port DDC checker code to analyzer

pkg/analyzer/lib/src/task/strong/checker.dart

+// Copyright (c) 2015, 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.
+
+// TODO(jmesserly): this was ported from package:dev_compiler, and needs to be
+// refactored to fit into analyzer.
+library analyzer.src.task.strong.checker;
+
+import 'package:analyzer/analyzer.dart';
+import 'package:analyzer/src/generated/ast.dart';
+import 'package:analyzer/src/generated/element.dart';
+import 'package:analyzer/src/generated/scanner.dart' show Token, TokenType;
+
+import 'info.dart';
+import 'rules.dart';
+
+/// Checks for overriding declarations of fields and methods. This is used to
+/// check overrides between classes and superclasses, interfaces, and mixin
+/// applications.
+class _OverrideChecker {
+  bool _failure = false;
+  final TypeRules _rules;
+  final ErrorReporter _reporter;
+
+  _OverrideChecker(this._rules, this._reporter);
+
+  void check(ClassDeclaration node) {
+    if (node.element.type.isObject) return;
+    _checkSuperOverrides(node);
+    _checkMixinApplicationOverrides(node);
+    _checkAllInterfaceOverrides(node);
+  }
+
+  /// Check overrides from mixin applications themselves. For example, in:
+  ///
+  ///      A extends B with E, F
+  ///
+  ///  we check:
+  ///
+  ///      B & E against B (equivalently how E overrides B)
+  ///      B & E & F against B & E (equivalently how F overrides both B and E)
+  void _checkMixinApplicationOverrides(ClassDeclaration node) {
+    var type = node.element.type;
+    var parent = type.superclass;
+    var mixins = type.mixins;
+
+    // Check overrides from applying mixins
+    for (int i = 0; i < mixins.length; i++) {
+      var seen = new Set<String>();
+      var current = mixins[i];
+      var errorLocation = node.withClause.mixinTypes[i];
+      for (int j = i - 1; j >= 0; j--) {
+        _checkIndividualOverridesFromType(
+            current, mixins[j], errorLocation, seen);
+      }
+      _checkIndividualOverridesFromType(current, parent, errorLocation, seen);
+    }
+  }
+
+  /// Check overrides between a class and its superclasses and mixins. For
+  /// example, in:
+  ///
+  ///      A extends B with E, F
+  ///
+  /// we check A against B, B super classes, E, and F.
+  ///
+  /// Internally we avoid reporting errors twice and we visit classes bottom up
+  /// to ensure we report the most immediate invalid override first. For
+  /// example, in the following code we'll report that `Test` has an invalid
+  /// override with respect to `Parent` (as opposed to an invalid override with
+  /// respect to `Grandparent`):
+  ///
+  ///     class Grandparent {
+  ///         m(A a) {}
+  ///     }
+  ///     class Parent extends Grandparent {
+  ///         m(A a) {}
+  ///     }
+  ///     class Test extends Parent {
+  ///         m(B a) {} // invalid override
+  ///     }
+  void _checkSuperOverrides(ClassDeclaration node) {
+    var seen = new Set<String>();
+    var current = node.element.type;
+    var visited = new Set<InterfaceType>();
+    do {
+      visited.add(current);
+      current.mixins.reversed
+          .forEach((m) => _checkIndividualOverridesFromClass(node, m, seen));
+      _checkIndividualOverridesFromClass(node, current.superclass, seen);
+      current = current.superclass;
+    } while (!current.isObject && !visited.contains(current));
+  }
+
+  /// Checks that implementations correctly override all reachable interfaces.
+  /// In particular, we need to check these overrides for the definitions in
+  /// the class itself and each its superclasses. If a superclass is not
+  /// abstract, then we can skip its transitive interfaces. For example, in:
+  ///
+  ///     B extends C implements G
+  ///     A extends B with E, F implements H, I
+  ///
+  /// we check:
+  ///
+  ///     C against G, H, and I
+  ///     B against G, H, and I
+  ///     E against H and I // no check against G because B is a concrete class
+  ///     F against H and I
+  ///     A against H and I
+  void _checkAllInterfaceOverrides(ClassDeclaration node) {
+    var seen = new Set<String>();
+    // Helper function to collect all reachable interfaces.
+    find(InterfaceType interfaceType, Set result) {
+      if (interfaceType == null || interfaceType.isObject) return;
+      if (result.contains(interfaceType)) return;
+      result.add(interfaceType);
+      find(interfaceType.superclass, result);
+      interfaceType.mixins.forEach((i) => find(i, result));
+      interfaceType.interfaces.forEach((i) => find(i, result));
+    }
+
+    // Check all interfaces reachable from the `implements` clause in the
+    // current class against definitions here and in superclasses.
