pkg/kernel/lib/verifier.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 kernel.checks;

 import 'ast.dart';
 import 'transformations/flags.dart';

 void verifyProgram(Program program) {
   VerifyingVisitor.check(program);
 }

 class VerificationError {
   final TreeNode context;

   final TreeNode node;

   final String details;

   VerificationError(this.context, this.node, this.details);

   toString() {
     Location location;
     try {
       location = node?.location ?? context?.location;
     } catch (_) {
       // TODO(ahe): Fix the compiler instead.
     }
     if (location != null) {
       String file = location.file ?? "";
       return "$file:${location.line}:${location.column}: Verification error:"
           " $details";
     } else {
       return "Verification error: $details\n"
           "Context: '$context'.\n"
           "Node: '$node'.";
     }
   }
 }

 enum TypedefState { Done, BeingChecked }

 /// Checks that a kernel program is well-formed.
 ///
 /// This does not include any kind of type checking.
 class VerifyingVisitor extends RecursiveVisitor {
   final Set<Class> classes = new Set<Class>();
   final Set<Typedef> typedefs = new Set<Typedef>();
   Set<TypeParameter> typeParametersInScope = new Set<TypeParameter>();
   final List<VariableDeclaration> variableStack = <VariableDeclaration>[];
   final Map<Typedef, TypedefState> typedefState = <Typedef, TypedefState>{};
   bool classTypeParametersAreInScope = false;

   /// If true, relax certain checks for *outline* mode. For example, don't
   /// attempt to validate constructor initializers.
   bool isOutline = false;

   bool inCatchBlock = false;

   Library currentLibrary;

   Member currentMember;

   Class currentClass;

   TreeNode currentParent;

   TreeNode get context => currentMember ?? currentClass;

   static void check(Program program) {
     program.accept(new VerifyingVisitor());
   }

   defaultTreeNode(TreeNode node) {
     visitChildren(node);
   }

   problem(TreeNode node, String details, {TreeNode context}) {
     context ??= this.context;
     throw new VerificationError(context, node, details);
   }

   TreeNode enterParent(TreeNode node) {
     if (!identical(node.parent, currentParent)) {
       problem(
           node,
           "Incorrect parent pointer on ${node.runtimeType}:"
           " expected '${currentParent.runtimeType}',"
           " but found: '${node.parent.runtimeType}'.");
     }
     var oldParent = currentParent;
     currentParent = node;
     return oldParent;
   }

   void exitParent(TreeNode oldParent) {
     currentParent = oldParent;
   }

   int enterLocalScope() => variableStack.length;

   void exitLocalScope(int stackHeight) {
     for (int i = stackHeight; i < variableStack.length; ++i) {
       undeclareVariable(variableStack[i]);
     }
     variableStack.length = stackHeight;
   }

   void visitChildren(TreeNode node) {
     var oldParent = enterParent(node);
     node.visitChildren(this);
     exitParent(oldParent);
   }

   void visitWithLocalScope(TreeNode node) {
     int stackHeight = enterLocalScope();
     visitChildren(node);
     exitLocalScope(stackHeight);
   }

   void declareMember(Member member) {
     if (member.transformerFlags & TransformerFlag.seenByVerifier != 0) {
       problem(member.function,
           "Member '$member' has been declared more than once.");
     }
     member.transformerFlags |= TransformerFlag.seenByVerifier;
   }

   void undeclareMember(Member member) {
     member.transformerFlags &= ~TransformerFlag.seenByVerifier;
   }

   void declareVariable(VariableDeclaration variable) {
     if (variable.flags & VariableDeclaration.FlagInScope != 0) {
       problem(variable, "Variable '$variable' declared more than once.");
     }
     variable.flags |= VariableDeclaration.FlagInScope;
     variableStack.add(variable);
   }

   void undeclareVariable(VariableDeclaration variable) {
     variable.flags &= ~VariableDeclaration.FlagInScope;
   }

   void declareTypeParameters(List<TypeParameter> parameters) {
     for (int i = 0; i < parameters.length; ++i) {
       var parameter = parameters[i];
       if (parameter.bound == null) {
         problem(
             currentParent, "Missing bound for type parameter '$parameter'.");
       }
       if (!typeParametersInScope.add(parameter)) {
         problem(parameter, "Type parameter '$parameter' redeclared.");
       }
     }
   }

   void undeclareTypeParameters(List<TypeParameter> parameters) {
     typeParametersInScope.removeAll(parameters);
   }

   void checkVariableInScope(VariableDeclaration variable, TreeNode where) {
     if (variable.flags & VariableDeclaration.FlagInScope == 0) {
       problem(where, "Variable '$variable' used out of scope.");
     }
   }

