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[dart2wasm] Refactor method specialization to use inheritance
We've been using enums to denote procedure types and lowerings, but with object literals and invocation-level lowering, the code to handle the enums become increasingly complex. This CL separates out the logic to individual classes instead. Change-Id: I896dcfe1a00d649bf19d8e5315ed1deca3c3dad3 Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/290606 Reviewed-by: Joshua Litt <[email protected]> Commit-Queue: Srujan Gaddam <[email protected]>
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‎pkg/dart2wasm/lib/js_lowering_config.dart

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// Copyright (c) 2023, 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:_js_interop_checks/src/transformations/js_util_optimizer.dart'
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show InlineExtensionIndex;
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import 'package:kernel/ast.dart';
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bool parametersNeedParens(List<String> parameters) =>
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parameters.isEmpty || parameters.length > 1;
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/// A general config class for an interop method.
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///
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/// dart2wasm needs to create a trampoline method in JS that then calls the
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/// interop member in question. In order to do so, we need information on things
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/// like the name of the member, how many parameters it takes in, and more.
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abstract class JSLoweringConfig {
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final Procedure interopMethod;
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final String jsString;
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final InlineExtensionIndex _inlineExtensionIndex;
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late final bool firstParameterIsObject =
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_inlineExtensionIndex.isInstanceInteropMember(interopMethod);
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JSLoweringConfig(
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this.interopMethod, this.jsString, this._inlineExtensionIndex);
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FunctionNode get function => interopMethod.function;
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Uri get fileUri => interopMethod.fileUri;
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/// Whether this config is associated with a constructor or factory.
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bool get isConstructor;
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/// The parameters that determine arity of the interop procedure that is
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/// created from this config.
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List<VariableDeclaration> get parameters;
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/// Returns the string that will be the body of the JS trampoline.
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///
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/// [object] is the callee if there is one for this config. [callArguments] is
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/// the remaining arguments of the `interopMethod`.
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String bodyString(String object, List<String> callArguments);
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/// Compute and return the JS trampoline string needed for this method
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/// lowering.
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String generateJS(List<String> parameterNames) {
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final object = isConstructor
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? ''
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: firstParameterIsObject
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? parameterNames[0]
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: 'globalThis';
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final callArguments =
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firstParameterIsObject ? parameterNames.sublist(1) : parameterNames;
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final callArgumentsString = callArguments.join(',');
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final functionParameters = firstParameterIsObject
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? '$object${callArguments.isEmpty ? '' : ',$callArgumentsString'}'
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: callArgumentsString;
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final body = bodyString(object, callArguments);
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if (parametersNeedParens(parameterNames)) {
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return '($functionParameters) => $body';
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} else {
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return '$functionParameters => $body';
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}
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}
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}
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/// Config class for interop members that get lowered on the procedure side.
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abstract class JSProcedureLoweringConfig extends JSLoweringConfig {
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JSProcedureLoweringConfig(
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super.interopMethod, super.jsString, super._inlineExtensionIndex);
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@override
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List<VariableDeclaration> get parameters => function.positionalParameters;
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}
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class JSConstructorLoweringConfig extends JSProcedureLoweringConfig {
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JSConstructorLoweringConfig(
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super.interopMethod, super.jsString, super._inlineExtensionIndex);
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@override
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bool get isConstructor => true;
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@override
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String bodyString(String object, List<String> callArguments) =>
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"new $jsString(${callArguments.join(',')})";
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}
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class JSGetterLoweringConfig extends JSProcedureLoweringConfig {
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JSGetterLoweringConfig(
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super.interopMethod, super.jsString, super._inlineExtensionIndex);
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@override
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bool get isConstructor => false;
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@override
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String bodyString(String object, List<String> callArguments) =>
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'$object.$jsString';
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}
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class JSSetterLoweringConfig extends JSProcedureLoweringConfig {
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JSSetterLoweringConfig(
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super.interopMethod, super.jsString, super._inlineExtensionIndex);
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@override
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bool get isConstructor => false;
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@override
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String bodyString(String object, List<String> callArguments) =>
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'$object.$jsString = ${callArguments[0]}';
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}
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class JSMethodLoweringConfig extends JSProcedureLoweringConfig {
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JSMethodLoweringConfig(
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super.interopMethod, super.jsString, super._inlineExtensionIndex);
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@override
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bool get isConstructor => false;
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@override
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String bodyString(String object, List<String> callArguments) =>
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"$object.$jsString(${callArguments.join(',')})";
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}
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class JSOperatorLoweringConfig extends JSProcedureLoweringConfig {
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JSOperatorLoweringConfig(
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super.interopMethod, super.jsString, super._inlineExtensionIndex);
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@override
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bool get isConstructor => false;
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@override
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String bodyString(String object, List<String> callArguments) {
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if (jsString == '[]') {
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return '$object[${callArguments[0]}]';
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} else if (jsString == '[]=') {
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return '$object[${callArguments[0]}] = ${callArguments[1]}';
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} else {
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throw 'Unsupported operator: $jsString';
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}
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}
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}
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/// Config class for interop members that get lowered on the invocation side.
