[cfe] Use declared nullability in replacement visitors

Legacy erasure on FutureOr<T*> would not yield FutureOr<T*>* as intended. Change-Id: Ie2ec44900ddd2ee0daa7fd8a5b655e568153b59f Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/162640 Reviewed-by: Dmitry Stefantsov <dmitryas@google.com> Commit-Queue: Johnni Winther <johnniwinther@google.com>
2024-09-16 03:07:49 +00:00 · 2020-09-14 08:40:39 +00:00 · 2020-09-14 08:40:39 +00:00 · 3f6af87cd4
parent ba78db411a
commit 3f6af87cd4
76 changed files with 107 additions and 107 deletions
--- a/pkg/front_end/lib/src/fasta/type_inference/type_demotion.dart
+++ b/pkg/front_end/lib/src/fasta/type_inference/type_demotion.dart
@ -105,11 +105,11 @@ class _DemotionNullabilityNormalization extends ReplacementVisitor {
  @override
  Nullability visitNullability(DartType node) {
    if (forNonNullableByDefault) {
-      if (node.nullability == Nullability.legacy) {
+      if (node.declaredNullability == Nullability.legacy) {
        return Nullability.nonNullable;
      }
    } else {
-      if (node.nullability != Nullability.legacy) {
+      if (node.declaredNullability != Nullability.legacy) {
        return Nullability.legacy;
      }
    }
--- a/pkg/front_end/testcases/inference/async_await.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/async_await.dart.outline.expect
@ -22,7 +22,7 @@ abstract class MyFuture extends core::Object implements asy::Future<core::int*>
  abstract member-signature method catchError(core::Function* onError, {(core::Object*) →* core::bool* test}) → asy::Future<core::int*>*; -> asy::Future::catchError
  abstract member-signature method whenComplete(() →* FutureOr<void>* action) → asy::Future<core::int*>*; -> asy::Future::whenComplete
  abstract member-signature method asStream() → asy::Stream<core::int*>*; -> asy::Future::asStream
-  abstract member-signature method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<core::int*>onTimeout}) → asy::Future<core::int*>*; -> asy::Future::timeout
+  abstract member-signature method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<core::int*>* onTimeout}) → asy::Future<core::int*>*; -> asy::Future::timeout
 }
 static method test() → void async 
  ;
--- a/pkg/front_end/testcases/inference/async_await.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/async_await.dart.strong.expect
@ -23,7 +23,7 @@ abstract class MyFuture extends core::Object implements asy::Future<core::int*>
  abstract member-signature method catchError(core::Function* onError, {(core::Object*) →* core::bool* test = #C1}) → asy::Future<core::int*>*; -> asy::Future::catchError
  abstract member-signature method whenComplete(() →* FutureOr<void>* action) → asy::Future<core::int*>*; -> asy::Future::whenComplete
  abstract member-signature method asStream() → asy::Stream<core::int*>*; -> asy::Future::asStream
-  abstract member-signature method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<core::int*>onTimeout = #C1}) → asy::Future<core::int*>*; -> asy::Future::timeout
+  abstract member-signature method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<core::int*>* onTimeout = #C1}) → asy::Future<core::int*>*; -> asy::Future::timeout
 }
 static method test() → void async {
  core::int* x0;
--- a/pkg/front_end/testcases/inference/async_await.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/async_await.dart.strong.transformed.expect
@ -24,7 +24,7 @@ abstract class MyFuture extends core::Object implements asy::Future<core::int*>
  abstract member-signature method catchError(core::Function* onError, {(core::Object*) →* core::bool* test = #C1}) → asy::Future<core::int*>*; -> asy::Future::catchError
  abstract member-signature method whenComplete(() →* FutureOr<void>* action) → asy::Future<core::int*>*; -> asy::Future::whenComplete
  abstract member-signature method asStream() → asy::Stream<core::int*>*; -> asy::Future::asStream
-  abstract member-signature method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<core::int*>onTimeout = #C1}) → asy::Future<core::int*>*; -> asy::Future::timeout
+  abstract member-signature method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<core::int*>* onTimeout = #C1}) → asy::Future<core::int*>*; -> asy::Future::timeout
 }
 static method test() → void /* originally async */ {
  final asy::_AsyncAwaitCompleter<dynamic>* :async_completer = new asy::_AsyncAwaitCompleter::•<dynamic>();
--- a/pkg/front_end/testcases/inference/future_then.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/future_then.dart.outline.expect
@ -29,7 +29,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#whenComplete, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#asStream, 0, const <core::Type*>[], const <dynamic>[], core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#timeout, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#onTimeout: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method test() → void
--- a/pkg/front_end/testcases/inference/future_then.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/future_then.dart.strong.expect
@ -29,7 +29,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method test() → void {
--- a/pkg/front_end/testcases/inference/future_then.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/future_then.dart.strong.transformed.expect
@ -30,7 +30,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method test() → void {
