cannot find macro `vec` in this scope

Question

I am trying to add Frontier as a dependency in my substrate-parachain-template.

     Compiling sp-npos-elections v4.0.0-dev (https://github.com/paritytech/substrate?branch=polkadot-v0.9.25#3348e144)
  error: cannot find macro `vec` in this scope
     --> /home/user2038/.cargo/git/checkouts/substrate-7e08433d4c370a21/3348e14/primitives/npos-elections/src/reduce.rs:604:21
      |
  604 |                     let min_edge = vec![min_voter, min_target];
      |                                    ^^^
      |
      = note: consider importing one of these items:
              codec::alloc::vec
              crate::vec
              scale_info::prelude::vec
              sp_std::vec

  error: cannot find macro `vec` in this scope
    --> /home/user2038/.cargo/git/checkouts/substrate-7e08433d4c370a21/3348e14/primitives/npos-elections/src/phragmms.rs:52:20
     |
  52 |     let mut winners = vec![];
     |                       ^^^
     |
     = note: consider importing one of these items:
             codec::alloc::vec
             crate::vec
             scale_info::prelude::vec
             sp_std::vec

From this post https://stackoverflow.com/questions/70477868/substrate-cannot-find-type-vec-in-this-scope, perhaps I need to make a pallet to fix this error? That sounds weird...

It seems this solves it: https://users.rust-lang.org/t/whats-different-between-these-two-features-style/47292/5 with reference https://github.com/paritytech/substrate/blob/master/utils/wasm-builder/src/wasm_project.rs#L324-L349

but how can I apply that in my project???

Is there another solution? How can I solve this?

Answer 1

Check your deps std features.

I think you might missing something like xxx/std.

Answer 2

I solved it by adding default-features = false, in my Frontier dependencies in my runtime/Cargo.toml

# Frontier
pallet-evm = { git = "https://github.com/paritytech/frontier", default-features = false, branch = "polkadot-v0.9.25" }

but strangely, in my node/Cargo.toml, there is no need to add that:

#Frontier
fp-rpc = { git = "https://github.com/paritytech/frontier", branch = "polkadot-v0.9.25" }

Answer 3

I think the compiler actually already tells you what you need to do. vec![] is not included in any of the crates you are using. So in order to use it, you need to import it.

This is how this could look like:

    use codec::vec;