pkg/front_end/lib/src/fasta/scope.dart - sdk.git - Git at Google

 // Copyright (c) 2016, 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.

 library fasta.scope;

 import 'builder/builder.dart' show Builder, NameIterator, TypeVariableBuilder;

 import 'builder/extension_builder.dart';

 import 'fasta_codes.dart'
     show
         LocatedMessage,
         Message,
         messageInternalProblemExtendingUnmodifiableScope,
         templateAccessError,
         templateDuplicatedDeclarationUse,
         templateDuplicatedNamePreviouslyUsedCause;

 import 'problems.dart' show internalProblem, unsupported;

 class MutableScope {
   /// Names declared in this scope.
   Map<String, Builder> local;

   /// Setters declared in this scope.
   Map<String, Builder> setters;

   /// The extensions declared in this scope.
   ///
   /// This includes all available extensions even if the extensions are not
   /// accessible by name because of duplicate imports.
   ///
   /// For instance:
   ///
   ///   lib1.dart:
   ///     extension Extension on String {
   ///       method1() {}
   ///       staticMethod1() {}
   ///     }
   ///   lib2.dart:
   ///     extension Extension on String {
   ///       method2() {}
   ///       staticMethod2() {}
   ///     }
   ///   main.dart:
   ///     import 'lib1.dart';
   ///     import 'lib2.dart';
   ///
   ///     main() {
   ///       'foo'.method1(); // This method is available.
   ///       'foo'.method2(); // This method is available.
   ///       // These methods are not available because Extension is ambiguous:
   ///       Extension.staticMethod1();
   ///       Extension.staticMethod2();
   ///     }
   ///
   List<ExtensionBuilder> _extensions;

   /// The scope that this scope is nested within, or `null` if this is the top
   /// level scope.
   Scope parent;

   final String classNameOrDebugName;

   MutableScope(this.local, this.setters, this._extensions, this.parent,
       this.classNameOrDebugName) {
     assert(classNameOrDebugName != null);
   }

   String toString() => "Scope($classNameOrDebugName, ${local.keys})";
 }

 class Scope extends MutableScope {
   /// Indicates whether an attempt to declare new names in this scope should
   /// succeed.
   final bool isModifiable;

   Map<String, Builder> labels;

   Map<String, Builder> forwardDeclaredLabels;

   Map<String, int> usedNames;

   Scope(
       {Map<String, Builder> local,
       Map<String, Builder> setters,
       List<ExtensionBuilder> extensions,
       Scope parent,
       String debugName,
       this.isModifiable: true})
       : super(local, setters = setters ?? const <String, Builder>{}, extensions,
             parent, debugName);

   Scope.top({bool isModifiable: false})
       : this(
             local: <String, Builder>{},
             setters: <String, Builder>{},
             debugName: "top",
             isModifiable: isModifiable);

   Scope.immutable()
       : this(
             local: const <String, Builder>{},
             setters: const <String, Builder>{},
             debugName: "immutable",
             isModifiable: false);

   Scope.nested(Scope parent, String debugName, {bool isModifiable: true})
       : this(
             local: <String, Builder>{},
             setters: <String, Builder>{},
             parent: parent,
             debugName: debugName,
             isModifiable: isModifiable);

   Iterator<Builder> get iterator {
     return new ScopeLocalDeclarationIterator(this);
   }

   NameIterator get nameIterator {
     return new ScopeLocalDeclarationNameIterator(this);
   }

   Scope copyWithParent(Scope parent, String debugName) {
     return new Scope(
         local: super.local,
         setters: super.setters,
         extensions: _extensions,
         parent: parent,
         debugName: debugName,
         isModifiable: isModifiable);
   }

   /// Don't use this. Use [becomePartOf] instead.
   void set local(_) => unsupported("local=", -1, null);

   /// Don't use this. Use [becomePartOf] instead.
   void set setters(_) => unsupported("setters=", -1, null);

   /// Don't use this. Use [becomePartOf] instead.
   void set parent(_) => unsupported("parent=", -1, null);

