Could it make sense for the standard library to expose a public demangle function? The stdlib already tests that this is possible here: https://github.com/apple/swift/blob/b7daed7958956f5e91a66a9a3bc1c959f9471ef6/test/stdlib/Runtime.swift.gyb#L24
Implementation wise, it seems pretty trivial, but I assume maybe there's some other considerations when adding this?