   visitProgram(Program program) {
     try {
       for (var library in program.libraries) {
         for (var class_ in library.classes) {
           if (!classes.add(class_)) {
             problem(class_, "Class '$class_' declared more than once.");
           }
         }
         for (var typedef_ in library.typedefs) {
           if (!typedefs.add(typedef_)) {
             problem(typedef_, "Typedef '$typedef_' declared more than once.");
           }
         }
         library.members.forEach(declareMember);
         for (var class_ in library.classes) {
           class_.members.forEach(declareMember);
         }
       }
       visitChildren(program);
     } finally {
       for (var library in program.libraries) {
         library.members.forEach(undeclareMember);
         for (var class_ in library.classes) {
           class_.members.forEach(undeclareMember);
         }
       }
       variableStack.forEach(undeclareVariable);
     }
   }

   void visitLibrary(Library node) {
     currentLibrary = node;
     super.visitLibrary(node);
     currentLibrary = null;
   }

   void checkTypedef(Typedef node) {
     var state = typedefState[node];
     if (state == TypedefState.Done) return;
     if (state == TypedefState.BeingChecked) {
       problem(node, "The typedef '$node' refers to itself", context: node);
     }
     assert(state == null);
     typedefState[node] = TypedefState.BeingChecked;
     var savedTypeParameters = typeParametersInScope;
     typeParametersInScope = node.typeParameters.toSet();
     var savedParent = currentParent;
     currentParent = node;
     // Visit children without checking the parent pointer on the typedef itself
     // since this can be called from a context other than its true parent.
     node.visitChildren(this);
     currentParent = savedParent;
     typeParametersInScope = savedTypeParameters;
     typedefState[node] = TypedefState.Done;
   }

   visitTypedef(Typedef node) {
     checkTypedef(node);
     // Enter and exit the node to check the parent pointer on the typedef node.
     exitParent(enterParent(node));
   }

   visitField(Field node) {
     currentMember = node;
     var oldParent = enterParent(node);
     bool isTopLevel = node.parent == currentLibrary;
     if (isTopLevel && !node.isStatic) {
       problem(node, "The top-level field '${node.name.name}' should be static",
           context: node);
     }
     if (node.isConst && !node.isStatic) {
       problem(node, "The const field '${node.name.name}' should be static",
           context: node);
     }
     classTypeParametersAreInScope = !node.isStatic;
     node.initializer?.accept(this);
     node.type.accept(this);
     classTypeParametersAreInScope = false;
     visitList(node.annotations, this);
     exitParent(oldParent);
     currentMember = null;
   }

   visitProcedure(Procedure node) {
     currentMember = node;
     var oldParent = enterParent(node);
     classTypeParametersAreInScope = !node.isStatic;
     node.function.accept(this);
     classTypeParametersAreInScope = false;
     visitList(node.annotations, this);
     exitParent(oldParent);
     currentMember = null;
   }

   visitConstructor(Constructor node) {
     currentMember = node;
     classTypeParametersAreInScope = true;
     // The constructor member needs special treatment due to parameters being
     // in scope in the initializer list.
     var oldParent = enterParent(node);
     int stackHeight = enterLocalScope();
     visitChildren(node.function);
     visitList(node.initializers, this);
     if (!isOutline) {
       checkInitializers(node);
     }
     exitLocalScope(stackHeight);
     classTypeParametersAreInScope = false;
     visitList(node.annotations, this);
     exitParent(oldParent);
     classTypeParametersAreInScope = false;
     currentMember = null;
   }

   visitClass(Class node) {
     currentClass = node;
     declareTypeParameters(node.typeParameters);
     var oldParent = enterParent(node);
     classTypeParametersAreInScope = false;
     visitList(node.annotations, this);
     classTypeParametersAreInScope = true;
     visitList(node.typeParameters, this);
     visitList(node.fields, this);
     visitList(node.constructors, this);
     visitList(node.procedures, this);
     exitParent(oldParent);
     undeclareTypeParameters(node.typeParameters);
     currentClass = null;
   }

   visitFunctionNode(FunctionNode node) {
     declareTypeParameters(node.typeParameters);
     bool savedInCatchBlock = inCatchBlock;
     inCatchBlock = false;
     visitWithLocalScope(node);
     inCatchBlock = savedInCatchBlock;
     undeclareTypeParameters(node.typeParameters);
   }

   visitFunctionType(FunctionType node) {
     for (int i = 1; i < node.namedParameters.length; ++i) {
       if (node.namedParameters[i - 1].compareTo(node.namedParameters[i]) >= 0) {
         problem(currentParent,
             "Named parameters are not sorted on function type ($node).");
       }
     }
     declareTypeParameters(node.typeParameters);
     for (var typeParameter in node.typeParameters) {
       typeParameter.bound?.accept(this);
     }
     visitList(node.positionalParameters, this);
     visitList(node.namedParameters, this);
     node.returnType.accept(this);
     undeclareTypeParameters(node.typeParameters);
   }

   visitBlock(Block node) {
     visitWithLocalScope(node);
   }

   visitForStatement(ForStatement node) {
     visitWithLocalScope(node);
   }

   visitForInStatement(ForInStatement node) {
     visitWithLocalScope(node);
   }

   visitLet(Let node) {
     visitWithLocalScope(node);
   }

   visitCatch(Catch node) {
     bool savedInCatchBlock = inCatchBlock;
     inCatchBlock = true;
     visitWithLocalScope(node);
     inCatchBlock = savedInCatchBlock;
   }

