From 2cace0a8302f72fa1537cd0c7db66923fb3c21ff Mon Sep 17 00:00:00 2001
From: Victor Hom <vh62@cornell.edu>
Date: Sun, 23 Jul 2017 21:34:24 -0400
Subject: [PATCH] Fix: handle array-destructuring with obj assignment in prefer
 const (fixes #8308)

---
 lib/rules/prefer-const.js       | 11 +++++++++++
 tests/lib/rules/prefer-const.js | 14 ++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/lib/rules/prefer-const.js b/lib/rules/prefer-const.js
index 1395e0a8a08e..de98b022da4b 100644
--- a/lib/rules/prefer-const.js
+++ b/lib/rules/prefer-const.js
@@ -199,6 +199,17 @@ function groupByDestructuring(variables, ignoreReadBeforeAssign) {
         }
     }
 
+    for (const key of identifierMap.keys()) {
+        const destructureGroup = identifierMap.get(key);
+        const destructureElement = destructureGroup[0];
+
+        if (destructureElement && destructureElement.parent && destructureElement.parent.elements) {
+            if (destructureElement.parent.elements.length !== destructureGroup.length) {
+                identifierMap.delete(key);
+            }
+        }
+    }
+
     return identifierMap;
 }
 
diff --git a/tests/lib/rules/prefer-const.js b/tests/lib/rules/prefer-const.js
index 984649cb415e..82ecfc1afa65 100644
--- a/tests/lib/rules/prefer-const.js
+++ b/tests/lib/rules/prefer-const.js
@@ -56,6 +56,12 @@ ruleTester.run("prefer-const", rule, {
         "let a; function foo() { if (a) {} a = bar(); }",
         "let a; function foo() { a = a || bar(); baz(a); }",
         "let a; function foo() { bar(++a); }",
+        "let predicate; [typeNode.returnType, predicate] = foo();",
+        "let predicate; let rest; [typeNode.returnType, predicate, ...rest] = foo();",
+        {
+            code: "let predicate; [typeNode.returnType, predicate] = foo();",
+            options: [{ destructuring: "all" }]
+        },
         {
             code: [
                 "let id;",
@@ -270,6 +276,14 @@ ruleTester.run("prefer-const", rule, {
                 { message: "'a' is never reassigned. Use 'const' instead.", type: "Identifier" }
             ]
         },
+        {
+            code: "let [ foo, bar ] = baz();",
+            output: "const [ foo, bar ] = baz();",
+            errors: [
+                { message: "'foo' is never reassigned. Use 'const' instead.", type: "Identifier" },
+                { message: "'bar' is never reassigned. Use 'const' instead.", type: "Identifier" }
+            ]
+        },
         {
             code: "let {a} = obj",
             output: "const {a} = obj",