Auto merge of #10467 - blyxyas:underscore_typed, r=Jarcho

Add `let_with_type_underscore` lint

Fixes #10463
changelog: [`let_with_type_underscore`]: Add the lint.
This commit is contained in:
bors 2023-03-09 16:35:30 +00:00
commit 5f9873497f
16 changed files with 178 additions and 65 deletions

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@ -4643,6 +4643,7 @@ Released 2018-09-13
[`let_underscore_must_use`]: https://rust-lang.github.io/rust-clippy/master/index.html#let_underscore_must_use
[`let_underscore_untyped`]: https://rust-lang.github.io/rust-clippy/master/index.html#let_underscore_untyped
[`let_unit_value`]: https://rust-lang.github.io/rust-clippy/master/index.html#let_unit_value
[`let_with_type_underscore`]: https://rust-lang.github.io/rust-clippy/master/index.html#let_with_type_underscore
[`linkedlist`]: https://rust-lang.github.io/rust-clippy/master/index.html#linkedlist
[`logic_bug`]: https://rust-lang.github.io/rust-clippy/master/index.html#logic_bug
[`lossy_float_literal`]: https://rust-lang.github.io/rust-clippy/master/index.html#lossy_float_literal

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@ -227,6 +227,7 @@ pub(crate) static LINTS: &[&crate::LintInfo] = &[
crate::let_underscore::LET_UNDERSCORE_LOCK_INFO,
crate::let_underscore::LET_UNDERSCORE_MUST_USE_INFO,
crate::let_underscore::LET_UNDERSCORE_UNTYPED_INFO,
crate::let_with_type_underscore::LET_WITH_TYPE_UNDERSCORE_INFO,
crate::lifetimes::EXTRA_UNUSED_LIFETIMES_INFO,
crate::lifetimes::NEEDLESS_LIFETIMES_INFO,
crate::literal_representation::DECIMAL_LITERAL_REPRESENTATION_INFO,

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@ -0,0 +1,45 @@
use clippy_utils::diagnostics::span_lint_and_help;
use rustc_hir::*;
use rustc_lint::{LateContext, LateLintPass};
use rustc_middle::lint::in_external_macro;
use rustc_session::{declare_lint_pass, declare_tool_lint};
declare_clippy_lint! {
/// ### What it does
/// Detects when a variable is declared with an explicit type of `_`.
/// ### Why is this bad?
/// It adds noise, `: _` provides zero clarity or utility.
/// ### Example
/// ```rust,ignore
/// let my_number: _ = 1;
/// ```
/// Use instead:
/// ```rust,ignore
/// let my_number = 1;
/// ```
#[clippy::version = "1.69.0"]
pub LET_WITH_TYPE_UNDERSCORE,
complexity,
"unneeded underscore type (`_`) in a variable declaration"
}
declare_lint_pass!(UnderscoreTyped => [LET_WITH_TYPE_UNDERSCORE]);
impl LateLintPass<'_> for UnderscoreTyped {
fn check_local<'tcx>(&mut self, cx: &LateContext<'tcx>, local: &'tcx Local<'tcx>) {
if_chain! {
if !in_external_macro(cx.tcx.sess, local.span);
if let Some(ty) = local.ty; // Ensure that it has a type defined
if let TyKind::Infer = &ty.kind; // that type is '_'
if local.span.ctxt() == ty.span.ctxt();
then {
span_lint_and_help(cx,
LET_WITH_TYPE_UNDERSCORE,
local.span,
"variable declared with type underscore",
Some(ty.span.with_lo(local.pat.span.hi())),
"remove the explicit type `_` declaration"
)
}
};
}
}

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@ -167,6 +167,7 @@ mod large_stack_arrays;
mod len_zero;
mod let_if_seq;
mod let_underscore;
mod let_with_type_underscore;
mod lifetimes;
mod literal_representation;
mod loops;
@ -930,6 +931,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
store.register_late_pass(|_| Box::new(collection_is_never_read::CollectionIsNeverRead));
store.register_late_pass(|_| Box::new(missing_assert_message::MissingAssertMessage));
store.register_early_pass(|| Box::new(redundant_async_block::RedundantAsyncBlock));
store.register_late_pass(|_| Box::new(let_with_type_underscore::UnderscoreTyped));
// add lints here, do not remove this comment, it's used in `new_lint`
}

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@ -2,7 +2,7 @@
//! The ICE is mainly caused by using `hir_ty_to_ty`. See the discussion in the PR for details.
#![warn(clippy::use_self)]
#![allow(dead_code)]
#![allow(dead_code, clippy::let_with_type_underscore)]
struct Foo;

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@ -9,7 +9,8 @@
clippy::unnecessary_operation,
clippy::branches_sharing_code,
clippy::match_single_binding,
clippy::let_unit_value
clippy::let_unit_value,
clippy::let_with_type_underscore
)]
#[macro_use]

