Getting Transaction simulation failed: Error processing Instruction 0: custom program error: 0x6, while creating permanent delegate

Question

My instruction for creating permanent-delegate is

invoke(
        &initialize_permanent_delegate(
            &ctx.accounts.token_program.key(),
            &ctx.accounts.mint_account.key(),
            &ctx.accounts.authority.key(),
        )?,
        &[
            ctx.accounts.token_program.to_account_info(),
            ctx.accounts.mint_account.to_account_info(),
            ctx.accounts.authority.to_account_info(),
        ],
    )?;

and my account struct is

#[derive(Accounts)]
#[instruction(params: TokenParams)]
pub struct MintToken<'info> {
    /// CHECK: This is the token that we want to mint
    #[account(
        mut,
        seeds = [b"mint"],
        bump,
        mint::authority = authority,
        mint::freeze_authority = authority,
    )]
    pub mint_account: InterfaceAccount<'info, Mint>,

    /// CHECK: the authority of the mint account
    #[account(mut)]
    pub authority: Signer<'info>,

    #[account(address = Token2022::id())]
    pub token_program: Program<'info, Token2022>,
}

but getting Error: failed to send transaction: Transaction simulation failed: Error processing Instruction 0: custom program error: 0x6

Answer 1

You must initialize the permanent delegate before initializing the mint.

The error that you see 0x6 corresponds to AlreadyInUse, which means that it's failing because the mint is already initialized.

You can see the error code at https://github.com/solana-labs/solana-program-library/blob/10d9c63d91bf736387bca8ba5503bf3b3cf425c8/token/program-2022/src/error.rs#L39