util: skip type checks in internal getSystemErrorName

Backport-PR-URL: #18916
PR-URL: #18546
Reviewed-By: James M Snell <jasnell@gmail.com>

Author: joyeecheung

lib/internal/util.js

@@ -208,11 +208,6 @@ function getConstructorOf(obj) {
 }
 
 function getSystemErrorName(err) {
-  if (typeof err !== 'number' || err >= 0 || !Number.isSafeInteger(err)) {
-    throw new errors.TypeError('ERR_INVALID_ARG_TYPE', 'err',
-                               'negative number');
-  }
-
   const entry = errmap.get(err);
   return entry ? entry[0] : `Unknown system error ${err}`;
 }

lib/util.js

@@ -54,7 +54,7 @@ const {
   customInspectSymbol,
   deprecate,
   getConstructorOf,
-  getSystemErrorName,
+  getSystemErrorName: internalErrorName,
   isError,
   promisify,
   join,
@@ -1071,6 +1071,14 @@ function callbackify(original) {
   return callbackified;
 }
 
+function getSystemErrorName(err) {
+  if (typeof err !== 'number' || err >= 0 || !Number.isSafeInteger(err)) {
+    throw new errors.TypeError('ERR_INVALID_ARG_TYPE', 'err',
+                               'negative number');
+  }
+  return internalErrorName(err);
+}
+
 // Keep the `exports =` so that various functions can still be monkeypatched
 module.exports = exports = {
   _errnoException,