From 1cc606d4d0fca262e309c778896cbc5787511dd9 Mon Sep 17 00:00:00 2001
From: Sebastian McKenzie <sebmck@gmail.com>
Date: Wed, 7 Jan 2015 07:58:04 +1100
Subject: [PATCH] make import reassignment illegal @eventualbuddha

---
 lib/6to5/transformation/modules/_default.js   | 49 +++++++++++++++++++
 .../disallow-import-remapping-2/actual.js     |  2 +
 .../disallow-import-remapping-2/options.json  |  3 ++
 .../disallow-import-remapping/actual.js       |  2 +
 .../disallow-import-remapping/options.json    |  3 ++
 5 files changed, 59 insertions(+)
 create mode 100644 test/fixtures/transformation/es6-modules-common/disallow-import-remapping-2/actual.js
 create mode 100644 test/fixtures/transformation/es6-modules-common/disallow-import-remapping-2/options.json
 create mode 100644 test/fixtures/transformation/es6-modules-common/disallow-import-remapping/actual.js
 create mode 100644 test/fixtures/transformation/es6-modules-common/disallow-import-remapping/options.json

diff --git a/lib/6to5/transformation/modules/_default.js b/lib/6to5/transformation/modules/_default.js
index d067eece2a..391ceda34f 100644
--- a/lib/6to5/transformation/modules/_default.js
+++ b/lib/6to5/transformation/modules/_default.js
@@ -9,7 +9,11 @@ function DefaultFormatter(file) {
   this.file = file;
 
   this.localExports = this.getLocalExports();
+  this.localImports = this.getLocalImports();
+
   this.remapAssignments();
+
+  this.checkImportAssignments();
 }
 
 DefaultFormatter.prototype.getLocalExports = function () {
@@ -27,6 +31,51 @@ DefaultFormatter.prototype.getLocalExports = function () {
   return localExports;
 };
 
+DefaultFormatter.prototype.getLocalImports = function () {
+  var localImports = {};
+
+  traverse(this.file.ast, {
+    enter: function (node) {
+      if (t.isImportDeclaration(node)) {
+        _.extend(localImports, t.getIds(node, true));
+      }
+    }
+  });
+
+  return localImports;
+};
+
+DefaultFormatter.prototype.checkImportAssignments = function () {
+  var localImports = this.localImports;
+  var file = this.file;
+
+  var isLocalReference = function (node, scope) {
+    return t.isIdentifier(node) && localImports[node.name];
+  };
+
+  var check = function (node) {
+    if (isLocalReference(node)) {
+      throw file.errorWithNode(node, "Illegal assignment of module import");
+    }
+  };
+
+  traverse(file.ast, {
+    enter: function (node, parent, scope) {
+      if (t.isAssignmentExpression(node)) {
+
+        var left = node.left;
+        if (t.isMemberExpression(left)) {
+          while (left.object) left = left.object;
+        }
+
+        check(left);
+      } else if (t.isDeclaration(node) && !t.isImportDeclaration(node)) {
+        _.each(t.getIds(node, true), check);
+      }
+    }
+  });
+};
+
 DefaultFormatter.prototype.remapExportAssignment = function (node) {
   return t.assignmentExpression(
     "=",
diff --git a/test/fixtures/transformation/es6-modules-common/disallow-import-remapping-2/actual.js b/test/fixtures/transformation/es6-modules-common/disallow-import-remapping-2/actual.js
new file mode 100644
index 0000000000..1d832634ed
--- /dev/null
+++ b/test/fixtures/transformation/es6-modules-common/disallow-import-remapping-2/actual.js
@@ -0,0 +1,2 @@
+import { foo } from "foo";
+var foo;
diff --git a/test/fixtures/transformation/es6-modules-common/disallow-import-remapping-2/options.json b/test/fixtures/transformation/es6-modules-common/disallow-import-remapping-2/options.json
new file mode 100644
index 0000000000..a9357a58d2
--- /dev/null
+++ b/test/fixtures/transformation/es6-modules-common/disallow-import-remapping-2/options.json
@@ -0,0 +1,3 @@
+{
+  "throws": "Illegal assignment of module import"
+}
diff --git a/test/fixtures/transformation/es6-modules-common/disallow-import-remapping/actual.js b/test/fixtures/transformation/es6-modules-common/disallow-import-remapping/actual.js
new file mode 100644
index 0000000000..e1b913ccf6
--- /dev/null
+++ b/test/fixtures/transformation/es6-modules-common/disallow-import-remapping/actual.js
@@ -0,0 +1,2 @@
+import { foo } from "foo";
+foo = 1;
diff --git a/test/fixtures/transformation/es6-modules-common/disallow-import-remapping/options.json b/test/fixtures/transformation/es6-modules-common/disallow-import-remapping/options.json
new file mode 100644
index 0000000000..a9357a58d2
--- /dev/null
+++ b/test/fixtures/transformation/es6-modules-common/disallow-import-remapping/options.json
@@ -0,0 +1,3 @@
+{
+  "throws": "Illegal assignment of module import"
+}