6to5-core - npm Package Compare versions

Comparing version 2.13.0 to 2.13.1

lib/6to5/transformation/transformers/es6-let-scoping.js

@@ -60,2 +60,3 @@ "use strict";
 
+exports.Program =
 exports.BlockStatement = function (block, parent, scope, context, file) {
@@ -86,2 +87,3 @@ if (!t.isLoop(parent)) {
   this.outsideLetReferences = {};
+  this.hasLetReferences     = false;
   this.letReferences        = {};
@@ -100,6 +102,11 @@ this.body                 = [];
 
-  // this is a block within a `Function` so we can safely leave it be
-  if (t.isFunction(this.parent)) return;
+  var needsClosure = this.getLetReferences();
+  this.checkTDZ();
 
-  var needsClosure = this.getLetReferences();
+  // this is a block within a `Function/Program` so we can safely leave it be
+  if (t.isFunction(this.parent) || t.isProgram(this.block)) return;
+
+  // we can skip everything
+  if (!this.hasLetReferences) return;
+
   if (needsClosure) {
@@ -116,2 +123,44 @@ this.needsClosure();
 
+LetScoping.prototype.checkTDZ = function () {
+  var state = {
+    letRefs: this.letReferences,
+    file: this.file
+  };
+
+  traverse(this.block, {
+    enter: function (node, parent, scope, context, state) {
+      if (!t.isIdentifier(node)) return;
+      if (!t.isReferenced(node, parent)) return;
+
+      var declared = state.letRefs[node.name];
+      if (!declared) return;
+
+      // declared node is different in this scope
+      if (scope.get(node.name, true) !== declared) return;
+
+      var declaredLoc  = declared.loc;
+      var referenceLoc = node.loc;
+
+      if (!declaredLoc || !referenceLoc) return;
+
+      // does this reference appear on a line before the declaration?
+      var before = referenceLoc.start.line < declaredLoc.start.line;
+
+      if (referenceLoc.start.line === declaredLoc.start.line) {
+        // this reference appears on the same line
+        // check it appears before the declaration
+        before = referenceLoc.start.col < declaredLoc.start.col;
+      }
+
+      if (before) {
+        throw state.file.errorWithNode(node, "Temporal dead zone - accessing a variable before it's initialized");
+      }
+    }
+  }, this.scope, state);
+};
+
+/**
+ * Description
+ */
+
 LetScoping.prototype.remap = function () {
@@ -246,4 +295,8 @@ var letRefs = this.letReferences;
     _.extend(this.letReferences, keys);
+    this.hasLetReferences = true;
   }
 
+  // no let references so we can just quit
+  if (!this.hasLetReferences) return;
+
   // set let references to plain var references
@@ -250,0 +303,0 @@ standardiseLets(declarators);

lib/6to5/transformation/transformers/spec-block-scoped-functions.js

@@ -10,2 +10,5 @@ "use strict";
 
+  // this is to avoid triggering the TDZ detection
+  node.id.loc = null;
+
   var declar = t.variableDeclaration("let", [
@@ -12,0 +15,0 @@ t.variableDeclarator(node.id, t.toExpression(node))

package.json

 {
   "name": "6to5-core",
   "description": "Turn ES6 code into readable vanilla ES5 with source maps",
-  "version": "2.13.0",
+  "version": "2.13.1",
   "author": "Sebastian McKenzie <[e-mail]>",
@@ -6,0 +6,0 @@ "homepage": "https://6to5.org/",

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