   /// This scope becomes equivalent to [scope]. This is used for parts to
   /// become part of their library's scope.
   void becomePartOf(Scope scope) {
     assert(parent.parent == null);
     assert(scope.parent.parent == null);
     super.local = scope.local;
     super.setters = scope.setters;
     super.parent = scope.parent;
     super._extensions = scope._extensions;
   }

   Scope createNestedScope(String debugName, {bool isModifiable: true}) {
     return new Scope.nested(this, debugName, isModifiable: isModifiable);
   }

   Scope withTypeVariables(List<TypeVariableBuilder> typeVariables) {
     if (typeVariables == null) return this;
     Scope newScope =
         new Scope.nested(this, "type variables", isModifiable: false);
     for (TypeVariableBuilder t in typeVariables) {
       newScope.local[t.name] = t;
     }
     return newScope;
   }

   /// Create a special scope for use by labeled statements. This scope doesn't
   /// introduce a new scope for local variables, only for labels. This deals
   /// with corner cases like this:
   ///
   ///     L: var x;
   ///     x = 42;
   ///     print("The answer is $x.");
   Scope createNestedLabelScope() {
     return new Scope(
         local: local,
         setters: setters,
         extensions: _extensions,
         parent: parent,
         debugName: "label",
         isModifiable: true);
   }

   void recordUse(String name, int charOffset, Uri fileUri) {
     if (isModifiable) {
       usedNames ??= <String, int>{};
       usedNames.putIfAbsent(name, () => charOffset);
     }
   }

   Builder lookupIn(String name, int charOffset, Uri fileUri,
       Map<String, Builder> map, bool isInstanceScope) {
     Builder builder = map[name];
     if (builder == null) return null;
     if (builder.next != null) {
       return new AmbiguousBuilder(name.isEmpty ? classNameOrDebugName : name,
           builder, charOffset, fileUri);
     } else if (!isInstanceScope && builder.isDeclarationInstanceMember) {
       return null;
     } else {
       return builder;
     }
   }

   Builder lookup(String name, int charOffset, Uri fileUri,
       {bool isInstanceScope: true}) {
     recordUse(name, charOffset, fileUri);
     Builder builder =
         lookupIn(name, charOffset, fileUri, local, isInstanceScope);
     if (builder != null) return builder;
     builder = lookupIn(name, charOffset, fileUri, setters, isInstanceScope);
     if (builder != null && !builder.hasProblem) {
       return new AccessErrorBuilder(name, builder, charOffset, fileUri);
     }
     if (!isInstanceScope) {
       // For static lookup, do not search the parent scope.
       return builder;
     }
     return builder ?? parent?.lookup(name, charOffset, fileUri);
   }

   Builder lookupSetter(String name, int charOffset, Uri fileUri,
       {bool isInstanceScope: true}) {
     recordUse(name, charOffset, fileUri);
     Builder builder =
         lookupIn(name, charOffset, fileUri, setters, isInstanceScope);
     if (builder != null) return builder;
     builder = lookupIn(name, charOffset, fileUri, local, isInstanceScope);
     if (builder != null && !builder.hasProblem) {
       return new AccessErrorBuilder(name, builder, charOffset, fileUri);
     }
     if (!isInstanceScope) {
       // For static lookup, do not search the parent scope.
       return builder;
     }
     return builder ?? parent?.lookupSetter(name, charOffset, fileUri);
   }

   bool hasLocalLabel(String name) => labels != null && labels.containsKey(name);

   void declareLabel(String name, Builder target) {
     if (isModifiable) {
       labels ??= <String, Builder>{};
       labels[name] = target;
     } else {
       internalProblem(
           messageInternalProblemExtendingUnmodifiableScope, -1, null);
     }
   }

   void forwardDeclareLabel(String name, Builder target) {
     declareLabel(name, target);
     forwardDeclaredLabels ??= <String, Builder>{};
     forwardDeclaredLabels[name] = target;
   }

   bool claimLabel(String name) {
     if (forwardDeclaredLabels == null ||
         forwardDeclaredLabels.remove(name) == null) return false;
     if (forwardDeclaredLabels.length == 0) {
       forwardDeclaredLabels = null;
     }
     return true;
   }

