Repository navigation
TS2448 used before its declaration error for recursive function #22975
Description
TypeScript Version: 2.9
Search Terms:
Control flow, recursive functions, used before its declaration.
Code
Live in the wild
https://github.com/webpack/webpack/blob/8498fc091e5375c7c41630723e8fa7916fcc1511/lib/util/cachedMerge.js#L1
const mergeCache = new WeakMap();
function cachedMerge(first, ...args) {
if (args.length === 0) return first;
if (args.length > 1) {
return cachedMerge(first, cachedMerge(...args));
}
const second = args[0];
let innerCache = mergeCache.get(first);
if (innerCache === undefined) {
innerCache = new WeakMap();
mergeCache.set(first, innerCache);
}
const cachedMerge = innerCache.get(second);
if (cachedMerge !== undefined) return cachedMerge;
const newMerge = Object.assign({}, first, second);
innerCache.set(second, newMerge);
return newMerge;
};Expected behavior:
No Error
Actual behavior:
lib/util/cachedMerge.js:12:10 - error TS2448: Block-scoped variable 'cachedMerge' used before its declaration.
12 return cachedMerge(first, cachedMerge(...args));
~~~~~~~~~~~
lib/util/cachedMerge.js:12:29 - error TS2448: Block-scoped variable 'cachedMerge' used before its declaration.
12 return cachedMerge(first, cachedMerge(...args));
~~~~~~~~~~~
Related Issues:
Activity
mhegazy commentedon Mar 29, 2018
that is a bug alright. but i would recommend changing the variable name to avoid the confusion.
mohsen1 commentedon Apr 11, 2018
Nathan Shively-Sanders (@sandersn) Daniel Rosenwasser (@DanielRosenwasser) This is the last item in todo list of migrating Webpack to use TypeScript
webpack/webpack#6862
sandersn commentedon Apr 11, 2018
This error looks correct to me. If you ever run
It will be an error. If you try the original sample in Chrome, you get a TDZ error from the const. If you run it through babel first you get an error that you can't call
undefined. (Babel generates avar cacheMergedwith the default settings on the REPL, at least.)mhegazy commentedon Apr 11, 2018
looking at it again, it is not a compiler bug, it is an actual bug. this code will not execude if the number of arguments is greater than 2.