   @override
   visitRethrow(Rethrow node) {
     if (!inCatchBlock) {
       problem(node, "Rethrow must be inside a Catch block.");
     }
   }

   visitVariableDeclaration(VariableDeclaration node) {
     var parent = node.parent;
     if (parent is! Block &&
         !(parent is Catch && parent.body != node) &&
         !(parent is FunctionNode && parent.body != node) &&
         parent is! FunctionDeclaration &&
         !(parent is ForStatement && parent.body != node) &&
         !(parent is ForInStatement && parent.body != node) &&
         parent is! Let &&
         parent is! LocalInitializer) {
       problem(
           node,
           "VariableDeclaration must be a direct child of a Block, "
           "not ${parent.runtimeType}.");
     }
     visitChildren(node);
     declareVariable(node);
   }

   visitVariableGet(VariableGet node) {
     checkVariableInScope(node.variable, node);
     visitChildren(node);
   }

   visitVariableSet(VariableSet node) {
     checkVariableInScope(node.variable, node);
     visitChildren(node);
   }

   @override
   visitStaticGet(StaticGet node) {
     visitChildren(node);
     if (node.target == null) {
       problem(node, "StaticGet without target.");
     }
     // Currently Constructor.hasGetter returns `false` even though fasta uses it
     // as a getter for internal purposes:
     //
     // Fasta is letting all call site of a redirecting constructor be resolved
     // to the real target.  In order to resolve it, it seems to add a body into
     // the redirecting-factory constructor which caches the target constructor.
     // That cache is via a `StaticGet(real-constructor)` node, which we make
     // here pass the verifier.
     if (!node.target.hasGetter && node.target is! Constructor) {
       problem(node, "StaticGet of '${node.target}' without getter.");
     }
     if (node.target.isInstanceMember) {
       problem(node, "StaticGet of '${node.target}' that's an instance member.");
     }
   }

   @override
   visitStaticSet(StaticSet node) {
     visitChildren(node);
     if (node.target == null) {
       problem(node, "StaticSet without target.");
     }
     if (!node.target.hasSetter) {
       problem(node, "StaticSet to '${node.target}' without setter.");
     }
     if (node.target.isInstanceMember) {
       problem(node, "StaticSet to '${node.target}' that's an instance member.");
     }
   }

   @override
   visitStaticInvocation(StaticInvocation node) {
     checkTargetedInvocation(node.target, node);
     if (node.target.isInstanceMember) {
       problem(node,
           "StaticInvocation of '${node.target}' that's an instance member.");
     }
     if (node.isConst &&
         (!node.target.isConst ||
             !node.target.isExternal ||
             node.target.kind != ProcedureKind.Factory)) {
       problem(
           node,
           "Constant StaticInvocation of '${node.target}' that isn't"
           " a const external factory.");
     }
   }

   void checkTargetedInvocation(Member target, InvocationExpression node) {
     visitChildren(node);
     if (target == null) {
       problem(node, "${node.runtimeType} without target.");
     }
     if (target.function == null) {
       problem(node, "${node.runtimeType} without function.");
     }
     if (!areArgumentsCompatible(node.arguments, target.function)) {
       problem(node,
           "${node.runtimeType} with incompatible arguments for '${target}'.");
     }
     int expectedTypeParameters = target is Constructor
         ? target.enclosingClass.typeParameters.length
         : target.function.typeParameters.length;
     if (node.arguments.types.length != expectedTypeParameters) {
       problem(
           node,
           "${node.runtimeType} with wrong number of type arguments"
           " for '${target}'.");
     }
   }

   @override
   visitDirectPropertyGet(DirectPropertyGet node) {
     visitChildren(node);
     if (node.target == null) {
       problem(node, "DirectPropertyGet without target.");
     }
     if (!node.target.hasGetter) {
       problem(node, "DirectPropertyGet of '${node.target}' without getter.");
     }
     if (!node.target.isInstanceMember) {
       problem(
           node,
           "DirectPropertyGet of '${node.target}' that isn't an"
           " instance member.");
     }
   }

