Put IR builder visitors in a different library than IrBuilder.

pkg/compiler/lib/src/cps_ir/cps_ir_builder_visitor.dart

Index: pkg/compiler/lib/src/cps_ir/cps_ir_builder_visitor.dart
diff --git a/pkg/compiler/lib/src/cps_ir/cps_ir_builder_visitor.dart b/pkg/compiler/lib/src/cps_ir/cps_ir_builder_visitor.dart
deleted file mode 100644
index fd1f21d09bde30b70c2ea1006da5416c718943dc..0000000000000000000000000000000000000000
--- a/pkg/compiler/lib/src/cps_ir/cps_ir_builder_visitor.dart
+++ /dev/null
@@ -1,1847 +0,0 @@
-// Copyright (c) 2013, 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.
-
-part of dart2js.ir_builder;
-
-/**
- * This task iterates through all resolved elements and builds [ir.Node]s. The
- * nodes are stored in the [nodes] map and accessible through [hasIr] and
- * [getIr].
- *
- * The functionality of the IrNodes is added gradually, therefore elements might
- * have an IR or not, depending on the language features that are used. For
- * elements that do have an IR, the tree [ast.Node]s and the [Token]s are not
- * used in the rest of the compilation. This is ensured by setting the element's
- * cached tree to `null` and also breaking the token stream to crash future
- * attempts to parse.
- *
- * The type inferrer works on either IR nodes or tree nodes. The IR nodes are
- * then translated into the SSA form for optimizations and code generation.
- * Long-term, once the IR supports the full language, the backend can be
- * re-implemented to work directly on the IR.
- */
-class IrBuilderTask extends CompilerTask {
-  final Map<Element, ir.ExecutableDefinition> nodes =
-      <Element, ir.ExecutableDefinition>{};
-  final bool generateSourceMap;
-
-  IrBuilderTask(Compiler compiler, {this.generateSourceMap: true})
-      : super(compiler);
-
-  String get name => 'IR builder';
-
-  bool hasIr(Element element) => nodes.containsKey(element.implementation);
-
-  ir.ExecutableDefinition getIr(ExecutableElement element) {
-    return nodes[element.implementation];
-  }
-
-  ir.ExecutableDefinition buildNode(AstElement element) {
-    if (!canBuild(element)) return null;
-
-    TreeElements elementsMapping = element.resolvedAst.elements;
-    element = element.implementation;
-    return compiler.withCurrentElement(element, () {
-      SourceInformationBuilder sourceInformationBuilder = generateSourceMap
-          ? new PositionSourceInformationBuilder(element)
-          : const SourceInformationBuilder();
-
-      IrBuilderVisitor builder =
-          compiler.backend is JavaScriptBackend
-          ? new JsIrBuilderVisitor(
-              elementsMapping, compiler, sourceInformationBuilder)
-          : new DartIrBuilderVisitor(
-              elementsMapping, compiler, sourceInformationBuilder);
-      ir.ExecutableDefinition definition =
-            builder.buildExecutable(element);
-      if (definition != null) {
-        nodes[element] = definition;
-      }
-      return definition;
-    });
-  }
-
-  void buildNodes() {
-    measure(() {
-      Set<Element> resolved = compiler.enqueuer.resolution.resolvedElements;
-      resolved.forEach(buildNode);
-    });
-  }
-
-  bool canBuild(Element element) {
-    if (element is TypedefElement) return false;
-    if (element is FunctionElement) {
-      // TODO(sigurdm): Support native functions for dart2js.
-      assert(invariant(element, !element.isNative));
-
-      if (element is ConstructorElement) {
-        if (!element.isGenerativeConstructor) {
-          // TODO(kmillikin,sigurdm): Support constructors.
-          return false;
-        }
-        if (element.isSynthesized) {
-          // Do generate CPS for synthetic constructors.
-          return true;
-        }
-      }
-    } else if (element is! FieldElement) {
-      compiler.internalError(element, "Unexpected element type $element");
-    }
-    return compiler.backend.shouldOutput(element);
-  }
-
-  bool get inCheckedMode {
-    bool result = false;
-    assert((result = true));
-    return result;
-  }
-
-}
-
-class _GetterElements {
-  ir.Primitive result;
-  ir.Primitive index;
-  ir.Primitive receiver;
-
-  _GetterElements({this.result, this.index, this.receiver}) ;
-}
-
-/**
- * A tree visitor that builds [IrNodes]. The visit methods add statements using
- * to the [builder] and return the last added statement for trees that represent
- * an expression.
- */
-abstract class IrBuilderVisitor extends ResolvedVisitor<ir.Primitive>
-    with IrBuilderMixin<ast.Node> {
-  final Compiler compiler;
-  final SourceInformationBuilder sourceInformationBuilder;
-
-  // In SSA terms, join-point continuation parameters are the phis and the
-  // continuation invocation arguments are the corresponding phi inputs.  To
-  // support name introduction and renaming for source level variables, we use
-  // nested (delimited) visitors for constructing subparts of the IR that will
-  // need renaming.  Each source variable is assigned an index.
-  //
-  // Each nested visitor maintains a list of free variable uses in the body.
-  // These are implemented as a list of parameters, each with their own use
-  // list of references.  When the delimited subexpression is plugged into the
-  // surrounding context, the free occurrences can be captured or become free
-  // occurrences in the next outer delimited subexpression.
-  //
-  // Each nested visitor maintains a list that maps indexes of variables
-  // assigned in the delimited subexpression to their reaching definition ---
-  // that is, the definition in effect at the hole in 'current'.  These are
-  // used to determine if a join-point continuation needs to be passed
-  // arguments, and what the arguments are.
-
-  /// Construct a top-level visitor.
-  IrBuilderVisitor(TreeElements elements,
-                   this.compiler,
-                   this.sourceInformationBuilder)
-      : super(elements);
-
-  /**
-   * Builds the [ir.ExecutableDefinition] for an executable element. In case the
-   * function uses features that cannot be expressed in the IR, this element
-   * returns `null`.
-   */
-  ir.ExecutableDefinition buildExecutable(ExecutableElement element);
-
-  ClosureScope getClosureScopeForNode(ast.Node node);
-  ClosureEnvironment getClosureEnvironment();
-
-  /// Normalizes the argument list to a static invocation (i.e. where the target
-  /// element is known).
-  ///
-  /// For the JS backend, inserts default arguments and normalizes order of
-  /// named arguments.
-  ///
-  /// For the Dart backend, returns [arguments].
-  List<ir.Primitive> normalizeStaticArguments(
-      Selector selector,
-      FunctionElement target,
-      List<ir.Primitive> arguments);
-
-  /// Normalizes the argument list of a dynamic invocation (i.e. where the
-  /// target element is unknown).
-  ///
-  /// For the JS backend, normalizes order of named arguments.
-  ///
-  /// For the Dart backend, returns [arguments].
-  List<ir.Primitive> normalizeDynamicArguments(
-      Selector selector,
-      List<ir.Primitive> arguments);
-
-  ir.FunctionDefinition _makeFunctionBody(FunctionElement element,
-                                          ast.FunctionExpression node) {
-    FunctionSignature signature = element.functionSignature;
-    List<ParameterElement> parameters = [];
-    signature.orderedForEachParameter(parameters.add);
-
-    irBuilder.buildFunctionHeader(parameters,
-                                  closureScope: getClosureScopeForNode(node),
-                                  env: getClosureEnvironment());
-
-    List<ConstantExpression> defaults = new List<ConstantExpression>();
-    signature.orderedOptionalParameters.forEach((ParameterElement element) {
-      defaults.add(getConstantForVariable(element));
-    });
-
-    List<ir.Initializer> initializers;
-    if (element.isSynthesized) {
-      assert(element is ConstructorElement);
-      return irBuilder.makeConstructorDefinition(const <ConstantExpression>[],
-          const <ir.Initializer>[]);
-    } else if (element.isGenerativeConstructor) {
-      if (element.isExternal) {
-        return irBuilder.makeAbstractConstructorDefinition(defaults);
-      } else {
-        initializers = buildConstructorInitializers(node, element);
-        visit(node.body);
-        return irBuilder.makeConstructorDefinition(defaults, initializers);
-      }
-    } else {
-      visit(node.body);
-      return irBuilder.makeFunctionDefinition(defaults);
-    }
-  }
-
-  List<ir.Initializer> buildConstructorInitializers(
-      ast.FunctionExpression function, ConstructorElement element) {
-    List<ir.Initializer> result = <ir.Initializer>[];
-    FunctionSignature signature = element.functionSignature;
-
-    void tryAddInitializingFormal(ParameterElement parameterElement) {
-      if (parameterElement.isInitializingFormal) {
-        InitializingFormalElement initializingFormal = parameterElement;
-        withBuilder(irBuilder.makeInitializerBuilder(), () {
-          ir.Primitive value = irBuilder.buildLocalGet(parameterElement);
-          result.add(irBuilder.makeFieldInitializer(
-              initializingFormal.fieldElement,
-              irBuilder.makeRunnableBody(value)));
-        });
-      }
-    }
-
-    // TODO(sigurdm): Preserve initializing formals as initializing formals.
