| /* |
| * Copyright (c) 2018, 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. |
| */ |
| /** |
| * @assertion Instantiate to bound then computes an actual type argument list |
| * for [G] as follows: |
| * |
| * Let [Ui],[1] be [Si], for all [i] in [1 .. k]. (This is the "current value" |
| * of the bound for type variable [i], at step [1]; in general we will |
| * consider the current step, [m], and use data for that step, e.g., the bound |
| * [Ui],[m], to compute the data for step [m + 1]). |
| * |
| * Let [-->m] be a relation among the type variables [X1 .. Xk] such that |
| * [Xp -->m Xq] iff [Xq] occurs in [Up],[m] (so each type variable is related |
| * to, that is, depends on, every type variable in its bound, possibly |
| * including itself). Let [==>m] be the transitive closure of [-->m]. For each |
| * [m], let [Ui],[m+1], for [i] in [1 .. k], be determined by the following |
| * iterative process: |
| * |
| * 1. If there exists a [j] in [1 .. k] such that [Xj ==>m X0j] (that is, if |
| * the dependency graph has a cycle) let [M1 .. Mp] be the strongly connected |
| * components (SCCs) with respect to [-->m] (that is, the maximal subsets of |
| * [X1 .. Xk] where every pair of variables in each subset are related in both |
| * directions by [==>m]; note that the SCCs are pairwise disjoint; also, they |
| * are uniquely defined up to reordering, and the order does not matter). Let |
| * [M] be the union of [M1 .. Mp] (that is, all variables that participate in |
| * a dependency cycle). Let [i] be in [1 .. k]. If [Xi] does not belong to [M] |
| * then [Ui,m+1 = Ui,m]. Otherwise there exists a [q] such that [Xi] belongs |
| * to [Mq]; [Ui,m+1] is then obtained from [Ui,m] by replacing every covariant |
| * occurrence of a variable in [Mq] by [dynamic], and replacing every |
| * contravariant occurrence of a variable in [Mq] by [Null]. |
| * |
| * 2. Otherwise, (if no dependency cycle exists) let [j] be the lowest number |
| * such that [Xj] occurs in [Up,m] for some [p] and [Xj -/->m Xq] for all [q] |
| * in [1..k] (that is, [Uj,m] is closed, that is, the current bound of [Xj] |
| * does not contain any type variables; but [Xj] is being depended on by the |
| * bound of some other type variable). Then, for all [i] in [1 .. k], [Ui,m+1] |
| * is obtained from [Ui,m] by replacing every covariant occurrence of [Xj] by |
| * [Uj,m], and replacing every contravariant occurrence of [Xj] by [Null]. |
| * |
| * 3. Otherwise, (when no dependencies exist) terminate with the result |
| * [<U1,m ..., Uk,m>]. |
| * @description Checks that instantiate-to-bounds works correctly for [typedef] |
| * with two related parameters: [typedef G<X extends A<X>, Y extends A<Y>> = |
| * void Function<Y1 extends Y>(X, Y)] |
| * @author iarkh@unipro.ru |
| */ |
| class A<X> {} |
| typedef G<X extends A<X>, Y extends A<Y>> = void Function<Y1 extends Y>(X, Y); |
| |
| main() { |
| G source; //# 01: compile-time error |
| } |
