pkg/_js_interop_checks/lib/src/transformations/js_util_wasm_optimizer.dart - sdk.git - Git at Google

 // Copyright (c) 2022, 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.

 import 'package:kernel/ast.dart';
 import 'package:kernel/class_hierarchy.dart';
 import 'package:kernel/core_types.dart';
 import 'package:kernel/type_environment.dart';

 import '../js_interop.dart'
     show
         getJSName,
         hasAnonymousAnnotation,
         hasStaticInteropAnnotation,
         hasJSInteropAnnotation;

 /// Replaces:
 ///   1) Factory constructors in classes with `@staticInterop` annotations with
 ///      calls to `js_util_wasm.callConstructorVarArgs`.
 ///   2) External methods in `@staticInterop` class extensions to their
 ///      corresponding `js_util_wasm` calls.
 /// TODO(joshualitt): In the long term we'd like to have the same
 /// `JsUtilOptimizer` for all web backends. This is to ensure uniform semantics
 /// across all web backends. Some known challenges remain, and there may be
 /// unknown challenges that appear as we proceed. Known challenges include:
 ///   1) Some constructs may need to be restricted on Dart2wasm, for example
 ///      callbacks must be fully typed for the time being, though we could
 ///      generalize this using `Function.apply`, but this is currently not
 ///      implemented on Dart2wasm.
 ///   2) We may want to handle this lowering differently on Dart2wasm in the
 ///      long term. Currently, js_util on Wasm is implemented using a single
 ///      trampoline per js_util function. We may want to specialize these
 ///      trampolines based off the interop type, to avoid megamorphic behavior.
 ///      This would have code size implications though, so we would need to
 ///      proceed carefully.
 /// TODO(joshualitt): A few of the functions in this file use js_utils in a
 /// naive way, and could be optimized further. In particular, there are a few
 /// complex operations in [JsUtilWasmOptimizer] where it is obvious a value is
 /// flowing from / to JS, and we have a few options for optimization:
 ///    1) Integrate with `js_ast` and emit custom JavaScript for each of these
 ///       operations.
 ///    2) Use the `raw` variants of the js_util calls.
 ///    3) Move more of the logic for these calls into JS where it will likely be
 ///       faster.
 class JsUtilWasmOptimizer extends Transformer {
   final Procedure _callMethodTarget;
   final Procedure _callConstructorTarget;
   final Procedure _globalThisTarget;
   final Procedure _getPropertyTarget;
   final Procedure _setPropertyTarget;
   final Procedure _jsifyTarget;
   final Procedure _dartifyTarget;
   final Procedure _newObjectTarget;
   final Class _jsValueClass;

   final CoreTypes _coreTypes;
   final StatefulStaticTypeContext _staticTypeContext;
   Map<Reference, ExtensionMemberDescriptor>? _extensionMemberIndex;
   final Set<Class> _transformedClasses = {};

   JsUtilWasmOptimizer(this._coreTypes, ClassHierarchy hierarchy)
       : _callMethodTarget = _coreTypes.index
             .getTopLevelProcedure('dart:js_util_wasm', 'callMethodVarArgs'),
         _globalThisTarget = _coreTypes.index
             .getTopLevelProcedure('dart:js_util_wasm', 'globalThis'),
         _callConstructorTarget = _coreTypes.index.getTopLevelProcedure(
             'dart:js_util_wasm', 'callConstructorVarArgs'),
         _getPropertyTarget = _coreTypes.index
             .getTopLevelProcedure('dart:js_util_wasm', 'getProperty'),
         _setPropertyTarget = _coreTypes.index
             .getTopLevelProcedure('dart:js_util_wasm', 'setProperty'),
         _jsifyTarget =
             _coreTypes.index.getTopLevelProcedure('dart:js_util_wasm', 'jsify'),
         _dartifyTarget = _coreTypes.index
             .getTopLevelProcedure('dart:js_util_wasm', 'dartify'),
         _newObjectTarget = _coreTypes.index
             .getTopLevelProcedure('dart:js_util_wasm', 'newObject'),
         _jsValueClass =
             _coreTypes.index.getClass('dart:js_util_wasm', 'JSValue'),
         _staticTypeContext = StatefulStaticTypeContext.stacked(
             TypeEnvironment(_coreTypes, hierarchy)) {}

