lang: Implement Key trait without to_account_info() calls

[armaniferrante]

Currently the Key trait is implemented via a wasteful call to to_account_info which incurs a clone on the AccountInfo.

[fanatid]

I'm not sure how to do this properly, but with cargo-asm I see a clone with to_account_info().key (but was able to run only with bpf toolchain, not bpfel target).

Decide to count instructions with sol_log_compute_units:

*ctx.accounts.value.to_account_info().key == clock::ID; // 162
ctx.accounts.value.to_account_info().key == &clock::ID; // 162
*ctx.accounts.value.to_account_info().key == clock::id(); // 176
ctx.accounts.value.key() == clock::id(); // 190
*ctx.accounts.value.mykey() == clock::id(); // 95
*ctx.accounts.value.mykey() == clock::ID; // 82
ctx.accounts.value.mykey2() == clock::id(); // 105

with patched anchor:

impl<'info, T: solana_program::sysvar::Sysvar> Sysvar<'info, T> {
    pub fn mykey(&self) -> &Pubkey {
        self.info.key
    }
    pub fn mykey2(&self) -> Pubkey {
        *self.info.key
    }
}

I think to add ToAccountInfoRef trait and change Key trait to KeyRef with method key which return reference, sounds good?

[armaniferrante]

I'm not sure how to do this properly, but with cargo-asm I see a clone with to_account_info().key (but was able to run only with bpf toolchain, not bpfel target).

Decide to count instructions with sol_log_compute_units:

*ctx.accounts.value.to_account_info().key == clock::ID; // 162
ctx.accounts.value.to_account_info().key == &clock::ID; // 162
*ctx.accounts.value.to_account_info().key == clock::id(); // 176
ctx.accounts.value.key() == clock::id(); // 190
*ctx.accounts.value.mykey() == clock::id(); // 95
*ctx.accounts.value.mykey() == clock::ID; // 82
ctx.accounts.value.mykey2() == clock::id(); // 105

with patched anchor:

impl<'info, T: solana_program::sysvar::Sysvar> Sysvar<'info, T> {
    pub fn mykey(&self) -> &Pubkey {
        self.info.key
    }
    pub fn mykey2(&self) -> Pubkey {
        *self.info.key
    }
}

I think to add ToAccountInfoRef trait and change Key trait to KeyRef with method key which return reference, sounds good?

Sounds great.

[fanatid]

Looks like there is a nicer way to solve an issue... use AsRef. But we need it solana_program::account_info::AccountInfo 😞
If we will have AsRef we would able to write: constraint = ctx.accounts.cpi_account.as_ref().owner == spl_token::ID

[fanatid]

Submitted pull request ⬆️
Current code in branch in my fork: https://github.com/fanatid/anchor/tree/cheaper-key

Waiting solana 1.7.11

[fanatid]

1.7.11 is out, but not all required crates are published