+    var localInterfaces = new Set<InterfaceType>();
+    var type = node.element.type;
+    type.interfaces.forEach((i) => find(i, localInterfaces));
+    _checkInterfacesOverrides(node, localInterfaces, seen,
+        includeParents: true);
+
+    // Check also how we override locally the interfaces from parent classes if
+    // the parent class is abstract. Otherwise, these will be checked as
+    // overrides on the concrete superclass.
+    var superInterfaces = new Set<InterfaceType>();
+    var parent = type.superclass;
+    // TODO(sigmund): we don't seem to be reporting the analyzer error that a
+    // non-abstract class is not implementing an interface. See
+    // https://github.com/dart-lang/dart-dev-compiler/issues/25
+    while (parent != null && parent.element.isAbstract) {
+      parent.interfaces.forEach((i) => find(i, superInterfaces));
+      parent = parent.superclass;
+    }
+    _checkInterfacesOverrides(node, superInterfaces, seen,
+        includeParents: false);
+  }
+
+  /// Checks that [cls] and its super classes (including mixins) correctly
+  /// overrides each interface in [interfaces]. If [includeParents] is false,
+  /// then mixins are still checked, but the base type and it's transitive
+  /// supertypes are not.
+  ///
+  /// [cls] can be either a [ClassDeclaration] or a [InterfaceType]. For
+  /// [ClassDeclaration]s errors are reported on the member that contains the
+  /// invalid override, for [InterfaceType]s we use [errorLocation] instead.
+  void _checkInterfacesOverrides(
+      cls, Iterable<InterfaceType> interfaces, Set<String> seen,
+      {Set<InterfaceType> visited,
+      bool includeParents: true,
+      AstNode errorLocation}) {
+    var node = cls is ClassDeclaration ? cls : null;
+    var type = cls is InterfaceType ? cls : node.element.type;
+
+    if (visited == null) {
+      visited = new Set<InterfaceType>();
+    } else if (visited.contains(type)) {
+      // Malformed type.
+      return;
+    } else {
+      visited.add(type);
+    }
+
+    // Check direct overrides on [type]
+    for (var interfaceType in interfaces) {
+      if (node != null) {
+        _checkIndividualOverridesFromClass(node, interfaceType, seen);
+      } else {
+        _checkIndividualOverridesFromType(
+            type, interfaceType, errorLocation, seen);
+      }
+    }
+
+    // Check overrides from its mixins
+    for (int i = 0; i < type.mixins.length; i++) {
+      var loc =
+          errorLocation != null ? errorLocation : node.withClause.mixinTypes[i];
+      for (var interfaceType in interfaces) {
+        // We copy [seen] so we can report separately if more than one mixin or
+        // the base class have an invalid override.
+        _checkIndividualOverridesFromType(
+            type.mixins[i], interfaceType, loc, new Set.from(seen));
+      }
+    }
+
+    // Check overrides from its superclasses
+    if (includeParents) {
+      var parent = type.superclass;
+      if (parent.isObject) return;
+      var loc = errorLocation != null ? errorLocation : node.extendsClause;
+      // No need to copy [seen] here because we made copies above when reporting
+      // errors on mixins.
+      _checkInterfacesOverrides(parent, interfaces, seen,
+          visited: visited, includeParents: true, errorLocation: loc);
+    }
+  }
+
+  /// Check that individual methods and fields in [subType] correctly override
+  /// the declarations in [baseType].
+  ///
+  /// The [errorLocation] node indicates where errors are reported, see
+  /// [_checkSingleOverride] for more details.
+  ///
+  /// The set [seen] is used to avoid reporting overrides more than once. It
+  /// is used when invoking this function multiple times when checking several
+  /// types in a class hierarchy. Errors are reported only the first time an
+  /// invalid override involving a specific member is encountered.
+  _checkIndividualOverridesFromType(InterfaceType subType,
+      InterfaceType baseType, AstNode errorLocation, Set<String> seen) {
+    void checkHelper(ExecutableElement e) {
+      if (e.isStatic) return;
+      if (seen.contains(e.name)) return;
+      if (_checkSingleOverride(e, baseType, null, errorLocation)) {
+        seen.add(e.name);
+      }
+    }
+    subType.methods.forEach(checkHelper);
+    subType.accessors.forEach(checkHelper);
+  }
+
+  /// Check that individual methods and fields in [subType] correctly override
+  /// the declarations in [baseType].
