From f9cfb38ef10b94f539ae47f00b36210f70cc90cd Mon Sep 17 00:00:00 2001
From: Toru Nagashima <star.ctor@gmail.com>
Date: Thu, 9 May 2019 06:31:58 +0900
Subject: [PATCH] Fix: ignore return statements in dead code (fixes #11647)

---
 lib/rules/no-useless-return.js       |  9 ++++++++-
 tests/lib/rules/no-useless-return.js | 17 ++++++++++++-----
 2 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/lib/rules/no-useless-return.js b/lib/rules/no-useless-return.js
index bb11b4b3619..2ac7112872d 100644
--- a/lib/rules/no-useless-return.js
+++ b/lib/rules/no-useless-return.js
@@ -255,7 +255,14 @@ module.exports = {
                 if (node.argument) {
                     markReturnStatementsOnCurrentSegmentsAsUsed();
                 }
-                if (node.argument || astUtils.isInLoop(node) || isInFinally(node)) {
+                if (
+                    node.argument ||
+                    astUtils.isInLoop(node) ||
+                    isInFinally(node) ||
+
+                    // Ignore `return` statements in unreachable places (https://github.com/eslint/eslint/issues/11647).
+                    !scopeInfo.codePath.currentSegments.some(s => s.reachable)
+                ) {
                     return;
                 }
 
diff --git a/tests/lib/rules/no-useless-return.js b/tests/lib/rules/no-useless-return.js
index 56ad245c2c9..669d245241f 100644
--- a/tests/lib/rules/no-useless-return.js
+++ b/tests/lib/rules/no-useless-return.js
@@ -165,6 +165,17 @@ ruleTester.run("no-useless-return", rule, {
             throw new Error('foo');
             while (false);
           } catch (err) {}
+        `,
+
+        // https://github.com/eslint/eslint/issues/11647
+        `
+          function foo(arg) {
+            throw new Error("Debugging...");
+            if (!arg) {
+              return;
+            }
+            console.log(arg);
+          }
         `
     ],
 
@@ -418,11 +429,7 @@ ruleTester.run("no-useless-return", rule, {
         },
         {
             code: "function foo() { return; return; }",
-            output: "function foo() {  return; }", // Other case is fixed in the second pass.
-            errors: [
-                { message: "Unnecessary return statement.", type: "ReturnStatement" },
-                { message: "Unnecessary return statement.", type: "ReturnStatement" }
-            ]
+            output: "function foo() {  return; }"
         }
     ].map(invalidCase => Object.assign({ errors: [{ message: "Unnecessary return statement.", type: "ReturnStatement" }] }, invalidCase))
 });