bool_comparison triggers 3 times on same code.

[matthiaskrgr]

rustfmt had this code in src/config/config_type.rs:431:45

            /// Returns true if the config key was explicitely set and is the default value.
            pub fn is_default(&self, key: &str) -> bool {
                $(
                    if let stringify!($i) = key {
                        return self.$i.1 && self.$i.2 == $def;
                    }
                 )+
                false
            }

which triggers bool_comparison lint 3 times, 2 times for false and one time for true:

warning: equality checks against false can be replaced by a negation
   --> src/config/config_type.rs:431:45
    |
431 |                           return self.$i.1 && self.$i.2 == $def;
    |                                               ^^^^^^^^^ help: try simplifying it as shown: `!self.$i.2`
    |
   ::: src/config/mod.rs:37:1
    |
37  | / create_config! {
38  | |     // Fundamental stuff
39  | |     max_width: usize, 100, true, "Maximum width of each line";
40  | |     hard_tabs: bool, false, true, "Use tab characters for indentation, spaces for alignment";
...   |
153 | |     make_backup: bool, false, false, "Backup changed files";
154 | | }
    | |_- in this macro invocation
    |
    = note: #[warn(clippy::bool_comparison)] on by default
    = help: for further information visit https://rust-lang-nursery.github.io/rust-clippy/v0.0.212/index.html#bool_comparison

warning: equality checks against false can be replaced by a negation
   --> src/config/config_type.rs:431:45
    |
431 |                           return self.$i.1 && self.$i.2 == $def;
    |                                               ^^^^^^^^^ help: try simplifying it as shown: `!self.$i.2`
    |
   ::: src/config/mod.rs:37:1
    |
37  | / create_config! {
38  | |     // Fundamental stuff
39  | |     max_width: usize, 100, true, "Maximum width of each line";
40  | |     hard_tabs: bool, false, true, "Use tab characters for indentation, spaces for alignment";
...   |
153 | |     make_backup: bool, false, false, "Backup changed files";
154 | | }
    | |_- in this macro invocation
    |
    = help: for further information visit https://rust-lang-nursery.github.io/rust-clippy/v0.0.212/index.html#bool_comparison

warning: equality checks against true are unnecessary
   --> src/config/config_type.rs:431:45
    |
431 |                           return self.$i.1 && self.$i.2 == $def;
    |                                               ^^^^^^^^^ help: try simplifying it as shown: `self.$i.2`
    |
   ::: src/config/mod.rs:37:1
    |
37  | / create_config! {
38  | |     // Fundamental stuff
39  | |     max_width: usize, 100, true, "Maximum width of each line";
40  | |     hard_tabs: bool, false, true, "Use tab characters for indentation, spaces for alignment";
...   |
153 | |     make_backup: bool, false, false, "Backup changed files";
154 | | }
    | |_- in this macro invocation
    |
    = help: for further information visit https://rust-lang-nursery.github.io/rust-clippy/v0.0.212/index.html#bool_comparison

maybe it should be disabled in macros?

[flip1995]

Yes this needs a macro check.

[giogam]

I can take this if it's ok

[oli-obk]

It's all yours!

[giogam]

@matthiaskrgr
@oli-obk
Ok, I added the macro check in clippy_lints/src/needless_bool.rs. I wrote this code that triggers the bug and I manually tested my change against this

use std::cell::Cell;

macro_rules! bool_comparison_trigger {
    ($($i:ident: $def:expr, $stb:expr );+  $(;)*) => (

        #[derive(Clone)]
        pub struct Trigger {
            $($i: (Cell<bool>, bool, bool)),+
        }

        #[allow(dead_code)]
        impl Trigger {
            pub fn trigger(&self, key: &str) -> bool {
                $(
                    if let stringify!($i) = key {
                        return self.$i.1 && self.$i.2 == $def;
                    }
                 )+
                false
            }
        }
    )
}

fn main() {
    bool_comparison_trigger! {
        test_one:   false, false;
        test_three: false, false;
        test_two:   true, true;
    }
    
    let x = false;
    if x == true {};
    if x == false {};
}

and this is the output

warning: equality checks against true are unnecessary
  --> /Users/cybot/Desktop/t/src/main.rs:33:8
   |
33 |     if x == true {};
   |        ^^^^^^^^^ help: try simplifying it as shown: `x`
   |
   = note: #[warn(clippy::bool_comparison)] on by default
   = help: for further information visit https://rust-lang-nursery.github.io/rust-clippy/v0.0.212/index.html#bool_comparison

warning: equality checks against false can be replaced by a negation
  --> /Users/cybot/Desktop/t/src/main.rs:34:8
   |
34 |     if x == false {};
   |        ^^^^^^^^^^ help: try simplifying it as shown: `!x`
   |
   = help: for further information visit https://rust-lang-nursery.github.io/rust-clippy/v0.0.212/index.html#bool_comparison

should I add some automated test under tests/ui/needless_bool.rs?

[matthiaskrgr]

Some tests would be lovely, indeed :)