How to disable unused code warnings in Rust?

Question

struct SemanticDirection;

fn main() {}

warning: struct is never used: `SemanticDirection`
 --> src/main.rs:1:1
  |
1 | struct SemanticDirection;
  | ^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: #[warn(dead_code)] on by default

I will turn these warnings back on for anything serious, but I am just tinkering with the language and this is driving me bats.

I tried adding #[allow(dead_code)] to my code, but that did not work.

Answer 1

You can either:

• Add an allow attribute on a struct, module, function, etc.:

  #[allow(dead_code)]
  struct SemanticDirection;
  

• Add a crate-level allow attribute; notice the !:

  #![allow(dead_code)]
  

• Pass it to rustc:

  rustc -A dead_code main.rs
  

• Pass it using cargo via the RUSTFLAGS environment variable:

  RUSTFLAGS="$RUSTFLAGS -A dead_code" cargo build