+  ///
+  /// The [errorLocation] node indicates where errors are reported, see
+  /// [_checkSingleOverride] for more details.
+  _checkIndividualOverridesFromClass(
+      ClassDeclaration node, InterfaceType baseType, Set<String> seen) {
+    for (var member in node.members) {
+      if (member is ConstructorDeclaration) continue;
+      if (member is FieldDeclaration) {
+        if (member.isStatic) continue;
+        for (var variable in member.fields.variables) {
+          var element = variable.element as PropertyInducingElement;
+          var name = element.name;
+          if (seen.contains(name)) continue;
+          var getter = element.getter;
+          var setter = element.setter;
+          bool found = _checkSingleOverride(getter, baseType, variable, member);
+          if (!variable.isFinal &&
+              !variable.isConst &&
+              _checkSingleOverride(setter, baseType, variable, member)) {
+            found = true;
+          }
+          if (found) seen.add(name);
+        }
+      } else {
+        if ((member as MethodDeclaration).isStatic) continue;
+        var method = (member as MethodDeclaration).element;
+        if (seen.contains(method.name)) continue;
+        if (_checkSingleOverride(method, baseType, member, member)) {
+          seen.add(method.name);
+        }
+      }
+    }
+  }
+
+  /// Checks that [element] correctly overrides its corresponding member in
+  /// [type]. Returns `true` if an override was found, that is, if [element] has
+  /// a corresponding member in [type] that it overrides.
+  ///
+  /// The [errorLocation] is a node where the error is reported. For example, a
+  /// bad override of a method in a class with respect to its superclass is
+  /// reported directly at the method declaration. However, invalid overrides
+  /// from base classes to interfaces, mixins to the base they are applied to,
+  /// or mixins to interfaces are reported at the class declaration, since the
+  /// base class or members on their own were not incorrect, only combining them
+  /// with the interface was problematic. For example, these are example error
+  /// locations in these cases:
+  ///
+  ///     error: base class introduces an invalid override. The type of B.foo is
+  ///     not a subtype of E.foo:
+  ///       class A extends B implements E { ... }
+  ///               ^^^^^^^^^
+  ///
+  ///     error: mixin introduces an invalid override. The type of C.foo is not
+  ///     a subtype of E.foo:
+  ///       class A extends B with C implements E { ... }
+  ///                              ^
+  ///
+  /// When checking for overrides from a type and it's super types, [node] is
+  /// the AST node that defines [element]. This is used to determine whether the
+  /// type of the element could be inferred from the types in the super classes.
+  bool _checkSingleOverride(ExecutableElement element, InterfaceType type,
+      AstNode node, AstNode errorLocation) {
+    assert(!element.isStatic);
+
+    FunctionType subType = _rules.elementType(element);
+    // TODO(vsm): Test for generic
+    FunctionType baseType = _getMemberType(type, element);
+
+    if (baseType == null) return false;
+    if (!_rules.isAssignable(subType, baseType)) {
+      // See whether non-assignable cases fit one of our common patterns:
+      //
+      // Common pattern 1: Inferable return type (on getters and methods)
+      //   class A {
+      //     int get foo => ...;
+      //     String toString() { ... }
+      //   }
+      //   class B extends A {
+      //     get foo => e; // no type specified.
+      //     toString() { ... } // no return type specified.
+      //   }
+      _recordMessage(new InvalidMethodOverride(
+          errorLocation, element, type, subType, baseType));
+    }
+    return true;
+  }
+
+  void _recordMessage(StaticInfo info) {
+    if (info == null) return;
+    var error = info.toAnalysisError();
+    if (error.errorCode.errorSeverity == ErrorSeverity.ERROR) _failure = true;
+    _reporter.reportError(error);
+  }
+}
+
+/// Checks the body of functions and properties.
+class CodeChecker extends RecursiveAstVisitor {
+  final TypeRules rules;
+  final ErrorReporter reporter;
+  final _OverrideChecker _overrideChecker;
+  bool _failure = false;
+  bool get failure => _failure || _overrideChecker._failure;
+
+  void reset() {
+    _failure = false;
+    _overrideChecker._failure = false;
+  }
+
+  CodeChecker(TypeRules rules, ErrorReporter reporter)
+      : rules = rules,
+        reporter = reporter,
+        _overrideChecker = new _OverrideChecker(rules, reporter);
+
+  @override
+  void visitComment(Comment node) {
+    // skip, no need to do typechecking inside comments (they may contain
+    // comment references which would require resolution).
