sdk/pkg/front_end/testcases/general/top_level_variance_test.dart

// 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.
// @dart=2.9
// Testing that instantiate-to-bound and super-bounded types take the
// variance of formal type parameters into account when a type alias is
// used as a raw type.

// Standard type comparison support.

typedef F<X> = void Function<Y extends X>();
F<X> toF<X>(X x) => null;

// Material specific to this test.

typedef Fcov<X> = X Function();
typedef Fcon<X> = Function(X);
typedef Finv<X> = X Function(X);

typedef FcovBound<X extends num> = X Function();
typedef FconBound<X extends num> = Function(X);
typedef FinvBound<X extends num> = X Function(X);

class A<X> {}

typedef FcovCyclicBound<X extends A<X>> = X Function();
typedef FconCyclicBound<X extends A<X>> = Function(X);
typedef FinvCyclicBound<X extends A<X>> = X Function(X);

typedef FcovCyclicCoBound<X extends Function(X)> = X Function();
typedef FconCyclicCoBound<X extends Function(X)> = Function(X);
typedef FinvCyclicCoBound<X extends Function(X)> = X Function(X);

class B<X> {}

void testTopLevel() {
  // I2b initial value for a covariant type parameter w/o bound: dynamic.
  Fcov source1;
  var fsource1 = toF(source1);
  F<Fcov<dynamic>> target1 = fsource1;

  // I2b initial value for a contravariant type parameter w/o bound: dynamic.
  Fcon source2;
  var fsource2 = toF(source2);
  F<Fcon<dynamic>> target2 = fsource2;

  // I2b initial value for an invariant type parameter w/o bound: dynamic.
  Finv source3;
  var fsource3 = toF(source3);
  F<Finv<dynamic>> target3 = fsource3;

  // I2b initial value for a covariant type parameter: bound.
  FcovBound source4;
  var fsource4 = toF(source4);
  F<FcovBound<num>> target4 = fsource4;

  // I2b initial value for a contravariant type parameter: bound.
  FconBound source5;
  var fsource5 = toF(source5);
  F<FconBound<num>> target5 = fsource5;

  // I2b initial value for an invariant type parameter: bound.
  FinvBound source6;
  var fsource6 = toF(source6);
  F<FinvBound<num>> target6 = fsource6;

  // I2b for a covariant type parameter w F-bound: Use bound, then break
  // cycle by replacing covariant occurrence by `dynamic`. Resulting type
  // is super-bounded: FcovCyclicBound<A<Null>> is regular-bounded.
  FcovCyclicBound source7;
  var fsource7 = toF(source7);
  F<FcovCyclicBound<A<dynamic>>> target7 = fsource7;

  // I2b for a contravariant type parameter w F-bound: Use bound, then break
  // cycle by replacing contravariant occurrence by `Null`. Resulting type
  // is super-bounded: FconCyclicBound<A<Object>> is regular-bounded.
  FconCyclicBound source8;
  var fsource8 = toF(source8);
  F<FconCyclicBound<A<Null>>> target8 = fsource8;

  // I2b for an invariant type parameter w F-bound: Use bound, then break
  // cycle by replacing invariant occurrence by `dynamic`. Resulting type is
  // _not_ super-bounded: FinvCyclicBound<A<dynamic>> not regular-bounded.
  FinvCyclicBound source9; //# 01: compile-time error
  // var fsource9 = toF(source9);
  // F<FinvCyclicBound<A<dynamic>>> target9 = fsource9;

  // I2b for a covariant type parameter w F-bound: Use bound, then break
  // cycle by replacing contravariant occurrence by `Null`. Resulting type
  // is super-bounded: FcovCyclicBound<Function(Object)> is regular-bounded.
  FcovCyclicCoBound source10;
  var fsource10 = toF(source10);
  F<FcovCyclicCoBound<Function(Null)>> target10 = fsource10;

  // I2b for a contravariant type parameter w F-bound: Use bound, then break
  // cycle by replacing covariant occurrence by `dynamic`. Resulting type
  // FconCyclicCoBound<Function(dynamic)> is regular-bounded.
  FconCyclicCoBound source11;
  var fsource11 = toF(source11);
  F<FconCyclicCoBound<Function(dynamic)>> target11 = fsource11;

  // I2b for an invariant type parameter w F-bound: Use bound, then break
  // cycle by replacing invariant occurrence by `dynamic`. Resulting type
  // F<FinvCyclicCoBound<Function(dynamic)>> is regular-bounded.
  FinvCyclicCoBound source12;
  var fsource12 = toF(source12);
  F<FinvCyclicCoBound<Function(dynamic)>> target12 = fsource12;
}

void testNested() {
  // Everything gets the same treatment when the cases from
  // `testTopLevel` are duplicated at the nested level.

  B<Fcov> source1;
  var fsource1 = toF(source1);
  F<B<Fcov<dynamic>>> target1 = fsource1;

  B<Fcon> source2;
  var fsource2 = toF(source2);
  F<B<Fcon<dynamic>>> target2 = fsource2;

  B<Finv> source3;
  var fsource3 = toF(source3);
  F<B<Finv<dynamic>>> target3 = fsource3;

  B<FcovBound> source4;
  var fsource4 = toF(source4);
  F<B<FcovBound<num>>> target4 = fsource4;

  B<FconBound> source5;
  var fsource5 = toF(source5);
  F<B<FconBound<num>>> target5 = fsource5;

  B<FinvBound> source6;
  var fsource6 = toF(source6);
  F<B<FinvBound<num>>> target6 = fsource6;

  B<FcovCyclicBound> source7;
  var fsource7 = toF(source7);
  F<B<FcovCyclicBound<A<dynamic>>>> target7 = fsource7;

  B<FconCyclicBound> source8;
  var fsource8 = toF(source8);
  F<B<FconCyclicBound<A<Null>>>> target8 = fsource8;

  B<FinvCyclicBound> source9; //# 02: compile-time error
  // var fsource9 = toF(source9);
  // F<B<FinvCyclicBound<A<dynamic>>>> target9 = fsource9;

  B<FcovCyclicCoBound> source10;
  var fsource10 = toF(source10);
  F<B<FcovCyclicCoBound<Function(Null)>>> target10 = fsource10;

  B<FconCyclicCoBound> source11;
  var fsource11 = toF(source11);
  F<B<FconCyclicCoBound<Function(dynamic)>>> target11 = fsource11;

  B<FinvCyclicCoBound> source12;
  var fsource12 = toF(source12);
  F<B<FinvCyclicCoBound<Function(dynamic)>>> target12 = fsource12;
}

main() {
  testTopLevel();
  testNested();
}