   Map<String, Builder> get unclaimedForwardDeclarations {
     return forwardDeclaredLabels;
   }

   Builder lookupLabel(String name) {
     return (labels == null ? null : labels[name]) ?? parent?.lookupLabel(name);
   }

   /// Declares that the meaning of [name] in this scope is [builder].
   ///
   /// If name was used previously in this scope, this method returns a message
   /// that can be used as context for reporting a compile-time error about
   /// [name] being used before its declared. [fileUri] is used to bind the
   /// location of this message.
   LocatedMessage declare(String name, Builder builder, Uri fileUri) {
     if (isModifiable) {
       if (usedNames?.containsKey(name) ?? false) {
         return templateDuplicatedNamePreviouslyUsedCause
             .withArguments(name)
             .withLocation(fileUri, usedNames[name], name.length);
       }
       local[name] = builder;
     } else {
       internalProblem(
           messageInternalProblemExtendingUnmodifiableScope, -1, null);
     }
     return null;
   }

   /// Adds [builder] to the extensions in this scope.
   void addExtension(ExtensionBuilder builder) {
     _extensions ??= [];
     _extensions.add(builder);
   }

   /// Calls [f] for each extension in this scope and parent scopes.
   void forEachExtension(void Function(ExtensionBuilder) f) {
     _extensions?.forEach(f);
     parent?.forEachExtension(f);
   }

   void merge(
       Scope scope,
       Builder computeAmbiguousDeclaration(
           String name, Builder existing, Builder member)) {
     Map<String, Builder> map = local;

     void mergeMember(String name, Builder member) {
       Builder existing = map[name];
       if (existing != null) {
         if (existing != member) {
           member = computeAmbiguousDeclaration(name, existing, member);
         }
       }
       map[name] = member;
     }

     scope.local.forEach(mergeMember);
     map = setters;
     scope.setters.forEach(mergeMember);
   }

   void forEach(f(String name, Builder member)) {
     local.forEach(f);
     setters.forEach(f);
   }

   String get debugString {
     StringBuffer buffer = new StringBuffer();
     int nestingLevel = writeOn(buffer);
     for (int i = nestingLevel; i >= 0; i--) {
       buffer.writeln("${'  ' * i}}");
     }
     return "$buffer";
   }

   int writeOn(StringSink sink) {
     int nestingLevel = (parent?.writeOn(sink) ?? -1) + 1;
     String indent = "  " * nestingLevel;
     sink.writeln("$indent{");
     local.forEach((String name, Builder member) {
       sink.writeln("$indent  $name");
     });
     setters.forEach((String name, Builder member) {
       sink.writeln("$indent  $name=");
     });
     return nestingLevel;
   }

   Scope computeMixinScope() {
     List<String> names = this.local.keys.toList();
     Map<String, Builder> local = <String, Builder>{};
     bool needsCopy = false;
     for (int i = 0; i < names.length; i++) {
       String name = names[i];
       Builder declaration = this.local[name];
       if (declaration.isStatic) {
         needsCopy = true;
       } else {
         local[name] = declaration;
       }
     }
     names = this.setters.keys.toList();
     Map<String, Builder> setters = <String, Builder>{};
     for (int i = 0; i < names.length; i++) {
       String name = names[i];
       Builder declaration = this.setters[name];
       if (declaration.isStatic) {
         needsCopy = true;
       } else {
         setters[name] = declaration;
       }
     }
     return needsCopy
         ? new Scope(
             local: local,
             setters: setters,
             extensions: _extensions,
             parent: parent,
             debugName: classNameOrDebugName,
             isModifiable: isModifiable)
         : this;
   }
 }

 class ScopeBuilder {
   final Scope scope;