   @override
   Library visitLibrary(Library lib) {
     _staticTypeContext.enterLibrary(lib);
     lib.transformChildren(this);
     _staticTypeContext.leaveLibrary(lib);
     _extensionMemberIndex = null;
     _transformedClasses.clear();
     return lib;
   }

   @override
   Member defaultMember(Member node) {
     _staticTypeContext.enterMember(node);
     node.transformChildren(this);
     _staticTypeContext.leaveMember(node);
     return node;
   }

   @override
   Procedure visitProcedure(Procedure node) {
     _staticTypeContext.enterMember(node);
     Statement? transformedBody;
     if (node.isExternal) {
       if (node.isFactory) {
         Class cls = node.enclosingClass!;
         if (hasStaticInteropAnnotation(cls)) {
           if (hasAnonymousAnnotation(cls)) {
             transformedBody = _getExternalAnonymousConstructorBody(node);
           } else {
             String jsName = getJSName(cls);
             String constructorName = jsName == '' ? cls.name : jsName;
             transformedBody =
                 _getExternalCallConstructorBody(node, constructorName);
           }
         }
       } else if (node.isExtensionMember) {
         var index = _extensionMemberIndex ??=
             _createExtensionMembersIndex(node.enclosingLibrary);
         var nodeDescriptor = index[node.reference];
         if (nodeDescriptor != null) {
           if (!nodeDescriptor.isStatic) {
             if (nodeDescriptor.kind == ExtensionMemberKind.Getter) {
               transformedBody = _getExternalExtensionGetterBody(node);
             } else if (nodeDescriptor.kind == ExtensionMemberKind.Setter) {
               transformedBody = _getExternalExtensionSetterBody(node);
             } else if (nodeDescriptor.kind == ExtensionMemberKind.Method) {
               transformedBody = _getExternalExtensionMethodBody(node);
             }
           }
         }
       } else if (hasJSInteropAnnotation(node)) {
         String selectorString = getJSName(node);
         late Expression target;
         if (selectorString.isEmpty) {
           target = _globalThis;
         } else {
           List<String> selectors = selectorString.split('.');
           target = getObjectOffGlobalThis(node, selectors);
         }
         if (node.isGetter) {
           transformedBody = _getExternalTopLevelGetterBody(node, target);
         } else if (node.isSetter) {
           transformedBody = _getExternalTopLevelSetterBody(node, target);
         } else {
           assert(node.kind == ProcedureKind.Method);
           transformedBody = _getExternalTopLevelMethodBody(node, target);
         }
       }
     }
     if (transformedBody != null) {
       node.function.body = transformedBody..parent = node.function;
       node.isExternal = false;
     } else {
       node.transformChildren(this);
     }
     _staticTypeContext.leaveMember(node);
     return node;
   }

   /// Returns and initializes `_extensionMemberIndex` to an index of the member
   /// reference to the member `ExtensionMemberDescriptor`, for all extension
   /// members in the given [library] of classes annotated with
   /// `@staticInterop`.
   Map<Reference, ExtensionMemberDescriptor> _createExtensionMembersIndex(
       Library library) {
     _extensionMemberIndex = {};
     library.extensions.forEach((extension) {
       DartType onType = extension.onType;
       if (onType is InterfaceType &&
           hasStaticInteropAnnotation(onType.className.asClass)) {
         extension.members.forEach((descriptor) {
           _extensionMemberIndex![descriptor.member] = descriptor;
         });
       }
     });
     return _extensionMemberIndex!;
   }

   DartType get _nullableJSValueType =>
       _jsValueClass.getThisType(_coreTypes, Nullability.nullable);

   DartType get _nonNullableJSValueType =>
       _jsValueClass.getThisType(_coreTypes, Nullability.nonNullable);

