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node_modules/jstransform/visitors/es6-rest-param-visitors.js

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+/**
+ * Copyright 2013-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+/*jslint node:true*/
+
+/**
+ * Desugars ES6 rest parameters into an ES3 arguments array.
+ *
+ * function printf(template, ...args) {
+ *   args.forEach(...);
+ * }
+ *
+ * We could use `Array.prototype.slice.call`, but that usage of arguments causes
+ * functions to be deoptimized in V8, so instead we use a for-loop.
+ *
+ * function printf(template) {
+ *   for (var args = [], $__0 = 1, $__1 = arguments.length; $__0 < $__1; $__0++)
+ *     args.push(arguments[$__0]);
+ *   args.forEach(...);
+ * }
+ *
+ */
+var Syntax = require('esprima-fb').Syntax;
+var utils = require('../src/utils');
+
+
+
+function _nodeIsFunctionWithRestParam(node) {
+  return (node.type === Syntax.FunctionDeclaration
+          || node.type === Syntax.FunctionExpression
+          || node.type === Syntax.ArrowFunctionExpression)
+         && node.rest;
+}
+
+function visitFunctionParamsWithRestParam(traverse, node, path, state) {
+  if (node.parametricType) {
+    utils.catchup(node.parametricType.range[0], state);
+    path.unshift(node);
+    traverse(node.parametricType, path, state);
+    path.shift();
+  }
+
+  // Render params.
+  if (node.params.length) {
+    path.unshift(node);
+    traverse(node.params, path, state);
+    path.shift();
+  } else {
+    // -3 is for ... of the rest.
+    utils.catchup(node.rest.range[0] - 3, state);
+  }
+  utils.catchupWhiteSpace(node.rest.range[1], state);
+  utils.catchup(node.body.range[0], state);
+
+  path.unshift(node);
+  traverse(node.body, path, state);
+  path.shift();
+
+  return false;
+}
+
+visitFunctionParamsWithRestParam.test = function(node, path, state) {
+  return _nodeIsFunctionWithRestParam(node);
+};
+
+function renderRestParamSetup(functionNode, state) {
+  var idx = state.localScope.tempVarIndex++;
+  var len = state.localScope.tempVarIndex++;
+
+  return 'for (var ' + functionNode.rest.name + '=[],' +
+    utils.getTempVar(idx) + '=' + functionNode.params.length + ',' +
+    utils.getTempVar(len) + '=arguments.length;' +
+    utils.getTempVar(idx) + '<' +  utils.getTempVar(len) + ';' +
+    utils.getTempVar(idx) + '++) ' +
+    functionNode.rest.name + '.push(arguments[' + utils.getTempVar(idx) + ']);';
+}
+
+function visitFunctionBodyWithRestParam(traverse, node, path, state) {
+  utils.catchup(node.range[0] + 1, state);
+  var parentNode = path[0];
+  utils.append(renderRestParamSetup(parentNode, state), state);
+  return true;
+}
+
+visitFunctionBodyWithRestParam.test = function(node, path, state) {
+  return node.type === Syntax.BlockStatement
+         && _nodeIsFunctionWithRestParam(path[0]);
+};
+
+exports.renderRestParamSetup = renderRestParamSetup;
+exports.visitorList = [
+  visitFunctionParamsWithRestParam,
+  visitFunctionBodyWithRestParam
+];