+  }
+
+  @override
+  void visitClassDeclaration(ClassDeclaration node) {
+    _overrideChecker.check(node);
+    super.visitClassDeclaration(node);
+  }
+
+  @override
+  void visitAssignmentExpression(AssignmentExpression node) {
+    var token = node.operator;
+    if (token.type != TokenType.EQ) {
+      _checkCompoundAssignment(node);
+    } else {
+      DartType staticType = _getStaticType(node.leftHandSide);
+      checkAssignment(node.rightHandSide, staticType);
+    }
+    node.visitChildren(this);
+  }
+
+  /// Check constructor declaration to ensure correct super call placement.
+  @override
+  void visitConstructorDeclaration(ConstructorDeclaration node) {
+    node.visitChildren(this);
+
+    final init = node.initializers;
+    for (int i = 0, last = init.length - 1; i < last; i++) {
+      final node = init[i];
+      if (node is SuperConstructorInvocation) {
+        _recordMessage(new InvalidSuperInvocation(node));
+      }
+    }
+  }
+
+  @override
+  void visitConstructorFieldInitializer(ConstructorFieldInitializer node) {
+    var field = node.fieldName;
+    var element = field.staticElement;
+    DartType staticType = rules.elementType(element);
+    checkAssignment(node.expression, staticType);
+    node.visitChildren(this);
+  }
+
+  @override
+  void visitForEachStatement(ForEachStatement node) {
+    // Check that the expression is an Iterable.
+    var expr = node.iterable;
+    var iterableType = node.awaitKeyword != null
+        ? rules.provider.streamType
+        : rules.provider.iterableType;
+    var loopVariable = node.identifier != null
+        ? node.identifier
+        : node.loopVariable?.identifier;
+    if (loopVariable != null) {
+      var iteratorType = loopVariable.staticType;
+      var checkedType = iterableType.substitute4([iteratorType]);
+      checkAssignment(expr, checkedType);
+    }
+    node.visitChildren(this);
+  }
+
+  @override
+  void visitForStatement(ForStatement node) {
+    if (node.condition != null) {
+      checkBoolean(node.condition);
+    }
+    node.visitChildren(this);
+  }
+
+  @override
+  void visitIfStatement(IfStatement node) {
+    checkBoolean(node.condition);
+    node.visitChildren(this);
+  }
+
+  @override
+  void visitDoStatement(DoStatement node) {
+    checkBoolean(node.condition);
+    node.visitChildren(this);
+  }
+
+  @override
+  void visitWhileStatement(WhileStatement node) {
+    checkBoolean(node.condition);
+    node.visitChildren(this);
+  }
+
+  @override
+  void visitSwitchStatement(SwitchStatement node) {
+    // SwitchStatement defines a boolean conversion to check the result of the
+    // case value == the switch value, but in dev_compiler we require a boolean
+    // return type from an overridden == operator (because Object.==), so
+    // checking in SwitchStatement shouldn't be necessary.
+    node.visitChildren(this);
+  }
+
+  @override
+  void visitListLiteral(ListLiteral node) {
+    var type = rules.provider.dynamicType;
+    if (node.typeArguments != null) {
+      var targs = node.typeArguments.arguments;
+      if (targs.length > 0) type = targs[0].type;
+    }
+    var elements = node.elements;
+    for (int i = 0; i < elements.length; i++) {
+      checkArgument(elements[i], type);
+    }
+    super.visitListLiteral(node);
+  }
+
+  @override
+  void visitMapLiteral(MapLiteral node) {
+    var ktype = rules.provider.dynamicType;
+    var vtype = rules.provider.dynamicType;
+    if (node.typeArguments != null) {
+      var targs = node.typeArguments.arguments;
+      if (targs.length > 0) ktype = targs[0].type;
+      if (targs.length > 1) vtype = targs[1].type;
+    }
+    var entries = node.entries;
+    for (int i = 0; i < entries.length; i++) {
+      var entry = entries[i];
+      checkArgument(entry.key, ktype);
+      checkArgument(entry.value, vtype);
+    }
+    super.visitMapLiteral(node);
+  }
+
+  // Check invocations
+  void checkArgumentList(ArgumentList node, FunctionType type) {
+    NodeList<Expression> list = node.arguments;
+    int len = list.length;
+    for (int i = 0; i < len; ++i) {
+      Expression arg = list[i];
+      ParameterElement element = arg.staticParameterElement;
+      if (element == null) {
+        if (type.parameters.length < len) {
+          // We found an argument mismatch, the analyzer will report this too,
+          // so no need to insert an error for this here.