   @override
   visitDirectPropertySet(DirectPropertySet node) {
     visitChildren(node);
     if (node.target == null) {
       problem(node, "DirectPropertySet without target.");
     }
     if (!node.target.hasSetter) {
       problem(node, "DirectPropertySet of '${node.target}' without setter.");
     }
     if (!node.target.isInstanceMember) {
       problem(node, "DirectPropertySet of '${node.target}' that is static.");
     }
   }

   @override
   visitDirectMethodInvocation(DirectMethodInvocation node) {
     checkTargetedInvocation(node.target, node);
     if (node.receiver == null) {
       problem(node, "DirectMethodInvocation without receiver.");
     }
   }

   @override
   visitConstructorInvocation(ConstructorInvocation node) {
     checkTargetedInvocation(node.target, node);
     if (node.target.enclosingClass.isAbstract) {
       problem(node, "ConstructorInvocation of abstract class.");
     }
     if (node.isConst && !node.target.isConst) {
       problem(
           node,
           "Constant ConstructorInvocation fo '${node.target}' that"
           " isn't const.");
     }
   }

   bool areArgumentsCompatible(Arguments arguments, FunctionNode function) {
     if (arguments.positional.length < function.requiredParameterCount) {
       return false;
     }
     if (arguments.positional.length > function.positionalParameters.length) {
       return false;
     }
     namedLoop:
     for (int i = 0; i < arguments.named.length; ++i) {
       var argument = arguments.named[i];
       String name = argument.name;
       for (int j = 0; j < function.namedParameters.length; ++j) {
         if (function.namedParameters[j].name == name) continue namedLoop;
       }
       return false;
     }
     return true;
   }

   @override
   visitContinueSwitchStatement(ContinueSwitchStatement node) {
     if (node.target == null) {
       problem(node, "No target.");
     } else if (node.target.parent == null) {
       problem(node, "Target has no parent.");
     } else {
       SwitchStatement statement = node.target.parent;
       for (SwitchCase switchCase in statement.cases) {
         if (switchCase == node.target) return;
       }
       problem(node, "Switch case isn't child of parent.");
     }
   }

   @override
   defaultMemberReference(Member node) {
     if (node.transformerFlags & TransformerFlag.seenByVerifier == 0) {
       problem(
           node, "Dangling reference to '$node', parent is: '${node.parent}'.");
     }
   }

   @override
   visitClassReference(Class node) {
     if (!classes.contains(node)) {
       problem(
           node, "Dangling reference to '$node', parent is: '${node.parent}'.");
     }
   }

   @override
   visitTypedefReference(Typedef node) {
     if (!typedefs.contains(node)) {
       problem(
           node, "Dangling reference to '$node', parent is: '${node.parent}'");
     }
   }

   @override
   visitTypeParameterType(TypeParameterType node) {
     var parameter = node.parameter;
     if (!typeParametersInScope.contains(parameter)) {
       problem(
           currentParent,
           "Type parameter '$parameter' referenced out of"
           " scope, parent is: '${parameter.parent}'.");
     }
     if (parameter.parent is Class && !classTypeParametersAreInScope) {
       problem(
           currentParent,
           "Type parameter '$parameter' referenced from"
           " static context, parent is: '${parameter.parent}'.");
     }
   }

   @override
   visitInterfaceType(InterfaceType node) {
     node.visitChildren(this);
     if (node.typeArguments.length != node.classNode.typeParameters.length) {
       problem(
           currentParent,
           "Type $node provides ${node.typeArguments.length}"
           " type arguments but the class declares"
           " ${node.classNode.typeParameters.length} parameters.");
     }
   }

   @override
   visitTypedefType(TypedefType node) {
     checkTypedef(node.typedefNode);
     node.visitChildren(this);
     if (node.typeArguments.length != node.typedefNode.typeParameters.length) {
       problem(
           currentParent,
           "The typedef type $node provides ${node.typeArguments.length}"
           " type arguments but the typedef declares"
           " ${node.typedefNode.typeParameters.length} parameters.");
     }
   }
 }

 class CheckParentPointers extends Visitor {
   static void check(TreeNode node) {
     node.accept(new CheckParentPointers(node.parent));
   }

   TreeNode parent;

   CheckParentPointers([this.parent]);

   defaultTreeNode(TreeNode node) {
     if (node.parent != parent) {
       throw new VerificationError(
           parent,
           node,
           "Parent pointer on '${node.runtimeType}' "
           "is '${node.parent.runtimeType}' "
           "but should be '${parent.runtimeType}'.");
     }
     var oldParent = parent;
     parent = node;
     node.visitChildren(this);
     parent = oldParent;
   }
 }

 void checkInitializers(Constructor constructor) {
   // TODO(ahe): I'll add more here in other CLs.
 }
	// 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 kernel.checks;

	import 'ast.dart';
	import 'transformations/flags.dart';

	void verifyProgram(Program program) {
	VerifyingVisitor.check(program);
	}

	class VerificationError {
	final TreeNode context;

	final TreeNode node;

	final String details;

