#2349. Add more tests for constant constructors of the extension types (

#2352)

Add more tests for constant constructors of the extension types.

Co-authored-by: Erik Ernst <[email protected]>, fixing a couple of typos.

LanguageFeatures/Extension-types/static_analysis_extension_types_A21_t08.dart

@@ -0,0 +1,35 @@
+// 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 An extension type declaration DV named Name may declare one or
+/// more constructors. A constructor which is declared in an extension type
+/// declaration is also known as an extension type constructor.
+///
+/// The <representationDeclaration> works as a constructor. The optional
+/// ('.' <identifierOrNew>) in the grammar is used to declare this constructor
+/// with a name of the form <identifier> '.' <identifier> (at times described as
+/// a "named constructor"), or <identifier> '.' 'new'. It is a constant
+/// constructor if and only if the reserved word const occurs just after
+/// extension type in the header of the declaration. Other constructors may be
+/// declared const or not, following the normal rules for constant constructors.
+///
+/// @description Checks that if an extension type declaration declares a
+/// constant constructor then it can be used in a constant expression
+/// @author [email protected]
+/// @issue 53935
+
+// SharedOptions=--enable-experiment=inline-class
+
+import "../../Utils/expect.dart";
+
+extension type const Num(num id) {
+  const Num.add(Num v1, Num v2) : this((v1 as num) + (v2 as num));
+  const Num.sub(Num v1, Num v2) : this((v1 as num) - (v2 as num));
+  const Num.mul(Num v1, Num v2) : this((v1 as num) * (v2 as num));
+}
+
+void main() {
+  const n = Num.sub(Num.mul(Num(7), Num(7)), Num(7));
+  Expect.equals(42, n.id);
+}

LanguageFeatures/Extension-types/static_analysis_extension_types_A21_t09.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 An extension type declaration DV named Name may declare one or
+/// more constructors. A constructor which is declared in an extension type
+/// declaration is also known as an extension type constructor.
+///
+/// The <representationDeclaration> works as a constructor. The optional
+/// ('.' <identifierOrNew>) in the grammar is used to declare this constructor
+/// with a name of the form <identifier> '.' <identifier> (at times described as
+/// a "named constructor"), or <identifier> '.' 'new'. It is a constant
+/// constructor if and only if the reserved word const occurs just after
+/// extension type in the header of the declaration. Other constructors may be
+/// declared const or not, following the normal rules for constant constructors.
+///
+/// @description Checks that it is a compile-time error if not a constant is
+/// used in an evaluation of a constant expression in an extension type constant
+/// constructor
+/// @author [email protected]
+
+// SharedOptions=--enable-experiment=inline-class
+
+extension type const Num(num id) {
+  const Num.add(Num v1, Num v2) : this(v1.id + (v2 as num));
+//                                     ^^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+  const Num.sub(Num v1, Num v2) : this((v1 as num) - v2.id);
+//                                                   ^^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+}
+
+void main() {
+  print(Num);
+}

LanguageFeatures/Extension-types/static_analysis_extension_types_A21_t10.dart

@@ -0,0 +1,39 @@
+// 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 An extension type declaration DV named Name may declare one or
+/// more constructors. A constructor which is declared in an extension type
+/// declaration is also known as an extension type constructor.
+///
+/// The <representationDeclaration> works as a constructor. The optional
+/// ('.' <identifierOrNew>) in the grammar is used to declare this constructor
+/// with a name of the form <identifier> '.' <identifier> (at times described as
+/// a "named constructor"), or <identifier> '.' 'new'. It is a constant
+/// constructor if and only if the reserved word const occurs just after
+/// extension type in the header of the declaration. Other constructors may be
+/// declared const or not, following the normal rules for constant constructors.
+///
+/// @description Checks that if an extension type declaration declares a
+/// constant constructor then it can be used in a constant expression
+/// @author [email protected]
+/// @issue 53936,53395
+
+// SharedOptions=--enable-experiment=inline-class
+
+import "../../Utils/expect.dart";
+
+extension type const E<T>(Object? id) {
+  const E.cast(Object? v) : this(v as T);
+}
+
+typedef TypeAlias<T> = T;
+extension type const TypeOf<T>(T _) {}
+
+void main() {
+  Expect.equals("a", (const E<String>.cast("a")).id);
+  Expect.equals("b", (const E<TypeAlias<String>>.cast("b")).id);
+  Expect.equals("c", (const E<TypeOf<String>>.cast("c")).id);
+  Expect.equals("d", (const E<String>.cast(TypeOf<String>("d"))).id);
+  Expect.equals("e", (const E<TypeOf<String>>.cast(TypeOf<String>("e"))).id);
+}