-    signature.orderedForEachParameter(tryAddInitializingFormal);
-
-    if (function.initializers == null) return result;
-    bool explicitSuperInitializer = false;
-    for(ast.Node initializer in function.initializers) {
-      if (initializer is ast.SendSet) {
-        // Field initializer.
-        FieldElement field = elements[initializer];
-        withBuilder(irBuilder.makeInitializerBuilder(), () {
-          ir.Primitive value = visit(initializer.arguments.head);
-          ir.RunnableBody body = irBuilder.makeRunnableBody(value);
-          result.add(irBuilder.makeFieldInitializer(field, body));
-        });
-      } else if (initializer is ast.Send) {
-        // Super or this initializer.
-        if (ast.Initializers.isConstructorRedirect(initializer)) {
-          giveup(initializer, "constructor redirect (this) initializer");
-        }
-        ConstructorElement constructor = elements[initializer].implementation;
-        Selector selector = elements.getSelector(initializer);
-        List<ir.RunnableBody> arguments =
-            initializer.arguments.mapToList((ast.Node argument) {
-          return withBuilder(irBuilder.makeInitializerBuilder(), () {
-            ir.Primitive value = visit(argument);
-            return irBuilder.makeRunnableBody(value);
-          });
-        });
-        result.add(irBuilder.makeSuperInitializer(constructor,
-                                                  arguments,
-                                                  selector));
-        explicitSuperInitializer = true;
-      } else {
-        compiler.internalError(initializer,
-                               "Unexpected initializer type $initializer");
-      }
-
-    }
-    if (!explicitSuperInitializer) {
-      // No super initializer found. Try to find the default constructor if
-      // the class is not Object.
-      ClassElement enclosingClass = element.enclosingClass;
-      if (!enclosingClass.isObject) {
-        ClassElement superClass = enclosingClass.superclass;
-        FunctionElement target = superClass.lookupDefaultConstructor();
-        if (target == null) {
-          compiler.internalError(superClass,
-              "No default constructor available.");
-        }
-        Selector selector = new Selector.callDefaultConstructor();
-        result.add(irBuilder.makeSuperInitializer(target,
-                                                  <ir.RunnableBody>[],
-                                                  selector));
-      }
-    }
-    return result;
-  }
-
-  ir.Primitive visit(ast.Node node) => node.accept(this);
-
-  // ==== Statements ====
-  visitBlock(ast.Block node) {
-    irBuilder.buildBlock(node.statements.nodes, build);
-  }
-
-  ir.Primitive visitBreakStatement(ast.BreakStatement node) {
-    if (!irBuilder.buildBreak(elements.getTargetOf(node))) {
-      compiler.internalError(node, "'break' target not found");
-    }
-    return null;
-  }
-
-  ir.Primitive visitContinueStatement(ast.ContinueStatement node) {
-    if (!irBuilder.buildContinue(elements.getTargetOf(node))) {
-      compiler.internalError(node, "'continue' target not found");
-    }
-    return null;
-  }
-
-  // Build(EmptyStatement, C) = C
-  ir.Primitive visitEmptyStatement(ast.EmptyStatement node) {
-    assert(irBuilder.isOpen);
-    return null;
-  }
-
-  // Build(ExpressionStatement(e), C) = C'
-  //   where (C', _) = Build(e, C)
-  ir.Primitive visitExpressionStatement(ast.ExpressionStatement node) {
-    assert(irBuilder.isOpen);
-    visit(node.expression);
-    return null;
-  }
-
-  visitFor(ast.For node) {
-    List<LocalElement> loopVariables = <LocalElement>[];
-    if (node.initializer is ast.VariableDefinitions) {
-      ast.VariableDefinitions definitions = node.initializer;
-      for (ast.Node node in definitions.definitions.nodes) {
-        LocalElement loopVariable = elements[node];
-        loopVariables.add(loopVariable);
-      }
-    }
-
-    JumpTarget target = elements.getTargetDefinition(node);
-    irBuilder.buildFor(
-        buildInitializer: subbuild(node.initializer),
-        buildCondition: subbuild(node.condition),
-        buildBody: subbuild(node.body),
-        buildUpdate: subbuildSequence(node.update),
-        closureScope: getClosureScopeForNode(node),
-        loopVariables: loopVariables,
-        target: target);
-  }
-
-  visitIf(ast.If node) {
-    irBuilder.buildIf(
-        build(node.condition),
-        subbuild(node.thenPart),
-        subbuild(node.elsePart));
-  }
-
-  ir.Primitive visitLabeledStatement(ast.LabeledStatement node) {
-    ast.Statement body = node.statement;
-    if (body is ast.Loop) return visit(body);
-    JumpTarget target = elements.getTargetDefinition(body);
-    JumpCollector jumps = new JumpCollector(target);
-    irBuilder.state.breakCollectors.add(jumps);
-    IrBuilder innerBuilder = irBuilder.makeDelimitedBuilder();
-    withBuilder(innerBuilder, () {
-      visit(body);
-    });
-    irBuilder.state.breakCollectors.removeLast();
-    bool hasBreaks = !jumps.isEmpty;
-    ir.Continuation joinContinuation;
-    if (hasBreaks) {
-      if (innerBuilder.isOpen) {
-        jumps.addJump(innerBuilder);
-      }
-
-      // All jumps to the break continuation must be in the scope of the
-      // continuation's binding.  The continuation is bound just outside the
-      // body to satisfy this property without extra analysis.
-      // As a consequence, the break continuation needs parameters for all
-      // local variables in scope at the exit from the body.
-      List<ir.Parameter> parameters =
-          new List<ir.Parameter>.generate(irBuilder.environment.length, (i) {
-        return new ir.Parameter(irBuilder.environment.index2variable[i]);
-      });
-      joinContinuation = new ir.Continuation(parameters);
-      irBuilder.invokeFullJoin(joinContinuation, jumps, recursive: false);
-      irBuilder.add(new ir.LetCont(joinContinuation,
-          innerBuilder._root));
-      for (int i = 0; i < irBuilder.environment.length; ++i) {
-        irBuilder.environment.index2value[i] = parameters[i];
-      }
-    } else {
-      if (innerBuilder._root != null) {
-        irBuilder.add(innerBuilder._root);
-        irBuilder._current = innerBuilder._current;
-        irBuilder.environment = innerBuilder.environment;
-      }
-    }
-    return null;
-  }
-
-  visitWhile(ast.While node) {
-    irBuilder.buildWhile(
-        buildCondition: subbuild(node.condition),
-        buildBody: subbuild(node.body),
-        target: elements.getTargetDefinition(node),
-        closureScope: getClosureScopeForNode(node));
-  }
-
-  visitForIn(ast.ForIn node) {
-    // [node.declaredIdentifier] can be either an [ast.VariableDefinitions]
-    // (defining a new local variable) or a send designating some existing
-    // variable.
-    ast.Node identifier = node.declaredIdentifier;
-    ast.VariableDefinitions variableDeclaration =
-        identifier.asVariableDefinitions();
-    Element variableElement = elements.getForInVariable(node);
-    Selector selector = elements.getSelector(identifier);
-
-    irBuilder.buildForIn(
-        buildExpression: subbuild(node.expression),
-        buildVariableDeclaration: subbuild(variableDeclaration),
-        variableElement: variableElement,
-        variableSelector: selector,
-        buildBody: subbuild(node.body),
-        target: elements.getTargetDefinition(node),
-        closureScope: getClosureScopeForNode(node));
-  }
-
-  ir.Primitive visitVariableDefinitions(ast.VariableDefinitions node) {
-    assert(irBuilder.isOpen);
-    if (node.modifiers.isConst) {
-      for (ast.SendSet definition in node.definitions.nodes) {
-        assert(!definition.arguments.isEmpty);
-        assert(definition.arguments.tail.isEmpty);
-        VariableElement element = elements[definition];
-        ConstantExpression value = getConstantForVariable(element);
-        irBuilder.declareLocalConstant(element, value);
-      }
-    } else {
-      for (ast.Node definition in node.definitions.nodes) {
-        Element element = elements[definition];
-        ir.Primitive initialValue;
-        // Definitions are either SendSets if there is an initializer, or
-        // Identifiers if there is no initializer.
-        if (definition is ast.SendSet) {
-          assert(!definition.arguments.isEmpty);
-          assert(definition.arguments.tail.isEmpty);
-          initialValue = visit(definition.arguments.head);
-        } else {
-          assert(definition is ast.Identifier);
-        }
-        irBuilder.declareLocalVariable(element, initialValue: initialValue);
-      }
-    }
-    return null;
-  }
-
-  // Build(Return(e), C) = C'[InvokeContinuation(return, x)]
-  //   where (C', x) = Build(e, C)
-  //
-  // Return without a subexpression is translated as if it were return null.
