function-return.js

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// |reftest| shell-option(--enable-shadow-realms) skip-if(!xulRuntime.shell)

// The output of Function.prototype.toString must match the |NativeFunction| production.

// https://tc39.es/ecma262/#sec-function.prototype.tostring

//

// NativeFunction :

//   function NativeFunctionAccessor? PropertyName[~Yield, ~Await]? ( FormalParameters[~Yield, ~Await] ) { [ native code ] }

//

// NativeFunctionAccessor :

//   get

//   set

function assertMatchesNativeFunction(f) {

  var source = f.toString();

  // Starts with "function".

  assertEq(/^function\b/.test(source), true);

  // Remove the optional |NativeFunctionAccessor| part.

  var nativeAccesorRe = /^(?<start>\s*function)(?<accessor>\s+[gs]et)(?<end>\s+[^(].*)$/;

  var match = nativeAccesorRe.exec(source);

  if (match) {

    source = match.groups.start + match.groups.end;

  // The body must include the string "[native code".

  var closeCurly = source.lastIndexOf("}");

  var openCurly = source.lastIndexOf("{");

  assertEq(openCurly < closeCurly, true);

  var body = source.slice(openCurly + 1, closeCurly);

  assertEq(/^\s*\[native code\]\s*$/.test(body), true);

  // Verify |PropertyName| and |FormalParameters| are syntactically correct by parsing the source

  // code. But we first need to replace the "[native code]" substring.

  source = source.slice(0, openCurly) + "{}";

  // Also prepend "void" to parse the function source code as a FunctionExpression, because we

  // don't necessarily have a name part.

  source = "void " + source;

  try {

    Function(source);

  } catch {

    assertEq(true, false, `${source} doesn't match NativeFunction`);

let sr = new ShadowRealm();

var f = sr.evaluate("function f() { }; f");

assertMatchesNativeFunction(f);

f.name = "koala"

assertMatchesNativeFunction(f);

Object.defineProperty(f, "name", { writable: true, value: "koala" });

assertMatchesNativeFunction(f);

f.name = "panda"

assertMatchesNativeFunction(f);

f.name = "has whitespace, therefore shouldn't match the PropertyName production";

assertMatchesNativeFunction(f);

f.name = 123;

assertMatchesNativeFunction(f);

Object.defineProperty(f, "name", { get() { throw new Error("unexpected side-effect"); } });

assertMatchesNativeFunction(f);

if (typeof reportCompare === 'function')

    reportCompare(true, true);