	VerificationError(this.context, this.node, this.details);

	toString() {
	Location location;
	try {
	location = node?.location ?? context?.location;
	} catch (_) {
	// TODO(ahe): Fix the compiler instead.
	}
	if (location != null) {
	String file = location.file ?? "";
	return "$file:${location.line}:${location.column}: Verification error:"
	" $details";
	} else {
	return "Verification error: $details\n"
	"Context: '$context'.\n"
	"Node: '$node'.";
	}
	}
	}

	enum TypedefState { Done, BeingChecked }

	/// Checks that a kernel program is well-formed.
	///
	/// This does not include any kind of type checking.
	class VerifyingVisitor extends RecursiveVisitor {
	final Set<Class> classes = new Set<Class>();
	final Set<Typedef> typedefs = new Set<Typedef>();
	Set<TypeParameter> typeParametersInScope = new Set<TypeParameter>();
	final List<VariableDeclaration> variableStack = <VariableDeclaration>[];
	final Map<Typedef, TypedefState> typedefState = <Typedef, TypedefState>{};
	bool classTypeParametersAreInScope = false;

	/// If true, relax certain checks for outline mode. For example, don't
	/// attempt to validate constructor initializers.
	bool isOutline = false;

	bool inCatchBlock = false;

	Library currentLibrary;

	Member currentMember;

	Class currentClass;

	TreeNode currentParent;

	TreeNode get context => currentMember ?? currentClass;

	static void check(Program program) {
	program.accept(new VerifyingVisitor());
	}

	defaultTreeNode(TreeNode node) {
	visitChildren(node);
	}

	problem(TreeNode node, String details, {TreeNode context}) {
	context ??= this.context;
	throw new VerificationError(context, node, details);
	}

	TreeNode enterParent(TreeNode node) {
	if (!identical(node.parent, currentParent)) {
	problem(
	node,
	"Incorrect parent pointer on ${node.runtimeType}:"
	" expected '${currentParent.runtimeType}',"
	" but found: '${node.parent.runtimeType}'.");
	}
	var oldParent = currentParent;
	currentParent = node;
	return oldParent;
	}

	void exitParent(TreeNode oldParent) {
	currentParent = oldParent;
	}

	int enterLocalScope() => variableStack.length;

	void exitLocalScope(int stackHeight) {
	for (int i = stackHeight; i < variableStack.length; ++i) {
	undeclareVariable(variableStack[i]);
	}
	variableStack.length = stackHeight;
	}

	void visitChildren(TreeNode node) {
	var oldParent = enterParent(node);
	node.visitChildren(this);
	exitParent(oldParent);
	}

	void visitWithLocalScope(TreeNode node) {
	int stackHeight = enterLocalScope();
	visitChildren(node);
	exitLocalScope(stackHeight);
	}

	void declareMember(Member member) {
	if (member.transformerFlags & TransformerFlag.seenByVerifier != 0) {
	problem(member.function,
	"Member '$member' has been declared more than once.");
	}
	member.transformerFlags \|= TransformerFlag.seenByVerifier;
	}

	void undeclareMember(Member member) {
	member.transformerFlags &= ~TransformerFlag.seenByVerifier;
	}

	void declareVariable(VariableDeclaration variable) {
	if (variable.flags & VariableDeclaration.FlagInScope != 0) {
	problem(variable, "Variable '$variable' declared more than once.");
	}
	variable.flags \|= VariableDeclaration.FlagInScope;
	variableStack.add(variable);
	}

	void undeclareVariable(VariableDeclaration variable) {
	variable.flags &= ~VariableDeclaration.FlagInScope;
	}

	void declareTypeParameters(List<TypeParameter> parameters) {
	for (int i = 0; i < parameters.length; ++i) {
	var parameter = parameters[i];
	if (parameter.bound == null) {
	problem(
	currentParent, "Missing bound for type parameter '$parameter'.");
	}
	if (!typeParametersInScope.add(parameter)) {
	problem(parameter, "Type parameter '$parameter' redeclared.");
	}
	}
	}

	void undeclareTypeParameters(List<TypeParameter> parameters) {
	typeParametersInScope.removeAll(parameters);
	}

	void checkVariableInScope(VariableDeclaration variable, TreeNode where) {
	if (variable.flags & VariableDeclaration.FlagInScope == 0) {
	problem(where, "Variable '$variable' used out of scope.");
	}
	}