-  ir.Primitive visitReturn(ast.Return node) {
-    assert(irBuilder.isOpen);
-    assert(invariant(node, node.beginToken.value != 'native'));
-    irBuilder.buildReturn(build(node.expression));
-    return null;
-  }
-
-  visitTryStatement(ast.TryStatement node) {
-    // Try/catch is not yet implemented in the JS backend.
-    if (this.irBuilder.tryStatements == null) {
-      return giveup(node, 'try/catch in the JS backend');
-    }
-    // Multiple catch blocks are not yet implemented.
-    if (node.catchBlocks.isEmpty ||
-        node.catchBlocks.nodes.tail == null) {
-      return giveup(node, 'not exactly one catch block');
-    }
-    // 'on T' catch blocks are not yet implemented.
-    if ((node.catchBlocks.nodes.head as ast.CatchBlock).onKeyword != null) {
-      return giveup(node, '"on T" catch block');
-    }
-    // Finally blocks are not yet implemented.
-    if (node.finallyBlock != null) {
-      return giveup(node, 'try/finally');
-    }
-
-    List<CatchClauseInfo> catchClauseInfos = <CatchClauseInfo>[];
-    for (ast.CatchBlock catchClause in node.catchBlocks.nodes) {
-      assert(catchClause.exception != null);
-      LocalVariableElement exceptionVariable = elements[catchClause.exception];
-      LocalVariableElement stackTraceVariable;
-      if (catchClause.trace != null) {
-        stackTraceVariable = elements[catchClause.trace];
-      }
-      catchClauseInfos.add(new CatchClauseInfo(
-          exceptionVariable: exceptionVariable,
-          stackTraceVariable: stackTraceVariable,
-          buildCatchBlock: subbuild(catchClause.block)));
-    }
-
-    irBuilder.buildTry(
-        tryStatementInfo: irBuilder.tryStatements[node],
-        buildTryBlock: subbuild(node.tryBlock),
-        catchClauseInfos: catchClauseInfos);
-  }
-
-  // ==== Expressions ====
-  ir.Primitive visitConditional(ast.Conditional node) {
-    return irBuilder.buildConditional(
-        build(node.condition),
-        subbuild(node.thenExpression),
-        subbuild(node.elseExpression));
-  }
-
-  // For all simple literals:
-  // Build(Literal(c), C) = C[let val x = Constant(c) in [], x]
-  ir.Primitive visitLiteralBool(ast.LiteralBool node) {
-    assert(irBuilder.isOpen);
-    return translateConstant(node);
-  }
-
-  ir.Primitive visitLiteralDouble(ast.LiteralDouble node) {
-    assert(irBuilder.isOpen);
-    return translateConstant(node);
-  }
-
-  ir.Primitive visitLiteralInt(ast.LiteralInt node) {
-    assert(irBuilder.isOpen);
-    return translateConstant(node);
-  }
-
-  ir.Primitive visitLiteralNull(ast.LiteralNull node) {
-    assert(irBuilder.isOpen);
-    return translateConstant(node);
-  }
-
-  ir.Primitive visitLiteralString(ast.LiteralString node) {
-    assert(irBuilder.isOpen);
-    return translateConstant(node);
-  }
-
-  ConstantExpression getConstantForNode(ast.Node node) {
-    ConstantExpression constant =
-        compiler.backend.constantCompilerTask.compileNode(node, elements);
-    assert(invariant(node, constant != null,
-        message: 'No constant computed for $node'));
-    return constant;
-  }
-
-  ConstantExpression getConstantForVariable(VariableElement element) {
-    ConstantExpression constant =
-        compiler.backend.constants.getConstantForVariable(element);
-    assert(invariant(element, constant != null,
-            message: 'No constant computed for $element'));
-    return constant;
-  }
-
-  ir.Primitive visitLiteralList(ast.LiteralList node) {
-    if (node.isConst) {
-      return translateConstant(node);
-    }
-    List<ir.Primitive> values = node.elements.nodes.mapToList(visit);
-    InterfaceType type = elements.getType(node);
-    return irBuilder.buildListLiteral(type, values);
-  }
-
-  ir.Primitive visitLiteralMap(ast.LiteralMap node) {
-    if (node.isConst) {
-      return translateConstant(node);
-    }
-    InterfaceType type = elements.getType(node);
-    return irBuilder.buildMapLiteral(
-        type,
-        node.entries.nodes.map((e) => e.key),
-        node.entries.nodes.map((e) => e.value),
-        build);
-  }
-
-  ir.Primitive visitLiteralSymbol(ast.LiteralSymbol node) {
-    assert(irBuilder.isOpen);
-    return translateConstant(node);
-  }
-
-  ir.Primitive visitIdentifier(ast.Identifier node) {
-    // "this" is the only identifier that should be met by the visitor.
-    assert(node.isThis());
-    return irBuilder.buildThis();
-  }
-
-  ir.Primitive visitParenthesizedExpression(
-      ast.ParenthesizedExpression node) {
-    assert(irBuilder.isOpen);
-    return visit(node.expression);
-  }
-
-  // Stores the result of visiting a CascadeReceiver, so we can return it from
-  // its enclosing Cascade.
-  ir.Primitive _currentCascadeReceiver;
-
-  ir.Primitive visitCascadeReceiver(ast.CascadeReceiver node) {
-    assert(irBuilder.isOpen);
-    return _currentCascadeReceiver = visit(node.expression);
-  }
-
-  ir.Primitive visitCascade(ast.Cascade node) {
-    assert(irBuilder.isOpen);
-    var oldCascadeReceiver = _currentCascadeReceiver;
-    // Throw away the result of visiting the expression.
-    // Instead we return the result of visiting the CascadeReceiver.
-    this.visit(node.expression);
-    ir.Primitive receiver = _currentCascadeReceiver;
-    _currentCascadeReceiver = oldCascadeReceiver;
-    return receiver;
-  }
-
-  // ==== Sends ====
-  ir.Primitive visitAssert(ast.Send node) {
-    assert(irBuilder.isOpen);
-    return giveup(node, 'Assert');
-  }
-
-  ir.Primitive visitNamedArgument(ast.NamedArgument node) {
-    assert(irBuilder.isOpen);
-    return visit(node.expression);
-  }
-
-  ir.Primitive visitClosureSend(ast.Send node) {
-    assert(irBuilder.isOpen);
-    Element element = elements[node];
-    Selector selector = elements.getSelector(node);
-    ir.Primitive receiver = (element == null)
-        ? visit(node.selector)
-        : irBuilder.buildLocalGet(element);
-    List<ir.Primitive> arguments = node.arguments.mapToList(visit);
-    arguments = normalizeDynamicArguments(selector, arguments);
-    return irBuilder.buildCallInvocation(receiver, selector, arguments);
-  }
-
-  /// If [node] is null, returns this.
-  /// If [node] is super, returns null (for special handling)
-  /// Otherwise visits [node] and returns the result.
-  ir.Primitive visitReceiver(ast.Expression node) {
-    if (node == null) return irBuilder.buildThis();
-    if (node.isSuper()) return null;
-    return visit(node);
-  }
-
-  /// Returns `true` if [node] is a super call.
-  // TODO(johnniwinther): Remove the need for this.
-  bool isSuperCall(ast.Send node) {
-    return node != null && node.receiver != null && node.receiver.isSuper();
-  }
-
-  ir.Primitive visitDynamicSend(ast.Send node) {
-    assert(irBuilder.isOpen);
-    Selector selector = elements.getSelector(node);
-    ir.Primitive receiver = visitReceiver(node.receiver);
-    List<ir.Primitive> arguments = node.arguments.mapToList(visit);
-    arguments = normalizeDynamicArguments(selector, arguments);
-    return irBuilder.buildDynamicInvocation(receiver, selector, arguments);
-  }
-
-  _GetterElements translateGetter(ast.Send node, Selector selector) {
-    Element element = elements[node];
-    ir.Primitive result;
-    ir.Primitive receiver;
-    ir.Primitive index;
-
-    if (element != null && element.isConst) {
-      // Reference to constant local, top-level or static field
-      result = translateConstant(node);
-    } else if (Elements.isLocal(element)) {
-      // Reference to local variable
-      result = irBuilder.buildLocalGet(element);
-    } else if (element == null ||
-               Elements.isInstanceField(element) ||
-               Elements.isInstanceMethod(element) ||
-               selector.isIndex ||
-               // TODO(johnniwinther): clean up semantics of resolution.
-               node.isSuperCall) {
-      // Dynamic dispatch to a getter. Sometimes resolution will suggest a
-      // target element, but in these cases we must still emit a dynamic
-      // dispatch. The target element may be an instance method in case we are
-      // converting a method to a function object.
-
-      receiver = visitReceiver(node.receiver);
-      List<ir.Primitive> arguments = new List<ir.Primitive>();
-      if (selector.isIndex) {
-        index = visit(node.arguments.head);
-        arguments.add(index);
-      }
-
-      assert(selector.kind == SelectorKind.GETTER ||
-             selector.kind == SelectorKind.INDEX);
-      if (isSuperCall(node)) {
-        result = irBuilder.buildSuperInvocation(element, selector, arguments);
-      } else {
-        result =
-            irBuilder.buildDynamicInvocation(receiver, selector, arguments);
-      }
-    } else if (element.isField || element.isGetter || element.isErroneous ||
-               element.isSetter) {
-      // TODO(johnniwinther): Change handling of setter selectors.