   Expression _jsifyVariable(VariableDeclaration variable) =>
       StaticInvocation(_jsifyTarget, Arguments([VariableGet(variable)]));

   StaticInvocation get _globalThis =>
       StaticInvocation(_globalThisTarget, Arguments([]));

   /// Takes a list of [selectors] and returns an object off of
   /// `globalThis`. We could optimize this with a custom method built with
   /// js_ast.
   Expression getObjectOffGlobalThis(Procedure node, List<String> selectors) {
     Expression currentTarget = _globalThis;
     for (String selector in selectors) {
       currentTarget = _getProperty(node, currentTarget, selector);
     }
     return currentTarget;
   }

   /// Returns a new function body for the given [node] external factory method
   /// for a class annotated with `@anonymous`.
   ///
   /// This lowers a factory function with named arguments to the creation of a
   /// new object literal, and a series of `setProperty` calls.
   Block _getExternalAnonymousConstructorBody(Procedure node) {
     List<Statement> body = [];
     final object = VariableDeclaration('|anonymousObject',
         initializer: StaticInvocation(_newObjectTarget, Arguments([])),
         type: _nonNullableJSValueType);
     body.add(object);
     for (VariableDeclaration variable in node.function.namedParameters) {
       body.add(ExpressionStatement(
           _setProperty(node, VariableGet(object), variable.name!, variable)));
     }
     body.add(ReturnStatement(VariableGet(object)));
     return Block(body);
   }

   /// Returns a new function body for the given [node] external method.
   ///
   /// The new function body will call `js_util_wasm.callConstructorVarArgs`
   /// for the given external method.
   ReturnStatement _getExternalCallConstructorBody(
       Procedure node, String constructorName) {
     var function = node.function;
     var callConstructorInvocation = StaticInvocation(
         _callConstructorTarget,
         Arguments([
           _globalThis,
           StringLiteral(constructorName),
           ListLiteral(
               function.positionalParameters.map(_jsifyVariable).toList(),
               typeArgument: _nonNullableJSValueType)
         ]))
       ..fileOffset = node.fileOffset;
     return ReturnStatement(callConstructorInvocation);
   }

   Expression _dartify(Expression expression) =>
       StaticInvocation(_dartifyTarget, Arguments([expression]));

   /// Returns a new [Expression] for the given [node] external getter.
   ///
   /// The new [Expression] is equivalent to:
   /// `js_util_wasm.getProperty([object], [getterName])`.
   Expression _getProperty(
           Procedure node, Expression object, String getterName) =>
       StaticInvocation(
           _getPropertyTarget, Arguments([object, StringLiteral(getterName)]))
         ..fileOffset = node.fileOffset;

   /// Returns a new function body for the given [node] external getter.
   ReturnStatement _getExternalGetterBody(
           Procedure node, Expression object, String getterName) =>
       ReturnStatement(_dartify(_getProperty(node, object, getterName)));

   ReturnStatement _getExternalExtensionGetterBody(Procedure node) =>
       _getExternalGetterBody(
           node,
           VariableGet(node.function.positionalParameters.single),
           _getExtensionMemberName(node));

   ReturnStatement _getExternalTopLevelGetterBody(
           Procedure node, Expression target) =>
       _getExternalGetterBody(node, target, node.name.text);

   /// Returns a new [Expression] for the given [node] external setter.
   ///
   /// The new [Expression] is equivalent to:
   /// `js_util_wasm.setProperty([object], [setterName], [value])`.
   Expression _setProperty(Procedure node, Expression object, String setterName,
           VariableDeclaration value) =>
       StaticInvocation(_setPropertyTarget,
           Arguments([object, StringLiteral(setterName), _jsifyVariable(value)]))
         ..fileOffset = node.fileOffset;

   /// Returns a new function body for the given [node] external setter.
   ReturnStatement _getExternalSetterBody(Procedure node, Expression object,
           String setterName, VariableDeclaration value) =>
       ReturnStatement(_dartify(_setProperty(node, object, setterName, value)));

