From 905bf49df884a598bb2ad1a965023efbcfd6dd19 Mon Sep 17 00:00:00 2001
From: Boopathi Rajaa <me@boopathi.in>
Date: Sat, 8 Jul 2017 15:52:36 +0200
Subject: [PATCH] [DCE] Fix removal of ArrayPattern

+ (Fix 617)
---
 .../__tests__/dead-code-elimination-test.js   | 22 +++++++++++++
 .../src/index.js                              | 32 ++++++++++++-------
 2 files changed, 42 insertions(+), 12 deletions(-)

diff --git a/packages/babel-plugin-minify-dead-code-elimination/__tests__/dead-code-elimination-test.js b/packages/babel-plugin-minify-dead-code-elimination/__tests__/dead-code-elimination-test.js
index cb42baadd..3e4476b64 100644
--- a/packages/babel-plugin-minify-dead-code-elimination/__tests__/dead-code-elimination-test.js
+++ b/packages/babel-plugin-minify-dead-code-elimination/__tests__/dead-code-elimination-test.js
@@ -2426,4 +2426,26 @@ describe("dce-plugin", () => {
     }
   `
   );
+
+  thePlugin(
+    "should bail out for Array and Object Pattern - fix issue#617",
+    `
+      function foo(arr) {
+        let [a, b] = arr;
+        console.log(a);
+      }
+    `
+  );
+
+  thePlugin(
+    "should bail out for Array and Object Pattern - fix issue#617",
+    `
+      function foo() {
+        return getPromise().then(arr => {
+          let { a, b } = arr;
+          console.log(a);
+        });
+      }
+    `
+  );
 });
diff --git a/packages/babel-plugin-minify-dead-code-elimination/src/index.js b/packages/babel-plugin-minify-dead-code-elimination/src/index.js
index b030a9330..09fc01158 100644
--- a/packages/babel-plugin-minify-dead-code-elimination/src/index.js
+++ b/packages/babel-plugin-minify-dead-code-elimination/src/index.js
@@ -228,21 +228,29 @@ module.exports = ({ types: t, traverse }) => {
               continue;
             }
 
-            if (
-              binding.path.isVariableDeclarator() &&
-              binding.path.node.init &&
-              !scope.isPure(binding.path.node.init) &&
-              binding.path.parentPath.node.declarations
-            ) {
-              if (binding.path.parentPath.node.declarations.length !== 1) {
-                continue;
-              }
-              // Bail out for ArrayPattern and ObjectPattern
+            if (binding.path.isVariableDeclarator()) {
               if (!binding.path.get("id").isIdentifier()) {
+                // deopt for object and array pattern
                 continue;
               }
 
-              binding.path.parentPath.replaceWith(binding.path.node.init);
+              // if declarator has some impure init expression
+              // var x = foo();
+              // => foo();
+              if (
+                binding.path.node.init &&
+                !scope.isPure(binding.path.node.init) &&
+                binding.path.parentPath.node.declarations
+              ) {
+                // binding path has more than one declarations
+                if (binding.path.parentPath.node.declarations.length !== 1) {
+                  continue;
+                }
+                binding.path.parentPath.replaceWith(binding.path.node.init);
+              } else {
+                updateReferences(binding.path, this);
+                removeOrVoid(binding.path);
+              }
             } else {
               updateReferences(binding.path, this);
               removeOrVoid(binding.path);
@@ -403,7 +411,7 @@ module.exports = ({ types: t, traverse }) => {
               }
             }
           }
-        }
+        } // end-for-of
       }
     },