--- a/pkg/front_end/testcases/inference/future_then_2.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/future_then_2.dart.outline.expect
@ -29,7 +29,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#whenComplete, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#asStream, 0, const <core::Type*>[], const <dynamic>[], core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#timeout, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#onTimeout: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method test() → void
--- a/pkg/front_end/testcases/inference/future_then_2.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/future_then_2.dart.strong.expect
@ -29,7 +29,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method test() → void {
--- a/pkg/front_end/testcases/inference/future_then_2.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/future_then_2.dart.strong.transformed.expect
@ -30,7 +30,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method test() → void {
--- a/pkg/front_end/testcases/inference/future_then_3.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/future_then_3.dart.outline.expect
@ -29,7 +29,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#whenComplete, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#asStream, 0, const <core::Type*>[], const <dynamic>[], core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#timeout, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#onTimeout: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method test() → void
--- a/pkg/front_end/testcases/inference/future_then_3.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/future_then_3.dart.strong.expect
@ -29,7 +29,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method test() → void {
--- a/pkg/front_end/testcases/inference/future_then_3.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/future_then_3.dart.strong.transformed.expect
@ -30,7 +30,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method test() → void {
--- a/pkg/front_end/testcases/inference/future_then_4.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/future_then_4.dart.outline.expect
@ -29,7 +29,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#whenComplete, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#asStream, 0, const <core::Type*>[], const <dynamic>[], core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#timeout, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#onTimeout: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method test() → void
--- a/pkg/front_end/testcases/inference/future_then_4.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/future_then_4.dart.strong.expect
@ -29,7 +29,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method test() → void {
--- a/pkg/front_end/testcases/inference/future_then_4.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/future_then_4.dart.strong.transformed.expect
@ -30,7 +30,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method test() → void {
--- a/pkg/front_end/testcases/inference/future_then_5.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/future_then_5.dart.outline.expect
@ -29,7 +29,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#whenComplete, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#asStream, 0, const <core::Type*>[], const <dynamic>[], core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#timeout, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#onTimeout: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method test() → void
--- a/pkg/front_end/testcases/inference/future_then_5.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/future_then_5.dart.strong.expect
@ -29,7 +29,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method test() → void {
--- a/pkg/front_end/testcases/inference/future_then_5.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/future_then_5.dart.strong.transformed.expect
@ -30,7 +30,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method test() → void {
--- a/pkg/front_end/testcases/inference/future_then_6.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/future_then_6.dart.outline.expect
@ -29,7 +29,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#whenComplete, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#asStream, 0, const <core::Type*>[], const <dynamic>[], core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#timeout, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#onTimeout: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method test() → void
--- a/pkg/front_end/testcases/inference/future_then_6.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/future_then_6.dart.strong.expect
@ -29,7 +29,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method test() → void {
--- a/pkg/front_end/testcases/inference/future_then_6.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/future_then_6.dart.strong.transformed.expect
@ -30,7 +30,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method test() → void {
--- a/pkg/front_end/testcases/inference/future_then_conditional.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/future_then_conditional.dart.outline.expect