   ReturnStatement _getExternalExtensionSetterBody(Procedure node) {
     final parameters = node.function.positionalParameters;
     assert(parameters.length == 2);
     return _getExternalSetterBody(node, VariableGet(parameters.first),
         _getExtensionMemberName(node), parameters.last);
   }

   ReturnStatement _getExternalTopLevelSetterBody(
           Procedure node, Expression target) =>
       _getExternalSetterBody(node, target, node.name.text,
           node.function.positionalParameters.single);

   /// Returns a new function body for the given [node] external method.
   ///
   /// The new function body is equivalent to:
   /// `js_util_wasm.callMethodVarArgs([object], [methodName], [values])`.
   ReturnStatement _getExternalMethodBody(Procedure node, Expression object,
       String methodName, List<VariableDeclaration> values) {
     final callMethodInvocation = _dartify(StaticInvocation(
         _callMethodTarget,
         Arguments([
           object,
           StringLiteral(methodName),
           ListLiteral(values.map(_jsifyVariable).toList(),
               typeArgument: _nullableJSValueType)
         ])))
       ..fileOffset = node.fileOffset;
     return ReturnStatement(callMethodInvocation);
   }

   ReturnStatement _getExternalExtensionMethodBody(Procedure node) {
     final parameters = node.function.positionalParameters;
     assert(parameters.length > 0);
     return _getExternalMethodBody(node, VariableGet(parameters.first),
         _getExtensionMemberName(node), parameters.sublist(1));
   }

   ReturnStatement _getExternalTopLevelMethodBody(
           Procedure node, Expression target) =>
       _getExternalMethodBody(
           node, target, node.name.text, node.function.positionalParameters);

   /// Returns the extension member name.
   ///
   /// Returns either the name from the `@JS` annotation if non-empty, or the
   /// declared name of the extension member. Does not return the CFE generated
   /// name for the top level member for this extension member.
   String _getExtensionMemberName(Procedure node) {
     var jsAnnotationName = getJSName(node);
     if (jsAnnotationName.isNotEmpty) {
       return jsAnnotationName;
     }
     return _extensionMemberIndex![node.reference]!.name.text;
   }
 }
	// Copyright (c) 2022, 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.

	import 'package:kernel/ast.dart';
	import 'package:kernel/class_hierarchy.dart';
	import 'package:kernel/core_types.dart';
	import 'package:kernel/type_environment.dart';

	import '../js_interop.dart'
	show
	getJSName,
	hasAnonymousAnnotation,
	hasStaticInteropAnnotation,
	hasJSInteropAnnotation;

	/// Replaces:
	/// 1) Factory constructors in classes with `@staticInterop` annotations with
	/// calls to `js_util_wasm.callConstructorVarArgs`.
	/// 2) External methods in `@staticInterop` class extensions to their
	/// corresponding `js_util_wasm` calls.
	/// TODO(joshualitt): In the long term we'd like to have the same
	/// `JsUtilOptimizer` for all web backends. This is to ensure uniform semantics
	/// across all web backends. Some known challenges remain, and there may be
	/// unknown challenges that appear as we proceed. Known challenges include:
	/// 1) Some constructs may need to be restricted on Dart2wasm, for example
	/// callbacks must be fully typed for the time being, though we could
	/// generalize this using `Function.apply`, but this is currently not
	/// implemented on Dart2wasm.
	/// 2) We may want to handle this lowering differently on Dart2wasm in the
	/// long term. Currently, js_util on Wasm is implemented using a single
	/// trampoline per js_util function. We may want to specialize these
	/// trampolines based off the interop type, to avoid megamorphic behavior.
	/// This would have code size implications though, so we would need to
	/// proceed carefully.
	/// TODO(joshualitt): A few of the functions in this file use js_utils in a
	/// naive way, and could be optimized further. In particular, there are a few
	/// complex operations in [JsUtilWasmOptimizer] where it is obvious a value is
	/// flowing from / to JS, and we have a few options for optimization:
	/// 1) Integrate with `js_ast` and emit custom JavaScript for each of these
	/// operations.
	/// 2) Use the `raw` variants of the js_util calls.
	/// 3) Move more of the logic for these calls into JS where it will likely be
	/// faster.
	class JsUtilWasmOptimizer extends Transformer {
	final Procedure _callMethodTarget;
	final Procedure _callConstructorTarget;
	final Procedure _globalThisTarget;
	final Procedure _getPropertyTarget;
	final Procedure _setPropertyTarget;
	final Procedure _jsifyTarget;
	final Procedure _dartifyTarget;
	final Procedure _newObjectTarget;
	final Class _jsValueClass;

