add proper ordering to function param logic - fixes #549

lib/6to5/transformation/transform.js

@@ -71,8 +71,8 @@ _.each({
   templateLiterals:          require("./transformers/es6-template-literals"),
   propertyMethodAssignment:  require("./transformers/es6-property-method-assignment"),
   computedPropertyNames:     require("./transformers/es6-computed-property-names"),
-  destructuring:             require("./transformers/es6-destructuring"),
   defaultParameters:         require("./transformers/es6-default-parameters"),
+  destructuring:             require("./transformers/es6-destructuring"),
   forOf:                     require("./transformers/es6-for-of"),
   unicodeRegex:              require("./transformers/es6-unicode-regex"),
   abstractReferences:        require("./transformers/es7-abstract-references"),

lib/6to5/transformation/transformers/es6-default-parameters.js

@@ -15,7 +15,7 @@ exports.Function = function (node, parent, scope, context, file) {
   var iife = false;
   var def;
 
-  var checkTDZ = function (ids) {
+  var checkTDZ = function (param, def, ids) {
     var check = function (node, parent) {
       if (!t.isReferencedIdentifier(node, parent)) return;
 
@@ -29,7 +29,10 @@ exports.Function = function (node, parent, scope, context, file) {
     };
 
     check(def, node);
-    traverse(def, { enter: check });
+
+    if (!t.isPattern(param)) {
+      traverse(def, { enter: check });
+    }
   };
 
   for (var i = 0; i < node.defaults.length; i++) {
@@ -42,7 +45,7 @@ exports.Function = function (node, parent, scope, context, file) {
     // are to the right - ie. uninitialized parameters
     var rightIds = ids.slice(i);
     for (var i2 = 0; i2 < rightIds.length; i2++) {
-      checkTDZ(rightIds[i2]);
+      checkTDZ(param, def, rightIds[i2]);
     }
 
     // we're accessing a variable that's already defined within this function
@@ -66,12 +69,14 @@ exports.Function = function (node, parent, scope, context, file) {
       continue;
     }
 
-    body.push(util.template("default-parameter", {
+    var def = util.template("default-parameter", {
       VARIABLE_NAME: node.params[i],
       DEFAULT_VALUE: def,
       ARGUMENT_KEY:  t.literal(+i),
       ARGUMENTS:     argsIdentifier
-    }, true));
+    }, true);
+    def._blockHoist = node.defaults.length - i;
+    body.push(def);
   }
 
   // we need to cut off all trailing default parameters

lib/6to5/transformation/transformers/es6-destructuring.js

@@ -8,13 +8,27 @@ var buildVariableAssign = function (opts, id, init) {
   var op = opts.operator;
   if (t.isMemberExpression(id)) op = "=";
 
+  var node;
+
   if (op) {
-    return t.expressionStatement(t.assignmentExpression(op, id, init));
+    node = t.expressionStatement(t.assignmentExpression(op, id, init));
   } else {
-    return t.variableDeclaration(opts.kind, [
+    node = t.variableDeclaration(opts.kind, [
       t.variableDeclarator(id, init)
     ]);
   }
+
+  node._blockHoist = opts.blockHoist;
+
+  return node;
+};
+
+var buildVariableDeclar = function (opts, id, init) {
+  var declar = t.variableDeclaration("var", [
+    t.variableDeclarator(id, init)
+  ]);
+  declar._blockHoist = opts.blockHoist;
+  return declar;
 };
 
 var push = function (opts, nodes, elem, parentId) {
@@ -100,9 +114,7 @@ var pushArrayPattern = function (opts, nodes, pattern, parentId) {
   var toArray = opts.file.toArray(parentId, !hasSpreadElement && pattern.elements.length);
 
   var _parentId = opts.scope.generateUidBasedOnNode(parentId, opts.file);
-  nodes.push(t.variableDeclaration("var", [
-    t.variableDeclarator(_parentId, toArray)
-  ]));
+  nodes.push(buildVariableDeclar(opts, _parentId, toArray));
   parentId = _parentId;
 
   for (i = 0; i < pattern.elements.length; i++) {
@@ -138,11 +150,7 @@ var pushPattern = function (opts) {
 
   if (!t.isArrayExpression(parentId) && !t.isMemberExpression(parentId) && !t.isIdentifier(parentId)) {
     var key = scope.generateUidBasedOnNode(parentId, file);
-
-    nodes.push(t.variableDeclaration("var", [
-      t.variableDeclarator(key, parentId)
-    ]));
-
+    nodes.push(buildVariableDeclar(opts, key, parentId));
     parentId = key;
   }
 
@@ -181,19 +189,20 @@ exports.Function = function (node, parent, scope, context, file) {
 
   var hasDestructuring = false;
 
-  node.params = node.params.map(function (pattern) {
+  node.params = node.params.map(function (pattern, i) {
     if (!t.isPattern(pattern)) return pattern;
 
     hasDestructuring = true;
     var parentId = file.generateUidIdentifier("ref", scope);
 
     pushPattern({
-      kind:    "var",
-      nodes:   nodes,
-      pattern: pattern,
-      id:      parentId,
-      file:    file,
-      scope:   scope
+      blockHoist: node.params.length - i,
+      pattern:    pattern,
+      nodes:      nodes,
+      scope:      scope,
+      file:       file,
+      kind:       "var",
+      id:         parentId
     });
 
     return parentId;
@@ -294,12 +303,12 @@ exports.VariableDeclaration = function (node, parent, scope, context, file) {
     var patternId = declar.init;
     var pattern   = declar.id;
     var opts = {
-      kind:    node.kind,
-      nodes:   nodes,
       pattern: pattern,
-      id:      patternId,
+      nodes:   nodes,
+      scope:   scope,
+      kind:    node.kind,
       file:    file,
-      scope:   scope
+      id:      patternId,
     };
 
     if (t.isPattern(pattern) && patternId) {

lib/6to5/transformation/transformers/optional-undeclared-variable-check.js

@@ -1,5 +1,3 @@
-var t = require("../../types");
-
 exports.optional = true;
 
 exports.Identifier = function (node, parent, scope, context, file) {

test/fixtures/transformation/es6-default-parameters/destructuring/exec.js

@@ -0,0 +1,19 @@
+function required(msg) {
+  throw new Error(msg);
+}
+
+function sum(
+  { arr = required('arr is required') } = { arr: arr = [] },
+  length = arr.length
+) {
+  let i = 0;
+  let acc = 0;
+  for (let item of arr) {
+    if (i >= length) return acc;
+    acc += item;
+    i++;
+  }
+  return acc;
+}
+
+assert.equal(sum({arr:[1,2]}), 3);