@ -29,7 +29,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#whenComplete, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#asStream, 0, const <core::Type*>[], const <dynamic>[], core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#timeout, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#onTimeout: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method test() → void
--- a/pkg/front_end/testcases/inference/future_then_conditional.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/future_then_conditional.dart.strong.expect
@ -29,7 +29,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method test() → void {
--- a/pkg/front_end/testcases/inference/future_then_conditional.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/future_then_conditional.dart.strong.transformed.expect
@ -30,7 +30,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method test() → void {
--- a/pkg/front_end/testcases/inference/future_then_conditional_2.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/future_then_conditional_2.dart.outline.expect
@ -29,7 +29,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#whenComplete, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#asStream, 0, const <core::Type*>[], const <dynamic>[], core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#timeout, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#onTimeout: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method test() → void
--- a/pkg/front_end/testcases/inference/future_then_conditional_2.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/future_then_conditional_2.dart.strong.expect
@ -29,7 +29,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method test() → void {
--- a/pkg/front_end/testcases/inference/future_then_conditional_2.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/future_then_conditional_2.dart.strong.transformed.expect
@ -30,7 +30,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method test() → void {
--- a/pkg/front_end/testcases/inference/future_then_conditional_3.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/future_then_conditional_3.dart.outline.expect
@ -29,7 +29,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#whenComplete, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#asStream, 0, const <core::Type*>[], const <dynamic>[], core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#timeout, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#onTimeout: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method test() → void
--- a/pkg/front_end/testcases/inference/future_then_conditional_3.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/future_then_conditional_3.dart.strong.expect
@ -29,7 +29,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method test() → void {
--- a/pkg/front_end/testcases/inference/future_then_conditional_3.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/future_then_conditional_3.dart.strong.transformed.expect
@ -30,7 +30,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method test() → void {
--- a/pkg/front_end/testcases/inference/future_then_conditional_4.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/future_then_conditional_4.dart.outline.expect
@ -29,7 +29,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#whenComplete, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#asStream, 0, const <core::Type*>[], const <dynamic>[], core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#timeout, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#onTimeout: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method test() → void
--- a/pkg/front_end/testcases/inference/future_then_conditional_4.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/future_then_conditional_4.dart.strong.expect
@ -29,7 +29,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method test() → void {
--- a/pkg/front_end/testcases/inference/future_then_conditional_4.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/future_then_conditional_4.dart.strong.transformed.expect
@ -30,7 +30,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method test() → void {
--- a/pkg/front_end/testcases/inference/future_then_conditional_5.dart
+++ b/pkg/front_end/testcases/inference/future_then_conditional_5.dart
@ -20,17 +20,17 @@ void test() {
      /*@ returnType=Future<int*>* */ (/*@ type=bool* */ x) async =>
          x ? 2 : await new MyFuture<int>.value(3));
  Future<int> t2 = f. /*@ typeArgs=int* */ /*@target=Future.then*/ then(
-      /*@returnType=FutureOr<int*>*/ (/*@ type=bool* */ x) async {
+      /*@returnType=FutureOr<int*>**/ (/*@ type=bool* */ x) async {
    return /*info:DOWN_CAST_COMPOSITE*/ await x
        ? 2
        : new MyFuture<int>.value(3);
  });
  Future<int> t5 = f. /*@ typeArgs=int* */ /*@target=Future.then*/ then(
      /*info:INFERRED_TYPE_CLOSURE,error:INVALID_CAST_FUNCTION_EXPR*/
-      /*@ returnType=FutureOr<int*> */ (/*@ type=bool* */ x) =>
+      /*@returnType=FutureOr<int*>**/ (/*@ type=bool* */ x) =>
          x ? 2 : new MyFuture<int>.value(3));
  Future<int> t6 = f. /*@ typeArgs=int* */ /*@target=Future.then*/ then(
-      /*@ returnType=FutureOr<int*> */ (/*@ type=bool* */ x) {
+      /*@returnType=FutureOr<int*>**/ (/*@ type=bool* */ x) {
    return /*info:DOWN_CAST_COMPOSITE*/ x ? 2 : new MyFuture<int>.value(3);
  });
 }
--- a/pkg/front_end/testcases/inference/future_then_conditional_5.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/future_then_conditional_5.dart.outline.expect
