error[E0277]: can't compare `solana_program::pubkey::Pubkey` with `spl_memo::solana_program::pubkey::Pubkey`

Question

Tackling the error below trying to compile my anchor program

Error: Function _ZN112_$LT$solana_program..instruction..InstructionError$u20$as$u20$solana_frozen_abi..abi_example..AbiEnumVisitor$GT$13visit_for_abi17h644e86fc07351350E Stack offset of 4608 exceeded max offset of 4096 by 512 bytes, please minimize large stack variables
   Compiling anchor-lang v0.28.0
   Compiling spl-token-2022 v0.9.0
error[E0277]: can't compare `solana_program::pubkey::Pubkey` with `spl_memo::solana_program::pubkey::Pubkey`
  --> src/extension/memo_transfer/mod.rs:42:20
   |
42 |         program_id == &spl_memo::id() || program_id == &spl_memo::v1::id()
   |                    ^^ no implementation for `solana_program::pubkey::Pubkey == spl_memo::solana_program::pubkey::Pubkey`
   |
   = help: the trait `PartialEq<spl_memo::solana_program::pubkey::Pubkey>` is not implemented for `solana_program::pubkey::Pubkey`
   = help: the trait `PartialEq` is implemented for `solana_program::pubkey::Pubkey`
   = help: for that trait implementation, expected `solana_program::pubkey::Pubkey`, found `spl_memo::solana_program::pubkey::Pubkey`
   = note: required for `&solana_program::pubkey::Pubkey` to implement `PartialEq<&spl_memo::solana_program::pubkey::Pubkey>`

error[E0277]: can't compare `solana_program::pubkey::Pubkey` with `spl_memo::solana_program::pubkey::Pubkey`
  --> src/extension/memo_transfer/mod.rs:42:53
   |
42 |         program_id == &spl_memo::id() || program_id == &spl_memo::v1::id()
   |                                                     ^^ no implementation for `solana_program::pubkey::Pubkey == spl_memo::solana_program::pubkey::Pubkey`
   |
   = help: the trait `PartialEq<spl_memo::solana_program::pubkey::Pubkey>` is not implemented for `solana_program::pubkey::Pubkey`
   = help: the trait `PartialEq` is implemented for `solana_program::pubkey::Pubkey`
   = help: for that trait implementation, expected `solana_program::pubkey::Pubkey`, found `spl_memo::solana_program::pubkey::Pubkey`
   = note: required for `&solana_program::pubkey::Pubkey` to implement `PartialEq<&spl_memo::solana_program::pubkey::Pubkey>`

error[E0599]: no function or associated item named `get_packed_len` found for struct `spl_token::state::Account` in the current scope
   --> src/state.rs:306:57
    |
306 |                         .get(spl_token::state::Account::get_packed_len())
    |                                                         ^^^^^^^^^^^^^^ function or associated item not found in `Account`
    |
    = help: items from traits can only be used if the trait is in scope
help: the following trait is implemented but not in scope; perhaps add a `use` for it:
    |
3   + use spl_memo::solana_program::program_pack::Pack;
    |

error[E0277]: can't compare `solana_program::pubkey::Pubkey` with `spl_memo::solana_program::pubkey::Pubkey`
   --> src/lib.rs:106:62
    |
106 |     if spl_token_program_id != &id() && spl_token_program_id != &spl_token::id() {
    |                                                              ^^ no implementation for `solana_program::pubkey::Pubkey == spl_memo::solana_program::pubkey::Pubkey`
    |
    = help: the trait `PartialEq<spl_memo::solana_program::pubkey::Pubkey>` is not implemented for `solana_program::pubkey::Pubkey`
    = help: the trait `PartialEq` is implemented for `solana_program::pubkey::Pubkey`
    = help: for that trait implementation, expected `solana_program::pubkey::Pubkey`, found `spl_memo::solana_program::pubkey::Pubkey`
    = note: required for `&solana_program::pubkey::Pubkey` to implement `PartialEq<&spl_memo::solana_program::pubkey::Pubkey>`

Some errors have detailed explanations: E0277, E0599.
For more information about an error, try `rustc --explain E0277`.
error: could not compile `spl-token-2022` (lib) due to 4 previous errors
warning: build failed, waiting for other jobs to finish...

My environment looks like this

solana-cli 2.0.4 (src:0b1143e1; feat:2304137539, client:Agave)

anchor-cli 0.28.0

My program's Cargo.toml dependencies

[dependencies]
anchor-lang = "0.28.0"
mpl-core-candy-guard = "0.2.1"
mpl-core-candy-machine-core = "0.2.1"
solana-program="=1.16.21" 

Answer 1

It's tough to tell without more info, but for some reason your build is saying that solana_program::pubkey::Pubkey == spl_memo::solana_program::pubkey::Pubkey is not implemented, so the version of solana_program used by spl_memo is considered different from the base solana_program.

Take a look through your Cargo.lock to see if one of them is pulling in v2 of solana-program, causing the discrepancy. Everything else looks ok based on the Cargo.toml, but cargo does unexpected things sometimes.