Capture this.

frog/leg/ssa/closure.dart

 // Copyright (c) 2012, 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.
 
 class ClosureFieldElement extends Element {
   ClosureFieldElement(SourceString name, ClassElement enclosing)
       : super(name, ElementKind.FIELD, enclosing);
 
   bool isInstanceMember() => true;
   bool isAssignable() => false;
 
   String toString() => "ClosureFieldElement($name)";
 }
 
 // The box-element for a scope, and the captured variables that need to be
 // stored in the box.
 class ClosureScope {
   Element boxElement;
   Map<Element, Element> capturedVariableMapping;
 
   ClosureScope(this.boxElement, this.capturedVariableMapping);
 }
 
 class ClosureData {
   // The globalizedClosureElement will be null for methods that are not local
   // closures.
   final ClassElement globalizedClosureElement;
   // The callElement will be null for methods that are not local closures.
   final FunctionElement callElement;
+  // The [thisElement] makes handling 'this' easier by treating it like any
+  // other argument. It is only set for instance-members.
+  final Element thisElement;
 
   // Maps free locals, arguments and function elements to their captured
   // copies.
   final Map<Element, Element> freeVariableMapping;
   // Maps closure-fields to their captured elements. This is somehow the inverse
   // mapping of [freeVariableMapping], but whereas [freeVariableMapping] does
   // not deal with boxes, here we map instance-fields (which might represent
   // boxes) to their boxElement.
   final Map<Element, Element> capturedFieldMapping;
 
   // Maps scopes ([Loop] and [FunctionExpression] nodes) to their
   // [ClosureScope] which contains their box and the
   // captured variables that are stored in the box.
   // This map will be empty if the method/closure of this [ClosureData] does not
   // contain any nested closure.
   final Map<Node, ClosureScope> capturingScopes;
 
   final Set<Element> usedVariablesInTry;
 
-  ClosureData(this.globalizedClosureElement, this.callElement)
+  ClosureData(this.globalizedClosureElement, this.callElement, this.thisElement)
       : this.freeVariableMapping = new Map<Element, Element>(),
         this.capturedFieldMapping = new Map<Element, Element>(),
         this.capturingScopes = new Map<Node, ClosureScope>(),
         this.usedVariablesInTry = new Set<Element>();
 }
 
 Map<Node, ClosureData> _closureDataCache;
 Map<Node, ClosureData> get closureDataCache() {
   if (_closureDataCache === null) {
     _closureDataCache = new HashMap<Node, ClosureData>();
@@ skipping 114 matching lines @@
       assert(element !== null);
       declareLocal(element);
     }
     // We still need to visit the right-hand sides of the init-assignments.
     // Simply visit all children. We will visit the locals again and make them
     // used, but that should not be a problem.
     node.visitChildren(this);
   }
 
   visitIdentifier(Identifier node) {
-    // TODO(floitsch): handle 'this'.
-    if (node.isThis() && insideClosure) {
-      compiler.unimplemented("ClosureAnalyzer.visitIdentifier this-capture",
-                             node: node);
+    if (node.isThis()) {
+      useLocal(closureData.thisElement);
     }
     node.visitChildren(this);
   }
 
   visitSend(Send node) {
     Element element = elements[node];
     if (Elements.isLocal(element)) {
       useLocal(element);
-    } else if (element === null && node.receiver === null) {
-      if (insideClosure) {
-        compiler.unimplemented("ClosureTranslator.visitSend this-capture");
-      }
+    } else if (node.receiver === null &&
+               Elements.isInstanceSend(node, elements)) {

[ngeoffray, 2012/02/08 13:31:24]

How about isThisSend in that case? It could also check for 'this' as receiver. I
know visitChildren will do it, but you could just visit the arguments if
isThisSend returns true, or just keep the code as it is, as calling useLocal
multiple times is harmless.

[floitsch, 2012/02/08 14:36:53]

I prefer keeping it the way it is.

+      useLocal(closureData.thisElement);
     }
     node.visitChildren(this);
   }
 
   // If variables that are declared in the [node] scope are captured and need
   // to be boxed create a box-element and update the [capturingScopes] in the
   // current [closureData].
   // The boxed variables are updated in the [capturedVariableMapping].
   void attachCapturedScopeVariables(Node node) {
     Element box = null;
@@ skipping 40 matching lines @@
     FunctionElement callElement =
         new FunctionElement.from(Namer.CLOSURE_INVOCATION_NAME,
                                  element,
                                  globalizedElement);
     globalizedElement.backendMembers =
         const EmptyLink<Element>().prepend(callElement);
     globalizedElement.isResolved = true;
     ClassElement objectClass =
         compiler.coreLibrary.find(const SourceString('Object'));
     globalizedElement.supertype = new SimpleType(Types.OBJECT, objectClass);
-    return new ClosureData(globalizedElement, callElement);
+    // The nested function's 'this' is the same as the one for the outer
+    // function. It could be [null] if we are inside a static method.
+    Element thisElement = closureData.thisElement;
+    return new ClosureData(globalizedElement, callElement, thisElement);
   }
 
   visitFunctionExpression(FunctionExpression node) {
+    FunctionElement element = elements[node];
     bool isClosure = (closureData !== null);
 
     if (isClosure) closures.add(node);
 
     bool oldInsideClosure = insideClosure;
     FunctionElement oldFunctionElement = currentFunctionElement;
     ClosureData oldClosureData = closureData;
     List<Element> oldScopeVariables = scopeVariables;
 
 
     insideClosure = isClosure;
     currentFunctionElement = elements[node];
-    closureData = insideClosure ?
-                  globalizeClosure(node) :
-                  new ClosureData(null, null);
+    if (insideClosure) {
+      closureData = globalizeClosure(node);
+    } else {
+      Element thisElement = null;
+      // TODO(floitsch): we should not need to look for generative constructors.

[ngeoffray, 2012/02/08 13:31:24]

Improve comment?

[floitsch, 2012/02/08 14:36:53]

Done.

+      if (element.isInstanceMember() ||
+          element.kind == ElementKind.GENERATIVE_CONSTRUCTOR) { 
+        thisElement = new Element(const SourceString("this"),
+                                  ElementKind.PARAMETER,
+                                  element);
+      }
+      closureData = new ClosureData(null, null, thisElement);
+    }
     scopeVariables = new List<Element>();
 
     // TODO(floitsch): a named function is visible from inside itself. Add
     // the element to the block.
 
+    // We have to declare the implicit 'this' parameter.
+    if (!insideClosure && closureData.thisElement !== null) {
+      declareLocal(closureData.thisElement);
+    }
+
     node.visitChildren(this);
 
     attachCapturedScopeVariables(node);
 
     closureDataCache[node] = closureData;
 
     ClosureData savedClosureData = closureData;
     bool savedInsideClosure = insideClosure;
 
     // Restore old values.
@@ skipping 21 matching lines @@
     }
   }
 
   visitTryStatement(TryStatement node) {
     // TODO(ngeoffray): implement finer grain state.
     inTryCatchOrFinally = true;
     node.visitChildren(this);
     inTryCatchOrFinally = false;
   }
 }