-      // Access to a static field or getter (non-static case handled above).
-      // Even if there is only a setter, we compile as if it was a getter,
-      // so the vm can fail at runtime.
-      assert(selector.kind == SelectorKind.GETTER ||
-             selector.kind == SelectorKind.SETTER);
-      result = irBuilder.buildStaticGet(element, selector,
-          sourceInformation: sourceInformationBuilder.buildGet(node));
-    } else if (Elements.isStaticOrTopLevelFunction(element)) {
-      // Convert a top-level or static function to a function object.
-      result = translateConstant(node);
-    } else {
-      throw "Unexpected SendSet getter: $node, $element";
-    }
-    return new _GetterElements(
-        result: result,index: index, receiver: receiver);
-  }
-
-  ir.Primitive visitGetterSend(ast.Send node) {
-    assert(irBuilder.isOpen);
-    return translateGetter(node, elements.getSelector(node)).result;
-
-  }
-
-  ir.Primitive translateLogicalOperator(ast.Operator op,
-                                        ast.Expression left,
-                                        ast.Expression right) {
-    ir.Primitive leftValue = visit(left);
-
-    ir.Primitive buildRightValue(IrBuilder rightBuilder) {
-      return withBuilder(rightBuilder, () => visit(right));
-    }
-
-    return irBuilder.buildLogicalOperator(
-        leftValue, buildRightValue, isLazyOr: op.source == '||');
-  }
-
-  ir.Primitive visitOperatorSend(ast.Send node) {
-    assert(irBuilder.isOpen);
-    ast.Operator op = node.selector;
-    if (isUserDefinableOperator(op.source)) {
-      return visitDynamicSend(node);
-    }
-    if (op.source == '&&' || op.source == '||') {
-      assert(node.receiver != null);
-      assert(!node.arguments.isEmpty);
-      assert(node.arguments.tail.isEmpty);
-      return translateLogicalOperator(op, node.receiver, node.arguments.head);
-    }
-    if (op.source == "!") {
-      assert(node.receiver != null);
-      assert(node.arguments.isEmpty);
-      return irBuilder.buildNegation(visit(node.receiver));
-    }
-    if (op.source == "!=") {
-      assert(node.receiver != null);
-      assert(!node.arguments.isEmpty);
-      assert(node.arguments.tail.isEmpty);
-      return irBuilder.buildNegation(visitDynamicSend(node));
-    }
-    assert(invariant(node, op.source == "is" || op.source == "as",
-           message: "unexpected operator $op"));
-    DartType type = elements.getType(node.typeAnnotationFromIsCheckOrCast);
-    ir.Primitive receiver = visit(node.receiver);
-    return irBuilder.buildTypeOperator(
-        receiver, type,
-        isTypeTest: op.source == "is",
-        isNotCheck: node.isIsNotCheck);
-  }
-
-  // Build(StaticSend(f, arguments), C) = C[C'[InvokeStatic(f, xs)]]
-  //   where (C', xs) = arguments.fold(Build, C)
-  ir.Primitive visitStaticSend(ast.Send node) {
-    assert(irBuilder.isOpen);
-    Element element = elements[node];
-    assert(!element.isConstructor);
-    // TODO(lry): support foreign functions.
-    if (element.isForeign(compiler.backend)) {
-      return giveup(node, 'StaticSend: foreign');
-    }
-
-    Selector selector = elements.getSelector(node);
-
-    if (selector.isCall && (element.isGetter || element.isField)) {
-      // We are invoking a static field or getter as if it was a method, e.g:
-      //
-      //     get foo => {..}
-      //     main() {  foo(1, 2, 3);  }
-      //
-      // We invoke the getter of 'foo' and then invoke the 'call' method
-      // on the result, using the given arguments.
-      Selector getter = new Selector.getterFrom(selector);
-      Selector call = new Selector.callClosureFrom(selector);
-      ir.Primitive receiver = irBuilder.buildStaticGet(element, getter);
-      List<ir.Primitive> arguments = node.arguments.mapToList(visit);
-      arguments = normalizeDynamicArguments(selector, arguments);
-      return irBuilder.buildCallInvocation(receiver, call, arguments);
-    } else if (selector.isGetter) {
-      // We are reading a static field or invoking a static getter.
-      return irBuilder.buildStaticGet(element, selector);
-    } else {
-      // We are invoking a static method.
-      assert(selector.isCall);
-      assert(element is FunctionElement);
-      List<ir.Primitive> arguments = node.arguments.mapToList(visit);
-      arguments = normalizeStaticArguments(selector, element, arguments);
-      return irBuilder.buildStaticInvocation(element, selector, arguments,
-          sourceInformation: sourceInformationBuilder.buildCall(node));
-    }
-  }
-
-  ir.Primitive visitSuperSend(ast.Send node) {
-    assert(irBuilder.isOpen);
-    Selector selector = elements.getSelector(node);
-    Element target = elements[node];
-
-    if (selector.isCall && (target.isGetter || target.isField)) {
-      // We are invoking a field or getter as if it was a method, e.g:
-      //
-      //     class A { get foo => {..} }
-      //     class B extends A {
-      //         m() {
-      //           super.foo(1, 2, 3);  }
-      //         }
-      //     }
-      //
-      // We invoke the getter of 'foo' and then invoke the 'call' method on
-      // the result, using the given arguments.
-      Selector getter = new Selector.getterFrom(selector);
-      Selector call = new Selector.callClosureFrom(selector);
-      ir.Primitive receiver =
-          irBuilder.buildSuperInvocation(target, getter, []);
-      List<ir.Primitive> arguments = node.arguments.mapToList(visit);
-      arguments = normalizeDynamicArguments(selector, arguments);
-      return irBuilder.buildCallInvocation(receiver, call, arguments);
-    } else if (selector.isCall) {
-      // We are invoking a method.
-      assert(target is FunctionElement);
-      List<ir.Primitive> arguments = node.arguments.mapToList(visit);
-      arguments = normalizeStaticArguments(selector, target, arguments);
-      return irBuilder.buildSuperInvocation(target, selector, arguments);
-    } else {
-      // We are invoking a getter, operator, indexer, etc.
-      List<ir.Primitive> arguments = node.argumentsNode == null
-          ? <ir.Primitive>[]
-          : node.arguments.mapToList(visit);
-      return irBuilder.buildSuperInvocation(target, selector, arguments);
-    }
-  }
-
-  visitTypePrefixSend(ast.Send node) {
-    compiler.internalError(node, "visitTypePrefixSend should not be called.");
-  }
-
-  ir.Primitive visitTypeLiteralSend(ast.Send node) {
-    assert(irBuilder.isOpen);
-    // If the user is trying to invoke the type literal or variable,
-    // it must be treated as a function call.
-    if (node.argumentsNode != null) {
-      // TODO(sigurdm): Handle this to match proposed semantics of issue #19725.
-      return giveup(node, 'Type literal invoked as function');
-    }
-
-    DartType type = elements.getTypeLiteralType(node);
-    if (type is TypeVariableType) {
-      ir.Primitive prim = new ir.ReifyTypeVar(type.element);
-      irBuilder.add(new ir.LetPrim(prim));
-      return prim;
-    } else {
-      return translateConstant(node);
-    }
-  }
-
-  ir.Primitive visitSendSet(ast.SendSet node) {
-    assert(irBuilder.isOpen);
-    Element element = elements[node];
-    ast.Operator op = node.assignmentOperator;
-    // For complex operators, this is the result of getting (before assigning)
-    ir.Primitive originalValue;
-    // For []+= style operators, this saves the index.
-    ir.Primitive index;
-    ir.Primitive receiver;
-    // This is what gets assigned.
-    ir.Primitive valueToStore;
-    Selector selector = elements.getSelector(node);
-    Selector operatorSelector =
-        elements.getOperatorSelectorInComplexSendSet(node);
-    Selector getterSelector =
-        elements.getGetterSelectorInComplexSendSet(node);
-    assert(
-        // Indexing send-sets have an argument for the index.
-        (selector.isIndexSet ? 1 : 0) +
-        // Non-increment send-sets have one more argument.
-        (ast.Operator.INCREMENT_OPERATORS.contains(op.source) ? 0 : 1)
-            == node.argumentCount());
-
-    ast.Node getAssignArgument() {
-      assert(invariant(node, !node.arguments.isEmpty,
-                       message: "argument expected"));
-      return selector.isIndexSet
-          ? node.arguments.tail.head
-          : node.arguments.head;
-    }
-
-    // Get the value into valueToStore
-    if (op.source == "=") {
-      if (selector.isIndexSet) {
-        receiver = visitReceiver(node.receiver);
-        index = visit(node.arguments.head);
-      } else if (element == null || Elements.isInstanceField(element)) {
-        receiver = visitReceiver(node.receiver);
-      }
-      valueToStore = visit(getAssignArgument());
-    } else {
-      // Get the original value into getter
-      assert(ast.Operator.COMPLEX_OPERATORS.contains(op.source));
-
-      _GetterElements getterResult = translateGetter(node, getterSelector);
-      index = getterResult.index;
-      receiver = getterResult.receiver;
-      originalValue = getterResult.result;
-
-      // Do the modification of the value in getter.