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@ -9,7 +9,8 @@
clippy::unnecessary_operation,
clippy::branches_sharing_code,
clippy::match_single_binding,
clippy::let_unit_value
clippy::let_unit_value,
clippy::let_with_type_underscore
)]
#[macro_use]

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@ -1,5 +1,5 @@
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_f64.rs:21:17
--> $DIR/default_numeric_fallback_f64.rs:22:17
|
LL | let x = 0.12;
| ^^^^ help: consider adding suffix: `0.12_f64`
@ -7,139 +7,139 @@ LL | let x = 0.12;
= note: `-D clippy::default-numeric-fallback` implied by `-D warnings`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_f64.rs:22:18
--> $DIR/default_numeric_fallback_f64.rs:23:18
|
LL | let x = [1., 2., 3.];
| ^^ help: consider adding suffix: `1.0_f64`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_f64.rs:22:22
--> $DIR/default_numeric_fallback_f64.rs:23:22
|
LL | let x = [1., 2., 3.];
| ^^ help: consider adding suffix: `2.0_f64`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_f64.rs:22:26
--> $DIR/default_numeric_fallback_f64.rs:23:26
|
LL | let x = [1., 2., 3.];
| ^^ help: consider adding suffix: `3.0_f64`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_f64.rs:23:28
--> $DIR/default_numeric_fallback_f64.rs:24:28
|
LL | let x = if true { (1., 2.) } else { (3., 4.) };
| ^^ help: consider adding suffix: `1.0_f64`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_f64.rs:23:32
--> $DIR/default_numeric_fallback_f64.rs:24:32
|
LL | let x = if true { (1., 2.) } else { (3., 4.) };
| ^^ help: consider adding suffix: `2.0_f64`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_f64.rs:23:46
--> $DIR/default_numeric_fallback_f64.rs:24:46
|
LL | let x = if true { (1., 2.) } else { (3., 4.) };
| ^^ help: consider adding suffix: `3.0_f64`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_f64.rs:23:50
--> $DIR/default_numeric_fallback_f64.rs:24:50
|
LL | let x = if true { (1., 2.) } else { (3., 4.) };
| ^^ help: consider adding suffix: `4.0_f64`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_f64.rs:24:23
--> $DIR/default_numeric_fallback_f64.rs:25:23
|
LL | let x = match 1. {
| ^^ help: consider adding suffix: `1.0_f64`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_f64.rs:25:18
--> $DIR/default_numeric_fallback_f64.rs:26:18
|
LL | _ => 1.,
| ^^ help: consider adding suffix: `1.0_f64`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_f64.rs:44:21
--> $DIR/default_numeric_fallback_f64.rs:45:21
|
LL | let y = 1.;
| ^^ help: consider adding suffix: `1.0_f64`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_f64.rs:52:21
--> $DIR/default_numeric_fallback_f64.rs:53:21
|
LL | let y = 1.;
| ^^ help: consider adding suffix: `1.0_f64`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_f64.rs:58:21
--> $DIR/default_numeric_fallback_f64.rs:59:21
|
LL | let y = 1.;
| ^^ help: consider adding suffix: `1.0_f64`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_f64.rs:66:21
--> $DIR/default_numeric_fallback_f64.rs:67:21
|
LL | let y = 1.;
| ^^ help: consider adding suffix: `1.0_f64`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_f64.rs:78:9
--> $DIR/default_numeric_fallback_f64.rs:79:9
|
LL | 1.
| ^^ help: consider adding suffix: `1.0_f64`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_f64.rs:84:27
--> $DIR/default_numeric_fallback_f64.rs:85:27
|
LL | let f = || -> _ { 1. };
| ^^ help: consider adding suffix: `1.0_f64`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_f64.rs:88:29
--> $DIR/default_numeric_fallback_f64.rs:89:29
|
LL | let f = || -> f64 { 1. };
| ^^ help: consider adding suffix: `1.0_f64`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_f64.rs:102:21
--> $DIR/default_numeric_fallback_f64.rs:103:21
|
LL | generic_arg(1.);
| ^^ help: consider adding suffix: `1.0_f64`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_f64.rs:105:32
--> $DIR/default_numeric_fallback_f64.rs:106:32
|
LL | let x: _ = generic_arg(1.);
| ^^ help: consider adding suffix: `1.0_f64`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_f64.rs:123:28
--> $DIR/default_numeric_fallback_f64.rs:124:28
|
LL | GenericStruct { x: 1. };
| ^^ help: consider adding suffix: `1.0_f64`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_f64.rs:126:36
--> $DIR/default_numeric_fallback_f64.rs:127:36
|
LL | let _ = GenericStruct { x: 1. };
| ^^ help: consider adding suffix: `1.0_f64`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_f64.rs:144:24
--> $DIR/default_numeric_fallback_f64.rs:145:24
|
LL | GenericEnum::X(1.);
| ^^ help: consider adding suffix: `1.0_f64`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_f64.rs:164:23
--> $DIR/default_numeric_fallback_f64.rs:165:23
|
LL | s.generic_arg(1.);
| ^^ help: consider adding suffix: `1.0_f64`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_f64.rs:171:21
--> $DIR/default_numeric_fallback_f64.rs:172:21
|
LL | let x = 22.;
| ^^^ help: consider adding suffix: `22.0_f64`