+          continue;
+        }
+        element = type.parameters[i];
+        // TODO(vsm): When can this happen?
+        assert(element != null);
+      }
+      DartType expectedType = rules.elementType(element);
+      if (expectedType == null) expectedType = rules.provider.dynamicType;
+      checkArgument(arg, expectedType);
+    }
+  }
+
+  void checkArgument(Expression arg, DartType expectedType) {
+    // Preserve named argument structure, so their immediate parent is the
+    // method invocation.
+    if (arg is NamedExpression) {
+      arg = (arg as NamedExpression).expression;
+    }
+    checkAssignment(arg, expectedType);
+  }
+
+  void checkFunctionApplication(
+      Expression node, Expression f, ArgumentList list) {
+    if (rules.isDynamicCall(f)) {
+      // If f is Function and this is a method invocation, we should have
+      // gotten an analyzer error, so no need to issue another error.
+      _recordDynamicInvoke(node, f);
+    } else {
+      checkArgumentList(list, rules.getTypeAsCaller(f));
+    }
+  }
+
+  @override
+  visitMethodInvocation(MethodInvocation node) {
+    var target = node.realTarget;
+    if (rules.isDynamicTarget(target) &&
+        !_isObjectMethod(node, node.methodName)) {
+      _recordDynamicInvoke(node, target);
+
+      // Mark the tear-off as being dynamic, too. This lets us distinguish
+      // cases like:
+      //
+      //     dynamic d;
+      //     d.someMethod(...); // the whole method call must be a dynamic send.
+      //
+      // ... from case like:
+      //
+      //     SomeType s;
+      //     s.someDynamicField(...); // static get, followed by dynamic call.
+      //
+      // The first case is handled here, the second case is handled below when
+      // we call [checkFunctionApplication].
+      DynamicInvoke.set(node.methodName, true);
+    } else {
+      checkFunctionApplication(node, node.methodName, node.argumentList);
+    }
+    node.visitChildren(this);
+  }
+
+  @override
+  void visitFunctionExpressionInvocation(FunctionExpressionInvocation node) {
+    checkFunctionApplication(node, node.function, node.argumentList);
+    node.visitChildren(this);
+  }
+
+  @override
+  void visitRedirectingConstructorInvocation(
+      RedirectingConstructorInvocation node) {
+    var type = node.staticElement.type;
+    checkArgumentList(node.argumentList, type);
+    node.visitChildren(this);
+  }
+
+  @override
+  void visitSuperConstructorInvocation(SuperConstructorInvocation node) {
+    var element = node.staticElement;
+    if (element == null) {
+      _recordMessage(new MissingTypeError(node));
+    } else {
+      var type = node.staticElement.type;
+      checkArgumentList(node.argumentList, type);
+    }
+    node.visitChildren(this);
+  }
+
+  void _checkReturnOrYield(Expression expression, AstNode node,
+      {bool yieldStar: false}) {
+    var body = node.getAncestor((n) => n is FunctionBody);
+    var type = rules.getExpectedReturnType(body, yieldStar: yieldStar);
+    if (type == null) {
+      // We have a type mismatch: the async/async*/sync* modifier does
+      // not match the return or yield type.  We should have already gotten an
+      // analyzer error in this case.
+      return;
+    }
+    // TODO(vsm): Enforce void or dynamic (to void?) when expression is null.
+    if (expression != null) checkAssignment(expression, type);
+  }
+
+  @override
+  void visitExpressionFunctionBody(ExpressionFunctionBody node) {
+    _checkReturnOrYield(node.expression, node);
+    node.visitChildren(this);
+  }
+
+  @override
+  void visitReturnStatement(ReturnStatement node) {
+    _checkReturnOrYield(node.expression, node);
+    node.visitChildren(this);
+  }
+
+  @override
+  void visitYieldStatement(YieldStatement node) {
+    _checkReturnOrYield(node.expression, node, yieldStar: node.star != null);
+    node.visitChildren(this);
+  }
+
+  @override
+  void visitPropertyAccess(PropertyAccess node) {
+    var target = node.realTarget;
+    if (rules.isDynamicTarget(target) &&
+        !_isObjectProperty(target, node.propertyName)) {
+      _recordDynamicInvoke(node, target);
+    }
+    node.visitChildren(this);
+  }
+
+  @override
+  void visitPrefixedIdentifier(PrefixedIdentifier node) {
+    final target = node.prefix;
+    if (rules.isDynamicTarget(target) &&
+        !_isObjectProperty(target, node.identifier)) {
+      _recordDynamicInvoke(node, target);
+    }
+    node.visitChildren(this);
+  }
+
+  @override
+  void visitDefaultFormalParameter(DefaultFormalParameter node) {
+    // Check that defaults have the proper subtype.
