Johnni Winther
8467186ca0
This CL completes the migration of the first wave of interdependent libraries in package:kernel, including ast.dart. In order to ensure non-nullability on AST properties, the Transformer has been split in 2 variants: Transformer which doesn't support removal of nodes and RemovingTransformer which supports removal where allowed by the context using 'removal sentinels'. Start reviewing Transformer and RemovingTransformer in visitors.dart since many of the changes are caused by the changes here. Included in the migration are the mixin_deduplication.dart and unreachable_code_elimination.dart since these needed porting to the RemovingTransformer which was aided by opting in the libraries which only depended on ast.dart. TEST=existing Change-Id: I9e63b985bd24896c25edd4ee51e37770187bcc17 Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/184786 Commit-Queue: Johnni Winther <johnniwinther@google.com> Reviewed-by: Jens Johansen <jensj@google.com>
54 lines
1.6 KiB
Dart
54 lines
1.6 KiB
Dart
// Copyright (c) 2020, the Dart project authors. Please see the AUTHORS file
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// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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import '../ast.dart';
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/// Pairs of [TypeParameter]s that are currently assumed to be
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/// equivalent.
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///
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/// This is used to compute the equivalence relation on types coinductively.
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class Assumptions {
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Map<TypeParameter, TypeParameter> _assumptionMap =
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new Map<TypeParameter, TypeParameter>.identity();
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void _addAssumption(TypeParameter a, TypeParameter b) {
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assert(!_assumptionMap.containsKey(a));
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_assumptionMap[a] = b;
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}
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/// Assume that [a] and [b] are equivalent.
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void assume(TypeParameter a, TypeParameter b) {
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_addAssumption(a, b);
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}
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void _removeAssumption(TypeParameter a, TypeParameter b) {
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TypeParameter? assumption = _assumptionMap.remove(a);
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assert(identical(assumption, b));
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}
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/// Remove the assumption that [a] and [b] are equivalent.
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void forget(TypeParameter a, TypeParameter b) {
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_removeAssumption(a, b);
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}
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/// Returns `true` if [a] and [b] are assumed to be equivalent.
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bool isAssumed(TypeParameter a, TypeParameter b) {
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return identical(_assumptionMap[a], b);
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}
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@override
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String toString() {
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StringBuffer sb = new StringBuffer();
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sb.write('Assumptions(');
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String comma = '';
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_assumptionMap.forEach((TypeParameter a, TypeParameter b) {
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sb.write('$comma$a (${identityHashCode(a)})->'
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'$b (${identityHashCode(b)})');
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comma = ',';
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});
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sb.write(')');
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return sb.toString();
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}
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}
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