recursive private static gets missed in --noUnusedLocals

[beauxq]

TypeScript Version: 3.8.3

Search Terms:
noUnusedLocals, recursive

Code

class C {
    private static staticFactorial(n: number): number {  // no error
        return (n === 0) ? 1 : (n * C.staticFactorial(n - 1));
    }

    private static foo() {  // unused error
        return 42;
    }
}

function main() {
    function localFactorial(n: number): number {  // unused error
        return (n === 0) ? 1 : (n * localFactorial(n - 1));
    }
}

Expected behavior:
both localFactorial and staticFactorial have the same result when compiled with --noUnusedLocals

Actual behavior:
localFactorial triggers error
staticFactorial does not