microsoft / microsoft/TypeScript
checkJs can't correctly determine type of generic function parameter
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@ahejlsberg is already working on this.
Since Jun 12, 2019.
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Description
TypeScript Version: 3.4.5
jsdoc
checkJs
template
function
parameter
/**
* @template T
* @param {(left: T, right: T) => boolean} equals
* @returns {(xs: T[]) => T[]}
*/
const uniq = equals => xs => {
/** @type {T[]} */
const seen = []
const out = []
const len = xs.length
let j = 0
for(let i = 0; i < len; i++) {
const item = xs[i]
if(!seen.some(s => equals(s, item))) {
seen.push(item)
out[j++] = item
}
}
return out;
}
uniq((x, y) => x == y)([1, 3, 3, 7])
Expected behavior:
Typechecks fine
Actual behavior:
Type 'number' is not assignable to type 'T
Related Issues:
This seems related, but I don't think it's it
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