   ScopeBuilder(this.scope);

   void addMember(String name, Builder builder) {
     scope.local[name] = builder;
   }

   void addSetter(String name, Builder builder) {
     scope.setters[name] = builder;
   }

   void addExtension(ExtensionBuilder builder) {
     scope.addExtension(builder);
   }

   Builder operator [](String name) => scope.local[name];
 }

 abstract class ProblemBuilder extends Builder {
   final String name;

   final Builder builder;

   final int charOffset;

   final Uri fileUri;

   ProblemBuilder(this.name, this.builder, this.charOffset, this.fileUri);

   get target => null;

   bool get hasProblem => true;

   Message get message;

   @override
   String get fullNameForErrors => name;
 }

 /// Represents a [builder] that's being accessed incorrectly. For example, an
 /// attempt to write to a final field, or to read from a setter.
 class AccessErrorBuilder extends ProblemBuilder {
   AccessErrorBuilder(String name, Builder builder, int charOffset, Uri fileUri)
       : super(name, builder, charOffset, fileUri);

   @override
   Builder get parent => builder;

   @override
   bool get isFinal => builder.isFinal;

   @override
   bool get isField => builder.isField;

   @override
   bool get isRegularMethod => builder.isRegularMethod;

   @override
   bool get isGetter => !builder.isGetter;

   @override
   bool get isSetter => !builder.isSetter;

   @override
   bool get isDeclarationInstanceMember => builder.isDeclarationInstanceMember;

   @override
   bool get isClassInstanceMember => builder.isClassInstanceMember;

   @override
   bool get isExtensionInstanceMember => builder.isExtensionInstanceMember;

   @override
   bool get isStatic => builder.isStatic;

   @override
   bool get isTopLevel => builder.isTopLevel;

   @override
   bool get isTypeDeclaration => builder.isTypeDeclaration;

   @override
   bool get isLocal => builder.isLocal;

   @override
   Message get message => templateAccessError.withArguments(name);
 }

 class AmbiguousBuilder extends ProblemBuilder {
   AmbiguousBuilder(String name, Builder builder, int charOffset, Uri fileUri)
       : super(name, builder, charOffset, fileUri);

   @override
   Builder get parent => null;

   @override
   Message get message => templateDuplicatedDeclarationUse.withArguments(name);

   // TODO(ahe): Also provide context.

   Builder getFirstDeclaration() {
     Builder declaration = builder;
     while (declaration.next != null) {
       declaration = declaration.next;
     }
     return declaration;
   }
 }

 class ScopeLocalDeclarationIterator implements Iterator<Builder> {
   Iterator<Builder> local;
   final Iterator<Builder> setters;

   @override
   Builder current;

   ScopeLocalDeclarationIterator(Scope scope)
       : local = scope.local.values.iterator,
         setters = scope.setters.values.iterator;

   @override
   bool moveNext() {
     Builder next = current?.next;
     if (next != null) {
       current = next;
       return true;
     }
     if (local != null) {
       if (local.moveNext()) {
         current = local.current;
         return true;
       }
       local = null;
     }
     if (setters.moveNext()) {
       current = setters.current;
       return true;
     } else {
       current = null;
       return false;
     }
   }
 }

 class ScopeLocalDeclarationNameIterator extends ScopeLocalDeclarationIterator
     implements NameIterator {
   Iterator<String> localNames;
   final Iterator<String> setterNames;

   @override
   String name;

   ScopeLocalDeclarationNameIterator(Scope scope)
       : localNames = scope.local.keys.iterator,
         setterNames = scope.setters.keys.iterator,
         super(scope);

   @override
   bool moveNext() {
     Builder next = current?.next;
     if (next != null) {
       current = next;
       return true;
     }
     if (local != null) {
       if (local.moveNext()) {
         localNames.moveNext();
         current = local.current;
         name = localNames.current;
         return true;
       }
       localNames = null;
     }
     if (setters.moveNext()) {
       setterNames.moveNext();
       current = setters.current;
       name = setterNames.current;
       return true;
     } else {
       current = null;
       return false;
     }
   }
 }
	// Copyright (c) 2016, 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.

