182414 2018-02-01 17:02:21 -0800 Async arrow function with var declaration has incorrect shadowing 2023-10-15 11:58:56 -0700 1 1 1 Unclassified WebKit JavaScriptCore WebKit Local Build Unspecified Unspecified RESOLVED DUPLICATE 223533 InRadar P2 Normal --- 1 adamk webkit-unassigned ashvayka gskachkov lharker mark.lam matsaa theodorejb webkit-bug-importer ysuzuki oldest_to_newest 1395706 0 adamk 2018-02-01 17:02:21 -0800 The following code, run in the shell, should print "7", but prints "undefined": (async (v) => { print(v); var v; })(7) Without "async", this gets the right answer. 1395940 1 gskachkov 2018-02-02 12:01:29 -0800 Hmm, the same for common async function ``` (async function (v) { print(v); var v; })(7); ``` 1395942 2 gskachkov 2018-02-02 12:04:19 -0800 Yeah and the same for generator and async generators 1395949 3 ysuzuki 2018-02-02 12:21:24 -0800 Hm, shoud it print 7? Why doesn’t “var” hide? 1395964 4 gskachkov 2018-02-02 12:59:07 -0800 (In reply to Yusuke Suzuki from comment #3) > Hm, shoud it print 7? Why doesn’t “var” hide? I cann't find this rule in current spec but it was in ES5, there is a exist old tests: ``` https://github.com/tc39/test262/blob/master/test/language/function-code/S10.2.1_A5.2_T1.js https://github.com/tc39/test262/blob/master/test/language/function-code/S10.2.1_A5.1_T2.js ``` 1395972 5 adamk 2018-02-02 13:15:06 -0800 See step 27 of https://tc39.github.io/ecma262/#sec-functiondeclarationinstantiation. Basically, if a var-declared name has the same name as a parameter (and there aren't any parameter expressions, i.e., default parameter values or destructuring), the var declaration is ignored. 1760053 6 matsaa 2021-05-14 04:34:21 -0700 When running code through uglify-js it generates this type of code which breaks. var b=async (t,a,r)=> { console.log(a); var a = a; console.log(t); console.log(a); console.log(r); return { t, a, r }; }; b(1, 2, 3); replacing the var a = 1; with a=a works. the first console log says undefined when the var is left. the code works in firefox and chrome. so is this a bug in webkit or the other browsers? 1971200 7 webkit-bug-importer 2023-08-14 18:46:59 -0700 <rdar://problem/113883888> 1985200 8 ashvayka 2023-10-15 11:58:56 -0700 *** This bug has been marked as a duplicate of bug 223533 ***