From 57e656d87bc3c0a03440c44a262b21362ff52848 Mon Sep 17 00:00:00 2001
From: Ruben Verborgh <ruben@verborgh.org>
Date: Sun, 25 Nov 2018 19:29:58 +0100
Subject: [PATCH] Fix destructuring assignment in arrow functions. (#8916)

Fixes 8912.
---
 src/index.js                                               | 7 ++++++-
 .../destructuring/assignment-arrow-function-block/input.js | 1 +
 .../assignment-arrow-function-block/output.js              | 4 ++++
 .../assignment-arrow-function-no-block/input.js            | 1 +
 .../assignment-arrow-function-no-block/output.js           | 6 ++++++
 5 files changed, 18 insertions(+), 1 deletion(-)
 create mode 100644 test/fixtures/destructuring/assignment-arrow-function-block/input.js
 create mode 100644 test/fixtures/destructuring/assignment-arrow-function-block/output.js
 create mode 100644 test/fixtures/destructuring/assignment-arrow-function-no-block/input.js
 create mode 100644 test/fixtures/destructuring/assignment-arrow-function-no-block/output.js

diff --git a/src/index.js b/src/index.js
index ccc76fb918d9..3e8bd464298c 100644
--- a/src/index.js
+++ b/src/index.js
@@ -540,7 +540,12 @@ export default declare((api, options) => {
         destructuring.init(node.left, ref || node.right);
 
         if (ref) {
-          nodes.push(t.expressionStatement(t.cloneNode(ref)));
+          if (path.parentPath.isArrowFunctionExpression()) {
+            path.replaceWith(t.blockStatement([]));
+            nodes.push(t.returnStatement(t.cloneNode(ref)));
+          } else {
+            nodes.push(t.expressionStatement(t.cloneNode(ref)));
+          }
         }
 
         path.replaceWithMultiple(nodes);
diff --git a/test/fixtures/destructuring/assignment-arrow-function-block/input.js b/test/fixtures/destructuring/assignment-arrow-function-block/input.js
new file mode 100644
index 000000000000..71ebd5203878
--- /dev/null
+++ b/test/fixtures/destructuring/assignment-arrow-function-block/input.js
@@ -0,0 +1 @@
+() => { [a, b] = [1, 2] }
diff --git a/test/fixtures/destructuring/assignment-arrow-function-block/output.js b/test/fixtures/destructuring/assignment-arrow-function-block/output.js
new file mode 100644
index 000000000000..4dca9fc16ca5
--- /dev/null
+++ b/test/fixtures/destructuring/assignment-arrow-function-block/output.js
@@ -0,0 +1,4 @@
+() => {
+  a = 1;
+  b = 2;
+};
diff --git a/test/fixtures/destructuring/assignment-arrow-function-no-block/input.js b/test/fixtures/destructuring/assignment-arrow-function-no-block/input.js
new file mode 100644
index 000000000000..da9e7d37e015
--- /dev/null
+++ b/test/fixtures/destructuring/assignment-arrow-function-no-block/input.js
@@ -0,0 +1 @@
+() => [a, b] = [1, 2]
diff --git a/test/fixtures/destructuring/assignment-arrow-function-no-block/output.js b/test/fixtures/destructuring/assignment-arrow-function-no-block/output.js
new file mode 100644
index 000000000000..408faf04b5e8
--- /dev/null
+++ b/test/fixtures/destructuring/assignment-arrow-function-no-block/output.js
@@ -0,0 +1,6 @@
+() => {
+  var _ref = [1, 2];
+  a = _ref[0];
+  b = _ref[1];
+  return _ref;
+};