Fixes #2139. Add generator functions element type tests

Language/Functions/element_type_A01_t01.dart

@@ -0,0 +1,57 @@
+// Copyright (c) 2023, 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.
+
+/// @assertion We define the union-free type derived from a type T as follows:
+/// If T is of the form S? or the form FutureOr<S> then the union-free type
+/// derived from T is the union-free type derived from S. Otherwise, the
+/// union-free type derived from T is T
+///
+/// We define the element type of a generator function `f` as follows:
+/// Let S be the union-free type derived from the declared return type of f. If
+/// f is a synchronous generator and S implements Iterable<U> for some U then
+/// the element type of f is U.
+///
+/// @description Check that if the declared return type of a synchronous
+/// generator function `f` is `T`, and `S` is the union-free type derived from
+/// `T`, and `S` is of the form `Iterable<U>`, it is a compile-time error to
+/// yield an expression whose static type isn't assignable to `U`.
+/// @author [email protected]
+
+import "dart:async";
+
+Iterable<num?>? f1() sync* {
+  yield 1;
+  yield 3.14;
+  yield null; // Ok, element type is `num?`
+}
+
+Iterable<num>? f2() sync* {
+  yield 1;
+  yield null;
+//      ^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+}
+
+FutureOr<Iterable<num>?> f3() sync* {
+  yield 1;
+  yield null;
+//      ^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+  yield Future<Null>.value(null);
+//      ^^^^^^^^^^^^^^^^^^^^^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+  yield Future<num>.value(1);
+//      ^^^^^^^^^^^^^^^^^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+}
+
+main() {
+  f1();
+  f2();
+  f3();
+}

Language/Functions/element_type_A01_t02.dart

@@ -0,0 +1,50 @@
+// Copyright (c) 2023, 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.
+
+/// @assertion We define the union-free type derived from a type T as follows:
+/// If T is of the form S? or the form FutureOr<S> then the union-free type
+/// derived from T is the union-free type derived from S. Otherwise, the
+/// union-free type derived from T is T
+///
+/// We define the element type of a generator function `f` as follows:
+/// Let S be the union-free type derived from the declared return type of f. If
+/// f is a synchronous generator and S implements Iterable<U> for some U then
+/// the element type of f is U.
+///
+/// @description Check that if the declared return type of a synchronous
+/// generator function `f` is `T`, and `S` is the union-free type derived from
+/// `T`, and `S` is of the form `Iterable<U>`, it is a compile-time error to
+/// yield an expression whose static type isn't assignable to `U`.
+/// @author [email protected]
+
+import "dart:async";
+
+Iterable<int>? f1() sync* {
+  yield 1;
+  yield 3.14;
+//      ^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+  yield "2";
+//      ^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+}
+
+FutureOr<Iterable<int>?> f2() sync* {
+  yield 1;
+  yield 3.14;
+//      ^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+  yield "2";
+//      ^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+}
+
+main() {
+  f1();
+  f2();
+}

Language/Functions/element_type_A01_t03.dart

@@ -0,0 +1,32 @@
+// Copyright (c) 2023, 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.
+
+/// @assertion We define the union-free type derived from a type T as follows:
+/// If T is of the form S? or the form FutureOr<S> then the union-free type
+/// derived from T is the union-free type derived from S. Otherwise, the
+/// union-free type derived from T is T
+///
+/// We define the element type of a generator function `f` as follows:
+/// Let S be the union-free type derived from the declared return type of f. If
+/// f is a synchronous generator and S implements Iterable<U> for some U then
+/// the element type of f is U.
+///
+/// @description Check a run-time type of a return value of a synchronous
+/// generator function
+/// @author [email protected]
+
+import "dart:async";
+import "../../Utils/expect.dart";
+
+FutureOr<Iterable<int>?> foo() sync* {
+  yield 1;
+  yield 2;
+  yield 3;
+}
+
+main() {
+  FutureOr<Iterable<int>?> o = foo() as dynamic;
+  o as FutureOr<Iterable<int>>;
+  Expect.isRuntimeTypeImplementsIterable<int>(o);
+}

Language/Functions/element_type_A01_t04.dart

@@ -0,0 +1,34 @@
+// Copyright (c) 2023, 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.
+
+/// @assertion We define the union-free type derived from a type T as follows:
+/// If T is of the form S? or the form FutureOr<S> then the union-free type
+/// derived from T is the union-free type derived from S. Otherwise, the
+/// union-free type derived from T is T
+///
+/// We define the element type of a generator function `f` as follows:
+/// Let S be the union-free type derived from the declared return type of f. If
+/// f is a synchronous generator and S implements Iterable<U> for some U then
+/// the element type of f is U.
+///
+/// @description Let `f` be a synchronous generator function whose declared
+/// return type derives the union-free type `S`, and assume that `S` implements
+/// `Iterable<U>`. Then check that the element type of `f` is `U`.
+/// @author [email protected]
+
+import "dart:async";
+import "../../Utils/expect.dart";
+import "../../Utils/static_type_helper.dart";
+
+FutureOr<Iterable<int>?> foo() sync* {
+  yield 1;
+  yield 2;
+  yield 3;
+}
+
+main() {
+  var o = foo();
+  o.expectStaticType<Exactly<FutureOr<Iterable<int>?>>>();
+  Expect.isRuntimeTypeImplementsIterable<int>(o);
+}

