Migrate block 116.

tests/language_2/if_null_assignment_static_test.dart

+// Copyright (c) 2015, 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.
+
+// Verify that the static type of a ??= b is the least upper bound of the
+// static types of a and b.
+
+import "package:expect/expect.dart";
+
+bad() {
+  Expect.fail('Should not be executed');
+}
+
+/// Actually of type B so that the implicit downcasts below succeed at runtime.
+A theA = new B();
+B theB = new B();
+
+class A {
+  String a;
+}
+
+class B extends A {
+  String b;
+}
+
+class C extends A {
+  String c;
+}
+
+A get a => null;
+
+void set a(A value) {}
+
+B get b => null;
+
+void set b(B value) {}
+
+class ClassWithStaticGetters {
+  static A get a => null;
+
+  static void set a(A value) {}
+
+  static B get b => null;
+
+  static void set b(B value) {}
+}
+
+class ClassWithInstanceGetters {
+  A get a => null;
+
+  void set a(A value) {}
+
+  B get b => null;
+
+  void set b(B value) {}
+}
+
+class DerivedClass extends ClassWithInstanceGetters {
+  A get a => bad();
+
+  void set a(A value) {
+    bad();
+  }
+
+  B get b => bad();
+
+  void set b(B value) {
+    bad();
+  }
+
+  void derivedTest() {
+    // The static type of super.v ??= e is the LUB of the static types of
+    // super.v and e.
+    (super.a ??= theA).a; //# 01: ok
+    (super.a ??= theA).b; //# 02: compile-time error
+    (super.a ??= theB).a; //# 03: ok
+    (super.a ??= theB).b; //# 04: compile-time error
+    (super.b ??= theA).a; //# 05: ok
+    (super.b ??= theA).b; //# 06: compile-time error
+
+    // Exactly the same static errors that would be caused by super.v = e
+    // are also generated in the case of super.v ??= e.
+    super.b ??= new C(); //# 07: compile-time error
+  }
+}
+
+main() {
+  new DerivedClass().derivedTest();
+
+  // The static type of v ??= e is the LUB of the static types of v and e.
+  (a ??= theA).a; //# 08: ok
+  (a ??= theA).b; //# 09: compile-time error
+  (a ??= theB).a; //# 10: ok
+  (a ??= theB).b; //# 11: compile-time error
+  (b ??= theA).a; //# 12: ok
+  (b ??= theA).b; //# 13: compile-time error
+
+  // Exactly the same static errors that would be caused by v = e are also
+  // generated in the case of v ??= e.
+  b ??= new C(); //# 14: compile-time error
+
+  // The static type of C.v ??= e is the LUB of the static types of C.v and e.
+  (ClassWithStaticGetters.a ??= theA).a; //# 15: ok
+  (ClassWithStaticGetters.a ??= theA).b; //# 16: compile-time error
+  (ClassWithStaticGetters.a ??= theB).a; //# 17: ok
+  (ClassWithStaticGetters.a ??= theB).b; //# 18: compile-time error
+  (ClassWithStaticGetters.b ??= theA).a; //# 19: ok
+  (ClassWithStaticGetters.b ??= theA).b; //# 20: compile-time error
+
+  // Exactly the same static errors that would be caused by C.v = e are
+  // also generated in the case of C.v ??= e.
+  ClassWithStaticGetters.b ??= new C(); //# 21: compile-time error
+
+  // The static type of e1.v ??= e2 is the LUB of the static types of e1.v and
+  // e2.
+  (new ClassWithInstanceGetters().a ??= theA).a; //# 22: ok
+  (new ClassWithInstanceGetters().a ??= theA).b; //# 23: compile-time error
+  (new ClassWithInstanceGetters().a ??= theB).a; //# 24: ok
+  (new ClassWithInstanceGetters().a ??= theB).b; //# 25: compile-time error
+  (new ClassWithInstanceGetters().b ??= theA).a; //# 26: ok
+  (new ClassWithInstanceGetters().b ??= theA).b; //# 27: compile-time error
+
+  // Exactly the same static errors that would be caused by e1.v = e2 are
+  // also generated in the case of e1.v ??= e2.
+  new ClassWithInstanceGetters().b ??= new C(); //# 28: compile-time error
+
+  // The static type of e1[e2] ??= e3 is the LUB of the static types of e1[e2]
+  // and e3.
+  ((<A>[null])[0] ??= theA).a; //# 29: ok
+  ((<A>[null])[0] ??= theA).b; //# 30: compile-time error
+  ((<A>[null])[0] ??= theB).a; //# 31: ok
+  ((<A>[null])[0] ??= theB).b; //# 32: compile-time error
+  ((<B>[null])[0] ??= theA).a; //# 33: ok
+  ((<B>[null])[0] ??= theA).b; //# 34: compile-time error
+
+  // Exactly the same static errors that would be caused by e1[e2] = e3 are
+  // also generated in the case of e1[e2] ??= e3.
+  (<B>[null])[0] ??= new C(); //# 35: compile-time error
+
+  // The static type of e1?.v op= e2 is the static type of e1.v op e2,
+  // therefore the static type of e1?.v ??= e2 is the static type of
+  // e1.v ?? e2, which is the LUB of the static types of e1?.v and e2.
+  (new ClassWithInstanceGetters()?.a ??= theA).a; //# 36: ok
+  (new ClassWithInstanceGetters()?.a ??= theA).b; //# 37: compile-time error
+  (new ClassWithInstanceGetters()?.a ??= theB).a; //# 38: ok
+  (new ClassWithInstanceGetters()?.a ??= theB).b; //# 39: compile-time error
+  (new ClassWithInstanceGetters()?.b ??= theA).a; //# 40: ok
+  (new ClassWithInstanceGetters()?.b ??= theA).b; //# 41: compile-time error
+
+  // Exactly the same static errors that would be caused by e1.v ??= e2 are
+  // also generated in the case of e1?.v ??= e2.
+  new ClassWithInstanceGetters()?.b ??= new C(); //# 42: compile-time error
+}