tor-browser

The Tor Browser
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default-parameters-emulates-undefined.js (1941B)

      1 // Copyright (C) 2020 Alexey Shvayka. All rights reserved.
      2 // This code is governed by the BSD license found in the LICENSE file.
      3 /*---
      4 esid: sec-function-definitions-runtime-semantics-instantiatefunctionobject
      5 description: >
      6  Initializer is not evaluated when argument is an object with
      7  [[IsHTMLDDA]] internal slot.
      8 info: |
      9  FunctionDeclaration :
     10    function BindingIdentifier ( FormalParameters ) { FunctionBody }
     11 
     12    [...]
     13    3. Let F be FunctionCreate(Normal, FormalParameters, FunctionBody,
     14    scope, strict).
     15    [...]
     16 
     17  [[Call]] ( thisArgument, argumentsList)
     18 
     19  [...]
     20  7. Let result be OrdinaryCallEvaluateBody(F, argumentsList).
     21  [...]
     22 
     23  OrdinaryCallEvaluateBody ( F, argumentsList )
     24 
     25  1. Let status be FunctionDeclarationInstantiation(F, argumentsList).
     26  [...]
     27 
     28  FunctionDeclarationInstantiation(func, argumentsList)
     29 
     30  [...]
     31  23. Let iteratorRecord be Record {[[iterator]]:
     32  CreateListIterator(argumentsList), [[done]]: false}.
     33  24. If hasDuplicates is true, then
     34    [...]
     35  25. Else,
     36    b. Let formalStatus be IteratorBindingInitialization for formals with
     37    iteratorRecord and env as arguments.
     38  [...]
     39 
     40  Runtime Semantics: IteratorBindingInitialization
     41 
     42  FormalsList : FormalsList , FormalParameter
     43 
     44  [...]
     45  23. Let iteratorRecord be Record {[[Iterator]]:
     46  CreateListIterator(argumentsList), [[Done]]: false}.
     47  24. If hasDuplicates is true, then
     48    [...]
     49  25. Else,
     50    a. Perform ? IteratorBindingInitialization for formals with
     51    iteratorRecord and env as arguments.
     52  [...]
     53 features: [default-parameters, IsHTMLDDA]
     54 ---*/
     55 
     56 let initCount = 0;
     57 const counter = function() {
     58  initCount += 1;
     59 };
     60 
     61 const arrow = (x = counter()) => x;
     62 const IsHTMLDDA = $262.IsHTMLDDA;
     63 
     64 assert.sameValue(arrow(IsHTMLDDA), IsHTMLDDA);
     65 assert.sameValue(initCount, 0);
     66 
     67 function fn(x, y = counter()) {
     68  return y;
     69 }
     70 
     71 assert.sameValue(fn(1, IsHTMLDDA), IsHTMLDDA);
     72 assert.sameValue(initCount, 0);
     73 
     74 reportCompare(0, 0);