	visitProgram(Program program) {
	try {
	for (var library in program.libraries) {
	for (var class_ in library.classes) {
	if (!classes.add(class_)) {
	problem(class_, "Class '$class_' declared more than once.");
	}
	}
	for (var typedef_ in library.typedefs) {
	if (!typedefs.add(typedef_)) {
	problem(typedef_, "Typedef '$typedef_' declared more than once.");
	}
	}
	library.members.forEach(declareMember);
	for (var class_ in library.classes) {
	class_.members.forEach(declareMember);
	}
	}
	visitChildren(program);
	} finally {
	for (var library in program.libraries) {
	library.members.forEach(undeclareMember);
	for (var class_ in library.classes) {
	class_.members.forEach(undeclareMember);
	}
	}
	variableStack.forEach(undeclareVariable);
	}
	}

	void visitLibrary(Library node) {
	currentLibrary = node;
	super.visitLibrary(node);
	currentLibrary = null;
	}

	void checkTypedef(Typedef node) {
	var state = typedefState[node];
	if (state == TypedefState.Done) return;
	if (state == TypedefState.BeingChecked) {
	problem(node, "The typedef '$node' refers to itself", context: node);
	}
	assert(state == null);
	typedefState[node] = TypedefState.BeingChecked;
	var savedTypeParameters = typeParametersInScope;
	typeParametersInScope = node.typeParameters.toSet();
	var savedParent = currentParent;
	currentParent = node;
	// Visit children without checking the parent pointer on the typedef itself
	// since this can be called from a context other than its true parent.
	node.visitChildren(this);
	currentParent = savedParent;
	typeParametersInScope = savedTypeParameters;
	typedefState[node] = TypedefState.Done;
	}

	visitTypedef(Typedef node) {
	checkTypedef(node);
	// Enter and exit the node to check the parent pointer on the typedef node.
	exitParent(enterParent(node));
	}

	visitField(Field node) {
	currentMember = node;
	var oldParent = enterParent(node);
	bool isTopLevel = node.parent == currentLibrary;
	if (isTopLevel && !node.isStatic) {
	problem(node, "The top-level field '${node.name.name}' should be static",
	context: node);
	}
	if (node.isConst && !node.isStatic) {
	problem(node, "The const field '${node.name.name}' should be static",
	context: node);
	}
	classTypeParametersAreInScope = !node.isStatic;
	node.initializer?.accept(this);
	node.type.accept(this);
	classTypeParametersAreInScope = false;
	visitList(node.annotations, this);
	exitParent(oldParent);
	currentMember = null;
	}

	visitProcedure(Procedure node) {
	currentMember = node;
	var oldParent = enterParent(node);
	classTypeParametersAreInScope = !node.isStatic;
	node.function.accept(this);
	classTypeParametersAreInScope = false;
	visitList(node.annotations, this);
	exitParent(oldParent);
	currentMember = null;
	}

	visitConstructor(Constructor node) {
	currentMember = node;
	classTypeParametersAreInScope = true;
	// The constructor member needs special treatment due to parameters being
	// in scope in the initializer list.
	var oldParent = enterParent(node);
	int stackHeight = enterLocalScope();
	visitChildren(node.function);
	visitList(node.initializers, this);
	if (!isOutline) {
	checkInitializers(node);
	}
	exitLocalScope(stackHeight);
	classTypeParametersAreInScope = false;
	visitList(node.annotations, this);
	exitParent(oldParent);
	classTypeParametersAreInScope = false;
	currentMember = null;
	}

	visitClass(Class node) {
	currentClass = node;
	declareTypeParameters(node.typeParameters);
	var oldParent = enterParent(node);
	classTypeParametersAreInScope = false;
	visitList(node.annotations, this);
	classTypeParametersAreInScope = true;
	visitList(node.typeParameters, this);
	visitList(node.fields, this);
	visitList(node.constructors, this);
	visitList(node.procedures, this);
	exitParent(oldParent);
	undeclareTypeParameters(node.typeParameters);
	currentClass = null;
	}

	visitFunctionNode(FunctionNode node) {
	declareTypeParameters(node.typeParameters);
	bool savedInCatchBlock = inCatchBlock;
	inCatchBlock = false;
	visitWithLocalScope(node);
	inCatchBlock = savedInCatchBlock;
	undeclareTypeParameters(node.typeParameters);
	}

	visitFunctionType(FunctionType node) {
	for (int i = 1; i < node.namedParameters.length; ++i) {
	if (node.namedParameters[i - 1].compareTo(node.namedParameters[i]) >= 0) {
	problem(currentParent,
	"Named parameters are not sorted on function type ($node).");
	}
	}
	declareTypeParameters(node.typeParameters);
	for (var typeParameter in node.typeParameters) {
	typeParameter.bound?.accept(this);
	}
	visitList(node.positionalParameters, this);
	visitList(node.namedParameters, this);
	node.returnType.accept(this);
	undeclareTypeParameters(node.typeParameters);
	}

	visitBlock(Block node) {
	visitWithLocalScope(node);
	}

	visitForStatement(ForStatement node) {
	visitWithLocalScope(node);
	}

	visitForInStatement(ForInStatement node) {
	visitWithLocalScope(node);
	}

	visitLet(Let node) {
	visitWithLocalScope(node);
	}

	visitCatch(Catch node) {
	bool savedInCatchBlock = inCatchBlock;
	inCatchBlock = true;
	visitWithLocalScope(node);
	inCatchBlock = savedInCatchBlock;
	}