-      ir.Primitive arg;
-      if (ast.Operator.INCREMENT_OPERATORS.contains(op.source)) {
-        arg = irBuilder.buildIntegerLiteral(1);
-      } else {
-        arg = visit(getAssignArgument());
-      }
-      valueToStore = new ir.Parameter(null);
-      ir.Continuation k = new ir.Continuation([valueToStore]);
-      ir.Expression invoke =
-          new ir.InvokeMethod(originalValue, operatorSelector, k, [arg]);
-      irBuilder.add(new ir.LetCont(k, invoke));
-    }
-
-    if (Elements.isLocal(element)) {
-      irBuilder.buildLocalSet(element, valueToStore);
-    } else if ((!node.isSuperCall && Elements.isErroneous(element)) ||
-                Elements.isStaticOrTopLevel(element)) {
-      irBuilder.buildStaticSet(
-          element, elements.getSelector(node), valueToStore);
-    } else {
-      // Setter or index-setter invocation
-      Selector selector = elements.getSelector(node);
-      assert(selector.kind == SelectorKind.SETTER ||
-          selector.kind == SelectorKind.INDEX);
-      if (selector.isIndexSet) {
-        if (isSuperCall(node)) {
-          irBuilder.buildSuperIndexSet(element, index, valueToStore);
-        } else {
-          irBuilder.buildDynamicIndexSet(receiver, index, valueToStore);
-        }
-      } else {
-        if (isSuperCall(node)) {
-          irBuilder.buildSuperSet(element, selector, valueToStore);
-        } else {
-          irBuilder.buildDynamicSet(receiver, selector, valueToStore);
-        }
-      }
-    }
-
-    if (node.isPostfix) {
-      assert(originalValue != null);
-      return originalValue;
-    } else {
-      return valueToStore;
-    }
-  }
-
-  ir.Primitive visitNewExpression(ast.NewExpression node) {
-    if (node.isConst) {
-      return translateConstant(node);
-    }
-    FunctionElement element = elements[node.send];
-    Selector selector = elements.getSelector(node.send);
-    DartType type = elements.getType(node);
-    ast.Node selectorNode = node.send.selector;
-    List<ir.Primitive> arguments =
-        node.send.arguments.mapToList(visit, growable:false);
-    arguments = normalizeStaticArguments(selector, element, arguments);
-    return irBuilder.buildConstructorInvocation(
-        element, selector, type, arguments);
-  }
-
-  ir.Primitive visitStringJuxtaposition(ast.StringJuxtaposition node) {
-    assert(irBuilder.isOpen);
-    ir.Primitive first = visit(node.first);
-    ir.Primitive second = visit(node.second);
-    return irBuilder.buildStringConcatenation([first, second]);
-  }
-
-  ir.Primitive visitStringInterpolation(ast.StringInterpolation node) {
-    assert(irBuilder.isOpen);
-    List<ir.Primitive> arguments = [];
-    arguments.add(visitLiteralString(node.string));
-    var it = node.parts.iterator;
-    while (it.moveNext()) {
-      ast.StringInterpolationPart part = it.current;
-      arguments.add(visit(part.expression));
-      arguments.add(visitLiteralString(part.string));
-    }
-    return irBuilder.buildStringConcatenation(arguments);
-  }
-
-  ir.Primitive translateConstant(ast.Node node) {
-    assert(irBuilder.isOpen);
-    return irBuilder.buildConstantLiteral(getConstantForNode(node));
-  }
-
-  ir.ExecutableDefinition nullIfGiveup(ir.ExecutableDefinition action()) {
-    try {
-      return action();
-    } catch(e, tr) {
-      if (e == ABORT_IRNODE_BUILDER) {
-        return null;
-      }
-      rethrow;
-    }
-  }
-
-  void internalError(String reason, {ast.Node node}) {
-    giveup(node);
-  }
-}
-
-final String ABORT_IRNODE_BUILDER = "IrNode builder aborted";
-
-dynamic giveup(ast.Node node, [String reason]) {
-  throw ABORT_IRNODE_BUILDER;
-}
-
-/// Classifies local variables and local functions as captured, if they
-/// are accessed from within a nested function.
-///
-/// This class is specific to the [DartIrBuilder], in that it gives up if it
-/// sees a feature that is currently unsupport by that builder. In particular,
-/// loop variables captured in a for-loop initializer, condition, or update
-/// expression are unsupported.
-class DartCapturedVariables extends ast.Visitor {
-  final TreeElements elements;
-  DartCapturedVariables(this.elements);
-
-  FunctionElement currentFunction;
-  bool insideInitializer = false;
-  Set<Local> capturedVariables = new Set<Local>();
-
-  Map<ast.TryStatement, TryStatementInfo> tryStatements =
-      <ast.TryStatement, TryStatementInfo>{};
-
-  List<TryStatementInfo> tryNestingStack = <TryStatementInfo>[];
-  bool get inTryStatement => tryNestingStack.isNotEmpty;
-
-  void markAsCaptured(Local local) {
-    capturedVariables.add(local);
-  }
-
-  visit(ast.Node node) => node.accept(this);
-
-  visitNode(ast.Node node) {
-    node.visitChildren(this);
-  }
-
-  visitFor(ast.For node) {
-    if (node.initializer != null) visit(node.initializer);
-    if (node.condition != null) visit(node.condition);
-    if (node.update != null) visit(node.update);
-
-    // Give up if a variable was captured outside of the loop body.
-    if (node.initializer is ast.VariableDefinitions) {
-      ast.VariableDefinitions definitions = node.initializer;
-      for (ast.Node node in definitions.definitions.nodes) {
-        LocalElement loopVariable = elements[node];
-        if (capturedVariables.contains(loopVariable)) {
-          return giveup(node, 'For-loop variable captured in loop header');
-        }
-      }
-    }
-
-    if (node.body != null) visit(node.body);
-  }
-
-  void handleSend(ast.Send node) {
-    Element element = elements[node];
-    if (Elements.isLocal(element) &&
-        !element.isConst &&
-        element.enclosingElement != currentFunction) {
-      LocalElement local = element;
-      markAsCaptured(local);
-    }
-  }
-
-  visitSend(ast.Send node) {
-    handleSend(node);
-    node.visitChildren(this);
-  }
-
-  visitSendSet(ast.SendSet node) {
-    handleSend(node);
-    Element element = elements[node];
-    if (Elements.isLocal(element)) {
-      LocalElement local = element;
-      if (insideInitializer) {
-        assert(local.isParameter);
-        // Initializers in an initializer-list can communicate via parameters.
-        // If a parameter is stored in an initializer list we box it.
-        // TODO(sigurdm): Fix this.
-        // Though these variables do not outlive the activation of the
-        // function, they still need to be boxed.  As a simplification, we
-        // treat them as if they are captured by a closure (i.e., they do
-        // outlive the activation of the function).
-        markAsCaptured(local);
-      } else if (inTryStatement) {
-        assert(local.isParameter || local.isVariable);
-        // Search for the position of the try block containing the variable
-        // declaration, or -1 if it is declared outside the outermost try.
-        int i = tryNestingStack.length - 1;
-        while (i >= 0 && !tryNestingStack[i].declared.contains(local)) {
-          --i;
-        }
-        // If there is a next inner try, then the variable should be boxed on
-        // entry to it.
-        if (i + 1 < tryNestingStack.length) {
-          tryNestingStack[i + 1].boxedOnEntry.add(local);
-        }
-      }
-    }
-    node.visitChildren(this);
-  }
-
-  visitFunctionExpression(ast.FunctionExpression node) {
-    FunctionElement oldFunction = currentFunction;
-    currentFunction = elements[node];
-    if (currentFunction.asyncMarker != AsyncMarker.SYNC) {
-      giveup(node, "cannot handle async/sync*/async* functions");
-    }
-    if (node.initializers != null) {
-      insideInitializer = true;
-      visit(node.initializers);
-      insideInitializer = false;
-    }
-    visit(node.body);
-    currentFunction = oldFunction;
-  }
-
-  visitTryStatement(ast.TryStatement node) {
-    TryStatementInfo info = new TryStatementInfo();
-    tryStatements[node] = info;
-    tryNestingStack.add(info);
-    visit(node.tryBlock);
-    assert(tryNestingStack.last == info);
-    tryNestingStack.removeLast();
-
-    visit(node.catchBlocks);
-    if (node.finallyBlock != null) visit(node.finallyBlock);
-  }
-
-  visitVariableDefinitions(ast.VariableDefinitions node) {
-    if (inTryStatement) {
-      for (ast.Node definition in node.definitions.nodes) {
-        LocalVariableElement local = elements[definition];
-        assert(local != null);
-        // In the closure conversion pass we check for isInitializingFormal,
-        // but I'm not sure it can arise.
