From 125cc477df578f130bf75c88b4fe45aea84c0a5b Mon Sep 17 00:00:00 2001
From: overlookmotel <theoverlookmotel@gmail.com>
Date: Tue, 4 May 2021 21:30:07 +0100
Subject: [PATCH] Throw if assign to import in loop

---
 .../src/rewrite-live-references.ts            | 40 ++++++++++------
 .../misc/import-const-throw/input.mjs         | 10 ++++
 .../misc/import-const-throw/output.js         | 46 +++++++++++++++++--
 3 files changed, 78 insertions(+), 18 deletions(-)

diff --git a/packages/babel-helper-module-transforms/src/rewrite-live-references.ts b/packages/babel-helper-module-transforms/src/rewrite-live-references.ts
index 0c9d8cedc1f6..2206d406af7b 100644
--- a/packages/babel-helper-module-transforms/src/rewrite-live-references.ts
+++ b/packages/babel-helper-module-transforms/src/rewrite-live-references.ts
@@ -355,23 +355,26 @@ const rewriteReferencesVisitor: Visitor<RewriteReferencesVisitorState> = {
   ) {
     const { scope, node } = path;
     const { left } = node;
-    const { exported, scope: programScope } = this;
+    const { exported, imported, scope: programScope } = this;
 
     if (!t.isVariableDeclaration(left)) {
-      let didTransform = false;
+      let didTransformExport = false,
+        importConstViolationName;
       const loopBodyScope = path.get("body").scope;
       for (const name of Object.keys(t.getOuterBindingIdentifiers(left))) {
-        if (
-          exported.get(name) &&
-          programScope.getBinding(name) === scope.getBinding(name)
-        ) {
-          didTransform = true;
-          if (loopBodyScope.hasOwnBinding(name)) {
-            loopBodyScope.rename(name);
+        if (programScope.getBinding(name) === scope.getBinding(name)) {
+          if (exported.get(name)) {
+            didTransformExport = true;
+            if (loopBodyScope.hasOwnBinding(name)) {
+              loopBodyScope.rename(name);
+            }
+          }
+          if (imported.get(name) && !importConstViolationName) {
+            importConstViolationName = name;
           }
         }
       }
-      if (!didTransform) {
+      if (!didTransformExport && !importConstViolationName) {
         return;
       }
 
@@ -379,10 +382,6 @@ const rewriteReferencesVisitor: Visitor<RewriteReferencesVisitorState> = {
       const bodyPath = path.get("body");
 
       const newLoopId = scope.generateUidIdentifierBasedOnNode(left);
-      bodyPath.unshiftContainer(
-        "body",
-        t.expressionStatement(t.assignmentExpression("=", left, newLoopId)),
-      );
       path
         .get("left")
         .replaceWith(
@@ -391,6 +390,19 @@ const rewriteReferencesVisitor: Visitor<RewriteReferencesVisitorState> = {
           ]),
         );
       scope.registerDeclaration(path.get("left"));
+
+      if (didTransformExport) {
+        bodyPath.unshiftContainer(
+          "body",
+          t.expressionStatement(t.assignmentExpression("=", left, newLoopId)),
+        );
+      }
+      if (importConstViolationName) {
+        bodyPath.unshiftContainer(
+          "body",
+          t.expressionStatement(buildImportThrow(importConstViolationName)),
+        );
+      }
     }
   },
 };
diff --git a/packages/babel-plugin-transform-modules-commonjs/test/fixtures/misc/import-const-throw/input.mjs b/packages/babel-plugin-transform-modules-commonjs/test/fixtures/misc/import-const-throw/input.mjs
index 01f93be0c990..650e21b272d8 100644
--- a/packages/babel-plugin-transform-modules-commonjs/test/fixtures/misc/import-const-throw/input.mjs
+++ b/packages/babel-plugin-transform-modules-commonjs/test/fixtures/misc/import-const-throw/input.mjs
@@ -35,3 +35,13 @@ Baz &&= 4;
 Foo++;
 Bar++;
 Baz++;
+
+for (Foo in {}) ;
+for (Bar in {}) {}
+for (Baz of []) {
+	let Baz;
+}
+
+for ({Foo} in {}) {}
+for ([Bar] in {}) {}
+for ([...Baz] in {}) {}
diff --git a/packages/babel-plugin-transform-modules-commonjs/test/fixtures/misc/import-const-throw/output.js b/packages/babel-plugin-transform-modules-commonjs/test/fixtures/misc/import-const-throw/output.js
index 3b91b30569a8..79d37c0932bf 100644
--- a/packages/babel-plugin-transform-modules-commonjs/test/fixtures/misc/import-const-throw/output.js
+++ b/packages/babel-plugin-transform-modules-commonjs/test/fixtures/misc/import-const-throw/output.js
@@ -6,8 +6,6 @@ var Bar = _interopRequireDefault(require("bar"));
 
 var _baz = require("baz");
 
-var _Baz;
-
 function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
 
 _foo.default = (42, function () {
@@ -91,6 +89,46 @@ _foo.default = (_foo.default + 1, function () {
 Bar = (Bar + 1, function () {
   throw new Error('"' + "Bar" + '" is read-only.');
 }());
-_Baz = +_baz.Baz, _baz.Baz = (_Baz + 1, function () {
+_baz.Baz = (_baz.Baz + 1, function () {
   throw new Error('"' + "Baz" + '" is read-only.');
-}()), _Baz;
+}());
+
+for (let _Foo in {}) {
+  (function () {
+    throw new Error('"' + "Foo" + '" is read-only.');
+  })();
+
+  ;
+}
+
+for (let _Bar in {}) {
+  (function () {
+    throw new Error('"' + "Bar" + '" is read-only.');
+  })();
+}
+
+for (let _Baz of []) {
+  (function () {
+    throw new Error('"' + "Baz" + '" is read-only.');
+  })();
+
+  let Baz;
+}
+
+for (let _Foo2 in {}) {
+  (function () {
+    throw new Error('"' + "Foo" + '" is read-only.');
+  })();
+}
+
+for (let _ref in {}) {
+  (function () {
+    throw new Error('"' + "Bar" + '" is read-only.');
+  })();
+}
+
+for (let _ref2 in {}) {
+  (function () {
+    throw new Error('"' + "Baz" + '" is read-only.');
+  })();
+}