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Fix array.filter( return type
When you filter away elements of some type, it would be nice if returned type changed. But it doesn't:
ts
const bad = ['a', 1, 'b'].filter((a) => typeof a === 'string')
// (string | number)[]My current fix is:
ts
const good = ['a', 1, 'b'].filter((a): a is string => typeof a === 'string')
// string[]
const good2 = ['a', null, 'b'].filter((a): a is NonNullable<typeof a> => !!a)
// string[]