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abstract class JSInvocationLoweringConfig extends JSLoweringConfig {
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final StaticInvocation invocation;
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JSInvocationLoweringConfig(super.interopMethod, super.jsString,
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super._inlineExtensionIndex, this.invocation);
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/// The parameters of the given `interopMethod` that were given a correspondig
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/// argument in the `invocation`.
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@override
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List<VariableDeclaration> get parameters;
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/// The expressions that were passed in the `invocation`.
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List<Expression> get arguments;
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}
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/// Config class for procedures that are lowered on the invocation-side, but
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/// only contain positional parameters.
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abstract class JSPositionalInvocationLoweringConfig
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extends JSInvocationLoweringConfig {
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JSPositionalInvocationLoweringConfig(super.interopMethod, super.jsString,
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super._inlineExtensionIndex, super.invocation);
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@override
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List<VariableDeclaration> get parameters => function.positionalParameters
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.sublist(0, invocation.arguments.positional.length);
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@override
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List<Expression> get arguments => invocation.arguments.positional;
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}
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class JSConstructorInvocationLoweringConfig
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extends JSPositionalInvocationLoweringConfig {
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JSConstructorInvocationLoweringConfig(super.interopMethod, super.jsString,
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super._inlineExtensionIndex, super.invocation);
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@override
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bool get isConstructor => true;
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@override
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String bodyString(String object, List<String> callArguments) =>
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"new $jsString(${callArguments.join(',')})";
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}
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class JSMethodInvocationLoweringConfig
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extends JSPositionalInvocationLoweringConfig {
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JSMethodInvocationLoweringConfig(super.interopMethod, super.jsString,
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super._inlineExtensionIndex, super.invocation);
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@override
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bool get isConstructor => false;
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@override
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String bodyString(String object, List<String> callArguments) =>
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"$object.$jsString(${callArguments.join(',')})";
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}
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/// Config class for object literals, which only use named arguments and are
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/// only lowered at the invocation-level.
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class JSObjectLiteralLoweringConfig extends JSInvocationLoweringConfig {
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JSObjectLiteralLoweringConfig(Procedure interopMethod,
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InlineExtensionIndex _inlineExtensionIndex, StaticInvocation invocation)
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: super(interopMethod, '', _inlineExtensionIndex, invocation);
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@override
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bool get isConstructor => true;
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@override
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List<VariableDeclaration> get parameters {
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// Compute the named parameters that were used in the given `invocation`.
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// Note that we preserve the procedure's ordering and not the invocation's.
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// This is also used below for the names of object literal arguments in
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// `generateJS`.
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final usedArgs =
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invocation.arguments.named.map((expr) => expr.name).toSet();
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return function.namedParameters
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.where((decl) => usedArgs.contains(decl.name))
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.toList();
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}
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@override
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String bodyString(String object, List<String> callArguments) {
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final keys = parameters.map((named) => named.name!).toList();
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final keyValuePairs = <String>[];
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for (int i = 0; i < callArguments.length; i++) {
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keyValuePairs.add('${keys[i]}: ${callArguments[i]}');
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}
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return '({${keyValuePairs.join(',')}})';
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}
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@override
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List<Expression> get arguments {
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// Return the args in the order of the procedure's parameters and not
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// the invocation.
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final namedArgs = <String, Expression>{};
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for (NamedExpression expr in invocation.arguments.named) {
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namedArgs[expr.name] = expr.value;
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}
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return parameters
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.map<Expression>((decl) => namedArgs[decl.name!]!)
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.toList();
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}
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}

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