-        assert(!local.isInitializingFormal);
-        tryNestingStack.last.declared.add(local);
-      }
-    }
-    node.visitChildren(this);
-  }
-}
-
-/// IR builder specific to the Dart backend, coupled to the [DartIrBuilder].
-class DartIrBuilderVisitor extends IrBuilderVisitor {
-  /// Promote the type of [irBuilder] to [DartIrBuilder].
-  DartIrBuilder get irBuilder => super.irBuilder;
-
-  DartIrBuilderVisitor(TreeElements elements,
-                       Compiler compiler,
-                       SourceInformationBuilder sourceInformationBuilder)
-      : super(elements, compiler, sourceInformationBuilder);
-
-  DartIrBuilder makeIRBuilder(ast.Node node, ExecutableElement element) {
-    DartCapturedVariables closures = new DartCapturedVariables(elements);
-    if (!element.isSynthesized) {
-      closures.visit(node);
-    }
-    return new DartIrBuilder(compiler.backend.constantSystem,
-                             element,
-                             closures);
-  }
-
-  /// Recursively builds the IR for the given nested function.
-  ir.FunctionDefinition makeSubFunction(ast.FunctionExpression node) {
-    FunctionElement element = elements[node];
-    assert(invariant(element, element.isImplementation));
-
-    IrBuilder builder = irBuilder.makeInnerFunctionBuilder(element);
-
-    return withBuilder(builder, () => _makeFunctionBody(element, node));
-  }
-
-  ir.Primitive visitFunctionExpression(ast.FunctionExpression node) {
-    return irBuilder.buildFunctionExpression(makeSubFunction(node));
-  }
-
-  visitFunctionDeclaration(ast.FunctionDeclaration node) {
-    LocalFunctionElement element = elements[node.function];
-    Object inner = makeSubFunction(node.function);
-    irBuilder.declareLocalFunction(element, inner);
-  }
-
-  ClosureScope getClosureScopeForNode(ast.Node node) => null;
-  ClosureEnvironment getClosureEnvironment() => null;
-
-  ir.ExecutableDefinition buildExecutable(ExecutableElement element) {
-    return nullIfGiveup(() {
-      if (element is FieldElement) {
-        return buildField(element);
-      } else if (element is FunctionElement) {
-        return buildFunction(element);
-      } else {
-        compiler.internalError(element, "Unexpected element type $element");
-      }
-    });
-  }
-
-  /// Returns a [ir.FieldDefinition] describing the initializer of [element].
-  ir.FieldDefinition buildField(FieldElement element) {
-    assert(invariant(element, element.isImplementation));
-    ast.VariableDefinitions definitions = element.node;
-    ast.Node fieldDefinition = definitions.definitions.nodes.first;
-    if (definitions.modifiers.isConst) {
-      // TODO(sigurdm): Just return const value.
-    }
-    assert(fieldDefinition != null);
-    assert(elements[fieldDefinition] != null);
-
-    IrBuilder builder = makeIRBuilder(fieldDefinition, element);
-
-    return withBuilder(builder, () {
-      builder.buildFieldInitializerHeader(
-          closureScope: getClosureScopeForNode(fieldDefinition));
-      ir.Primitive initializer;
-      if (fieldDefinition is ast.SendSet) {
-        ast.SendSet sendSet = fieldDefinition;
-        initializer = visit(sendSet.arguments.first);
-      }
-      return builder.makeFieldDefinition(initializer);
-    });
-  }
-
-  ir.FunctionDefinition buildFunction(FunctionElement element) {
-    assert(invariant(element, element.isImplementation));
-    ast.FunctionExpression node = element.node;
-    if (element.asyncMarker != AsyncMarker.SYNC) {
-      giveup(null, 'cannot handle async-await');
-    }
-
-    if (!element.isSynthesized) {
-      assert(node != null);
-      assert(elements[node] != null);
-    } else {
-      SynthesizedConstructorElementX constructor = element;
-      if (!constructor.isDefaultConstructor) {
-        giveup(null, 'cannot handle synthetic forwarding constructors');
-      }
-    }
-
-    IrBuilder builder = makeIRBuilder(node, element);
-
-    return withBuilder(builder, () => _makeFunctionBody(element, node));
-  }
-
-  List<ir.Primitive> normalizeStaticArguments(
-      Selector selector,
-      FunctionElement target,
-      List<ir.Primitive> arguments) {
-    return arguments;
-  }
-
-  List<ir.Primitive> normalizeDynamicArguments(
-      Selector selector,
-      List<ir.Primitive> arguments) {
-    return arguments;
-  }
-}
-
-/// IR builder specific to the JavaScript backend, coupled to the [JsIrBuilder].
-class JsIrBuilderVisitor extends IrBuilderVisitor {
-  /// Promote the type of [irBuilder] to [JsIrBuilder].
-  JsIrBuilder get irBuilder => super.irBuilder;
-
-  /// Result of closure conversion for the current body of code.
-  ///
-  /// Will be initialized upon entering the body of a function.
-  /// It is computed by the [ClosureTranslator].
-  ClosureClassMap closureMap;
-
-  /// During construction of a constructor factory, [fieldValues] maps fields
-  /// to the primitive containing their initial value.
-  Map<FieldElement, ir.Primitive> fieldValues = <FieldElement, ir.Primitive>{};
-
-  JsIrBuilderVisitor(TreeElements elements,
-                     Compiler compiler,
-                     SourceInformationBuilder sourceInformationBuilder)
-      : super(elements, compiler, sourceInformationBuilder);
-
-  /// Builds the IR for creating an instance of the closure class corresponding
-  /// to the given nested function.
-  ClosureClassElement makeSubFunction(ast.FunctionExpression node) {
-    ClosureClassMap innerMap =
-        compiler.closureToClassMapper.getMappingForNestedFunction(node);
-    ClosureClassElement closureClass = innerMap.closureClassElement;
-    return closureClass;
-  }
-
-  ir.Primitive visitFunctionExpression(ast.FunctionExpression node) {
-    return irBuilder.buildFunctionExpression(makeSubFunction(node));
-  }
-
-  visitFunctionDeclaration(ast.FunctionDeclaration node) {
-    LocalFunctionElement element = elements[node.function];
-    Object inner = makeSubFunction(node.function);
-    irBuilder.declareLocalFunction(element, inner);
-  }
-
-  Map mapValues(Map map, dynamic fn(dynamic)) {
-    Map result = {};
-    map.forEach((key, value) {
-      result[key] = fn(value);
-    });
-    return result;
-  }
-
-  /// Converts closure.dart's CapturedVariable into a ClosureLocation.
-  /// There is a 1:1 corresponce between these; we do this because the
-  /// IR builder should not depend on synthetic elements.
-  ClosureLocation getLocation(CapturedVariable v) {
-    if (v is BoxFieldElement) {
-      return new ClosureLocation(v.box, v);
-    } else {
-      ClosureFieldElement field = v;
-      return new ClosureLocation(null, field);
-    }
-  }
-
-  /// If the current function is a nested function with free variables (or a
-  /// captured reference to `this`), returns a [ClosureEnvironment]
-  /// indicating how to access these.
-  ClosureEnvironment getClosureEnvironment() {
-    if (closureMap.closureElement == null) return null;
-    return new ClosureEnvironment(
-        closureMap.closureElement,
-        closureMap.thisLocal,
-        mapValues(closureMap.freeVariableMap, getLocation));
-  }
-
-  /// If [node] has declarations for variables that should be boxed,
-  /// returns a [ClosureScope] naming a box to create, and enumerating the
-  /// variables that should be stored in the box.
-  ///
-  /// Also see [ClosureScope].
-  ClosureScope getClosureScopeForNode(ast.Node node) {
-    closurelib.ClosureScope scope = closureMap.capturingScopes[node];
-    if (scope == null) return null;
-    // We translate a ClosureScope from closure.dart into IR builder's variant
-    // because the IR builder should not depend on the synthetic elements
-    // created in closure.dart.
-    return new ClosureScope(scope.boxElement,
-                            mapValues(scope.capturedVariables, getLocation),
-                            scope.boxedLoopVariables);
-  }
-
-  /// Returns the [ClosureScope] for any function, possibly different from the
-  /// one currently being built.
