Issue #996: tests for Generic functions as type arguments and bounds added.

Author: iarkh

LanguageFeatures/Generic-functions-as-type-args/FutureOr_t01.dart

@@ -0,0 +1,52 @@
+/*
+ * Copyright (c) 2021, 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 Allow generic function types as type arguments and bounds
+ *
+ * The language disallows generic function types as type arguments and bounds.
+ *
+ *  late List<T Function<T>(T)> idFunctions; // INVALID.
+ *  var callback = [foo<T>(T value) => value]; // Inferred as above, then invalid.
+ *  late S Function<S extends T Function<T>(T)>(S) f; // INVALID.
+ *
+ * We remove that restriction, so a type argument and a bound can be a generic
+ * function type.
+ *
+ * This requires no new syntax, and in some cases only the removal of a single
+ * check. There might be some platforms where the implementation currently
+ * assumes that generic function types cannot occur as the value of type
+ * variables (an proof-of-concept attempt hit an assert in the VM). Such
+ * assumptions will need to be flushed out with tests and fixed.
+ *
+ * Because we already infer List<T Function<T>(T)> in the code above, this
+ * change will not affect type inference, it will just make the inferred type
+ * not be an error afterwards.
+ *
+ * We do not expect the removal of this restriction to affect the feasibility of
+ * type inference. After all, it's already possible to have a generic function
+ * type occurring covariantly in a type argument, like List<T Function<T>(T)
+ * Function()>.
+ * @description Checks that generic invariant function can be a type argument
+ * and bound of FutureOr.
+ * @author [email protected]
+ */
+//--enable-experiment=generic-metadata
+
+import "dart:async";
+import "../../Utils/expect.dart";
+
+T test1<T>(T i) => i;
+void test2<T>() {}
+T test3<T>() => 0 as T;
+void test4<T>(T i) {}
+
+main() {
+  FutureOr<T Function<T>(T)> f = test1;
+  Expect.throws(() { f = 1 as dynamic; });
+  Expect.throws(() { f = test2 as dynamic; });
+  Expect.throws(() { f = test3 as dynamic; });
+  Expect.throws(() { f = test4 as dynamic; });
+}

LanguageFeatures/Generic-functions-as-type-args/FutureOr_t02.dart

@@ -0,0 +1,53 @@
+/*
+ * Copyright (c) 2021, 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 Allow generic function types as type arguments and bounds
+ *
+ * The language disallows generic function types as type arguments and bounds.
+ *
+ *  late List<T Function<T>(T)> idFunctions; // INVALID.
+ *  var callback = [foo<T>(T value) => value]; // Inferred as above, then invalid.
+ *  late S Function<S extends T Function<T>(T)>(S) f; // INVALID.
+ *
+ * We remove that restriction, so a type argument and a bound can be a generic
+ * function type.
+ *
+ * This requires no new syntax, and in some cases only the removal of a single
+ * check. There might be some platforms where the implementation currently
+ * assumes that generic function types cannot occur as the value of type
+ * variables (an proof-of-concept attempt hit an assert in the VM). Such
+ * assumptions will need to be flushed out with tests and fixed.
+ *
+ * Because we already infer List<T Function<T>(T)> in the code above, this
+ * change will not affect type inference, it will just make the inferred type
+ * not be an error afterwards.
+ *
+ * We do not expect the removal of this restriction to affect the feasibility of
+ * type inference. After all, it's already possible to have a generic function
+ * type occurring covariantly in a type argument, like List<T Function<T>(T)
+ * Function()>.
+ * @description Checks that generic covariant function can be a type argument
+ * and bound of FutureOr.
+ * @author [email protected]
+ */
+//--enable-experiment=generic-metadata
+
+import "dart:async";
+import "../../Utils/expect.dart";
+
+T test1<T>(T i) => i;
+void test2<T>() {}
+T test3<T>() => 0 as T;
+void test4<T>(T i) {}
+
+main() {
+  FutureOr<void Function<T>()> f = test2;
+  f = test3;
+
+  Expect.throws(() { f = 1 as dynamic; });
+  Expect.throws(() { f = test1 as dynamic; });
+  Expect.throws(() { f = test4 as dynamic; });
+}

