References to this:
+ * If the code to extract contains references to this, these references have to be
+ * rewritten; otherwise they would refer to the global object in the transformed code.
+ * We do this by giving the extracted function an extra parameter thi$, and rewriting
+ * this to thi$ within the extracted code.
+ * For instance,
+ *
+ * Object.prototype.extend = function(src) {
+ * for(var p in src)
+ * this[p] = src[p];
+ * }
+ *
+ * becomes
+ *
+ * Object.prototype.extend = function(src) {
+ * for(var p in src)
+ * (function _forin_body_0(p, thi$) {
+ * thi$[p] = src[p];
+ * })(p, this);
+ * }
+ *
+ *
+ * break,continue,return:
+ * A break or continue statement within the extracted loop body that refers
+ * to the loop itself or an enclosing loop would become invalid in the transformed code. A return
+ * statement would no longer return from the enclosing function, but instead from the extracted function.
+ * We transform all three statements into return statements returning an object literal with a
+ * property type indicating whether this is a 'goto' (i.e., break or return)
+ * or a 'return'. In the former case, the 'target' property contains an integer identifying the jump target; in
+ * the latter case, the 'value' property contains the value to return.
+ * The return value of the extracted function is then examined to determine whether it completed normally
+ * (i.e., returned undefined), or whether it returned an object indicating special control flow.
+ * For example, consider this code from MooTools:
+ *
+ * for(var style in Element.ShortStyles) {
+ * if(property != style)
+ * continue;
+ * for(var s in Element.ShortStyles[style])
+ * result.push(this.getStyle(s));
+ * return result.join(' ');
+ * }
+ *
+ * Under {@link ForInBodyExtractionPolicy}, this is transformed into
+ *
+ * for(var style in Element.ShortStyles) {
+ * var s;
+ * re$ = (function _forin_body_0(style, thi$) {
+ * if(property != style)
+ * return { type: 'goto', target: 1 };
+ * for(s in Element.ShortStyles[style]) {
+ * (function _forin_body_2(s) {
+ * result.push(thi$.getStyle(s));
+ * })(s);
+ * }
+ * return { type: 'return', value: result.join(' ') };
+ * })(style, this);
+ * if(re$) {
+ * if(re$.type == 'return')
+ * return re$.value;
+ * if(re$.type == 'goto') {
+ * if(re$.target == 1)
+ * continue;
+ * }
+ * }
+ * }
+ *
+ * Note that at the CAst level, break and continue are represented as goto
+ * statements, which simplifies the translation somewhat. The numerical encoding of jump targets does not matter
+ * as long as the extracted function and the fixup code agree on which number represents which label.
+ *
+ *