	final CoreTypes _coreTypes;
	final StatefulStaticTypeContext _staticTypeContext;
	Map<Reference, ExtensionMemberDescriptor>? _extensionMemberIndex;
	final Set<Class> _transformedClasses = {};

	JsUtilWasmOptimizer(this._coreTypes, ClassHierarchy hierarchy)
	: _callMethodTarget = _coreTypes.index
	.getTopLevelProcedure('dart:js_util_wasm', 'callMethodVarArgs'),
	_globalThisTarget = _coreTypes.index
	.getTopLevelProcedure('dart:js_util_wasm', 'globalThis'),
	_callConstructorTarget = _coreTypes.index.getTopLevelProcedure(
	'dart:js_util_wasm', 'callConstructorVarArgs'),
	_getPropertyTarget = _coreTypes.index
	.getTopLevelProcedure('dart:js_util_wasm', 'getProperty'),
	_setPropertyTarget = _coreTypes.index
	.getTopLevelProcedure('dart:js_util_wasm', 'setProperty'),
	_jsifyTarget =
	_coreTypes.index.getTopLevelProcedure('dart:js_util_wasm', 'jsify'),
	_dartifyTarget = _coreTypes.index
	.getTopLevelProcedure('dart:js_util_wasm', 'dartify'),
	_newObjectTarget = _coreTypes.index
	.getTopLevelProcedure('dart:js_util_wasm', 'newObject'),
	_jsValueClass =
	_coreTypes.index.getClass('dart:js_util_wasm', 'JSValue'),
	_staticTypeContext = StatefulStaticTypeContext.stacked(
	TypeEnvironment(_coreTypes, hierarchy)) {}

	@override
	Library visitLibrary(Library lib) {
	_staticTypeContext.enterLibrary(lib);
	lib.transformChildren(this);
	_staticTypeContext.leaveLibrary(lib);
	_extensionMemberIndex = null;
	_transformedClasses.clear();
	return lib;
	}

	@override
	Member defaultMember(Member node) {
	_staticTypeContext.enterMember(node);
	node.transformChildren(this);
	_staticTypeContext.leaveMember(node);
	return node;
	}

	@override
	Procedure visitProcedure(Procedure node) {
	_staticTypeContext.enterMember(node);
	Statement? transformedBody;
	if (node.isExternal) {
	if (node.isFactory) {
	Class cls = node.enclosingClass!;
	if (hasStaticInteropAnnotation(cls)) {
	if (hasAnonymousAnnotation(cls)) {
	transformedBody = _getExternalAnonymousConstructorBody(node);
	} else {
	String jsName = getJSName(cls);
	String constructorName = jsName == '' ? cls.name : jsName;
	transformedBody =
	_getExternalCallConstructorBody(node, constructorName);
	}
	}
	} else if (node.isExtensionMember) {
	var index = _extensionMemberIndex ??=
	_createExtensionMembersIndex(node.enclosingLibrary);
	var nodeDescriptor = index[node.reference];
	if (nodeDescriptor != null) {
	if (!nodeDescriptor.isStatic) {
	if (nodeDescriptor.kind == ExtensionMemberKind.Getter) {
	transformedBody = _getExternalExtensionGetterBody(node);
	} else if (nodeDescriptor.kind == ExtensionMemberKind.Setter) {
	transformedBody = _getExternalExtensionSetterBody(node);
	} else if (nodeDescriptor.kind == ExtensionMemberKind.Method) {
	transformedBody = _getExternalExtensionMethodBody(node);
	}
	}
	}
	} else if (hasJSInteropAnnotation(node)) {
	String selectorString = getJSName(node);
	late Expression target;
	if (selectorString.isEmpty) {
	target = _globalThis;
	} else {
	List<String> selectors = selectorString.split('.');
	target = getObjectOffGlobalThis(node, selectors);
	}
	if (node.isGetter) {
	transformedBody = _getExternalTopLevelGetterBody(node, target);
	} else if (node.isSetter) {
	transformedBody = _getExternalTopLevelSetterBody(node, target);
	} else {
	assert(node.kind == ProcedureKind.Method);
	transformedBody = _getExternalTopLevelMethodBody(node, target);
	}
	}
	}
	if (transformedBody != null) {
	node.function.body = transformedBody..parent = node.function;
	node.isExternal = false;
	} else {
	node.transformChildren(this);
	}
	_staticTypeContext.leaveMember(node);
	return node;
	}

