faster brand check

benchmarks/fetch/webidl-is.mjs

@@ -0,0 +1,26 @@
+import { bench, run, barplot } from 'mitata'
+import { Headers, FormData } from '../../index.js'
+import { webidl } from '../../lib/web/fetch/webidl.js'
+
+const headers = new Headers()
+const fd = new FormData()
+
+barplot(() => {
+  bench('webidl.is.FormData (ok)', () => {
+    return webidl.is.FormData(fd)
+  })
+
+  bench('webidl.is.FormData (bad)', () => {
+    return !webidl.is.FormData(headers)
+  })
+
+  bench('instanceof (ok)', () => {
+    return fd instanceof FormData
+  })
+
+  bench('instanceof (bad)', () => {
+    return !(headers instanceof FormData)
+  })
+})
+
+await run()

lib/web/fetch/formdata.js

@@ -256,6 +256,6 @@ function makeEntry (name, value, filename) {
   return { name, value }
 }
 
-webidl.is.FormData = webidl.util.MakeTypeAssertion(FormData.prototype)
+webidl.is.FormData = webidl.util.MakeTypeAssertion(FormData)
 
 module.exports = { FormData, makeEntry, setFormDataState }

lib/web/fetch/request.js

@@ -986,7 +986,7 @@ Object.defineProperties(Request.prototype, {
   }
 })
 
-webidl.is.Request = webidl.util.MakeTypeAssertion(Request.prototype)
+webidl.is.Request = webidl.util.MakeTypeAssertion(Request)
 
 // https://fetch.spec.whatwg.org/#requestinfo
 webidl.converters.RequestInfo = function (V, prefix, argument) {

lib/web/fetch/response.js

@@ -619,7 +619,7 @@ webidl.converters.ResponseInit = webidl.dictionaryConverter([
   }
 ])
 
-webidl.is.Response = webidl.util.MakeTypeAssertion(Response.prototype)
+webidl.is.Response = webidl.util.MakeTypeAssertion(Response)
 
 module.exports = {
   isNetworkError,

lib/web/fetch/webidl.js

@@ -12,6 +12,8 @@ const BIGINT = 6
 const NULL = 7
 const OBJECT = 8 // function and object
 
+const FunctionPrototypeSymbolHasInstance = Function.call.bind(Function.prototype[Symbol.hasInstance])
+
 /** @type {import('../../../types/webidl').Webidl} */
 const webidl = {
   converters: {},
@@ -45,15 +47,15 @@ webidl.errors.invalidArgument = function (context) {
 
 // https://webidl.spec.whatwg.org/#implements
 webidl.brandCheck = function (V, I) {
-  if (!I.prototype.isPrototypeOf(V)) { // eslint-disable-line no-prototype-builtins
+  if (!FunctionPrototypeSymbolHasInstance(I, V)) {
     const err = new TypeError('Illegal invocation')
     err.code = 'ERR_INVALID_THIS' // node compat.
     throw err
   }
 }
 
 webidl.brandCheckMultiple = function (List) {
-  const prototypes = List.map((c) => webidl.util.MakeTypeAssertion(c.prototype))
+  const prototypes = List.map((c) => webidl.util.MakeTypeAssertion(c))
 
   return (V) => {
     if (prototypes.every(typeCheck => !typeCheck(V))) {
@@ -81,9 +83,8 @@ webidl.illegalConstructor = function () {
   })
 }
 
-const isPrototypeOf = Object.prototype.isPrototypeOf
-webidl.util.MakeTypeAssertion = function (Prototype) {
-  return (O) => isPrototypeOf.call(Prototype, O)
+webidl.util.MakeTypeAssertion = function (I) {
+  return (O) => FunctionPrototypeSymbolHasInstance(I, O)
 }
 
 // https://tc39.es/ecma262/#sec-ecmascript-data-types-and-values
@@ -462,13 +463,13 @@ webidl.nullableConverter = function (converter) {
   }
 }
 
-webidl.is.ReadableStream = webidl.util.MakeTypeAssertion(ReadableStream.prototype)
-webidl.is.Blob = webidl.util.MakeTypeAssertion(Blob.prototype)
-webidl.is.URLSearchParams = webidl.util.MakeTypeAssertion(URLSearchParams.prototype)
-webidl.is.File = webidl.util.MakeTypeAssertion((globalThis.File ?? require('node:buffer').File).prototype)
-webidl.is.URL = webidl.util.MakeTypeAssertion(URL.prototype)
-webidl.is.AbortSignal = webidl.util.MakeTypeAssertion(AbortSignal.prototype)
-webidl.is.MessagePort = webidl.util.MakeTypeAssertion(MessagePort.prototype)
+webidl.is.ReadableStream = webidl.util.MakeTypeAssertion(ReadableStream)
+webidl.is.Blob = webidl.util.MakeTypeAssertion(Blob)
+webidl.is.URLSearchParams = webidl.util.MakeTypeAssertion(URLSearchParams)
+webidl.is.File = webidl.util.MakeTypeAssertion(globalThis.File ?? require('node:buffer').File)
+webidl.is.URL = webidl.util.MakeTypeAssertion(URL)
+webidl.is.AbortSignal = webidl.util.MakeTypeAssertion(AbortSignal)
+webidl.is.MessagePort = webidl.util.MakeTypeAssertion(MessagePort)
 
 // https://webidl.spec.whatwg.org/#es-DOMString
 webidl.converters.DOMString = function (V, prefix, argument, opts) {

lib/web/websocket/stream/websocketerror.js

@@ -78,6 +78,6 @@ Object.defineProperties(WebSocketError.prototype, {
   }
 })
 
-webidl.is.WebSocketError = webidl.util.MakeTypeAssertion(WebSocketError.prototype)
+webidl.is.WebSocketError = webidl.util.MakeTypeAssertion(WebSocketError)
 
 module.exports = { WebSocketError, createUnvalidatedWebSocketError }

test/webidl/helpers.js

@@ -8,9 +8,7 @@ test('webidl.interfaceConverter', (t) => {
   class A {}
   class B {}
 
-  const converter = webidl.interfaceConverter(
-    webidl.util.MakeTypeAssertion(A.prototype)
-  )
+  const converter = webidl.interfaceConverter(webidl.util.MakeTypeAssertion(A))
 
   assert.throws(() => {
     converter(new B(), 'converter', 'converter')

types/webidl.d.ts

@@ -84,7 +84,7 @@ interface WebidlUtil {
    */
   Stringify (V: any): string
 
-  MakeTypeAssertion <T extends { prototype: T }>(Prototype: T['prototype']): (arg: any) => arg is T
+  MakeTypeAssertion <I extends abstract new (...args: any[]) => any>(I: I): (arg: any) => arg is InstanceType<I>
 }
 
 interface WebidlConverters {
@@ -176,7 +176,7 @@ interface WebidlConverters {
   [Key: string]: (...args: any[]) => unknown
 }
 
-type IsAssertion<T> = (arg: any) => arg is T
+type IsAssertion<T extends abstract new (...args: any[]) => any> = (arg: any) => arg is InstanceType<T>
 
 interface WebidlIs {
   Request: IsAssertion<undici.Request>