[cfe] Implement full subtyping rules for extension types vs FutureOr

Closes #55578

Change-Id: Id344e9057f42b3fc19a6ff83ce000775aec5789a
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/364720
Reviewed-by: Johnni Winther <johnniwinther@google.com>
Commit-Queue: Chloe Stefantsova <cstefantsova@google.com>

pkg/front_end/testcases/extension_types/issue55578.dart

@@ -0,0 +1,13 @@
+// Copyright (c) 2024, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:async';
+
+extension type E(Future<String> it) implements Future<String> {}
+
+foo(FutureOr<String> x) {}
+
+E bar() => throw 0;
+
+test() => foo(bar()); // Ok.

pkg/front_end/testcases/extension_types/issue55578.dart.strong.expect

@@ -0,0 +1,23 @@
+library;
+import self as self;
+import "dart:async" as asy;
+import "dart:core" as core;
+
+import "dart:async";
+
+extension type E(asy::Future<core::String> it) implements asy::Future<core::String> {
+  abstract extension-type-member representation-field get it() → asy::Future<core::String>;
+  constructor • = self::E|constructor#;
+  constructor tearoff • = self::E|constructor#_#new#tearOff;
+}
+static extension-type-member method E|constructor#(asy::Future<core::String> it) → self::E /* erasure=asy::Future<core::String> */ {
+  lowered final self::E /* erasure=asy::Future<core::String> */ #this = it;
+  return #this;
+}
+static extension-type-member method E|constructor#_#new#tearOff(asy::Future<core::String> it) → self::E /* erasure=asy::Future<core::String> */
+  return self::E|constructor#(it);
+static method foo(FutureOr<core::String>x) → dynamic {}
+static method bar() → self::E /* erasure=asy::Future<core::String> */
+  return throw 0;
+static method test() → dynamic
+  return self::foo(self::bar());

pkg/front_end/testcases/extension_types/issue55578.dart.strong.transformed.expect

@@ -0,0 +1,23 @@
+library;
+import self as self;
+import "dart:async" as asy;
+import "dart:core" as core;
+
+import "dart:async";
+
+extension type E(asy::Future<core::String> it) implements asy::Future<core::String> {
+  abstract extension-type-member representation-field get it() → asy::Future<core::String>;
+  constructor • = self::E|constructor#;
+  constructor tearoff • = self::E|constructor#_#new#tearOff;
+}
+static extension-type-member method E|constructor#(asy::Future<core::String> it) → self::E /* erasure=asy::Future<core::String> */ {
+  lowered final self::E /* erasure=asy::Future<core::String> */ #this = it;
+  return #this;
+}
+static extension-type-member method E|constructor#_#new#tearOff(asy::Future<core::String> it) → self::E /* erasure=asy::Future<core::String> */
+  return self::E|constructor#(it);
+static method foo(FutureOr<core::String>x) → dynamic {}
+static method bar() → self::E /* erasure=asy::Future<core::String> */
+  return throw 0;
+static method test() → dynamic
+  return self::foo(self::bar());

pkg/front_end/testcases/extension_types/issue55578.dart.textual_outline.expect

@@ -0,0 +1,9 @@
+import 'dart:async';
+
+extension type E(Future<String> it) implements Future<String> {}
+
+foo(FutureOr<String> x) {}
+
+E bar() => throw 0;
+
+test() => foo(bar());

pkg/front_end/testcases/extension_types/issue55578.dart.textual_outline_modelled.expect

@@ -0,0 +1,9 @@
+import 'dart:async';
+
+E bar() => throw 0;
+
+extension type E(Future<String> it) implements Future<String> {}
+
+foo(FutureOr<String> x) {}
+
+test() => foo(bar());

pkg/front_end/testcases/extension_types/issue55578.dart.weak.expect

@@ -0,0 +1,23 @@
+library;
+import self as self;
+import "dart:async" as asy;
+import "dart:core" as core;
+
+import "dart:async";
+
+extension type E(asy::Future<core::String> it) implements asy::Future<core::String> {
+  abstract extension-type-member representation-field get it() → asy::Future<core::String>;
+  constructor • = self::E|constructor#;
+  constructor tearoff • = self::E|constructor#_#new#tearOff;
+}
+static extension-type-member method E|constructor#(asy::Future<core::String> it) → self::E /* erasure=asy::Future<core::String> */ {
+  lowered final self::E /* erasure=asy::Future<core::String> */ #this = it;
+  return #this;
+}
+static extension-type-member method E|constructor#_#new#tearOff(asy::Future<core::String> it) → self::E /* erasure=asy::Future<core::String> */
+  return self::E|constructor#(it);
+static method foo(FutureOr<core::String>x) → dynamic {}
+static method bar() → self::E /* erasure=asy::Future<core::String> */
+  return throw 0;
+static method test() → dynamic
+  return self::foo(self::bar());