	@override
	visitRethrow(Rethrow node) {
	if (!inCatchBlock) {
	problem(node, "Rethrow must be inside a Catch block.");
	}
	}

	visitVariableDeclaration(VariableDeclaration node) {
	var parent = node.parent;
	if (parent is! Block &&
	!(parent is Catch && parent.body != node) &&
	!(parent is FunctionNode && parent.body != node) &&
	parent is! FunctionDeclaration &&
	!(parent is ForStatement && parent.body != node) &&
	!(parent is ForInStatement && parent.body != node) &&
	parent is! Let &&
	parent is! LocalInitializer) {
	problem(
	node,
	"VariableDeclaration must be a direct child of a Block, "
	"not ${parent.runtimeType}.");
	}
	visitChildren(node);
	declareVariable(node);
	}

	visitVariableGet(VariableGet node) {
	checkVariableInScope(node.variable, node);
	visitChildren(node);
	}

	visitVariableSet(VariableSet node) {
	checkVariableInScope(node.variable, node);
	visitChildren(node);
	}

	@override
	visitStaticGet(StaticGet node) {
	visitChildren(node);
	if (node.target == null) {
	problem(node, "StaticGet without target.");
	}
	// Currently Constructor.hasGetter returns `false` even though fasta uses it
	// as a getter for internal purposes:
	//
	// Fasta is letting all call site of a redirecting constructor be resolved
	// to the real target. In order to resolve it, it seems to add a body into
	// the redirecting-factory constructor which caches the target constructor.
	// That cache is via a `StaticGet(real-constructor)` node, which we make
	// here pass the verifier.
	if (!node.target.hasGetter && node.target is! Constructor) {
	problem(node, "StaticGet of '${node.target}' without getter.");
	}
	if (node.target.isInstanceMember) {
	problem(node, "StaticGet of '${node.target}' that's an instance member.");
	}
	}

	@override
	visitStaticSet(StaticSet node) {
	visitChildren(node);
	if (node.target == null) {
	problem(node, "StaticSet without target.");
	}
	if (!node.target.hasSetter) {
	problem(node, "StaticSet to '${node.target}' without setter.");
	}
	if (node.target.isInstanceMember) {
	problem(node, "StaticSet to '${node.target}' that's an instance member.");
	}
	}

	@override
	visitStaticInvocation(StaticInvocation node) {
	checkTargetedInvocation(node.target, node);
	if (node.target.isInstanceMember) {
	problem(node,
	"StaticInvocation of '${node.target}' that's an instance member.");
	}
	if (node.isConst &&
	(!node.target.isConst \|\|
	!node.target.isExternal \|\|
	node.target.kind != ProcedureKind.Factory)) {
	problem(
	node,
	"Constant StaticInvocation of '${node.target}' that isn't"
	" a const external factory.");
	}
	}

	void checkTargetedInvocation(Member target, InvocationExpression node) {
	visitChildren(node);
	if (target == null) {
	problem(node, "${node.runtimeType} without target.");
	}
	if (target.function == null) {
	problem(node, "${node.runtimeType} without function.");
	}
	if (!areArgumentsCompatible(node.arguments, target.function)) {
	problem(node,
	"${node.runtimeType} with incompatible arguments for '${target}'.");
	}
	int expectedTypeParameters = target is Constructor
	? target.enclosingClass.typeParameters.length
	: target.function.typeParameters.length;
	if (node.arguments.types.length != expectedTypeParameters) {
	problem(
	node,
	"${node.runtimeType} with wrong number of type arguments"
	" for '${target}'.");
	}
	}

	@override
	visitDirectPropertyGet(DirectPropertyGet node) {
	visitChildren(node);
	if (node.target == null) {
	problem(node, "DirectPropertyGet without target.");
	}
	if (!node.target.hasGetter) {
	problem(node, "DirectPropertyGet of '${node.target}' without getter.");
	}
	if (!node.target.isInstanceMember) {
	problem(
	node,
	"DirectPropertyGet of '${node.target}' that isn't an"
	" instance member.");
	}
	}