@ -29,7 +29,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#whenComplete, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#asStream, 0, const <core::Type*>[], const <dynamic>[], core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#timeout, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#onTimeout: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method test() → void
--- a/pkg/front_end/testcases/inference/future_then_conditional_5.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/future_then_conditional_5.dart.strong.expect
@ -29,18 +29,18 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method test() → void {
  asy::Future<core::bool*>* f;
  asy::Future<core::int*>* t1 = f.{asy::Future::then}<core::int*>((core::bool* x) → asy::Future<core::int*>* async => x ?{core::int*} 2 : await new self::MyFuture::value<core::int*>(3));
-  asy::Future<core::int*>* t2 = f.{asy::Future::then}<core::int*>((core::bool* x) → FutureOr<core::int*> async {
+  asy::Future<core::int*>* t2 = f.{asy::Future::then}<core::int*>((core::bool* x) → FutureOr<core::int*>* async {
    return (await x ?{core::Object*} 2 : new self::MyFuture::value<core::int*>(3)) as{TypeError} FutureOr<core::int*>*;
  });
-  asy::Future<core::int*>* t5 = f.{asy::Future::then}<core::int*>((core::bool* x) → FutureOr<core::int*> => (x ?{core::Object*} 2 : new self::MyFuture::value<core::int*>(3)) as{TypeError} FutureOr<core::int*>);
-  asy::Future<core::int*>* t6 = f.{asy::Future::then}<core::int*>((core::bool* x) → FutureOr<core::int*> {
-    return (x ?{core::Object*} 2 : new self::MyFuture::value<core::int*>(3)) as{TypeError} FutureOr<core::int*>;
+  asy::Future<core::int*>* t5 = f.{asy::Future::then}<core::int*>((core::bool* x) → FutureOr<core::int*>* => (x ?{core::Object*} 2 : new self::MyFuture::value<core::int*>(3)) as{TypeError} FutureOr<core::int*>*);
+  asy::Future<core::int*>* t6 = f.{asy::Future::then}<core::int*>((core::bool* x) → FutureOr<core::int*>* {
+    return (x ?{core::Object*} 2 : new self::MyFuture::value<core::int*>(3)) as{TypeError} FutureOr<core::int*>*;
  });
 }
 static method main() → dynamic {}
--- a/pkg/front_end/testcases/inference/future_then_conditional_5.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/future_then_conditional_5.dart.strong.transformed.expect
@ -30,7 +30,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method test() → void {
@ -71,7 +71,7 @@ static method test() → void {
    :async_completer.{asy::_AsyncAwaitCompleter::start}(:async_op);
    return :async_completer.{asy::Completer::future};
  });
-  asy::Future<core::int*>* t2 = f.{asy::Future::then}<core::int*>((core::bool* x) → FutureOr<core::int*> /* originally async */ {
+  asy::Future<core::int*>* t2 = f.{asy::Future::then}<core::int*>((core::bool* x) → FutureOr<core::int*>* /* originally async */ {
    final asy::_AsyncAwaitCompleter<core::int*>* :async_completer = new asy::_AsyncAwaitCompleter::•<core::int*>();
    FutureOr<core::int*>* :return_value;
    dynamic :async_stack_trace;
@ -100,9 +100,9 @@ static method test() → void {
    :async_completer.{asy::_AsyncAwaitCompleter::start}(:async_op);
    return :async_completer.{asy::Completer::future};
  });
-  asy::Future<core::int*>* t5 = f.{asy::Future::then}<core::int*>((core::bool* x) → FutureOr<core::int*> => (x ?{core::Object*} 2 : new self::MyFuture::value<core::int*>(3)) as{TypeError} FutureOr<core::int*>);
-  asy::Future<core::int*>* t6 = f.{asy::Future::then}<core::int*>((core::bool* x) → FutureOr<core::int*> {
-    return (x ?{core::Object*} 2 : new self::MyFuture::value<core::int*>(3)) as{TypeError} FutureOr<core::int*>;
+  asy::Future<core::int*>* t5 = f.{asy::Future::then}<core::int*>((core::bool* x) → FutureOr<core::int*>* => (x ?{core::Object*} 2 : new self::MyFuture::value<core::int*>(3)) as{TypeError} FutureOr<core::int*>*);
+  asy::Future<core::int*>* t6 = f.{asy::Future::then}<core::int*>((core::bool* x) → FutureOr<core::int*>* {
+    return (x ?{core::Object*} 2 : new self::MyFuture::value<core::int*>(3)) as{TypeError} FutureOr<core::int*>*;
  });
 }
 static method main() → dynamic {}
--- a/pkg/front_end/testcases/inference/future_then_conditional_6.dart
+++ b/pkg/front_end/testcases/inference/future_then_conditional_6.dart
@ -20,15 +20,15 @@ void test() {
      /*@ returnType=Future<int*>* */ (/*@ type=bool* */ x) async =>
          x ? 2 : await new Future<int>.value(3));
  Future<int> t2 = f. /*@ typeArgs=int* */ /*@target=Future.then*/ then(
-      /*@returnType=FutureOr<int*>*/ (/*@ type=bool* */ x) async {
+      /*@returnType=FutureOr<int*>**/ (/*@ type=bool* */ x) async {
    return /*info:DOWN_CAST_COMPOSITE*/ await x ? 2 : new Future<int>.value(3);
  });
  Future<int> t5 = f. /*@ typeArgs=int* */ /*@target=Future.then*/ then(
      /*info:INFERRED_TYPE_CLOSURE,error:INVALID_CAST_FUNCTION_EXPR*/
-      /*@ returnType=FutureOr<int*> */ (/*@ type=bool* */ x) =>
+      /*@returnType=FutureOr<int*>**/ (/*@ type=bool* */ x) =>
          x ? 2 : new Future<int>.value(3));
  Future<int> t6 = f. /*@ typeArgs=int* */ /*@target=Future.then*/ then(
-      /*@ returnType=FutureOr<int*> */ (/*@ type=bool* */ x) {
+      /*@returnType=FutureOr<int*>**/ (/*@ type=bool* */ x) {
    return /*info:DOWN_CAST_COMPOSITE*/ x ? 2 : new Future<int>.value(3);
  });
 }
--- a/pkg/front_end/testcases/inference/future_then_conditional_6.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/future_then_conditional_6.dart.outline.expect
