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// 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 local inference for the `inout` variance modifier.
// SharedOptions=--enable-experiment=variance
class Covariant<out T> {}
class Contravariant<in T> {}
class Invariant<inout T> {}
class Exactly<inout T> {}
class Upper {}
class Middle extends Upper {}
class Lower extends Middle {}
Exactly<T> inferInvInv<T>(Invariant<T> x, Invariant<T> y) => new Exactly<T>();
Exactly<T> inferInvCov<T>(Invariant<T> x, Covariant<T> y) => new Exactly<T>();
Exactly<T> inferInvContra<T>(Invariant<T> x, Contravariant<T> y) => new Exactly<T>();
main() {
Exactly<Middle> middle;
// Middle <: T <: Middle
// Choose Middle
var inferredMiddle = inferInvInv(Invariant<Middle>(), Invariant<Middle>());
middle = inferredMiddle;
// Lower <: T
// Middle <: T <: Middle
// Choose Middle since this merges to Middle <: T <: Middle
var inferredMiddle2 = inferInvCov(Invariant<Middle>(), Covariant<Lower>());
middle = inferredMiddle2;
// Middle <: T
// Middle <: T <: Middle
// Choose Middle since this merges to Middle <: T <: Middle
var inferredMiddle3 = inferInvCov(Invariant<Middle>(), Covariant<Middle>());
middle = inferredMiddle3;
// T <: Upper
// Middle <: T <: Middle
// Choose Middle since this merges to Middle <: T <: Middle
var inferredMiddle4 = inferInvContra(Invariant<Middle>(), Contravariant<Upper>());
middle = inferredMiddle4;
// T <: Middle
// Middle <: T <: Middle
// Choose Middle since this merges to Middle <: T <: Middle
var inferredMiddle5 = inferInvContra(Invariant<Middle>(), Contravariant<Middle>());
middle = inferredMiddle5;
}