Why allow invalid Mnemonics?

[pezcore]

Why does Mnemonic::parse_in_normalized_without_checksum_check exist? Isn't the main usefulness of this crate the fact that Mnemonic instances are guaranteed to be valid? Now if someone writes an application that presents a Mnemonic to a user, they have to manually trace the source of its initialization and make sure it wasn't created with parse_in_normalized_without_checksum_check or else they risk presenting an invalid mnemonic.

It makes sense for possibly-invalid mnemonics and operations thereof to be in scope of this crate, but I feel like their implementation shouldn't break the checksum validity invariant of Mnemonic. That way, application authors can simply trust that Mnemonic instances are valid.

[stevenroose]

That method is intended to be used with mnemonics for which the code author knows it is valid. Either because it has been checked in some other way or because it has been checked before, but the mnemonic wasn't stored as a Mnemonic type.

Any author using this method with a potentially invalid mnemonic is responsible for the possible negative effects of that. Obviously libraries returning mnemonics should refrain from returning invalid mnemonics.