	library fasta.scope;

	import 'builder/builder.dart' show Builder, NameIterator, TypeVariableBuilder;

	import 'builder/extension_builder.dart';

	import 'fasta_codes.dart'
	show
	LocatedMessage,
	Message,
	messageInternalProblemExtendingUnmodifiableScope,
	templateAccessError,
	templateDuplicatedDeclarationUse,
	templateDuplicatedNamePreviouslyUsedCause;

	import 'problems.dart' show internalProblem, unsupported;

	class MutableScope {
	/// Names declared in this scope.
	Map<String, Builder> local;

	/// Setters declared in this scope.
	Map<String, Builder> setters;

	/// The extensions declared in this scope.
	///
	/// This includes all available extensions even if the extensions are not
	/// accessible by name because of duplicate imports.
	///
	/// For instance:
	///
	/// lib1.dart:
	/// extension Extension on String {
	/// method1() {}
	/// staticMethod1() {}
	/// }
	/// lib2.dart:
	/// extension Extension on String {
	/// method2() {}
	/// staticMethod2() {}
	/// }
	/// main.dart:
	/// import 'lib1.dart';
	/// import 'lib2.dart';
	///
	/// main() {
	/// 'foo'.method1(); // This method is available.
	/// 'foo'.method2(); // This method is available.
	/// // These methods are not available because Extension is ambiguous:
	/// Extension.staticMethod1();
	/// Extension.staticMethod2();
	/// }
	///
	List<ExtensionBuilder> _extensions;

	/// The scope that this scope is nested within, or `null` if this is the top
	/// level scope.
	Scope parent;

	final String classNameOrDebugName;

	MutableScope(this.local, this.setters, this._extensions, this.parent,
	this.classNameOrDebugName) {
	assert(classNameOrDebugName != null);
	}

	String toString() => "Scope($classNameOrDebugName, ${local.keys})";
	}

	class Scope extends MutableScope {
	/// Indicates whether an attempt to declare new names in this scope should
	/// succeed.
	final bool isModifiable;

	Map<String, Builder> labels;

	Map<String, Builder> forwardDeclaredLabels;

	Map<String, int> usedNames;

	Scope(
	{Map<String, Builder> local,
	Map<String, Builder> setters,
	List<ExtensionBuilder> extensions,
	Scope parent,
	String debugName,
	this.isModifiable: true})
	: super(local, setters = setters ?? const <String, Builder>{}, extensions,
	parent, debugName);

	Scope.top({bool isModifiable: false})
	: this(
	local: <String, Builder>{},
	setters: <String, Builder>{},
	debugName: "top",
	isModifiable: isModifiable);

	Scope.immutable()
	: this(
	local: const <String, Builder>{},
	setters: const <String, Builder>{},
	debugName: "immutable",
	isModifiable: false);

	Scope.nested(Scope parent, String debugName, {bool isModifiable: true})
	: this(
	local: <String, Builder>{},
	setters: <String, Builder>{},
	parent: parent,
	debugName: debugName,
	isModifiable: isModifiable);

	Iterator<Builder> get iterator {
	return new ScopeLocalDeclarationIterator(this);
	}

	NameIterator get nameIterator {
	return new ScopeLocalDeclarationNameIterator(this);
	}

	Scope copyWithParent(Scope parent, String debugName) {
	return new Scope(
	local: super.local,
	setters: super.setters,
	extensions: _extensions,
	parent: parent,
	debugName: debugName,
	isModifiable: isModifiable);
	}

	/// Don't use this. Use [becomePartOf] instead.
	void set local(_) => unsupported("local=", -1, null);

	/// Don't use this. Use [becomePartOf] instead.
	void set setters(_) => unsupported("setters=", -1, null);

	/// Don't use this. Use [becomePartOf] instead.
	void set parent(_) => unsupported("parent=", -1, null);