	/// Returns and initializes `_extensionMemberIndex` to an index of the member
	/// reference to the member `ExtensionMemberDescriptor`, for all extension
	/// members in the given [library] of classes annotated with
	/// `@staticInterop`.
	Map<Reference, ExtensionMemberDescriptor> _createExtensionMembersIndex(
	Library library) {
	_extensionMemberIndex = {};
	library.extensions.forEach((extension) {
	DartType onType = extension.onType;
	if (onType is InterfaceType &&
	hasStaticInteropAnnotation(onType.className.asClass)) {
	extension.members.forEach((descriptor) {
	_extensionMemberIndex![descriptor.member] = descriptor;
	});
	}
	});
	return _extensionMemberIndex!;
	}

	DartType get _nullableJSValueType =>
	_jsValueClass.getThisType(_coreTypes, Nullability.nullable);

	DartType get _nonNullableJSValueType =>
	_jsValueClass.getThisType(_coreTypes, Nullability.nonNullable);

	Expression _jsifyVariable(VariableDeclaration variable) =>
	StaticInvocation(_jsifyTarget, Arguments([VariableGet(variable)]));

	StaticInvocation get _globalThis =>
	StaticInvocation(_globalThisTarget, Arguments([]));

	/// Takes a list of [selectors] and returns an object off of
	/// `globalThis`. We could optimize this with a custom method built with
	/// js_ast.
	Expression getObjectOffGlobalThis(Procedure node, List<String> selectors) {
	Expression currentTarget = _globalThis;
	for (String selector in selectors) {
	currentTarget = _getProperty(node, currentTarget, selector);
	}
	return currentTarget;
	}

	/// Returns a new function body for the given [node] external factory method
	/// for a class annotated with `@anonymous`.
	///
	/// This lowers a factory function with named arguments to the creation of a
	/// new object literal, and a series of `setProperty` calls.
	Block _getExternalAnonymousConstructorBody(Procedure node) {
	List<Statement> body = [];
	final object = VariableDeclaration('\|anonymousObject',
	initializer: StaticInvocation(_newObjectTarget, Arguments([])),
	type: _nonNullableJSValueType);
	body.add(object);
	for (VariableDeclaration variable in node.function.namedParameters) {
	body.add(ExpressionStatement(
	_setProperty(node, VariableGet(object), variable.name!, variable)));
	}
	body.add(ReturnStatement(VariableGet(object)));
	return Block(body);
	}

	/// Returns a new function body for the given [node] external method.
	///
	/// The new function body will call `js_util_wasm.callConstructorVarArgs`
	/// for the given external method.
	ReturnStatement _getExternalCallConstructorBody(
	Procedure node, String constructorName) {
	var function = node.function;
	var callConstructorInvocation = StaticInvocation(
	_callConstructorTarget,
	Arguments([
	_globalThis,
	StringLiteral(constructorName),
	ListLiteral(
	function.positionalParameters.map(_jsifyVariable).toList(),
	typeArgument: _nonNullableJSValueType)
	]))
	..fileOffset = node.fileOffset;
	return ReturnStatement(callConstructorInvocation);
	}

