Can't use aliases of the global Symbol value to refer to its properties in the same manner or create unique symbols

[falsandtru]

Although Nodejs also uses this technique, we can't do the same thing.

https://github.com/nodejs/node/search?q=primordials+symbol&unscoped_q=primordials+symbol

TypeScript Version: 3.7.x-dev.20200125

Search Terms:

Code

export { }
const Symbol = globalThis.Symbol;
const sym = Symbol();
[][Symbol.iterator];

Expected behavior:

const sym = Symbol(); // typeof sym
[][Symbol.iterator]; // Refer iterator method

Actual behavior:

const sym = Symbol(); // symbol
[][Symbol.iterator]; // error

Playground Link: http://www.typescriptlang.org/play/index.html?target=5&ts=3.8.0-dev.20200125&ssl=1&ssc=1&pln=2&pc=21#code/KYDwDg9gTgLgBAbzgXwFAGMIDsDO8DKAngLYBGEANnALxwDmFEpAhhQCoAWAljgHRFlKAbgzY8cHCRpwB5CgAoAlCIDaAXRWzKvLjGBRmMaGqA

Related Issues: #21603 #35478

[falsandtru]

Global variable reference greatly decreases the performance.

https://falsandtru.github.io/benchmark/suites/10/

But we can't avoid this performance problem with Symbol caused by global reference because of this issue.

[RyanCavanaugh]

I don't quite understand what you're doing or why, or why what you're doing doesn't justify a type assertion

[falsandtru]

what you're doing or why

To improve runtime performance as I explained above.

why what you're doing doesn't justify a type assertion

I'm not sure what you mean. What is meant by "justify a type assertion"?

[falsandtru]

@RyanCavanaugh Can you triage the other issues too?

[RyanCavanaugh]

@falsandtru if you can come cook dinner and tend to my kid I can work evenings

[falsandtru]

@RyanCavanaugh I'm not saying do it right now and the oldest issue in these days (#35896) was opened a month ago. Do you require me to wait more? 2 months?

[RyanCavanaugh]

@falsandtru your issues are very confusing and require a lot of time to try to piece together what you mean and what you want to happen. You'll have to forgive me that I take up more actionable issues first; other people have put in the work to make understandable reports and are treated as such.

[falsandtru]

Can't use aliases of the global Symbol value to refer to its properties in the same manner

And can't make unique symbols using an alias of the Symbol function. Don't miss it.

[falsandtru]

your issues are very confusing

Can you point out where I don't know? It is difficult to know it myself.

[ExE-Boss]

The global Symbol properties will be fixed by #24738 #42543, which converts them all to unique symbol types.

[bordoley]

One unfortunate side-effect of the inability to alias the Symbol constructor when defining unique symbol property keys for classes and objects is that it results in increased bundle size, even when compiled with terser (see: terser/terser#1337). Your compiled code becomes littered with Symbol() invocations.

Typically in libraries one will alias globals like Math to a local variable to work around terser failing to mangle built-ins, but given this TS limitation there is no way for one to do so.

[RyanCavanaugh]

The issue in the OP now behaves as desired, so I'm inclined to close this. @bordoley can you confirm or provide a failing repro?

[bordoley]

@RyanCavanaugh: I'll create a test repo, and file a new issue with an example that illustrates the issue.

[RyanCavanaugh]

Thanks!

[bordoley]

see: #53282