Remove OnceLock from ChainSpec

[emhane]

Describe the feature

Remove OnceLock wrapping SealedHeader in ChainSpec

blocked by #14355

Additional context

No response

[Ayushdubey86]

I am thinking to take this , once pr closes

[Ayushdubey86]

@emhane

Is this issue about removing the sealed_genesis_header() function from chainspec/src/spec.rs? If so, removing OnceLock from the struct could have widespread impact. Can I get more context on which functionalities should remain unaffected?

pub fn sealed_genesis_header(&self) -> SealedHeader {
SealedHeader::new(self.genesis_header().clone(), self.genesis_hash())
} -->chainspec/src/spec.rs

[emhane]

I have been assigned this issue to complete as one pr with #14355

thanks nonetheless @Ayushdubey86 , welcome to find any other issue. recommend starting with those labelled good first issue regardless of level to get familiarity with codebase. those without that label tend to require some kind of design choice or product context.

[emhane]

@klkvr @mattsse to remove OnceLock requires alloy Sealable::hash_slow to be const, which isn't possible on trait methods. it's also not possible on impl of Sealable for Header anyway because it handles Vec<u8> so we get

destructor of `std::vec::Vec<u8>` cannot be evaluated at compile-time

ref: #14441 (comment)

closing for now, needs higher level design