	@override
	visitDirectPropertySet(DirectPropertySet node) {
	visitChildren(node);
	if (node.target == null) {
	problem(node, "DirectPropertySet without target.");
	}
	if (!node.target.hasSetter) {
	problem(node, "DirectPropertySet of '${node.target}' without setter.");
	}
	if (!node.target.isInstanceMember) {
	problem(node, "DirectPropertySet of '${node.target}' that is static.");
	}
	}

	@override
	visitDirectMethodInvocation(DirectMethodInvocation node) {
	checkTargetedInvocation(node.target, node);
	if (node.receiver == null) {
	problem(node, "DirectMethodInvocation without receiver.");
	}
	}

	@override
	visitConstructorInvocation(ConstructorInvocation node) {
	checkTargetedInvocation(node.target, node);
	if (node.target.enclosingClass.isAbstract) {
	problem(node, "ConstructorInvocation of abstract class.");
	}
	if (node.isConst && !node.target.isConst) {
	problem(
	node,
	"Constant ConstructorInvocation fo '${node.target}' that"
	" isn't const.");
	}
	}

	bool areArgumentsCompatible(Arguments arguments, FunctionNode function) {
	if (arguments.positional.length < function.requiredParameterCount) {
	return false;
	}
	if (arguments.positional.length > function.positionalParameters.length) {
	return false;
	}
	namedLoop:
	for (int i = 0; i < arguments.named.length; ++i) {
	var argument = arguments.named[i];
	String name = argument.name;
	for (int j = 0; j < function.namedParameters.length; ++j) {
	if (function.namedParameters[j].name == name) continue namedLoop;
	}
	return false;
	}
	return true;
	}

	@override
	visitContinueSwitchStatement(ContinueSwitchStatement node) {
	if (node.target == null) {
	problem(node, "No target.");
	} else if (node.target.parent == null) {
	problem(node, "Target has no parent.");
	} else {
	SwitchStatement statement = node.target.parent;
	for (SwitchCase switchCase in statement.cases) {
	if (switchCase == node.target) return;
	}
	problem(node, "Switch case isn't child of parent.");
	}
	}

	@override
	defaultMemberReference(Member node) {
	if (node.transformerFlags & TransformerFlag.seenByVerifier == 0) {
	problem(
	node, "Dangling reference to '$node', parent is: '${node.parent}'.");
	}
	}

	@override
	visitClassReference(Class node) {
	if (!classes.contains(node)) {
	problem(
	node, "Dangling reference to '$node', parent is: '${node.parent}'.");
	}
	}

	@override
	visitTypedefReference(Typedef node) {
	if (!typedefs.contains(node)) {
	problem(
	node, "Dangling reference to '$node', parent is: '${node.parent}'");
	}
	}

	@override
	visitTypeParameterType(TypeParameterType node) {
	var parameter = node.parameter;
	if (!typeParametersInScope.contains(parameter)) {
	problem(
	currentParent,
	"Type parameter '$parameter' referenced out of"
	" scope, parent is: '${parameter.parent}'.");
	}
	if (parameter.parent is Class && !classTypeParametersAreInScope) {
	problem(
	currentParent,
	"Type parameter '$parameter' referenced from"
	" static context, parent is: '${parameter.parent}'.");
	}
	}

	@override
	visitInterfaceType(InterfaceType node) {
	node.visitChildren(this);
	if (node.typeArguments.length != node.classNode.typeParameters.length) {
	problem(
	currentParent,
	"Type $node provides ${node.typeArguments.length}"
	" type arguments but the class declares"
	" ${node.classNode.typeParameters.length} parameters.");
	}
	}

	@override
	visitTypedefType(TypedefType node) {
	checkTypedef(node.typedefNode);
	node.visitChildren(this);
	if (node.typeArguments.length != node.typedefNode.typeParameters.length) {
	problem(
	currentParent,
	"The typedef type $node provides ${node.typeArguments.length}"
	" type arguments but the typedef declares"
	" ${node.typedefNode.typeParameters.length} parameters.");
	}
	}
	}

	class CheckParentPointers extends Visitor {
	static void check(TreeNode node) {
	node.accept(new CheckParentPointers(node.parent));
	}

	TreeNode parent;

	CheckParentPointers([this.parent]);

	defaultTreeNode(TreeNode node) {
	if (node.parent != parent) {
	throw new VerificationError(
	parent,
	node,
	"Parent pointer on '${node.runtimeType}' "
	"is '${node.parent.runtimeType}' "
	"but should be '${parent.runtimeType}'.");
	}
	var oldParent = parent;
	parent = node;
	node.visitChildren(this);
	parent = oldParent;
	}
	}

	void checkInitializers(Constructor constructor) {
	// TODO(ahe): I'll add more here in other CLs.
	}