	/// This scope becomes equivalent to [scope]. This is used for parts to
	/// become part of their library's scope.
	void becomePartOf(Scope scope) {
	assert(parent.parent == null);
	assert(scope.parent.parent == null);
	super.local = scope.local;
	super.setters = scope.setters;
	super.parent = scope.parent;
	super._extensions = scope._extensions;
	}

	Scope createNestedScope(String debugName, {bool isModifiable: true}) {
	return new Scope.nested(this, debugName, isModifiable: isModifiable);
	}

	Scope withTypeVariables(List<TypeVariableBuilder> typeVariables) {
	if (typeVariables == null) return this;
	Scope newScope =
	new Scope.nested(this, "type variables", isModifiable: false);
	for (TypeVariableBuilder t in typeVariables) {
	newScope.local[t.name] = t;
	}
	return newScope;
	}

	/// Create a special scope for use by labeled statements. This scope doesn't
	/// introduce a new scope for local variables, only for labels. This deals
	/// with corner cases like this:
	///
	/// L: var x;
	/// x = 42;
	/// print("The answer is $x.");
	Scope createNestedLabelScope() {
	return new Scope(
	local: local,
	setters: setters,
	extensions: _extensions,
	parent: parent,
	debugName: "label",
	isModifiable: true);
	}

	void recordUse(String name, int charOffset, Uri fileUri) {
	if (isModifiable) {
	usedNames ??= <String, int>{};
	usedNames.putIfAbsent(name, () => charOffset);
	}
	}

	Builder lookupIn(String name, int charOffset, Uri fileUri,
	Map<String, Builder> map, bool isInstanceScope) {
	Builder builder = map[name];
	if (builder == null) return null;
	if (builder.next != null) {
	return new AmbiguousBuilder(name.isEmpty ? classNameOrDebugName : name,
	builder, charOffset, fileUri);
	} else if (!isInstanceScope && builder.isDeclarationInstanceMember) {
	return null;
	} else {
	return builder;
	}
	}

	Builder lookup(String name, int charOffset, Uri fileUri,
	{bool isInstanceScope: true}) {
	recordUse(name, charOffset, fileUri);
	Builder builder =
	lookupIn(name, charOffset, fileUri, local, isInstanceScope);
	if (builder != null) return builder;
	builder = lookupIn(name, charOffset, fileUri, setters, isInstanceScope);
	if (builder != null && !builder.hasProblem) {
	return new AccessErrorBuilder(name, builder, charOffset, fileUri);
	}
	if (!isInstanceScope) {
	// For static lookup, do not search the parent scope.
	return builder;
	}
	return builder ?? parent?.lookup(name, charOffset, fileUri);
	}

	Builder lookupSetter(String name, int charOffset, Uri fileUri,
	{bool isInstanceScope: true}) {
	recordUse(name, charOffset, fileUri);
	Builder builder =
	lookupIn(name, charOffset, fileUri, setters, isInstanceScope);
	if (builder != null) return builder;
	builder = lookupIn(name, charOffset, fileUri, local, isInstanceScope);
	if (builder != null && !builder.hasProblem) {
	return new AccessErrorBuilder(name, builder, charOffset, fileUri);
	}
	if (!isInstanceScope) {
	// For static lookup, do not search the parent scope.
	return builder;
	}
	return builder ?? parent?.lookupSetter(name, charOffset, fileUri);
	}

	bool hasLocalLabel(String name) => labels != null && labels.containsKey(name);

	void declareLabel(String name, Builder target) {
	if (isModifiable) {
	labels ??= <String, Builder>{};
	labels[name] = target;
	} else {
	internalProblem(
	messageInternalProblemExtendingUnmodifiableScope, -1, null);
	}
	}

	void forwardDeclareLabel(String name, Builder target) {
	declareLabel(name, target);
	forwardDeclaredLabels ??= <String, Builder>{};
	forwardDeclaredLabels[name] = target;
	}

	bool claimLabel(String name) {
	if (forwardDeclaredLabels == null \|\|
	forwardDeclaredLabels.remove(name) == null) return false;
	if (forwardDeclaredLabels.length == 0) {
	forwardDeclaredLabels = null;
	}
	return true;
	}