Language/Functions/element_type_A01_t05.dart

@@ -0,0 +1,37 @@
+// Copyright (c) 2023, 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.
+
+/// @assertion We define the union-free type derived from a type T as follows:
+/// If T is of the form S? or the form FutureOr<S> then the union-free type
+/// derived from T is the union-free type derived from S. Otherwise, the
+/// union-free type derived from T is T
+///
+/// We define the element type of a generator function `f` as follows:
+/// Let S be the union-free type derived from the declared return type of f. If
+/// f is a synchronous generator and S implements Iterable<U> for some U then
+/// the element type of f is U.
+///
+/// @description Let `f` be a synchronous generator function whose declared
+/// return type derives the union-free type `S`, and assume that `S` implements
+/// `Iterable<U>`. Then check that the element type of `f` is `U`.
+/// @author [email protected]
+
+import "../../Utils/expect.dart";
+
+Iterable<int?>? f1() sync* {
+  yield 1;
+  yield 2;
+  yield null;
+}
+
+Iterable<int>? f2() sync* {
+  yield 1;
+  yield 2;
+  yield 3;
+}
+
+main() {
+  Expect.isRuntimeTypeImplementsIterable<int?>(f1());
+  Expect.isRuntimeTypeImplementsIterable<int>(f2());
+}

Language/Functions/element_type_A01_t06.dart

@@ -0,0 +1,38 @@
+// Copyright (c) 2023, 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.
+
+/// @assertion We define the union-free type derived from a type T as follows:
+/// If T is of the form S? or the form FutureOr<S> then the union-free type
+/// derived from T is the union-free type derived from S. Otherwise, the
+/// union-free type derived from T is T
+///
+/// We define the element type of a generator function `f` as follows:
+/// Let S be the union-free type derived from the declared return type of f. If
+/// f is a synchronous generator and S implements Iterable<U> for some U then
+/// the element type of f is U.
+///
+/// @description Let `f` be a synchronous generator function whose declared
+/// return type derives the union-free type `S`, and assume that `S` implements
+/// `Iterable<U>`. Then check that the element type of `f` is `U`.
+/// @author [email protected]
+
+import "dart:async";
+import "../../Utils/expect.dart";
+
+FutureOr<Iterable<int?>?> f1() sync* {
+  yield 1;
+  yield 2;
+  yield null;
+}
+
+FutureOr<Iterable<int>?>? f2() sync* {
+  yield 1;
+  yield 2;
+  yield 3;
+}
+
+main() {
+  Expect.isRuntimeTypeImplementsIterable<int?>(f1());
+  Expect.isRuntimeTypeImplementsIterable<int>(f2());
+}

Language/Functions/element_type_A02_t01.dart

@@ -0,0 +1,58 @@
+// Copyright (c) 2023, 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.
+
+/// @assertion We define the union-free type derived from a type T as follows:
+/// If T is of the form S? or the form FutureOr<S> then the union-free type
+/// derived from T is the union-free type derived from S. Otherwise, the
+/// union-free type derived from T is T
+///
+/// We define the element type of a generator function `f` as follows:
+/// Let S be the union-free type derived from the declared return type of f.
+/// ...
+/// If `f` is an asynchronous generator and `S` implements `Stream<U>` for some
+/// `U` then the element type of `f` is `U`.
+///
+/// @description Check that if the declared return type of an asynchronous
+/// generator function `f` is `T`, and `S` is the union-free type derived from
+/// `T`, and `S` is of the form `Stream<U>`, it is a compile-time error to
+/// yield an expression whose static type isn't assignable to `U`.
+/// @author [email protected]
+
+import "dart:async";
+
+Stream<num?>? f1() async* {
+  yield 1;
+  yield 3.14;
+  yield null; // Ok, element type is `num?`
+}
+
+Stream<num>? f2() async* {
+  yield 1;
+  yield null;
+//      ^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+}
+
+FutureOr<Stream<num>?> f3() async* {
+  yield 1;
+  yield null;
+//      ^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+  yield Future<Null>.value(null);
+//      ^^^^^^^^^^^^^^^^^^^^^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+  yield Future<num>.value(1);
+//      ^^^^^^^^^^^^^^^^^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+}
+
+main() {
+  f1();
+  f2();
+  f3();
+}

Language/Functions/element_type_A02_t02.dart

@@ -0,0 +1,51 @@
+// Copyright (c) 2023, 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.
+
+/// @assertion We define the union-free type derived from a type T as follows:
+/// If T is of the form S? or the form FutureOr<S> then the union-free type
+/// derived from T is the union-free type derived from S. Otherwise, the
+/// union-free type derived from T is T
+///
+/// We define the element type of a generator function `f` as follows:
+/// Let S be the union-free type derived from the declared return type of f.
+/// ...
+/// If `f` is an asynchronous generator and `S` implements `Stream<U>` for some
+/// `U` then the element type of `f` is `U`.
+///
+/// @description Check that if the declared return type of an asynchronous
+/// generator function `f` is `T`, and `S` is the union-free type derived from
+/// `T`, and `S` is of the form `Stream<U>`, it is a compile-time error to
+/// yield an expression whose static type isn't assignable to `U`.
+/// @author [email protected]
+
+import "dart:async";
+
+Stream<int>? f1() async* {
+  yield 1;
+  yield 3.14;
+//      ^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+  yield "2";
+//      ^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+}
+
+FutureOr<Stream<int>?> f2() async* {
+  yield 1;
+  yield 3.14;
+//      ^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+  yield "2";
+//      ^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+}
+
+main() {
+  f1();
+  f2();
+}