Make the documentation about `#![allow(unused)]` more visible

[ChrisJefferson]

I like to build functions as a series of parts, for example I might write the following skeleton, then plan to fill in the loop

fn sorter(x: Vec<Vec<isize>>, modifier: bool) -> Vec<isize> {
    let mut out = vec![];
    for i in x {
   
    }
    out
}

If I run a cargo check on this, just to check for typos, I get:

warning: unused variable: `i`
  --> src/playgame.rs:35:9
   |
35 |     for i in x {}
   |         ^ help: consider prefixing with an underscore: `_i`
   |
   = note: `#[warn(unused_variables)]` on by default

warning: unused variable: `modifier`
  --> src/playgame.rs:33:31
   |
33 | fn sorter(x: Vec<Vec<isize>>, modifier: bool) -> Vec<isize> {
   |                               ^^^^^^^^ help: consider prefixing with an underscore: `_modifier`

warning: variable does not need to be mutable
  --> src/playgame.rs:34:9
   |
34 |     let mut out = vec![];
   |         ----^^^
   |         |
   |         help: remove this `mut`
   |
   = note: `#[warn(unused_mut)]` on by default

warning: function is never used: `sorter`
  --> src/playgame.rs:33:1
   |
33 | fn sorter(x: Vec<Vec<isize>>, modifier: bool) -> Vec<isize> {
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: `#[warn(dead_code)]` on by default

I feel it should be possible to encapsulate a set of warnings which represent "unused/dead", and have a way of disabling them while developing. I realise this could be abused by some people, but I find it hard to spot the important issues between these unused/dead issues while developing.

[Kampfkarren]

#![allow(dead_code)] at the root of your crate 🙂

[ChrisJefferson]

I tried this (should have said), but I ended up with:

#![allow(dead_code)]
#![allow(unused_assignments)]
#![allow(unused_attributes)]
#![allow(unused_imports)]
#![allow(unused_macros)]
#![allow(unused_mut)]
#![allow(unused_variables)]

And then, I also had to remember to go remove them all every so often, as I don't want these enabling forever, just while writing a new function.

Perhaps (I'll be honest, I'm maybe not positive what I want), I want a way to disable lints easily while initially making a function, then linting once I think I've got a valid piece of finished(ish) code.

[Centril]

There's always #![allow(unused)] to disable the whole group.

Perhaps (I'll be honest, I'm maybe not positive what I want), I want a way to disable lints easily while initially making a function, then linting once I think I've got a valid piece of finished(ish) code.

I don't think there's anything actionable here yet.

[ChrisJefferson]

That is, I think, what I want. That's not too much work to add and remove.

I hadn't found that there was a way of grouping together lints (I had tried googling, but I obviously did hit it). I'm not sure if there is a good way of making this more visible.

[estebank]

@Centril we could rework the lint output to be

warning: unused variable: `i`
  --> src/playgame.rs:35:9
   |
35 |     for i in x {}
   |         ^ help: consider prefixing with an underscore: `_i`
   |
   = note: `#[warn(unused_variables)]` (implied by `#[warn(unused)]`) on by default

[hkBst]

@estebank I think that is a very good idea! And I'm guessing this should be pretty simple to do, so

@rustbot label -A-docs E-easy

[karolzwolak]

@rustbot claim