Silence clippy lints in ascent!{ … } & ascent_run!{ … } macro expansions

[regexident]

Given a program

# Cargo.toml

[dependencies]
ascent = "0.4.0"

// main.rs

use ascent::ascent;

ascent! {
   relation edge(i32, i32);
   relation path(i32, i32);

   path(x, y) <-- edge(x, y);
   path(x, z) <-- edge(x, y), path(y, z);
}

fn main() {
    let mut prog = AscentProgram {
        edge: vec![(1, 2), (2, 3)],
        ..Default::default()
    };
    prog.run();
    println!("path: {:?}", prog.path);
}

Running cargo clippy results in a couple of clippy warnings:

• clippy::clone_on_copy
• clippy::let_unit_value

Full terminal output

warning: using `clone` on type `i32` which implements the `Copy` trait
 --> src/main.rs:5:13
  |
5 |    relation path(i32, i32);
  |             ^^^^
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#clone_on_copy
  = note: `#[warn(clippy::clone_on_copy)]` on by default
help: try removing the `clone` call
  |
5 ~    relation ascent! {
6 +    relation edge(i32, i32);
7 +    relation path(i32, i32);
8 + 
9 +    path(x, y) <-- edge(x, y);
10+    path(x, z) <-- edge(x, y), path(y, z);
11~ }(i32, i32);
  |

warning: using `clone` on type `i32` which implements the `Copy` trait
 --> src/main.rs:8:36
  |
8 |    path(x, z) <-- edge(x, y), path(y, z);
  |                                    ^ help: try dereferencing it: `*y`
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#clone_on_copy

warning: using `clone` on type `i32` which implements the `Copy` trait
 --> src/main.rs:8:27
  |
8 |    path(x, z) <-- edge(x, y), path(y, z);
  |                           ^ help: try dereferencing it: `*y`
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#clone_on_copy

warning: using `clone` on type `i32` which implements the `Copy` trait
 --> src/main.rs:4:13
  |
4 |    relation edge(i32, i32);
  |             ^^^^
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#clone_on_copy
help: try removing the `clone` call
  |
4 ~    relation ascent! {
5 +    relation edge(i32, i32);
6 +    relation path(i32, i32);
7 + 
8 +    path(x, y) <-- edge(x, y);
9 +    path(x, z) <-- edge(x, y), path(y, z);
10~ }(i32, i32);
  |

warning: this let-binding has unit value
 --> src/main.rs:4:13
  |
4 |    relation edge(i32, i32);
  |             ^^^^ help: omit the `let` binding: `edge;`
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#let_unit_value
  = note: `#[warn(clippy::let_unit_value)]` on by default

warning: `graph_queries` (bin "graph_queries") generated 5 warnings (run `cargo clippy --fix --bin "graph_queries"` to apply 5 suggestions)
    Finished dev [unoptimized + debuginfo] target(s) in 0.04s

[regexident]

For development purposes it might make sense to control lint-silencing with a feature that's enable by default.

[features]
default = ["silence-lints"]
silence-lints = []

So instead of …

#![allow(clippy::all)]

… the lints would be silenced like this:

#![cfg_attr(feature = "silence-lints", allow(clippy::all))]

This would allow for disabling the silencing during development for the purpose of catching anti-patterns, etc.