-  ClosureScope getClosureScopeForFunction(FunctionElement function) {
-    ClosureClassMap map =
-        compiler.closureToClassMapper.computeClosureToClassMapping(
-            function,
-            function.node,
-            elements);
-    closurelib.ClosureScope scope = map.capturingScopes[function.node];
-    if (scope == null) return null;
-    return new ClosureScope(scope.boxElement,
-                            mapValues(scope.capturedVariables, getLocation),
-                            scope.boxedLoopVariables);
-  }
-
-  ir.ExecutableDefinition buildExecutable(ExecutableElement element) {
-    return nullIfGiveup(() {
-      switch (element.kind) {
-        case ElementKind.GENERATIVE_CONSTRUCTOR:
-          return buildConstructor(element);
-
-        case ElementKind.GENERATIVE_CONSTRUCTOR_BODY:
-          return buildConstructorBody(element);
-
-        case ElementKind.FUNCTION:
-        case ElementKind.GETTER:
-        case ElementKind.SETTER:
-          return buildFunction(element);
-
-        default:
-          compiler.internalError(element, "Unexpected element type $element");
-      }
-    });
-  }
-
-  /// Builds the IR for an [expression] taken from a different [context].
-  ///
-  /// Such expressions need to be compiled with a different [sourceFile] and
-  /// [elements] mapping.
-  ir.Primitive inlineExpression(AstElement context, ast.Expression expression) {
-    JsIrBuilderVisitor visitor = new JsIrBuilderVisitor(
-        context.resolvedAst.elements,
-        compiler,
-        sourceInformationBuilder.forContext(context));
-    return visitor.withBuilder(irBuilder, () => visitor.visit(expression));
-  }
-
-  /// Builds the IR for a constant taken from a different [context].
-  ///
-  /// Such constants need to be compiled with a different [sourceFile] and
-  /// [elements] mapping.
-  ir.Primitive inlineConstant(AstElement context, ast.Expression exp) {
-    JsIrBuilderVisitor visitor = new JsIrBuilderVisitor(
-        context.resolvedAst.elements,
-        compiler,
-        sourceInformationBuilder.forContext(context));
-    return visitor.withBuilder(irBuilder, () => visitor.translateConstant(exp));
-  }
-
-  /// Builds the IR for a given constructor.
-  ///
-  /// 1. Evaluates all own or inherited field initializers.
-  /// 2. Creates the object and assigns its fields.
-  /// 3. Calls constructor body and super constructor bodies.
-  /// 4. Returns the created object.
-  ir.FunctionDefinition buildConstructor(ConstructorElement constructor) {
-    constructor = constructor.implementation;
-    ClassElement classElement = constructor.enclosingClass.implementation;
-
-    JsIrBuilder builder =
-        new JsIrBuilder(compiler.backend.constantSystem, constructor);
-
-    return withBuilder(builder, () {
-      // Setup parameters and create a box if anything is captured.
-      List<ParameterElement> parameters = [];
-      constructor.functionSignature.orderedForEachParameter(parameters.add);
-      builder.buildFunctionHeader(parameters,
-          closureScope: getClosureScopeForFunction(constructor));
-
-      // -- Step 1: evaluate field initializers ---
-      // Evaluate field initializers in constructor and super constructors.
-      List<ConstructorElement> constructorList = <ConstructorElement>[];
-      evaluateConstructorFieldInitializers(constructor, constructorList);
-
-      // All parameters in all constructors are now bound in the environment.
-      // BoxLocals for captured parameters are also in the environment.
-      // The initial value of all fields are now bound in [fieldValues].
-
-      // --- Step 2: create the object ---
-      // Get the initial field values in the canonical order.
-      List<ir.Primitive> instanceArguments = <ir.Primitive>[];
-      classElement.forEachInstanceField((ClassElement c, FieldElement field) {
-        ir.Primitive value = fieldValues[field];
-        if (value != null) {
-          instanceArguments.add(fieldValues[field]);
-        } else {
-          assert(Elements.isNativeOrExtendsNative(c));
-          // Native fields are initialized elsewhere.
-        }
-      }, includeSuperAndInjectedMembers: true);
-      ir.Primitive instance =
-          new ir.CreateInstance(classElement, instanceArguments);
-      irBuilder.add(new ir.LetPrim(instance));
-
-      // --- Step 3: call constructor bodies ---
-      for (ConstructorElement target in constructorList) {
-        ConstructorBodyElement bodyElement = getConstructorBody(target);
-        if (bodyElement == null) continue; // Skip if constructor has no body.
-        List<ir.Primitive> bodyArguments = <ir.Primitive>[];
-        for (Local param in getConstructorBodyParameters(bodyElement)) {
-          bodyArguments.add(irBuilder.environment.lookup(param));
-        }
-        irBuilder.buildInvokeDirectly(bodyElement, instance, bodyArguments);
-      }
-
-      // --- step 4: return the created object ----
-      irBuilder.buildReturn(instance);
-
-      return irBuilder.makeFunctionDefinition([]);
-    });
-  }
-
-  /// Evaluates all field initializers on [constructor] and all constructors
-  /// invoked through `this()` or `super()` ("superconstructors").
-  ///
-  /// The resulting field values will be available in [fieldValues]. The values
-  /// are not stored in any fields.
-  ///
-  /// This procedure assumes that the parameters to [constructor] are available
-  /// in the IR builder's environment.
-  ///
-  /// The parameters to superconstructors are, however, assumed *not* to be in
-  /// the environment, but will be put there by this procedure.
-  ///
-  /// All constructors will be added to [supers], with superconstructors first.
-  void evaluateConstructorFieldInitializers(ConstructorElement constructor,
-                                            List<ConstructorElement> supers) {
-    // Evaluate declaration-site field initializers.
-    ClassElement enclosingClass = constructor.enclosingClass.implementation;
-    enclosingClass.forEachInstanceField((ClassElement c, FieldElement field) {
-      if (field.initializer != null) {
-        fieldValues[field] = inlineExpression(field, field.initializer);
-      } else {
-        if (Elements.isNativeOrExtendsNative(c)) {
-          // Native field is initialized elsewhere.
-        } else {
-          // Fields without an initializer default to null.
-          // This value will be overwritten below if an initializer is found.
-          fieldValues[field] = irBuilder.buildNullLiteral();
-        }
-      }
-    });
-    // Evaluate initializing parameters, e.g. `Foo(this.x)`.
-    constructor.functionSignature.orderedForEachParameter(
-        (ParameterElement parameter) {
-      if (parameter.isInitializingFormal) {
-        InitializingFormalElement fieldParameter = parameter;
-        fieldValues[fieldParameter.fieldElement] =
-            irBuilder.buildLocalGet(parameter);
-      }
-    });
-    // Evaluate constructor initializers, e.g. `Foo() : x = 50`.
-    ast.FunctionExpression node = constructor.node;
-    bool hasConstructorCall = false; // Has this() or super() initializer?
-    if (node != null && node.initializers != null) {
-      for(ast.Node initializer in node.initializers) {
-        if (initializer is ast.SendSet) {
-          // Field initializer.
-          FieldElement field = elements[initializer];
-          fieldValues[field] =
-              inlineExpression(constructor, initializer.arguments.head);
-        } else if (initializer is ast.Send) {
-          // Super or this initializer.
-          ConstructorElement target = elements[initializer].implementation;
-          Selector selector = elements.getSelector(initializer);
-          List<ir.Primitive> arguments = initializer.arguments.mapToList(visit);
-          loadArguments(target, selector, arguments);
-          evaluateConstructorFieldInitializers(target, supers);
-          hasConstructorCall = true;
-        } else {
-          compiler.internalError(initializer,
-                                 "Unexpected initializer type $initializer");
-        }
-      }
-    }
-    // If no super() or this() was found, also call default superconstructor.
-    if (!hasConstructorCall && !enclosingClass.isObject) {
-      ClassElement superClass = enclosingClass.superclass;
-      FunctionElement target = superClass.lookupDefaultConstructor();
-      if (target == null) {
-        compiler.internalError(superClass, "No default constructor available.");
-      }
-      evaluateConstructorFieldInitializers(target, supers);
-    }
-    // Add this constructor after the superconstructors.
-    supers.add(constructor);
-  }
-
-  /// In preparation of inlining (part of) [target], the [arguments] are moved
-  /// into the environment bindings for the corresponding parameters.
-  ///
-  /// Defaults for optional arguments are evaluated in order to ensure
-  /// all parameters are available in the environment.
-  void loadArguments(FunctionElement target,
-                     Selector selector,
-                     List<ir.Primitive> arguments) {
-    target = target.implementation;
-    FunctionSignature signature = target.functionSignature;
-
-    // Establish a scope in case parameters are captured.
-    ClosureScope scope = getClosureScopeForFunction(target);
-    irBuilder._enterScope(scope);
-
-    // Load required parameters
-    int index = 0;
-    signature.forEachRequiredParameter((ParameterElement param) {
-      irBuilder.declareLocalVariable(param, initialValue: arguments[index]);
-      index++;
-    });
-
-    // Load optional parameters, evaluating default values for omitted ones.
-    signature.forEachOptionalParameter((ParameterElement param) {
-      ir.Primitive value;
-      // Load argument if provided.
-      if (signature.optionalParametersAreNamed) {
-        int nameIndex = selector.namedArguments.indexOf(param.name);
-        if (nameIndex != -1) {
-          int translatedIndex = selector.positionalArgumentCount + nameIndex;
-          value = arguments[translatedIndex];
-        }
-      } else if (index < arguments.length) {
-        value = arguments[index];
-      }
-      // Load default if argument was not provided.
