Migrate language_2/variance to NNBD.

Change-Id: I8e21f82dc241a63f78fb1f6a25669b1aa633788c
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/152080
Commit-Queue: Bob Nystrom <rnystrom@google.com>
Auto-Submit: Bob Nystrom <rnystrom@google.com>
Reviewed-by: Leaf Petersen <leafp@google.com>

tests/language/variance/syntax/variance_disabled_keyword_identifier_syntax_test.dart

@@ -0,0 +1,48 @@
+// Copyright (c) 2019, 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.
+
+// Tests identifier usage of keywords `out` and `inout`, correct usage of `in`.
+
+import "package:expect/expect.dart";
+
+class A<out> {}
+
+class B<inout> {}
+
+class C<out, inout> {}
+
+F<inout, out>() {}
+
+mixin G<out, inout> {}
+
+typedef H<inout, out> = out Function(inout);
+
+class OutParameter {
+  var out = 3;
+  int func(int out) {
+    return out;
+  }
+}
+
+class inout {
+  void out(int x) {}
+}
+
+var out = 5;
+
+main() {
+  OutParameter x = new OutParameter();
+  Expect.equals(2, x.func(2));
+  Expect.equals(3, x.out);
+
+  inout foo = inout();
+  foo.out(4);
+
+  Expect.equals(5, out);
+
+  var collection = [0, 1, 2];
+  for (var x in collection) {
+    Expect.isTrue(x is int);
+  }
+}

tests/language/variance/syntax/variance_disabled_syntax_test.dart

@@ -0,0 +1,76 @@
+// Copyright (c) 2019, 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.
+
+// Tests with `variance` flag disabled
+// Correct variance modifier usage will issue an error.
+
+import 'package:expect/expect.dart';
+
+abstract class A<in X> {
+//               ^^
+// [analyzer] SYNTACTIC_ERROR.EXPERIMENT_NOT_ENABLED
+// [cfe] This requires the 'variance' language feature to be enabled.
+  int foo(X bar);
+}
+
+class B<out X, in Y, inout Z> {}
+//      ^^^
+// [analyzer] SYNTACTIC_ERROR.EXPERIMENT_NOT_ENABLED
+// [cfe] This requires the 'variance' language feature to be enabled.
+//             ^^
+// [analyzer] SYNTACTIC_ERROR.EXPERIMENT_NOT_ENABLED
+// [cfe] This requires the 'variance' language feature to be enabled.
+//                   ^^^^^
+// [analyzer] SYNTACTIC_ERROR.EXPERIMENT_NOT_ENABLED
+// [cfe] This requires the 'variance' language feature to be enabled.
+
+class C<in T> extends A<T> {
+//      ^^
+// [analyzer] SYNTACTIC_ERROR.EXPERIMENT_NOT_ENABLED
+// [cfe] This requires the 'variance' language feature to be enabled.
+  @override
+  int foo(T bar) {
+    return 2;
+  }
+}
+
+mixin D<out T> {}
+//      ^^^
+// [analyzer] SYNTACTIC_ERROR.EXPERIMENT_NOT_ENABLED
+// [cfe] This requires the 'variance' language feature to be enabled.
+
+class E1 {}
+
+mixin E<in T extends E1> {}
+//      ^^
+// [analyzer] SYNTACTIC_ERROR.EXPERIMENT_NOT_ENABLED
+// [cfe] This requires the 'variance' language feature to be enabled.
+
+class F<out T> = Object with D<T>;
+//      ^^^
+// [analyzer] SYNTACTIC_ERROR.EXPERIMENT_NOT_ENABLED
+// [cfe] This requires the 'variance' language feature to be enabled.
+
+class G<out out> {}
+//      ^^^
+// [analyzer] SYNTACTIC_ERROR.EXPERIMENT_NOT_ENABLED
+// [cfe] This requires the 'variance' language feature to be enabled.
+
+class H<out inout> {}
+//      ^^^
+// [analyzer] SYNTACTIC_ERROR.EXPERIMENT_NOT_ENABLED
+// [cfe] This requires the 'variance' language feature to be enabled.
+
+main() {
+  B<int, String, bool> b = B();
+
+  C<int> c = C();
+  Expect.equals(2, c.foo(3));
+
+  F<int> f = F();
+
+  G<int> g = G();
+
+  H<int> h = H();
+}

tests/language/variance/syntax/variance_keyword_identifier_syntax_test.dart

@@ -0,0 +1,51 @@
+// Copyright (c) 2019, 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.
+
+// Tests identifier usage of keywords `out` and `inout`, correct usage of `in`
+// with the experimental flag `variance` enabled.
+
+// SharedOptions=--enable-experiment=variance
+
+import "package:expect/expect.dart";
+
+class A<out> {}
+
+class B<inout> {}
+
+class C<out, inout> {}
+
+F<inout, out>() {}
+
+mixin G<out, inout> {}
+
+typedef H<inout, out> = out Function(inout);
+
+class OutParameter {
+  var out = 3;
+  int func(int out) {
+    return out;
+  }
+}
+
+class inout {
+  void out(int x) {}
+}
+
+var out = 5;
+
+main() {
+  OutParameter x = new OutParameter();
+  Expect.equals(2, x.func(2));
+  Expect.equals(3, x.out);
+
+  inout foo = inout();
+  foo.out(4);
+
+  Expect.equals(5, out);
+
+  var collection = [0, 1, 2];
+  for (var x in collection) {
+    Expect.isTrue(x is int);
+  }
+}