@ -29,7 +29,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#whenComplete, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#asStream, 0, const <core::Type*>[], const <dynamic>[], core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#timeout, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#onTimeout: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method test() → void
--- a/pkg/front_end/testcases/inference/future_then_conditional_6.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/future_then_conditional_6.dart.strong.expect
@ -29,18 +29,18 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method test() → void {
  asy::Future<core::bool*>* f;
  asy::Future<core::int*>* t1 = f.{asy::Future::then}<core::int*>((core::bool* x) → asy::Future<core::int*>* async => x ?{core::int*} 2 : await asy::Future::value<core::int*>(3));
-  asy::Future<core::int*>* t2 = f.{asy::Future::then}<core::int*>((core::bool* x) → FutureOr<core::int*> async {
+  asy::Future<core::int*>* t2 = f.{asy::Future::then}<core::int*>((core::bool* x) → FutureOr<core::int*>* async {
    return (await x ?{core::Object*} 2 : asy::Future::value<core::int*>(3)) as{TypeError} FutureOr<core::int*>*;
  });
-  asy::Future<core::int*>* t5 = f.{asy::Future::then}<core::int*>((core::bool* x) → FutureOr<core::int*> => (x ?{core::Object*} 2 : asy::Future::value<core::int*>(3)) as{TypeError} FutureOr<core::int*>);
-  asy::Future<core::int*>* t6 = f.{asy::Future::then}<core::int*>((core::bool* x) → FutureOr<core::int*> {
-    return (x ?{core::Object*} 2 : asy::Future::value<core::int*>(3)) as{TypeError} FutureOr<core::int*>;
+  asy::Future<core::int*>* t5 = f.{asy::Future::then}<core::int*>((core::bool* x) → FutureOr<core::int*>* => (x ?{core::Object*} 2 : asy::Future::value<core::int*>(3)) as{TypeError} FutureOr<core::int*>*);
+  asy::Future<core::int*>* t6 = f.{asy::Future::then}<core::int*>((core::bool* x) → FutureOr<core::int*>* {
+    return (x ?{core::Object*} 2 : asy::Future::value<core::int*>(3)) as{TypeError} FutureOr<core::int*>*;
  });
 }
 static method main() → dynamic {}
--- a/pkg/front_end/testcases/inference/future_then_conditional_6.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/future_then_conditional_6.dart.strong.transformed.expect
@ -30,7 +30,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method test() → void {
@ -71,7 +71,7 @@ static method test() → void {
    :async_completer.{asy::_AsyncAwaitCompleter::start}(:async_op);
    return :async_completer.{asy::Completer::future};
  });
-  asy::Future<core::int*>* t2 = f.{asy::Future::then}<core::int*>((core::bool* x) → FutureOr<core::int*> /* originally async */ {
+  asy::Future<core::int*>* t2 = f.{asy::Future::then}<core::int*>((core::bool* x) → FutureOr<core::int*>* /* originally async */ {
    final asy::_AsyncAwaitCompleter<core::int*>* :async_completer = new asy::_AsyncAwaitCompleter::•<core::int*>();
    FutureOr<core::int*>* :return_value;
    dynamic :async_stack_trace;
@ -100,9 +100,9 @@ static method test() → void {
    :async_completer.{asy::_AsyncAwaitCompleter::start}(:async_op);
    return :async_completer.{asy::Completer::future};
  });
-  asy::Future<core::int*>* t5 = f.{asy::Future::then}<core::int*>((core::bool* x) → FutureOr<core::int*> => (x ?{core::Object*} 2 : asy::Future::value<core::int*>(3)) as{TypeError} FutureOr<core::int*>);
-  asy::Future<core::int*>* t6 = f.{asy::Future::then}<core::int*>((core::bool* x) → FutureOr<core::int*> {
-    return (x ?{core::Object*} 2 : asy::Future::value<core::int*>(3)) as{TypeError} FutureOr<core::int*>;
+  asy::Future<core::int*>* t5 = f.{asy::Future::then}<core::int*>((core::bool* x) → FutureOr<core::int*>* => (x ?{core::Object*} 2 : asy::Future::value<core::int*>(3)) as{TypeError} FutureOr<core::int*>*);
+  asy::Future<core::int*>* t6 = f.{asy::Future::then}<core::int*>((core::bool* x) → FutureOr<core::int*>* {
+    return (x ?{core::Object*} 2 : asy::Future::value<core::int*>(3)) as{TypeError} FutureOr<core::int*>*;
  });
 }
 static method main() → dynamic {}
--- a/pkg/front_end/testcases/inference/future_then_explicit_future.dart
+++ b/pkg/front_end/testcases/inference/future_then_explicit_future.dart
@ -12,7 +12,7 @@ m1() {
  var /*@type=Future<Future<List<int*>*>*>**/ x = f. /*@target=Future.then*/ then<
          Future<List<int>>>(
      /*error:ARGUMENT_TYPE_NOT_ASSIGNABLE*/
-      /*@returnType=FutureOr<Future<List<int*>*>*>*/ (/*@type=int**/ x) => /*@typeArgs=dynamic*/ []);
+      /*@returnType=FutureOr<Future<List<int*>*>*>**/ (/*@type=int**/ x) => /*@typeArgs=dynamic*/ []);
  Future<List<int>> y = x;
 }

--- a/pkg/front_end/testcases/inference/future_then_explicit_future.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/future_then_explicit_future.dart.strong.expect
@ -2,11 +2,11 @@ library test;
 //
 // Problems in library:
 //
-// pkg/front_end/testcases/inference/future_then_explicit_future.dart:15:98: Error: A value of type 'List<dynamic>' can't be assigned to a variable of type 'FutureOr<Future<List<int>>>'.
+// pkg/front_end/testcases/inference/future_then_explicit_future.dart:15:99: Error: A value of type 'List<dynamic>' can't be assigned to a variable of type 'FutureOr<Future<List<int>>>'.
 //  - 'List' is from 'dart:core'.
 //  - 'Future' is from 'dart:async'.