-      if (value == null) {
-        if (param.initializer != null) {
-          value = inlineExpression(target, param.initializer);
-        } else {
-          value = irBuilder.buildNullLiteral();
-        }
-      }
-      irBuilder.declareLocalVariable(param, initialValue: value);
-      index++;
-    });
-  }
-
-  /**
-   * Returns the constructor body associated with the given constructor or
-   * creates a new constructor body, if none can be found.
-   *
-   * Returns `null` if the constructor does not have a body.
-   */
-  ConstructorBodyElement getConstructorBody(FunctionElement constructor) {
-    // TODO(asgerf): This is largely inherited from the SSA builder.
-    // The ConstructorBodyElement has an invalid function signature, but we
-    // cannot add a BoxLocal as parameter, because BoxLocal is not an element.
-    // Instead of forging ParameterElements to forge a FunctionSignature, we
-    // need a way to create backend methods without creating more fake elements.
-
-    assert(constructor.isGenerativeConstructor);
-    assert(invariant(constructor, constructor.isImplementation));
-    if (constructor.isSynthesized) return null;
-    ast.FunctionExpression node = constructor.node;
-    // If we know the body doesn't have any code, we don't generate it.
-    if (!node.hasBody()) return null;
-    if (node.hasEmptyBody()) return null;
-    ClassElement classElement = constructor.enclosingClass;
-    ConstructorBodyElement bodyElement;
-    classElement.forEachBackendMember((Element backendMember) {
-      if (backendMember.isGenerativeConstructorBody) {
-        ConstructorBodyElement body = backendMember;
-        if (body.constructor == constructor) {
-          bodyElement = backendMember;
-        }
-      }
-    });
-    if (bodyElement == null) {
-      bodyElement = new ConstructorBodyElementX(constructor);
-      classElement.addBackendMember(bodyElement);
-
-      if (constructor.isPatch) {
-        // Create origin body element for patched constructors.
-        ConstructorBodyElementX patch = bodyElement;
-        ConstructorBodyElementX origin =
-            new ConstructorBodyElementX(constructor.origin);
-        origin.applyPatch(patch);
-        classElement.origin.addBackendMember(bodyElement.origin);
-      }
-    }
-    assert(bodyElement.isGenerativeConstructorBody);
-    return bodyElement;
-  }
-
-  /// The list of parameters to send from the generative constructor
-  /// to the generative constructor body.
-  ///
-  /// Boxed parameters are not in the list, instead, a [BoxLocal] is passed
-  /// containing the boxed parameters.
-  ///
-  /// For example, given the following constructor,
-  ///
-  ///     Foo(x, y) : field = (() => ++x) { print(x + y) }
-  ///
-  /// the argument `x` would be replaced by a [BoxLocal]:
-  ///
-  ///     Foo_body(box0, y) { print(box0.x + y) }
-  ///
-  List<Local> getConstructorBodyParameters(ConstructorBodyElement body) {
-    List<Local> parameters = <Local>[];
-    ClosureScope scope = getClosureScopeForFunction(body.constructor);
-    if (scope != null) {
-      parameters.add(scope.box);
-    }
-    body.functionSignature.orderedForEachParameter((ParameterElement param) {
-      if (scope != null && scope.capturedVariables.containsKey(param)) {
-        // Do not pass this parameter; the box will carry its value.
-      } else {
-        parameters.add(param);
-      }
-    });
-    return parameters;
-  }
-
-  /// Builds the IR for the body of a constructor.
-  ///
-  /// This function is invoked from one or more "factory" constructors built by
-  /// [buildConstructor].
-  ir.FunctionDefinition buildConstructorBody(ConstructorBodyElement body) {
-    ConstructorElement constructor = body.constructor;
-    ast.FunctionExpression node = constructor.node;
-    closureMap = compiler.closureToClassMapper.computeClosureToClassMapping(
-        constructor,
-        node,
-        elements);
-
-    JsIrBuilder builder =
-        new JsIrBuilder(compiler.backend.constantSystem, body);
-
-    return withBuilder(builder, () {
-      irBuilder.buildConstructorBodyHeader(getConstructorBodyParameters(body),
-                                           getClosureScopeForNode(node));
-      visit(node.body);
-      return irBuilder.makeFunctionDefinition([]);
-    });
-  }
-
-  ir.FunctionDefinition buildFunction(FunctionElement element) {
-    assert(invariant(element, element.isImplementation));
-    ast.FunctionExpression node = element.node;
-
-    assert(!element.isSynthesized);
-    assert(node != null);
-    assert(elements[node] != null);
-
-    closureMap = compiler.closureToClassMapper.computeClosureToClassMapping(
-        element,
-        node,
-        elements);
-    IrBuilder builder =
-        new JsIrBuilder(compiler.backend.constantSystem, element);
-    return withBuilder(builder, () => _makeFunctionBody(element, node));
-  }
-
-  /// Creates a primitive for the default value of [parameter].
-  ir.Primitive translateDefaultValue(ParameterElement parameter) {
-    if (parameter.initializer == null) {
-      return irBuilder.buildNullLiteral();
-    } else {
-      return inlineConstant(parameter.executableContext, parameter.initializer);
-    }
-  }
-
-  /// Inserts default arguments and normalizes order of named arguments.
-  List<ir.Primitive> normalizeStaticArguments(
-      Selector selector,
-      FunctionElement target,
-      List<ir.Primitive> arguments) {
-    target = target.implementation;
-    FunctionSignature signature = target.functionSignature;
-    if (!signature.optionalParametersAreNamed &&
-        signature.parameterCount == arguments.length) {
-      // Optimization: don't copy the argument list for trivial cases.
-      return arguments;
-    }
-
-    List<ir.Primitive> result = <ir.Primitive>[];
-    int i = 0;
-    signature.forEachRequiredParameter((ParameterElement element) {
-      result.add(arguments[i]);
-      ++i;
-    });
-
-    if (!signature.optionalParametersAreNamed) {
-      signature.forEachOptionalParameter((ParameterElement element) {
-        if (i < arguments.length) {
-          result.add(arguments[i]);
-          ++i;
-        } else {
-          result.add(translateDefaultValue(element));
-        }
-      });
-    } else {
-      int offset = i;
-      // Iterate over the optional parameters of the signature, and try to
-      // find them in [compiledNamedArguments]. If found, we use the
-      // value in the temporary list, otherwise the default value.
-      signature.orderedOptionalParameters.forEach((ParameterElement element) {
-        int nameIndex = selector.namedArguments.indexOf(element.name);
-        if (nameIndex != -1) {
-          int translatedIndex = offset + nameIndex;
-          result.add(arguments[translatedIndex]);
-        } else {
-          result.add(translateDefaultValue(element));
-        }
-      });
-    }
-    return result;
-  }
-
-  /// Normalizes order of named arguments.
-  List<ir.Primitive> normalizeDynamicArguments(
-      Selector selector,
-      List<ir.Primitive> arguments) {
-    assert(arguments.length == selector.argumentCount);
-    // Optimization: don't copy the argument list for trivial cases.
-    if (selector.namedArguments.isEmpty) return arguments;
-    List<ir.Primitive> result = <ir.Primitive>[];
-    for (int i=0; i < selector.positionalArgumentCount; i++) {
-      result.add(arguments[i]);
-    }
-    for (String argName in selector.getOrderedNamedArguments()) {
-      int nameIndex = selector.namedArguments.indexOf(argName);
-      int translatedIndex = selector.positionalArgumentCount + nameIndex;
-      result.add(arguments[translatedIndex]);
-    }
-    return result;
-  }
-}
-
-/// Interface for generating [SourceInformation] for the CPS.
-class SourceInformationBuilder {
-  const SourceInformationBuilder();
-
-  /// Create a [SourceInformationBuilder] for [element].
-  SourceInformationBuilder forContext(AstElement element) => this;
-
-  /// Generate [SourceInformation] for the read access in [node].
-  SourceInformation buildGet(ast.Node node) => null;
-
-  /// Generate [SourceInformation] for the invocation in [node].
-  SourceInformation buildCall(ast.Node node) => null;
-}
-
-/// [SourceInformationBuilder] that generates [PositionSourceInformation].
-class PositionSourceInformationBuilder implements SourceInformationBuilder {
-  final SourceFile sourceFile;
-  final String name;
-
-  PositionSourceInformationBuilder(AstElement element)
-      : sourceFile = element.compilationUnit.script.file,
-        name = element.name;
-
-  @override
-  SourceInformation buildGet(ast.Node node) {
-    return new PositionSourceInformation(
-        new TokenSourceLocation(sourceFile, node.getBeginToken(), name));
-  }
-
-  @override
-  SourceInformation buildCall(ast.Node node) {
-    return new PositionSourceInformation(
-        new TokenSourceLocation(sourceFile, node.getBeginToken(), name));
-  }
-
-  @override
-  SourceInformationBuilder forContext(AstElement element) {
-    return new PositionSourceInformationBuilder(element);
-  }
-}