tests/language/variance/syntax/variance_syntax_test.dart

@@ -0,0 +1,45 @@
+// Copyright (c) 2019, 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.
+
+// SharedOptions=--enable-experiment=variance
+
+import 'package:expect/expect.dart';
+
+abstract class A<in X> {
+  int foo(X bar);
+}
+
+class B<out X, in Y, inout Z> {}
+
+class C<in T> extends A<T> {
+  @override
+  int foo(T bar) {
+    return 2;
+  }
+}
+
+mixin D<out T> {}
+
+class E1 {}
+
+mixin E<in T extends E1> {}
+
+class F<out T> = Object with D<T>;
+
+class G<out out> {}
+
+class H<out inout> {}
+
+main() {
+  B<int, String, bool> b = B();
+
+  C<int> c = C();
+  Expect.equals(2, c.foo(3));
+
+  F<int> f = F();
+
+  G<int> g = G();
+
+  H<int> h = H();
+}

tests/language/variance/syntax/variance_type_parameter_error_syntax_test.dart

@@ -0,0 +1,68 @@
+// Copyright (c) 2019, 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.
+
+// Tests erroneous usages of variance in unapplicable type parameters.
+
+// SharedOptions=--enable-experiment=variance
+
+void A(out int foo) {
+//     ^^^
+// [analyzer] COMPILE_TIME_ERROR.UNDEFINED_CLASS
+// [cfe] 'out' isn't a type.
+//     ^
+// [cfe] Type 'out' not found.
+//             ^^^
+// [analyzer] SYNTACTIC_ERROR.EXPECTED_TOKEN
+// [cfe] Expected ')' before this.
+  List<out String> bar;
+  //  ^
+  // [analyzer] STATIC_TYPE_WARNING.UNDEFINED_OPERATOR
+  // [cfe] The operator '<' isn't defined for the class 'Type'.
+  //   ^^^
+  // [analyzer] STATIC_WARNING.UNDEFINED_IDENTIFIER
+  // [cfe] Expected ';' after this.
+  //   ^^^
+  // [analyzer] SYNTACTIC_ERROR.EXPECTED_TOKEN
+  // [cfe] Getter not found: 'out'.
+  //             ^
+  // [analyzer] STATIC_TYPE_WARNING.UNDEFINED_OPERATOR
+  // [cfe] The operator '>' isn't defined for the class 'Type'.
+  //               ^^^
+  // [analyzer] STATIC_WARNING.UNDEFINED_IDENTIFIER
+  // [cfe] Getter not found: 'bar'.
+}
+
+void B(out foo) {}
+//     ^^^
+// [analyzer] COMPILE_TIME_ERROR.UNDEFINED_CLASS
+// [cfe] 'out' isn't a type.
+//     ^
+// [cfe] Type 'out' not found.
+
+class C<in out X, out out Y> {}
+//         ^^^
+// [analyzer] SYNTACTIC_ERROR.MULTIPLE_VARIANCE_MODIFIERS
+// [cfe] Each type parameter can have at most one variance modifier.
+//                    ^^^
+// [analyzer] SYNTACTIC_ERROR.MULTIPLE_VARIANCE_MODIFIERS
+// [cfe] Each type parameter can have at most one variance modifier.
+
+class D<in out inout in out X> {}
+//         ^^^
+// [analyzer] SYNTACTIC_ERROR.MULTIPLE_VARIANCE_MODIFIERS
+// [cfe] Each type parameter can have at most one variance modifier.
+//             ^^^^^
+// [analyzer] SYNTACTIC_ERROR.MULTIPLE_VARIANCE_MODIFIERS
+// [cfe] Each type parameter can have at most one variance modifier.
+//                   ^^
+// [analyzer] SYNTACTIC_ERROR.MULTIPLE_VARIANCE_MODIFIERS
+// [cfe] Each type parameter can have at most one variance modifier.
+//                      ^^^
+// [analyzer] SYNTACTIC_ERROR.MULTIPLE_VARIANCE_MODIFIERS
+// [cfe] Each type parameter can have at most one variance modifier.
+
+typedef E<out T> = T Function(T a);
+//            ^
+// [analyzer] SYNTACTIC_ERROR.EXPECTED_TOKEN
+// [cfe] Expected ',' before this.

tests/language/variance/variance_downwards_inference_test.dart

@@ -0,0 +1,53 @@
+// Copyright (c) 2019, 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.
+
+// Tests downwards inference for explicit variance modifiers.
+
+// SharedOptions=--enable-experiment=variance
+
+class A<out T> {
+  final T _x;
+  A(T x):_x = x;
+  T get x => _x;
+  void set x(Object value) {}
+}
+
+class B<in T> {
+  B(List<T> x);
+  void set x(T val) {}
+}
+
+class C<out T, S> {
+  final T _x;
+  C(T x, S y):_x = x;
+  T get x => _x;
+  void set x(Object value) {}
+  void set y(S _value) {}
+}
+
+class D<in T> {
+  D(T x, void Function(T) y) {}
+  void set x(T val) {}
+}
+
+main() {
+  // int <: T <: Object
+  // Choose int
+  A<Object> a = new A(3)..x+=1;
+
+  // int <: T
+  // num <: T
+  // Choose num
+  B<int> b = new B(<num>[])..x=2.2;
+
+  // int <: T <: Object
+  // Choose int
+  // int <: S <: Object
+  // Choose Object
+  C<Object, Object> c = new C(3, 3)..x+=1..y="hello";
+
+  // int <: T <: num
+  // Choose num due to contravariant heuristic.
+  D<int> d = new D(3, (num x) {})..x=2.2;
+}