+    var parameter = node.parameter;
+    var parameterType = rules.elementType(parameter.element);
+    assert(parameterType != null);
+    var defaultValue = node.defaultValue;
+    if (defaultValue != null) {
+      checkAssignment(defaultValue, parameterType);
+    }
+
+    node.visitChildren(this);
+  }
+
+  @override
+  void visitFieldFormalParameter(FieldFormalParameter node) {
+    var element = node.element;
+    var typeName = node.type;
+    if (typeName != null) {
+      var type = rules.elementType(element);
+      var fieldElement =
+          node.identifier.staticElement as FieldFormalParameterElement;
+      var fieldType = rules.elementType(fieldElement.field);
+      if (!rules.isSubTypeOf(type, fieldType)) {
+        var staticInfo =
+            new InvalidParameterDeclaration(rules, node, fieldType);
+        _recordMessage(staticInfo);
+      }
+    }
+    node.visitChildren(this);
+  }
+
+  @override
+  void visitInstanceCreationExpression(InstanceCreationExpression node) {
+    var arguments = node.argumentList;
+    var element = node.staticElement;
+    if (element != null) {
+      var type = rules.elementType(node.staticElement);
+      checkArgumentList(arguments, type);
+    } else {
+      _recordMessage(new MissingTypeError(node));
+    }
+    node.visitChildren(this);
+  }
+
+  @override
+  void visitVariableDeclarationList(VariableDeclarationList node) {
+    TypeName type = node.type;
+    if (type == null) {
+      // No checks are needed when the type is var. Although internally the
+      // typing rules may have inferred a more precise type for the variable
+      // based on the initializer.
+    } else {
+      var dartType = getType(type);
+      for (VariableDeclaration variable in node.variables) {
+        var initializer = variable.initializer;
+        if (initializer != null) {
+          checkAssignment(initializer, dartType);
+        }
+      }
+    }
+    node.visitChildren(this);
+  }
+
+  void _checkRuntimeTypeCheck(AstNode node, TypeName typeName) {
+    var type = getType(typeName);
+    if (!rules.isGroundType(type)) {
+      _recordMessage(new NonGroundTypeCheckInfo(node, type));
+    }
+  }
+
+  @override
+  void visitAsExpression(AsExpression node) {
+    // We could do the same check as the IsExpression below, but that is
+    // potentially too conservative.  Instead, at runtime, we must fail hard
+    // if the Dart as and the DDC as would return different values.
+    node.visitChildren(this);
+  }
+
+  @override
+  void visitIsExpression(IsExpression node) {
+    _checkRuntimeTypeCheck(node, node.type);
+    node.visitChildren(this);
+  }
+
+  @override
+  void visitPrefixExpression(PrefixExpression node) {
+    if (node.operator.type == TokenType.BANG) {
+      checkBoolean(node.operand);
+    } else {
+      _checkUnary(node);
+    }
+    node.visitChildren(this);
+  }
+
+  @override
+  void visitPostfixExpression(PostfixExpression node) {
+    _checkUnary(node);
+    node.visitChildren(this);
+  }
+
+  void _checkUnary(/*PrefixExpression|PostfixExpression*/ node) {
+    var op = node.operator;
+    if (op.isUserDefinableOperator ||
+        op.type == TokenType.PLUS_PLUS ||
+        op.type == TokenType.MINUS_MINUS) {
+      if (rules.isDynamicTarget(node.operand)) {
+        _recordDynamicInvoke(node, node.operand);
+      }
+      // For ++ and --, even if it is not dynamic, we still need to check
+      // that the user defined method accepts an `int` as the RHS.
+      // We assume Analyzer has done this already.
+    }
+  }
+
+  @override
+  void visitBinaryExpression(BinaryExpression node) {
+    var op = node.operator;
+    if (op.isUserDefinableOperator) {
+      if (rules.isDynamicTarget(node.leftOperand)) {
+        // Dynamic invocation
+        // TODO(vsm): Move this logic to the resolver?