LanguageFeatures/Generic-functions-as-type-args/FutureOr_t03.dart

@@ -0,0 +1,52 @@
+/*
+ * Copyright (c) 2021, 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 Allow generic function types as type arguments and bounds
+ *
+ * The language disallows generic function types as type arguments and bounds.
+ *
+ *  late List<T Function<T>(T)> idFunctions; // INVALID.
+ *  var callback = [foo<T>(T value) => value]; // Inferred as above, then invalid.
+ *  late S Function<S extends T Function<T>(T)>(S) f; // INVALID.
+ *
+ * We remove that restriction, so a type argument and a bound can be a generic
+ * function type.
+ *
+ * This requires no new syntax, and in some cases only the removal of a single
+ * check. There might be some platforms where the implementation currently
+ * assumes that generic function types cannot occur as the value of type
+ * variables (an proof-of-concept attempt hit an assert in the VM). Such
+ * assumptions will need to be flushed out with tests and fixed.
+ *
+ * Because we already infer List<T Function<T>(T)> in the code above, this
+ * change will not affect type inference, it will just make the inferred type
+ * not be an error afterwards.
+ *
+ * We do not expect the removal of this restriction to affect the feasibility of
+ * type inference. After all, it's already possible to have a generic function
+ * type occurring covariantly in a type argument, like List<T Function<T>(T)
+ * Function()>.
+ * @description Checks that generic covariant function can be a type argument
+ * and bound of FutureOr.
+ * @author [email protected]
+ */
+//--enable-experiment=generic-metadata
+
+import "dart:async";
+import "../../Utils/expect.dart";
+
+T test1<T>(T i) => i;
+void test2<T>() {}
+T test3<T>() => 0 as T;
+void test4<T>(T i) {}
+
+main() {
+  FutureOr<T Function<T>()> f = test3;
+  Expect.throws(() { f = 1 as dynamic; });
+  Expect.throws(() { f = test1 as dynamic; });
+  Expect.throws(() { f = test2 as dynamic; });
+  Expect.throws(() { f = test4 as dynamic; });
+}

LanguageFeatures/Generic-functions-as-type-args/FutureOr_t04.dart

@@ -0,0 +1,52 @@
+/*
+ * Copyright (c) 2021, 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 Allow generic function types as type arguments and bounds
+ *
+ * The language disallows generic function types as type arguments and bounds.
+ *
+ *  late List<T Function<T>(T)> idFunctions; // INVALID.
+ *  var callback = [foo<T>(T value) => value]; // Inferred as above, then invalid.
+ *  late S Function<S extends T Function<T>(T)>(S) f; // INVALID.
+ *
+ * We remove that restriction, so a type argument and a bound can be a generic
+ * function type.
+ *
+ * This requires no new syntax, and in some cases only the removal of a single
+ * check. There might be some platforms where the implementation currently
+ * assumes that generic function types cannot occur as the value of type
+ * variables (an proof-of-concept attempt hit an assert in the VM). Such
+ * assumptions will need to be flushed out with tests and fixed.
+ *
+ * Because we already infer List<T Function<T>(T)> in the code above, this
+ * change will not affect type inference, it will just make the inferred type
+ * not be an error afterwards.
+ *
+ * We do not expect the removal of this restriction to affect the feasibility of
+ * type inference. After all, it's already possible to have a generic function
+ * type occurring covariantly in a type argument, like List<T Function<T>(T)
+ * Function()>.
+ * @description Checks that generic invariant function can be a type argument
+ * and bound of FutureOr.
+ * @author [email protected]
+ */
+//--enable-experiment=generic-metadata
+
+import "dart:async";
+import "../../Utils/expect.dart";
+
+T test1<T>(T i) => i;
+void test2<T>() {}
+T test3<T>() => 0 as T;
+void test4<T>(T i) {}
+
+main() {
+  FutureOr<void Function<T>(T)> f = test4;
+  f = test1;
+  Expect.throws(() { f = 1 as dynamic; });
+  Expect.throws(() { f = test2 as dynamic; });
+  Expect.throws(() { f = test3 as dynamic; });
+}