pkg/front_end/testcases/extension_types/issue55578.dart.weak.modular.expect

@@ -0,0 +1,23 @@
+library;
+import self as self;
+import "dart:async" as asy;
+import "dart:core" as core;
+
+import "dart:async";
+
+extension type E(asy::Future<core::String> it) implements asy::Future<core::String> {
+  abstract extension-type-member representation-field get it() → asy::Future<core::String>;
+  constructor • = self::E|constructor#;
+  constructor tearoff • = self::E|constructor#_#new#tearOff;
+}
+static extension-type-member method E|constructor#(asy::Future<core::String> it) → self::E /* erasure=asy::Future<core::String> */ {
+  lowered final self::E /* erasure=asy::Future<core::String> */ #this = it;
+  return #this;
+}
+static extension-type-member method E|constructor#_#new#tearOff(asy::Future<core::String> it) → self::E /* erasure=asy::Future<core::String> */
+  return self::E|constructor#(it);
+static method foo(FutureOr<core::String>x) → dynamic {}
+static method bar() → self::E /* erasure=asy::Future<core::String> */
+  return throw 0;
+static method test() → dynamic
+  return self::foo(self::bar());

pkg/front_end/testcases/extension_types/issue55578.dart.weak.outline.expect

@@ -0,0 +1,22 @@
+library;
+import self as self;
+import "dart:async" as asy;
+import "dart:core" as core;
+
+import "dart:async";
+
+extension type E(asy::Future<core::String> it) implements asy::Future<core::String> {
+  abstract extension-type-member representation-field get it() → asy::Future<core::String>;
+  constructor • = self::E|constructor#;
+  constructor tearoff • = self::E|constructor#_#new#tearOff;
+}
+static extension-type-member method E|constructor#(asy::Future<core::String> it) → self::E /* erasure=asy::Future<core::String> */
+  ;
+static extension-type-member method E|constructor#_#new#tearOff(asy::Future<core::String> it) → self::E /* erasure=asy::Future<core::String> */
+  return self::E|constructor#(it);
+static method foo(FutureOr<core::String>x) → dynamic
+  ;
+static method bar() → self::E /* erasure=asy::Future<core::String> */
+  ;
+static method test() → dynamic
+  ;

pkg/front_end/testcases/extension_types/issue55578.dart.weak.transformed.expect

@@ -0,0 +1,23 @@
+library;
+import self as self;
+import "dart:async" as asy;
+import "dart:core" as core;
+
+import "dart:async";
+
+extension type E(asy::Future<core::String> it) implements asy::Future<core::String> {
+  abstract extension-type-member representation-field get it() → asy::Future<core::String>;
+  constructor • = self::E|constructor#;
+  constructor tearoff • = self::E|constructor#_#new#tearOff;
+}
+static extension-type-member method E|constructor#(asy::Future<core::String> it) → self::E /* erasure=asy::Future<core::String> */ {
+  lowered final self::E /* erasure=asy::Future<core::String> */ #this = it;
+  return #this;
+}
+static extension-type-member method E|constructor#_#new#tearOff(asy::Future<core::String> it) → self::E /* erasure=asy::Future<core::String> */
+  return self::E|constructor#(it);
+static method foo(FutureOr<core::String>x) → dynamic {}
+static method bar() → self::E /* erasure=asy::Future<core::String> */
+  return throw 0;
+static method test() → dynamic
+  return self::foo(self::bar());

pkg/kernel/lib/src/types.dart

@@ -1283,9 +1283,16 @@ class IsFutureOrSubtypeOf extends TypeRelation<FutureOrType> {
   @override
   IsSubtypeOf isExtensionTypeRelated(
       ExtensionType s, FutureOrType t, Types types) {
-    // Rule 11.
-    return types.performNullabilityAwareSubtypeCheck(
-        s, t.typeArgument.withDeclaredNullability(t.nullability));
+    return types
+        // Rule 11.
+        .performNullabilityAwareSubtypeCheck(
+            s, t.typeArgument.withDeclaredNullability(t.nullability))
+        // Rule 10.
+        .orSubtypeCheckFor(
+            s,
+            new InterfaceType(types.hierarchy.coreTypes.futureClass,
+                t.nullability, [t.typeArgument]),
+            types);
   }
 }