``` const x = nameof y const y = 1; ``` At line 1 adjacent to ```nameof``` how does the user even know that there is a variable that will be declared named ```y```?
What is the output of ```x``` where there is no variable named ```y``` later declared? ``` const x = nameof y const z = 1; ``` On Sun, Jun 16, 2019 at 12:03 AM Ron Buckton <[email protected]> wrote: > > What should occur where the code is > > It would be "y" in all 3 places. > > > ... is a proposal for _more_ than only getting the _name_ of an > _declared_ and _initialized_ variable? > > It is a proposal for getting the name of a _declared_ variable. Whether it > is _initialized_ does not matter. > > > Should a ```RefefenceError``` _not_ be thrown simple because > ```nameof``` is used? > > No, an error is not thrown. ECMAScript is much more nuanced. Block scoped > variables from 'let' or 'const' exist and can be *referenced* (via closure > or export, currently) anywhere within the same block scope, even before > they are initialized. Until they have been *initialized* (the line of code > contain the declaration has been reached and evaluated), they exist in a > "Temporal Dead Zone" (TDZ). Attempting to *dereference* them (i.e. access > or store a value) while in this TDZ is what results in the ReferenceError. > > At no point does the `nameof` operator *dereference* the variable, so no > error need be thrown. > > From: guest271314 > Sent: Saturday, June 15, 4:29 PM > Subject: Re: Re: What do you think about a C# 6 like nameof() expression > for > To: Ron Buckton > Cc: [email protected] > > > > > What should occur where the code is > > ``` > const x = nameof y > await new Promise(resolve => setTimeout(resolve, 100000)); // should x be > "y" here? > await new Promise(resolve => setTimeout(resolve, 200000)); // should x be > "y" here? > await Promise.all([new Promise(resolve => setTimeout(resolve, 300000)), > ...doStuff()]); // should x be "y" here? > const y = 1; > ``` > > ? > > The immediately invoked arrow function example (where a > ```RefeferenceError``` is thrown) appears to demonstrate that to output the > expected result of ```nameof``` within the context of the code example > > ``` > const x = nameof y > const y = 1; > ``` > > is a proposal for _more_ than only getting the _name_ of an _declared_ and > _initialized_ variable? > > Should a ```RefefenceError``` _not_ be thrown simple because ```nameof``` > is used? > > On Sat, Jun 15, 2019 at 11:16 PM Ron Buckton <[email protected]> > wrote: > > ``` > const x = nameof y > const y = 1; > ``` > > `x` would have the value “y”. It would not matter if `y` were initialized > or had yet been reached during execution. It does not deviate from the > purpose of `let` or `const`, because you are not accessing the *value* of > the identifier. > > Also consider that this is legal ECMAScript in a module: > > ``` > export { y } > const y = 1; > ``` > > The binding for `y` exists within the same block scope, it just has not > yet been initialized. Exporting it via `export { y }`, closing over it via > `() => y`, or accessing it via `nameof y` would all be the same. In all > three cases you are accessing the **binding** of `y`, not the **value** > of `y`. Even in the `() => y` case, you don’t access the **value** of `y` > until you execute the function. > > *From:* guest271314 <[email protected]> > *Sent:* Saturday, June 15, 2019 3:57 PM > *To:* Ron Buckton <[email protected]> > *Cc:* [email protected] > *Subject:* Re: Re: What do you think about a C# 6 like nameof() > expression for > > > Sorry, I meant to say “not entirely correct”. > > You have not yet confirmed if in fact the expected output is referencing a > variable declared using ```const``` on the current line _before_ > initialization _on the next line_. > > That example appears to deviate from the purpose and usage of ```const```, > beyond the scope of ```nameof```, and if were implemented, a > ```ReferenceError``` should _not_ be thrown when a ```const``` variable > that has yet to be initialized _on the next line_ is referred to _on the > current line_? > > Aside from that example, the code which essentially already implements > ```nameof``` should be able to be found in the code which implements > ```ReferenceError``` relevant to ```const```. > > On Sat, Jun 15, 2019 at 10:47 PM Ron Buckton <[email protected]> > wrote: > > Sorry, I meant to say “not entirely correct”. > > *From:* Ron Buckton > *Sent:* Saturday, June 15, 2019 3:03 PM > *To:* guest271314 <[email protected]> > *Cc:* [email protected] > *Subject:* RE: Re: What do you think about a C# 6 like nameof() > expression for > > > At that point in the example code the identifer ```y``` does not exist. > > That is not entirely incorrect. The identifier `y` exists, but its binding > has not been initialized, otherwise you couldn’t refer to y in this case: > > > > >
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