-//       /*@returnType=FutureOr<Future<List<int*>*>*>*/ (/*@type=int**/ x) => /*@typeArgs=dynamic*/ []);
-//                                                                                                  ^
+//       /*@returnType=FutureOr<Future<List<int*>*>*>**/ (/*@type=int**/ x) => /*@typeArgs=dynamic*/ []);
+//                                                                                                   ^
 //
 // pkg/front_end/testcases/inference/future_then_explicit_future.dart:16:25: Error: A value of type 'Future<Future<List<int>>>' can't be assigned to a variable of type 'Future<List<int>>'.
 //  - 'Future' is from 'dart:async'.
@ -22,11 +22,11 @@ import "dart:async";

 static method m1() → dynamic {
  asy::Future<core::int*>* f;
-  asy::Future<asy::Future<core::List<core::int*>*>*>* x = f.{asy::Future::then}<asy::Future<core::List<core::int*>*>*>((core::int* x) → FutureOr<asy::Future<core::List<core::int*>*>*> => let final<BottomType> #t1 = invalid-expression "pkg/front_end/testcases/inference/future_then_explicit_future.dart:15:98: Error: A value of type 'List<dynamic>' can't be assigned to a variable of type 'FutureOr<Future<List<int>>>'.
+  asy::Future<asy::Future<core::List<core::int*>*>*>* x = f.{asy::Future::then}<asy::Future<core::List<core::int*>*>*>((core::int* x) → FutureOr<asy::Future<core::List<core::int*>*>*>* => let final<BottomType> #t1 = invalid-expression "pkg/front_end/testcases/inference/future_then_explicit_future.dart:15:99: Error: A value of type 'List<dynamic>' can't be assigned to a variable of type 'FutureOr<Future<List<int>>>'.
 - 'List' is from 'dart:core'.
 - 'Future' is from 'dart:async'.
-      /*@returnType=FutureOr<Future<List<int*>*>*>*/ (/*@type=int**/ x) => /*@typeArgs=dynamic*/ []);
-                                                                                                 ^" in <dynamic>[] as{TypeError} FutureOr<asy::Future<core::List<core::int*>*>*>);
+      /*@returnType=FutureOr<Future<List<int*>*>*>**/ (/*@type=int**/ x) => /*@typeArgs=dynamic*/ []);
+                                                                                                  ^" in <dynamic>[] as{TypeError} FutureOr<asy::Future<core::List<core::int*>*>*>*);
  asy::Future<core::List<core::int*>*>* y = let final<BottomType> #t2 = invalid-expression "pkg/front_end/testcases/inference/future_then_explicit_future.dart:16:25: Error: A value of type 'Future<Future<List<int>>>' can't be assigned to a variable of type 'Future<List<int>>'.
 - 'Future' is from 'dart:async'.
 - 'List' is from 'dart:core'.
--- a/pkg/front_end/testcases/inference/future_then_explicit_future.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/future_then_explicit_future.dart.strong.transformed.expect
@ -2,11 +2,11 @@ library test;
 //
 // Problems in library:
 //
-// pkg/front_end/testcases/inference/future_then_explicit_future.dart:15:98: Error: A value of type 'List<dynamic>' can't be assigned to a variable of type 'FutureOr<Future<List<int>>>'.
+// pkg/front_end/testcases/inference/future_then_explicit_future.dart:15:99: Error: A value of type 'List<dynamic>' can't be assigned to a variable of type 'FutureOr<Future<List<int>>>'.
 //  - 'List' is from 'dart:core'.
 //  - 'Future' is from 'dart:async'.
-//       /*@returnType=FutureOr<Future<List<int*>*>*>*/ (/*@type=int**/ x) => /*@typeArgs=dynamic*/ []);
-//                                                                                                  ^
+//       /*@returnType=FutureOr<Future<List<int*>*>*>**/ (/*@type=int**/ x) => /*@typeArgs=dynamic*/ []);
+//                                                                                                   ^
 //
 // pkg/front_end/testcases/inference/future_then_explicit_future.dart:16:25: Error: A value of type 'Future<Future<List<int>>>' can't be assigned to a variable of type 'Future<List<int>>'.
 //  - 'Future' is from 'dart:async'.
@ -22,11 +22,11 @@ import "dart:async";

 static method m1() → dynamic {
  asy::Future<core::int*>* f;
-  asy::Future<asy::Future<core::List<core::int*>*>*>* x = f.{asy::Future::then}<asy::Future<core::List<core::int*>*>*>((core::int* x) → FutureOr<asy::Future<core::List<core::int*>*>*> => let final<BottomType> #t1 = invalid-expression "pkg/front_end/testcases/inference/future_then_explicit_future.dart:15:98: Error: A value of type 'List<dynamic>' can't be assigned to a variable of type 'FutureOr<Future<List<int>>>'.
+  asy::Future<asy::Future<core::List<core::int*>*>*>* x = f.{asy::Future::then}<asy::Future<core::List<core::int*>*>*>((core::int* x) → FutureOr<asy::Future<core::List<core::int*>*>*>* => let final<BottomType> #t1 = invalid-expression "pkg/front_end/testcases/inference/future_then_explicit_future.dart:15:99: Error: A value of type 'List<dynamic>' can't be assigned to a variable of type 'FutureOr<Future<List<int>>>'.