	Map<String, Builder> get unclaimedForwardDeclarations {
	return forwardDeclaredLabels;
	}

	Builder lookupLabel(String name) {
	return (labels == null ? null : labels[name]) ?? parent?.lookupLabel(name);
	}

	/// Declares that the meaning of [name] in this scope is [builder].
	///
	/// If name was used previously in this scope, this method returns a message
	/// that can be used as context for reporting a compile-time error about
	/// [name] being used before its declared. [fileUri] is used to bind the
	/// location of this message.
	LocatedMessage declare(String name, Builder builder, Uri fileUri) {
	if (isModifiable) {
	if (usedNames?.containsKey(name) ?? false) {
	return templateDuplicatedNamePreviouslyUsedCause
	.withArguments(name)
	.withLocation(fileUri, usedNames[name], name.length);
	}
	local[name] = builder;
	} else {
	internalProblem(
	messageInternalProblemExtendingUnmodifiableScope, -1, null);
	}
	return null;
	}

	/// Adds [builder] to the extensions in this scope.
	void addExtension(ExtensionBuilder builder) {
	_extensions ??= [];
	_extensions.add(builder);
	}

	/// Calls [f] for each extension in this scope and parent scopes.
	void forEachExtension(void Function(ExtensionBuilder) f) {
	_extensions?.forEach(f);
	parent?.forEachExtension(f);
	}

	void merge(
	Scope scope,
	Builder computeAmbiguousDeclaration(
	String name, Builder existing, Builder member)) {
	Map<String, Builder> map = local;

	void mergeMember(String name, Builder member) {
	Builder existing = map[name];
	if (existing != null) {
	if (existing != member) {
	member = computeAmbiguousDeclaration(name, existing, member);
	}
	}
	map[name] = member;
	}

	scope.local.forEach(mergeMember);
	map = setters;
	scope.setters.forEach(mergeMember);
	}

	void forEach(f(String name, Builder member)) {
	local.forEach(f);
	setters.forEach(f);
	}

	String get debugString {
	StringBuffer buffer = new StringBuffer();
	int nestingLevel = writeOn(buffer);
	for (int i = nestingLevel; i >= 0; i--) {
	buffer.writeln("${' ' * i}}");
	}
	return "$buffer";
	}

	int writeOn(StringSink sink) {
	int nestingLevel = (parent?.writeOn(sink) ?? -1) + 1;
	String indent = " " * nestingLevel;
	sink.writeln("$indent{");
	local.forEach((String name, Builder member) {
	sink.writeln("$indent $name");
	});
	setters.forEach((String name, Builder member) {
	sink.writeln("$indent $name=");
	});
	return nestingLevel;
	}

	Scope computeMixinScope() {
	List<String> names = this.local.keys.toList();
	Map<String, Builder> local = <String, Builder>{};
	bool needsCopy = false;
	for (int i = 0; i < names.length; i++) {
	String name = names[i];
	Builder declaration = this.local[name];
	if (declaration.isStatic) {
	needsCopy = true;
	} else {
	local[name] = declaration;
	}
	}
	names = this.setters.keys.toList();
	Map<String, Builder> setters = <String, Builder>{};
	for (int i = 0; i < names.length; i++) {
	String name = names[i];
	Builder declaration = this.setters[name];
	if (declaration.isStatic) {
	needsCopy = true;
	} else {
	setters[name] = declaration;
	}
	}
	return needsCopy
	? new Scope(
	local: local,
	setters: setters,
	extensions: _extensions,
	parent: parent,
	debugName: classNameOrDebugName,
	isModifiable: isModifiable)
	: this;
	}
	}

	class ScopeBuilder {
	final Scope scope;