	Expression _dartify(Expression expression) =>
	StaticInvocation(_dartifyTarget, Arguments([expression]));

	/// Returns a new [Expression] for the given [node] external getter.
	///
	/// The new [Expression] is equivalent to:
	/// `js_util_wasm.getProperty([object], [getterName])`.
	Expression _getProperty(
	Procedure node, Expression object, String getterName) =>
	StaticInvocation(
	_getPropertyTarget, Arguments([object, StringLiteral(getterName)]))
	..fileOffset = node.fileOffset;

	/// Returns a new function body for the given [node] external getter.
	ReturnStatement _getExternalGetterBody(
	Procedure node, Expression object, String getterName) =>
	ReturnStatement(_dartify(_getProperty(node, object, getterName)));

	ReturnStatement _getExternalExtensionGetterBody(Procedure node) =>
	_getExternalGetterBody(
	node,
	VariableGet(node.function.positionalParameters.single),
	_getExtensionMemberName(node));

	ReturnStatement _getExternalTopLevelGetterBody(
	Procedure node, Expression target) =>
	_getExternalGetterBody(node, target, node.name.text);

	/// Returns a new [Expression] for the given [node] external setter.
	///
	/// The new [Expression] is equivalent to:
	/// `js_util_wasm.setProperty([object], [setterName], [value])`.
	Expression _setProperty(Procedure node, Expression object, String setterName,
	VariableDeclaration value) =>
	StaticInvocation(_setPropertyTarget,
	Arguments([object, StringLiteral(setterName), _jsifyVariable(value)]))
	..fileOffset = node.fileOffset;

	/// Returns a new function body for the given [node] external setter.
	ReturnStatement _getExternalSetterBody(Procedure node, Expression object,
	String setterName, VariableDeclaration value) =>
	ReturnStatement(_dartify(_setProperty(node, object, setterName, value)));

	ReturnStatement _getExternalExtensionSetterBody(Procedure node) {
	final parameters = node.function.positionalParameters;
	assert(parameters.length == 2);
	return _getExternalSetterBody(node, VariableGet(parameters.first),
	_getExtensionMemberName(node), parameters.last);
	}

	ReturnStatement _getExternalTopLevelSetterBody(
	Procedure node, Expression target) =>
	_getExternalSetterBody(node, target, node.name.text,
	node.function.positionalParameters.single);

	/// Returns a new function body for the given [node] external method.
	///
	/// The new function body is equivalent to:
	/// `js_util_wasm.callMethodVarArgs([object], [methodName], [values])`.
	ReturnStatement _getExternalMethodBody(Procedure node, Expression object,
	String methodName, List<VariableDeclaration> values) {
	final callMethodInvocation = _dartify(StaticInvocation(
	_callMethodTarget,
	Arguments([
	object,
	StringLiteral(methodName),
	ListLiteral(values.map(_jsifyVariable).toList(),
	typeArgument: _nullableJSValueType)
	])))
	..fileOffset = node.fileOffset;
	return ReturnStatement(callMethodInvocation);
	}

	ReturnStatement _getExternalExtensionMethodBody(Procedure node) {
	final parameters = node.function.positionalParameters;
	assert(parameters.length > 0);
	return _getExternalMethodBody(node, VariableGet(parameters.first),
	_getExtensionMemberName(node), parameters.sublist(1));
	}

	ReturnStatement _getExternalTopLevelMethodBody(
	Procedure node, Expression target) =>
	_getExternalMethodBody(
	node, target, node.name.text, node.function.positionalParameters);

	/// Returns the extension member name.
	///
	/// Returns either the name from the `@JS` annotation if non-empty, or the
	/// declared name of the extension member. Does not return the CFE generated
	/// name for the top level member for this extension member.
	String _getExtensionMemberName(Procedure node) {
	var jsAnnotationName = getJSName(node);
	if (jsAnnotationName.isNotEmpty) {
	return jsAnnotationName;
	}
	return _extensionMemberIndex![node.reference]!.name.text;
	}
	}