Reload Signer Lamport balance in Anchor

Question

How can we reload the lamport balance of a Signer to compare before/after a CPI?

If we have:

pub struct SomeIX<'info> {
    #[account(mut)]
    pub payer: Signer<'info>,
//etc...

and in our handler:

    let lamports_before = ctx.accounts.payer.lamports();
    //Some CPI where payer pays...
    //RELOAD?
    let lamports_after = ctx.accounts.payer.lamports();

For Token accounts, we can simply do: ctx.accounts.some_acc.reload()?;

But Signer has no reload function.

Answer 1

Have you tried accessing the account_info using ctx.accounts.payer.to_account_info().lamports() and seeing if that contains the updated value?

Answer 2

The answer is actually that the lamport balance updates automatically. For example when using the system program to transfer funds, the lamport balance will be updated after the CPI.

Lamports should be borrowed as mut.