Is it a good pattern to hint notes? (`Token::redeem_shield` example)

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1

:wave: While doing the Token contract tutorial I wonder what problems would be encountered if redeem_shield would be simplified (I see why a pop_notes example is wonderful for tutorial, so just asking my question here).

I mean pending_shields are filled from the public execution hence it’s not encrypted and available to anyone to see, so it makes sense to find the relevant note (with its header) user wants to redeem, load it into the PXE and then just remove from the pending_shields set privately using the prepared note as the hint.

I still wonder if remove even works this way. Intuition tells me it should just fail if the note isn’t in the set, but I’m having trouble to understand https://github.com/AztecProtocol/aztec-packages/blob/48914ba71039f18d7cea9fca65997c2a6e263b25/noir-projects/aztec-nr/aztec/src/state_vars/private_set.nr#L70: if my snippet would pass this assertion while de-serializing or not. Also I’m sure I missed something else and would be happy to learn what I’m overlooking.

And all remarks are welcome! Like is it bad to insert directly into a balance set, it feels like it shouldn’t hurt it, since I feel it’s just a trait for the token notes. How bad is it to have U128 inside a note instead of Field (anyway it will be checked, and I wonder why not there).

#[private]
fn redeem_shield(
    secret: Field, to: AztecAddress, 
    // note_the: TransparentNote
    note_content_serialized: [Field; 3]
) {
    let note_the = 
        TransparentNote::deserialize_content(note_content_serialized);
    assert(note_the.secret_hashed == compute_secret_hash(secret));
    let amount = note_the.amount;
    storage.pending_shields.remove(note_the);
    let to_keys = get_public_keys(to);
    storage.balances.at(to).set.insert(&mut TokenNote{
        amount, 
        npk_m_hashed: to_keys.npk_m.hash(), 
        randomness: dep::aztec::oracle::unsafe_rand::unsafe_rand(), header: dep::aztec::prelude::NoteHeader::empty()
    }).emit(encode_and_encrypt_note_with_keys(
        &mut context, 
        get_public_keys(context.msg_sender()).ovpk_m, 
        to_keys.ivpk_m, 
        to
    ));
}
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