lib: add missing assertions

Author: anonrig

lib/internal/validators.js

@@ -36,15 +36,15 @@ const { signals } = internalBinding('constants').os;
 
 /**
  * @param {*} value
- * @returns {boolean}
+ * @returns {value is number}
  */
 function isInt32(value) {
   return value === (value | 0);
 }
 
 /**
  * @param {*} value
- * @returns {boolean}
+ * @returns {value is number}
  */
 function isUint32(value) {
   return value === (value >>> 0);
@@ -291,6 +291,7 @@ function validateSignalName(signal, name = 'signal') {
  * @callback validateBuffer
  * @param {*} buffer
  * @param {string} [name='buffer']
+ * @returns {asserts buffer is ArrayBufferView}
  */
 
 /** @type {validateBuffer} */