LanguageFeatures/Generic-functions-as-type-args/FutureOr_t05.dart

@@ -0,0 +1,67 @@
+/*
+ * Copyright (c) 2021, 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 Allow generic function types as type arguments and bounds
+ *
+ * The language disallows generic function types as type arguments and bounds.
+ *
+ *  late List<T Function<T>(T)> idFunctions; // INVALID.
+ *  var callback = [foo<T>(T value) => value]; // Inferred as above, then invalid.
+ *  late S Function<S extends T Function<T>(T)>(S) f; // INVALID.
+ *
+ * We remove that restriction, so a type argument and a bound can be a generic
+ * function type.
+ *
+ * This requires no new syntax, and in some cases only the removal of a single
+ * check. There might be some platforms where the implementation currently
+ * assumes that generic function types cannot occur as the value of type
+ * variables (an proof-of-concept attempt hit an assert in the VM). Such
+ * assumptions will need to be flushed out with tests and fixed.
+ *
+ * Because we already infer List<T Function<T>(T)> in the code above, this
+ * change will not affect type inference, it will just make the inferred type
+ * not be an error afterwards.
+ *
+ * We do not expect the removal of this restriction to affect the feasibility of
+ * type inference. After all, it's already possible to have a generic function
+ * type occurring covariantly in a type argument, like List<T Function<T>(T)
+ * Function()>.
+ * @description Checks statically that generic invariant function can be a type
+ * argument and bound of FutureOr.
+ * @author [email protected]
+ */
+//--enable-experiment=generic-metadata
+
+import "dart:async";
+
+T test1<T>(T i) => i;
+void test2<T>() {}
+T test3<T>() => 0 as T;
+void test4<T>(T i) {}
+
+main() {
+  FutureOr<T Function<T>(T)> f1 = test1;
+
+  FutureOr<T Function<T>(T)> f2 = 1;
+//                                ^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  FutureOr<T Function<T>(T)> f3 = test2;
+//                                ^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  FutureOr<T Function<T>(T)> f4 = test3;
+//                                ^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  FutureOr<T Function<T>(T)> f5 = test4;
+//                                ^
+// [analyzer] unspecified
+// [cfe] unspecified
+}

LanguageFeatures/Generic-functions-as-type-args/FutureOr_t06.dart

@@ -0,0 +1,63 @@
+/*
+ * Copyright (c) 2021, 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 Allow generic function types as type arguments and bounds
+ *
+ * The language disallows generic function types as type arguments and bounds.
+ *
+ *  late List<T Function<T>(T)> idFunctions; // INVALID.
+ *  var callback = [foo<T>(T value) => value]; // Inferred as above, then invalid.
+ *  late S Function<S extends T Function<T>(T)>(S) f; // INVALID.
+ *
+ * We remove that restriction, so a type argument and a bound can be a generic
+ * function type.
+ *
+ * This requires no new syntax, and in some cases only the removal of a single
+ * check. There might be some platforms where the implementation currently
+ * assumes that generic function types cannot occur as the value of type
+ * variables (an proof-of-concept attempt hit an assert in the VM). Such
+ * assumptions will need to be flushed out with tests and fixed.
+ *
+ * Because we already infer List<T Function<T>(T)> in the code above, this
+ * change will not affect type inference, it will just make the inferred type
+ * not be an error afterwards.
+ *
+ * We do not expect the removal of this restriction to affect the feasibility of
+ * type inference. After all, it's already possible to have a generic function
+ * type occurring covariantly in a type argument, like List<T Function<T>(T)
+ * Function()>.
+ * @description Checks statically that generic covariant function can be a type
+ * argument and bound of FutureOr.
+ * @author [email protected]
+ */
+//--enable-experiment=generic-metadata
+
+import "dart:async";
+
+T test1<T>(T i) => i;
+void test2<T>() {}
+T test3<T>() => 0 as T;
+void test4<T>(T i) {}
+
+main() {
+  FutureOr<void Function<T>()> f1 = test2;
+  FutureOr<void Function<T>()> f2 = test3;
+
+  FutureOr<void Function<T>()> f3 = 1;
+//                                  ^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  FutureOr<void Function<T>()> f4 = test1;
+//                                  ^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  FutureOr<void Function<T>()> f5 = test4;
+//                                  ^
+// [analyzer] unspecified
+// [cfe] unspecified
+}