solana-program-examples/tokens/escrow/native/program/src/utils.rs

use crate::error::EscrowError;
use solana_program::{program_error::ProgramError, pubkey::Pubkey};

pub fn assert_is_associated_token_account(
    token_address: &Pubkey,
    owner: &Pubkey,
    mint: &Pubkey,
) -> Result<(), ProgramError> {
    let associated_token_account_address =
        &spl_associated_token_account::get_associated_token_address(owner, mint);

    if token_address != associated_token_account_address {
        return Err(EscrowError::TokenAccountMismatch.into());
    }

    Ok(())
}