Signing with PDAs

let seeds: &[&[u8]] = &[b"vault", &[ctx.bumps.vault]];
let signer: &[&[&[u8]]] = &[seeds];
 
token_interface::transfer_checked(
    CpiContext::new_with_signer(
        ctx.accounts.token_program.to_account_info(),
        accounts,
        signer,
    ),
    amount,
    decimals,
)?;

use anchor_lang::prelude::*;
use anchor_spl::token_interface::{
    self, Mint, TokenAccount, TokenInterface, TransferChecked,
};
 
#[account]
pub struct Vault {
    pub authority: Pubkey,
    pub bump: u8,
}
 
#[derive(Accounts)]
pub struct VaultWithdraw<'info> {
    #[account(seeds = [b"vault", vault.authority.as_ref()], bump = vault.bump)]
    pub vault: Account<'info, Vault>,
    #[account(mut, token::mint = mint, token::authority = vault)]
    pub vault_ata: InterfaceAccount<'info, TokenAccount>,
    #[account(mut, token::mint = mint)]
    pub user_ata: InterfaceAccount<'info, TokenAccount>,
    pub mint: InterfaceAccount<'info, Mint>,
    pub token_program: Interface<'info, TokenInterface>,
}
 
pub fn vault_withdraw(ctx: Context<VaultWithdraw>, amount: u64) -> Result<()> {
    // Bind the Pubkey to a local first. `ctx.accounts.vault.authority` is a
    // Pubkey by value; calling `.as_ref()` on a temporary inside the seed
    // array is an E0716 borrow error.
    let authority_key = ctx.accounts.vault.authority;
    let bump = ctx.accounts.vault.bump;
    let seeds: &[&[u8]] = &[b"vault", authority_key.as_ref(), &[bump]];
    let signer_seeds: &[&[&[u8]]] = &[seeds];
 
    token_interface::transfer_checked(
        CpiContext::new_with_signer(
            ctx.accounts.token_program.to_account_info(),
            TransferChecked {
                from: ctx.accounts.vault_ata.to_account_info(),
                mint: ctx.accounts.mint.to_account_info(),
                to: ctx.accounts.user_ata.to_account_info(),
                authority: ctx.accounts.vault.to_account_info(),
            },
            signer_seeds,
        ),
        amount,
        ctx.accounts.mint.decimals,
    )?;
    Ok(())
}