Deserialize arrays in Borsh?

[vedantroy]

I'm trying to use Borsh to deserialize a large array.

pixels: [(Pubkey, u8); 1_000 * 1_000],

I've added the following crate attribute:

#![feature(trivial_bounds)]

And I'm getting the error:

   |
76 | #[account]
   | ^^^^^^^^^^ the trait `BorshSerialize` is not implemented for `[(anchor_lang::prelude::Pubkey, u8); 1000000]`
   | 
  ::: /home/vedantroy/.cargo/registry/src/github.com-1ecc6299db9ec823/borsh-0.9.1/src/ser/mod.rs:44:18
   |
44 |     fn serialize<W: Write>(&self, writer: &mut W) -> Result<()>;
   |                  - required by this bound in `anchor_lang::AnchorSerialize::serialize`
   |
   = help: the following implementations were found:
             <[T; 0] as BorshSerialize>
             <[T; 1024] as BorshSerialize>
             <[T; 10] as BorshSerialize>
             <[T; 11] as BorshSerialize>
           and 37 others
   = note: required because of the requirements on the impl of `BorshSerialize` for `GameState`
   = note: this error originates in an attribute macro (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0277]: the trait bound `[(anchor_lang::prelude::Pubkey, u8); 1000000]: BorshDeserialize` is not satisfied
  --> programs/auction/src/lib.rs:76:1
   |
76 | #[account]
   | ^^^^^^^^^^ the trait `BorshDeserialize` is not implemented for `[(anchor_lang::prelude::Pubkey, u8); 1000000]`
   |
   = help: the following implementations were found:
             <[T; 0] as BorshDeserialize>
             <[T; 1024] as BorshDeserialize>
             <[T; 10] as BorshDeserialize>
             <[T; 11] as BorshDeserialize>
           and 36 others
   = note: required because of the requirements on the impl of `BorshDeserialize` for `GameState`
   = note: required by `anchor_lang::AnchorDeserialize::deserialize`
   = note: this error originates in an attribute macro (in Nightly builds, run with -Z macro-backtrace for more info)

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0277`.
error: could not compile `auction`

Is there any way to get around this?

[frol]

@vedantroy Use const-generics feature of borsh (just for the reference: near/borsh#36 (comment))

[frol]

@vedantroy BTW (unrelated to borsh), beware that such big arrays might cause various issues when you pass them around using stack. Consider storing that on a heap. https://stackoverflow.com/a/68122278/1178806