer.status
index bbb17dd..d94473f 100644
--- a/tests/co19_2/co19_2-analyzer.status
+++ b/tests/co19_2/co19_2-analyzer.status
@@ -2782,9 +2782,6 @@
 LibTest/io/RandomAccessFile/writeString_A01_t03: CompileTimeError # Dart 1 constants, https://github.com/dart-lang/sdk/issues/33894
 LibTest/io/Stdin/readLineSync_A03_t01: CompileTimeError # Dart 1 constants, https://github.com/dart-lang/sdk/issues/33894
 LibTest/io/Stdin/readLineSync_A03_t02: CompileTimeError # Dart 1 constants, https://github.com/dart-lang/sdk/issues/33894
-LibTest/io/Stdin/readLineSync_A03_t03: CompileTimeError # Erroneously awaits void
-LibTest/io/Stdin/readLineSync_A03_t04: CompileTimeError # Erroneously awaits void
-LibTest/io/Stdin/readLineSync_A04_t01: CompileTimeError # Erroneously awaits void
 LibTest/io/Stdout/add_A02_t01: CompileTimeError # Dart 1 constants, https://github.com/dart-lang/sdk/issues/33894
 LibTest/io/Stdout/encoding_A01_t01: CompileTimeError # Dart 1 constants, https://github.com/dart-lang/sdk/issues/33894
 LibTest/io/Stdout/writeAll_A01_t02: CompileTimeError # Dart 1 constants, https://github.com/dart-lang/sdk/issues/33894
diff --git a/tools/VERSION b/tools/VERSION
index 0ebcd39..7c09085 100644
--- a/tools/VERSION
+++ b/tools/VERSION
@@ -28,5 +28,4 @@
 MINOR 0
 PATCH 0
 PRERELEASE 69
-PRERELEASE_PATCH 3
-*
\ No newline at end of file
+PRERELEASE_PATCH 4
diff --git a/tools/patch_sdk.dart b/tools/patch_sdk.dart
index b4ca60d..e32065c 100644
--- a/tools/patch_sdk.dart
+++ b/tools/patch_sdk.dart
@@ -146,7 +146,7 @@
       throw "Unknown mode: $mode";
   }
 
-  _writeSync(
+  await _writeSync(
       librariesJson.toFilePath(),
       jsonEncode({
         mode: {"libraries": locations}