 - 'List' is from 'dart:core'.
 - 'Future' is from 'dart:async'.
-      /*@returnType=FutureOr<Future<List<int*>*>*>*/ (/*@type=int**/ x) => /*@typeArgs=dynamic*/ []);
-                                                                                                 ^" in <dynamic>[] as{TypeError} FutureOr<asy::Future<core::List<core::int*>*>*>);
+      /*@returnType=FutureOr<Future<List<int*>*>*>**/ (/*@type=int**/ x) => /*@typeArgs=dynamic*/ []);
+                                                                                                  ^" in <dynamic>[] as{TypeError} FutureOr<asy::Future<core::List<core::int*>*>*>*);
  asy::Future<core::List<core::int*>*>* y = let final<BottomType> #t2 = invalid-expression "pkg/front_end/testcases/inference/future_then_explicit_future.dart:16:25: Error: A value of type 'Future<Future<List<int>>>' can't be assigned to a variable of type 'Future<List<int>>'.
 - 'Future' is from 'dart:async'.
 - 'List' is from 'dart:core'.
--- a/pkg/front_end/testcases/inference/future_then_ifNull.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/future_then_ifNull.dart.outline.expect
@ -29,7 +29,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#whenComplete, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#asStream, 0, const <core::Type*>[], const <dynamic>[], core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#timeout, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#onTimeout: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method test() → void
--- a/pkg/front_end/testcases/inference/future_then_ifNull.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/future_then_ifNull.dart.strong.expect
@ -29,7 +29,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method test() → void {
--- a/pkg/front_end/testcases/inference/future_then_ifNull.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/future_then_ifNull.dart.strong.transformed.expect
@ -30,7 +30,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method test() → void {
--- a/pkg/front_end/testcases/inference/future_then_upwards.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/future_then_upwards.dart.outline.expect
@ -29,7 +29,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#whenComplete, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#asStream, 0, const <core::Type*>[], const <dynamic>[], core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#timeout, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#onTimeout: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method main() → void
--- a/pkg/front_end/testcases/inference/future_then_upwards.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/future_then_upwards.dart.strong.expect
@ -38,7 +38,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method main() → void {
--- a/pkg/front_end/testcases/inference/future_then_upwards.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/future_then_upwards.dart.strong.transformed.expect
@ -38,7 +38,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method main() → void {
--- a/pkg/front_end/testcases/inference/future_then_upwards_2.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/future_then_upwards_2.dart.outline.expect
@ -29,7 +29,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#whenComplete, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#asStream, 0, const <core::Type*>[], const <dynamic>[], core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#timeout, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#onTimeout: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method main() → void
--- a/pkg/front_end/testcases/inference/future_then_upwards_2.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/future_then_upwards_2.dart.strong.expect
@ -37,7 +37,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method main() → void {
--- a/pkg/front_end/testcases/inference/future_then_upwards_2.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/future_then_upwards_2.dart.strong.transformed.expect
@ -37,7 +37,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method main() → void {
--- a/pkg/front_end/testcases/inference/future_then_upwards_3.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/future_then_upwards_3.dart.outline.expect
@ -29,7 +29,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#whenComplete, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#asStream, 0, const <core::Type*>[], const <dynamic>[], core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#timeout, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#onTimeout: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method test() → void
--- a/pkg/front_end/testcases/inference/future_then_upwards_3.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/future_then_upwards_3.dart.strong.expect
@ -37,7 +37,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method test() → void {
--- a/pkg/front_end/testcases/inference/future_then_upwards_3.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/future_then_upwards_3.dart.strong.transformed.expect
@ -37,7 +37,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method test() → void {
--- a/pkg/front_end/testcases/inference/future_union_async_conditional.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/future_union_async_conditional.dart.outline.expect
@ -29,7 +29,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#whenComplete, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#asStream, 0, const <core::Type*>[], const <dynamic>[], core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#timeout, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#onTimeout: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method g1(core::bool* x) → asy::Future<core::int*>* async 
--- a/pkg/front_end/testcases/inference/future_union_async_conditional.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/future_union_async_conditional.dart.strong.expect
@ -29,7 +29,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method g1(core::bool* x) → asy::Future<core::int*>* async {
--- a/pkg/front_end/testcases/inference/future_union_async_conditional.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/future_union_async_conditional.dart.strong.transformed.expect
@ -29,7 +29,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method g1(core::bool* x) → asy::Future<core::int*>* /* originally async */ {
--- a/pkg/front_end/testcases/inference/future_union_async_conditional_2.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/future_union_async_conditional_2.dart.outline.expect