	ScopeBuilder(this.scope);

	void addMember(String name, Builder builder) {
	scope.local[name] = builder;
	}

	void addSetter(String name, Builder builder) {
	scope.setters[name] = builder;
	}

	void addExtension(ExtensionBuilder builder) {
	scope.addExtension(builder);
	}

	Builder operator [](String name) => scope.local[name];
	}

	abstract class ProblemBuilder extends Builder {
	final String name;

	final Builder builder;

	final int charOffset;

	final Uri fileUri;

	ProblemBuilder(this.name, this.builder, this.charOffset, this.fileUri);

	get target => null;

	bool get hasProblem => true;

	Message get message;

	@override
	String get fullNameForErrors => name;
	}

	/// Represents a [builder] that's being accessed incorrectly. For example, an
	/// attempt to write to a final field, or to read from a setter.
	class AccessErrorBuilder extends ProblemBuilder {
	AccessErrorBuilder(String name, Builder builder, int charOffset, Uri fileUri)
	: super(name, builder, charOffset, fileUri);

	@override
	Builder get parent => builder;

	@override
	bool get isFinal => builder.isFinal;

	@override
	bool get isField => builder.isField;

	@override
	bool get isRegularMethod => builder.isRegularMethod;

	@override
	bool get isGetter => !builder.isGetter;

	@override
	bool get isSetter => !builder.isSetter;

	@override
	bool get isDeclarationInstanceMember => builder.isDeclarationInstanceMember;

	@override
	bool get isClassInstanceMember => builder.isClassInstanceMember;

	@override
	bool get isExtensionInstanceMember => builder.isExtensionInstanceMember;

	@override
	bool get isStatic => builder.isStatic;

	@override
	bool get isTopLevel => builder.isTopLevel;

	@override
	bool get isTypeDeclaration => builder.isTypeDeclaration;

	@override
	bool get isLocal => builder.isLocal;

	@override
	Message get message => templateAccessError.withArguments(name);
	}

	class AmbiguousBuilder extends ProblemBuilder {
	AmbiguousBuilder(String name, Builder builder, int charOffset, Uri fileUri)
	: super(name, builder, charOffset, fileUri);

	@override
	Builder get parent => null;

	@override
	Message get message => templateDuplicatedDeclarationUse.withArguments(name);

	// TODO(ahe): Also provide context.

	Builder getFirstDeclaration() {
	Builder declaration = builder;
	while (declaration.next != null) {
	declaration = declaration.next;
	}
	return declaration;
	}
	}

	class ScopeLocalDeclarationIterator implements Iterator<Builder> {
	Iterator<Builder> local;
	final Iterator<Builder> setters;

	@override
	Builder current;

	ScopeLocalDeclarationIterator(Scope scope)
	: local = scope.local.values.iterator,
	setters = scope.setters.values.iterator;

	@override
	bool moveNext() {
	Builder next = current?.next;
	if (next != null) {
	current = next;
	return true;
	}
	if (local != null) {
	if (local.moveNext()) {
	current = local.current;
	return true;
	}
	local = null;
	}
	if (setters.moveNext()) {
	current = setters.current;
	return true;
	} else {
	current = null;
	return false;
	}
	}
	}

	class ScopeLocalDeclarationNameIterator extends ScopeLocalDeclarationIterator
	implements NameIterator {
	Iterator<String> localNames;
	final Iterator<String> setterNames;

	@override
	String name;

	ScopeLocalDeclarationNameIterator(Scope scope)
	: localNames = scope.local.keys.iterator,
	setterNames = scope.setters.keys.iterator,
	super(scope);

	@override
	bool moveNext() {
	Builder next = current?.next;
	if (next != null) {
	current = next;
	return true;
	}
	if (local != null) {
	if (local.moveNext()) {
	localNames.moveNext();
	current = local.current;
	name = localNames.current;
	return true;
	}
	localNames = null;
	}
	if (setters.moveNext()) {
	setterNames.moveNext();
	current = setters.current;
	name = setterNames.current;
	return true;
	} else {
	current = null;
	return false;
	}
	}
	}