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Default parameter values are implemented in dart2wasm via caller-side substitution. When the same parameter has different default values across different implementations within the same selector, a special sentinel value is passed by the caller, and the callee checks for this value and substitutes the actual default value. Change-Id: I8235145f93c2aee7e9ef603456380253b836fcef Cq-Include-Trybots: luci.dart.try:dart2wasm-linux-x64-d8-try Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/259040 Commit-Queue: Aske Simon Christensen <askesc@google.com> Reviewed-by: Joshua Litt <joshualitt@google.com>
111 lines
3.9 KiB
Dart
111 lines
3.9 KiB
Dart
// Copyright (c) 2022, 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 'package:dart2wasm/reference_extensions.dart';
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import 'package:kernel/ast.dart';
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/// Information about optional parameters and their default values for a
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/// member or a set of members belonging to the same override group.
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class ParameterInfo {
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final Member? member;
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int typeParamCount = 0;
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late final List<Constant?> positional;
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late final Map<String, Constant?> named;
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// Do not access these until the info is complete.
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late final List<String> names = named.keys.toList()..sort();
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late final Map<String, int> nameIndex = {
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for (int i = 0; i < names.length; i++) names[i]: positional.length + i
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};
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/// A special marker value to use for default parameter values to indicate
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/// that different implementations within the same selector have different
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/// default values.
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static final Constant defaultValueSentinel =
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UnevaluatedConstant(InvalidExpression("Default value sentinel"));
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int get paramCount => positional.length + named.length;
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static Constant? defaultValue(VariableDeclaration param) {
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Expression? initializer = param.initializer;
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if (initializer is ConstantExpression) {
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return initializer.constant;
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} else if (initializer == null) {
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return null;
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} else {
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throw "Non-constant default value";
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}
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}
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ParameterInfo.fromMember(Reference target) : member = target.asMember {
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FunctionNode? function = member!.function;
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if (target.isTearOffReference) {
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positional = [];
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named = {};
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} else if (function != null) {
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typeParamCount = (member is Constructor
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? member!.enclosingClass!.typeParameters
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: function.typeParameters)
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.length;
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positional = List.generate(function.positionalParameters.length, (i) {
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// A required parameter has no default value.
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if (i < function.requiredParameterCount) return null;
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return defaultValue(function.positionalParameters[i]);
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});
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named = {
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for (VariableDeclaration param in function.namedParameters)
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param.name!: defaultValue(param)
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};
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} else {
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// A setter parameter has no default value.
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positional = [if (target.isSetter) null];
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named = {};
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}
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}
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ParameterInfo.fromLocalFunction(FunctionNode function) : member = null {
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typeParamCount = function.typeParameters.length;
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positional = List.generate(function.positionalParameters.length, (i) {
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// A required parameter has no default value.
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if (i < function.requiredParameterCount) return null;
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return defaultValue(function.positionalParameters[i]);
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});
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named = {
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for (VariableDeclaration param in function.namedParameters)
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param.name!: defaultValue(param)
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};
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}
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void merge(ParameterInfo other) {
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assert(typeParamCount == other.typeParamCount);
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for (int i = 0; i < other.positional.length; i++) {
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if (i >= positional.length) {
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positional.add(other.positional[i]);
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} else {
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if (positional[i] == null) {
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positional[i] = other.positional[i];
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} else if (other.positional[i] != null) {
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if (positional[i] != other.positional[i]) {
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// Default value differs between implementations.
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positional[i] = defaultValueSentinel;
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}
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}
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}
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}
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for (String name in other.named.keys) {
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Constant? value = named[name];
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Constant? otherValue = other.named[name];
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if (value == null) {
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named[name] = otherValue;
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} else if (otherValue != null) {
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if (value != otherValue) {
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// Default value differs between implementations.
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named[name] = defaultValueSentinel;
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}
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}
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}
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}
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}
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