@ -29,7 +29,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#whenComplete, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#asStream, 0, const <core::Type*>[], const <dynamic>[], core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#timeout, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#onTimeout: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method g1(core::bool* x) → asy::Future<core::int*>* async 
--- a/pkg/front_end/testcases/inference/future_union_async_conditional_2.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/future_union_async_conditional_2.dart.strong.expect
@ -29,7 +29,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method g1(core::bool* x) → asy::Future<core::int*>* async {
--- a/pkg/front_end/testcases/inference/future_union_async_conditional_2.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/future_union_async_conditional_2.dart.strong.transformed.expect
@ -29,7 +29,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static method g1(core::bool* x) → asy::Future<core::int*>* /* originally async */ {
--- a/pkg/front_end/testcases/inference/future_union_downwards.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/future_union_downwards.dart.outline.expect
@ -29,7 +29,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#whenComplete, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#asStream, 0, const <core::Type*>[], const <dynamic>[], core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#timeout, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#onTimeout: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static field self::MyFuture<dynamic>* f;
--- a/pkg/front_end/testcases/inference/future_union_downwards.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/future_union_downwards.dart.strong.expect
@ -36,7 +36,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static field self::MyFuture<dynamic>* f;
--- a/pkg/front_end/testcases/inference/future_union_downwards.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/future_union_downwards.dart.strong.transformed.expect
@ -36,7 +36,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static field self::MyFuture<dynamic>* f;
--- a/pkg/front_end/testcases/inference/future_union_downwards_2.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/future_union_downwards_2.dart.outline.expect
@ -29,7 +29,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#whenComplete, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#asStream, 0, const <core::Type*>[], const <dynamic>[], core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#timeout, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#onTimeout: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static field self::MyFuture<dynamic>* f;
--- a/pkg/front_end/testcases/inference/future_union_downwards_2.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/future_union_downwards_2.dart.strong.expect
@ -29,7 +29,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static field self::MyFuture<dynamic>* f;
--- a/pkg/front_end/testcases/inference/future_union_downwards_2.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/future_union_downwards_2.dart.strong.transformed.expect
@ -29,7 +29,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static field self::MyFuture<dynamic>* f;
--- a/pkg/front_end/testcases/inference/future_union_downwards_3.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/future_union_downwards_3.dart.outline.expect
@ -29,7 +29,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#whenComplete, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#asStream, 0, const <core::Type*>[], const <dynamic>[], core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#timeout, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#onTimeout: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static field asy::Future<dynamic>* f;
--- a/pkg/front_end/testcases/inference/future_union_downwards_3.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/future_union_downwards_3.dart.strong.expect
@ -36,7 +36,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static field asy::Future<dynamic>* f;
--- a/pkg/front_end/testcases/inference/future_union_downwards_3.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/future_union_downwards_3.dart.strong.transformed.expect
@ -36,7 +36,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static field asy::Future<dynamic>* f;
--- a/pkg/front_end/testcases/inference/future_union_downwards_4.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/future_union_downwards_4.dart.outline.expect
@ -29,7 +29,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#whenComplete, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#asStream, 0, const <core::Type*>[], const <dynamic>[], core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#timeout, 0, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#onTimeout: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static field asy::Future<dynamic>* f;
--- a/pkg/front_end/testcases/inference/future_union_downwards_4.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/future_union_downwards_4.dart.strong.expect
@ -29,7 +29,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static field asy::Future<dynamic>* f;
--- a/pkg/front_end/testcases/inference/future_union_downwards_4.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/future_union_downwards_4.dart.strong.transformed.expect
@ -29,7 +29,7 @@ class MyFuture<T extends core::Object* = dynamic> extends core::Object implement
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[action]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
  no-such-method-forwarder method asStream() → asy::Stream<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C8, 0, #C3, #C6, core::Map::unmodifiable<core::Symbol*, dynamic>(#C7))) as{TypeError,ForDynamic} asy::Stream<self::MyFuture::T*>*;
-  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
+  no-such-method-forwarder method timeout(core::Duration* timeLimit, {generic-covariant-impl () →* FutureOr<self::MyFuture::T*>* onTimeout = #C1}) → asy::Future<self::MyFuture::T*>*
    return this.{self::MyFuture::noSuchMethod}(new core::_InvocationMirror::_withType(#C9, 0, #C3, core::List::unmodifiable<dynamic>(<dynamic>[timeLimit]), core::Map::unmodifiable<core::Symbol*, dynamic>(<core::Symbol*, dynamic>{#C10: onTimeout}))) as{TypeError,ForDynamic} asy::Future<self::MyFuture::T*>*;
 }
 static field asy::Future<dynamic>* f;
--- a/pkg/kernel/lib/src/legacy_erasure.dart
+++ b/pkg/kernel/lib/src/legacy_erasure.dart
@ -56,7 +56,7 @@ class _LegacyErasure extends ReplacementVisitor {
  _LegacyErasure(this.coreTypes);

  Nullability visitNullability(DartType node) {
-    if (node.nullability != Nullability.legacy) {
+    if (node.declaredNullability != Nullability.legacy) {
      return Nullability.legacy;
    }
    return null;