+        if (op.type != TokenType.EQ_EQ && op.type != TokenType.BANG_EQ) {
+          _recordDynamicInvoke(node, node.leftOperand);
+        }
+      } else {
+        var element = node.staticElement;
+        // Method invocation.
+        if (element is MethodElement) {
+          var type = element.type;
+          // Analyzer should enforce number of parameter types, but check in
+          // case we have erroneous input.
+          if (type.normalParameterTypes.isNotEmpty) {
+            checkArgument(node.rightOperand, type.normalParameterTypes[0]);
+          }
+        } else {
+          // TODO(vsm): Assert that the analyzer found an error here?
+        }
+      }
+    } else {
+      // Non-method operator.
+      switch (op.type) {
+        case TokenType.AMPERSAND_AMPERSAND:
+        case TokenType.BAR_BAR:
+          checkBoolean(node.leftOperand);
+          checkBoolean(node.rightOperand);
+          break;
+        case TokenType.BANG_EQ:
+          break;
+        case TokenType.QUESTION_QUESTION:
+          break;
+        default:
+          assert(false);
+      }
+    }
+    node.visitChildren(this);
+  }
+
+  @override
+  void visitConditionalExpression(ConditionalExpression node) {
+    checkBoolean(node.condition);
+    node.visitChildren(this);
+  }
+
+  @override
+  void visitIndexExpression(IndexExpression node) {
+    var target = node.realTarget;
+    if (rules.isDynamicTarget(target)) {
+      _recordDynamicInvoke(node, target);
+    } else {
+      var element = node.staticElement;
+      if (element is MethodElement) {
+        var type = element.type;
+        // Analyzer should enforce number of parameter types, but check in
+        // case we have erroneous input.
+        if (type.normalParameterTypes.isNotEmpty) {
+          checkArgument(node.index, type.normalParameterTypes[0]);
+        }
+      } else {
+        // TODO(vsm): Assert that the analyzer found an error here?
+      }
+    }
+    node.visitChildren(this);
+  }
+
+  DartType getType(TypeName name) {
+    return (name == null) ? rules.provider.dynamicType : name.type;
+  }
+
+  /// Analyzer checks boolean conversions, but we need to check too, because
+  /// it uses the default assignability rules that allow `dynamic` and `Object`
+  /// to be assigned to bool with no message.
+  void checkBoolean(Expression expr) =>
+      checkAssignment(expr, rules.provider.boolType);
+
+  void checkAssignment(Expression expr, DartType type) {
+    if (expr is ParenthesizedExpression) {
+      checkAssignment(expr.expression, type);
+    } else {
+      _recordMessage(rules.checkAssignment(expr, type));
+    }
+  }
+
+  DartType _specializedBinaryReturnType(
+      TokenType op, DartType t1, DartType t2, DartType normalReturnType) {
+    // This special cases binary return types as per 16.26 and 16.27 of the
+    // Dart language spec.
+    switch (op) {
+      case TokenType.PLUS:
+      case TokenType.MINUS:
+      case TokenType.STAR:
+      case TokenType.TILDE_SLASH:
+      case TokenType.PERCENT:
+      case TokenType.PLUS_EQ:
+      case TokenType.MINUS_EQ:
+      case TokenType.STAR_EQ:
+      case TokenType.TILDE_SLASH_EQ:
+      case TokenType.PERCENT_EQ:
+        if (t1 == rules.provider.intType &&
+            t2 == rules.provider.intType) return t1;
+        if (t1 == rules.provider.doubleType &&
+            t2 == rules.provider.doubleType) return t1;
+        // This particular combo is not spelled out in the spec, but all
+        // implementations and analyzer seem to follow this.
+        if (t1 == rules.provider.doubleType &&
+            t2 == rules.provider.intType) return t1;
+    }
+    return normalReturnType;
+  }
+
+  void _checkCompoundAssignment(AssignmentExpression expr) {
+    var op = expr.operator.type;
+    assert(op.isAssignmentOperator && op != TokenType.EQ);
+    var methodElement = expr.staticElement;
+    if (methodElement == null) {
+      // Dynamic invocation
+      _recordDynamicInvoke(expr, expr.leftHandSide);
+    } else {
+      // Sanity check the operator
+      assert(methodElement.isOperator);
+      var functionType = methodElement.type;
+      var paramTypes = functionType.normalParameterTypes;
+      assert(paramTypes.length == 1);
+      assert(functionType.namedParameterTypes.isEmpty);
+      assert(functionType.optionalParameterTypes.isEmpty);
+
+      // Check the lhs type
+      var staticInfo;
+      var rhsType = _getStaticType(expr.rightHandSide);
+      var lhsType = _getStaticType(expr.leftHandSide);
+      var returnType = _specializedBinaryReturnType(
+          op, lhsType, rhsType, functionType.returnType);
+
+      if (!rules.isSubTypeOf(returnType, lhsType)) {
+        final numType = rules.provider.numType;
+        // Try to fix up the numerical case if possible.
