fix(dce): handle array and object patterns in assignment expressions (#…

…882)

fix #871

packages/babel-plugin-minify-dead-code-elimination/__tests__/fixtures/issue-871/actual.js

@@ -0,0 +1,7 @@
+async function example() {
+  var foo, bar;
+  try {
+    [foo, bar] = await Promise.all([req(1), req(2)]);
+  } catch (e) {}
+  console.log(foo);
+}

packages/babel-plugin-minify-dead-code-elimination/__tests__/fixtures/issue-871/expected.js

@@ -0,0 +1,9 @@
+async function example() {
+  var foo, bar;
+
+  try {
+    [foo, bar] = await Promise.all([req(1), req(2)]);
+  } catch (e) {}
+
+  console.log(foo);
+}

packages/babel-plugin-minify-dead-code-elimination/src/index.js

@@ -235,10 +235,17 @@ module.exports = ({ types: t, traverse }) => {
                 bail = true;
               }
 
-              if (p.isAssignmentExpression() && !p.get("right").isPure()) {
-                mutations.push(() => p.replaceWith(p.get("right")));
-              } else {
-                mutations.push(() => removeOrVoid(p));
+              if (p.isAssignmentExpression()) {
+                if (
+                  t.isArrayPattern(p.node.left) ||
+                  t.isObjectPattern(p.node.left)
+                ) {
+                  bail = true;
+                } else if (p.get("right").isPure()) {
+                  mutations.push(() => removeOrVoid(p));
+                } else {
+                  mutations.push(() => p.replaceWith(p.get("right")));
+                }
               }
             });