| // 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 `out` variance modifier. |
| |
| // SharedOptions=--enable-experiment=variance |
| |
| class Covariant<out T> {} |
| |
| class Exactly<inout T> {} |
| |
| class Upper {} |
| class Middle extends Upper {} |
| class Lower extends Middle {} |
| |
| class CovBound<out T> { |
| CovBound(T x, void Function(T) y) {} |
| } |
| |
| Exactly<T> inferCovCov<T>(Covariant<T> x, Covariant<T> y) => new Exactly<T>(); |
| Exactly<T> inferCovBound<T>(CovBound<T> x) => new Exactly<T>(); |
| |
| main() { |
| Exactly<Upper> upper; |
| Exactly<Lower> lower; |
| |
| // Upper <: T |
| // Upper <: T |
| // Choose Upper |
| var inferredUpper = inferCovCov(Covariant<Upper>(), Covariant<Upper>()); |
| upper = inferredUpper; |
| |
| // Upper <: T |
| // Middle <: T |
| // Choose Upper since it is the lowest upper bound of Upper and Middle. |
| var inferredUpper2 = inferCovCov(Covariant<Upper>(), Covariant<Middle>()); |
| upper = inferredUpper2; |
| |
| // Upper <: T |
| // Lower <: T |
| // Choose Upper since it is the lowest upper bound of Upper and Lower. |
| var inferredUpper3 = inferCovCov(Covariant<Upper>(), Covariant<Lower>()); |
| upper = inferredUpper3; |
| |
| // Lower <: T <: Upper |
| // Choose Lower. |
| var inferredCovLower = inferCovBound(CovBound(Lower(), (Upper x) {})); |
| lower = inferredCovLower; |
| |
| // Lower <: T <: Middle |
| // Choose Lower. |
| var inferredCovLower2 = inferCovBound(CovBound(Lower(), (Middle x) {})); |
| lower = inferredCovLower2; |
| } |