nodejs
diff --git a/‎lib/internal/process/promises.js‎
Lines changed: 18 additions & 4 deletions b/‎lib/internal/process/promises.js‎
Lines changed: 18 additions & 4 deletions
diff --git a/‎test/parallel/test-promise-unhandled-warn.js‎
Lines changed: 17 additions & 2 deletions b/‎test/parallel/test-promise-unhandled-warn.js‎
Lines changed: 17 additions & 2 deletions
@@ -5,6 +5,7 @@ const {
   ArrayPrototypeShift,
   Error,
   ObjectDefineProperty,
+  ObjectPrototypeHasOwnProperty,
   SafeWeakMap,
 } = primordials;
 
@@ -79,6 +80,12 @@ function hasRejectionToWarn() {
   return tickInfo[kHasRejectionToWarn] === 1;
 }
 
+function isErrorLike(o) {
+  return typeof o === 'object' &&
+         o !== null &&
+         ObjectPrototypeHasOwnProperty(o, 'stack');
+}
+
 function getUnhandledRejectionsMode() {
   const { getOptionValue } = require('internal/options');
   switch (getOptionValue('--unhandled-rejections')) {
@@ -179,14 +186,21 @@ function emitUnhandledRejectionWarning(uid, reason) {
       `(rejection id: ${uid})`
   );
   try {
-    if (reason instanceof Error) {
+    if (isErrorLike(reason)) {
       warning.stack = reason.stack;
       process.emitWarning(reason.stack, unhandledRejectionErrName);
     } else {
       process.emitWarning(
         noSideEffectsToString(reason), unhandledRejectionErrName);
     }
-  } catch {}
+  } catch {
+    try {
+      process.emitWarning(
+        noSideEffectsToString(reason), unhandledRejectionErrName);
+    } catch {
+      // Ignore.
+    }
+  }
 
   process.emitWarning(warning);
 }
@@ -232,7 +246,7 @@ function processPromiseRejections() {
     try {
       switch (unhandledRejectionsMode) {
         case kStrictUnhandledRejections: {
-          const err = reason instanceof Error ?
+          const err = isErrorLike(reason) ?
             reason : generateUnhandledRejectionError(reason);
           // This destroys the async stack, don't clear it after
           triggerUncaughtException(err, true /* fromPromise */);
@@ -259,7 +273,7 @@ function processPromiseRejections() {
         case kThrowUnhandledRejections: {
           const handled = emit(reason, promise, promiseInfo);
           if (!handled) {
-            const err = reason instanceof Error ?
+            const err = isErrorLike(reason) ?
               reason : generateUnhandledRejectionError(reason);
               // This destroys the async stack, don't clear it after
             triggerUncaughtException(err, true /* fromPromise */);
 
@@ -2,6 +2,7 @@
 'use strict';
 
 const common = require('../common');
+const assert = require('assert');
 
 // Verify that ignoring unhandled rejection works fine and that no warning is
 // logged.
@@ -12,11 +13,25 @@ new Promise(() => {
 
 Promise.reject('test');
 
+function lookForMeInStackTrace() {
+  Promise.reject(new class ErrorLike {
+    constructor() {
+      Error.captureStackTrace(this);
+      this.message = 'ErrorLike';
+    }
+  }());
+}
+lookForMeInStackTrace();
+
 // Unhandled rejections trigger two warning per rejection. One is the rejection
 // reason and the other is a note where this warning is coming from.
-process.on('warning', common.mustCall(4));
+process.on('warning', common.mustCall((reason) => {
+  if (reason.message.includes('ErrorLike')) {
+    assert.match(reason.stack, /lookForMeInStackTrace/);
+  }
+}, 6));
 process.on('uncaughtException', common.mustNotCall('uncaughtException'));
-process.on('rejectionHandled', common.mustCall(2));
+process.on('rejectionHandled', common.mustCall(3));
 
 process.on('unhandledRejection', (reason, promise) => {
   // Handle promises but still warn!