+        if (rules.isSubTypeOf(lhsType, numType) &&
+            rules.isSubTypeOf(lhsType, rhsType)) {
+          // This is also slightly different from spec, but allows us to keep
+          // compound operators in the int += num and num += dynamic cases.
+          staticInfo = DownCast.create(
+              rules, expr.rightHandSide, Coercion.cast(rhsType, lhsType));
+          rhsType = lhsType;
+        } else {
+          // Static type error
+          staticInfo = new StaticTypeError(rules, expr, lhsType);
+        }
+        _recordMessage(staticInfo);
+      }
+
+      // Check the rhs type
+      if (staticInfo is! CoercionInfo) {
+        var paramType = paramTypes.first;
+        staticInfo = rules.checkAssignment(expr.rightHandSide, paramType);
+        _recordMessage(staticInfo);
+      }
+    }
+  }
+
+  bool _isObjectGetter(Expression target, SimpleIdentifier id) {
+    PropertyAccessorElement element =
+        rules.provider.objectType.element.getGetter(id.name);
+    return (element != null && !element.isStatic);
+  }
+
+  bool _isObjectMethod(Expression target, SimpleIdentifier id) {
+    MethodElement element =
+        rules.provider.objectType.element.getMethod(id.name);
+    return (element != null && !element.isStatic);
+  }
+
+  bool _isObjectProperty(Expression target, SimpleIdentifier id) {
+    return _isObjectGetter(target, id) || _isObjectMethod(target, id);
+  }
+
+  DartType _getStaticType(Expression expr) {
+    var type = expr.staticType;
+    if (type == null) {
+      reporter.reportError(new MissingTypeError(expr).toAnalysisError());
+    }
+    return type ?? rules.provider.dynamicType;
+  }
+
+  void _recordDynamicInvoke(AstNode node, AstNode target) {
+    reporter.reportError(new DynamicInvoke(rules, node).toAnalysisError());
+    // TODO(jmesserly): we may eventually want to record if the whole operation
+    // (node) was dynamic, rather than the target, but this is an easier fit
+    // with what we used to do.
+    DynamicInvoke.set(target, true);
+  }
+
+  void _recordMessage(StaticInfo info) {
+    if (info == null) return;
+    var error = info.toAnalysisError();
+    if (error.errorCode.errorSeverity == ErrorSeverity.ERROR) _failure = true;
+    reporter.reportError(error);
+
+    if (info is CoercionInfo) {
+      // TODO(jmesserly): if we're run again on the same AST, we'll produce the
+      // same annotations. This should be harmless. This might go away once
+      // CodeChecker is integrated better with analyzer, as it will know that
+      // checking has already been performed.
+      // assert(CoercionInfo.get(info.node) == null);
+      CoercionInfo.set(info.node, info);
+    }
+  }
+}
+
+
+/// Looks up the declaration that matches [member] in [type] and returns it's
+/// declared type.
+FunctionType _getMemberType(InterfaceType type, ExecutableElement member) =>
+    _memberTypeGetter(member)(type);
+
+typedef FunctionType _MemberTypeGetter(InterfaceType type);
+
+_MemberTypeGetter _memberTypeGetter(ExecutableElement member) {
+  String memberName = member.name;
+  final isGetter = member is PropertyAccessorElement && member.isGetter;
+  final isSetter = member is PropertyAccessorElement && member.isSetter;
+
+  FunctionType f(InterfaceType type) {
+    ExecutableElement baseMethod;
+    try {
+      if (isGetter) {
+        assert(!isSetter);
+        // Look for getter or field.
+        baseMethod = type.getGetter(memberName);
+      } else if (isSetter) {
+        baseMethod = type.getSetter(memberName);
+      } else {
+        baseMethod = type.getMethod(memberName);
+      }
+    } catch (e) {
+      // TODO(sigmund): remove this try-catch block (see issue #48).
+    }
+    if (baseMethod == null || baseMethod.isStatic) return null;
+    return baseMethod.type;
+  }
+  ;
+  return f;
+}