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@ -9,7 +9,8 @@
clippy::no_effect,
clippy::unnecessary_operation,
clippy::branches_sharing_code,
clippy::let_unit_value
clippy::let_unit_value,
clippy::let_with_type_underscore
)]
#[macro_use]

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@ -9,7 +9,8 @@
clippy::no_effect,
clippy::unnecessary_operation,
clippy::branches_sharing_code,
clippy::let_unit_value
clippy::let_unit_value,
clippy::let_with_type_underscore
)]
#[macro_use]

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@ -1,5 +1,5 @@
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_i32.rs:21:17
--> $DIR/default_numeric_fallback_i32.rs:22:17
|
LL | let x = 22;
| ^^ help: consider adding suffix: `22_i32`
@ -7,151 +7,151 @@ LL | let x = 22;
= note: `-D clippy::default-numeric-fallback` implied by `-D warnings`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_i32.rs:22:18
--> $DIR/default_numeric_fallback_i32.rs:23:18
|
LL | let x = [1, 2, 3];
| ^ help: consider adding suffix: `1_i32`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_i32.rs:22:21
--> $DIR/default_numeric_fallback_i32.rs:23:21
|
LL | let x = [1, 2, 3];
| ^ help: consider adding suffix: `2_i32`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_i32.rs:22:24
--> $DIR/default_numeric_fallback_i32.rs:23:24
|
LL | let x = [1, 2, 3];
| ^ help: consider adding suffix: `3_i32`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_i32.rs:23:28
--> $DIR/default_numeric_fallback_i32.rs:24:28
|
LL | let x = if true { (1, 2) } else { (3, 4) };
| ^ help: consider adding suffix: `1_i32`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_i32.rs:23:31
--> $DIR/default_numeric_fallback_i32.rs:24:31
|
LL | let x = if true { (1, 2) } else { (3, 4) };
| ^ help: consider adding suffix: `2_i32`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_i32.rs:23:44
--> $DIR/default_numeric_fallback_i32.rs:24:44
|
LL | let x = if true { (1, 2) } else { (3, 4) };
| ^ help: consider adding suffix: `3_i32`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_i32.rs:23:47
--> $DIR/default_numeric_fallback_i32.rs:24:47
|
LL | let x = if true { (1, 2) } else { (3, 4) };
| ^ help: consider adding suffix: `4_i32`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_i32.rs:24:23
--> $DIR/default_numeric_fallback_i32.rs:25:23
|
LL | let x = match 1 {
| ^ help: consider adding suffix: `1_i32`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_i32.rs:25:13
--> $DIR/default_numeric_fallback_i32.rs:26:13
|
LL | 1 => 1,
| ^ help: consider adding suffix: `1_i32`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_i32.rs:25:18
--> $DIR/default_numeric_fallback_i32.rs:26:18
|
LL | 1 => 1,
| ^ help: consider adding suffix: `1_i32`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_i32.rs:26:18
--> $DIR/default_numeric_fallback_i32.rs:27:18
|
LL | _ => 2,
| ^ help: consider adding suffix: `2_i32`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_i32.rs:45:21
--> $DIR/default_numeric_fallback_i32.rs:46:21
|
LL | let y = 1;
| ^ help: consider adding suffix: `1_i32`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_i32.rs:53:21
--> $DIR/default_numeric_fallback_i32.rs:54:21
|
LL | let y = 1;
| ^ help: consider adding suffix: `1_i32`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_i32.rs:59:21
--> $DIR/default_numeric_fallback_i32.rs:60:21
|
LL | let y = 1;
| ^ help: consider adding suffix: `1_i32`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_i32.rs:67:21
--> $DIR/default_numeric_fallback_i32.rs:68:21
|
LL | let y = 1;
| ^ help: consider adding suffix: `1_i32`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_i32.rs:79:9
--> $DIR/default_numeric_fallback_i32.rs:80:9
|
LL | 1
| ^ help: consider adding suffix: `1_i32`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_i32.rs:85:27
--> $DIR/default_numeric_fallback_i32.rs:86:27
|
LL | let f = || -> _ { 1 };
| ^ help: consider adding suffix: `1_i32`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_i32.rs:89:29
--> $DIR/default_numeric_fallback_i32.rs:90:29
|
LL | let f = || -> i32 { 1 };
| ^ help: consider adding suffix: `1_i32`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_i32.rs:103:21
--> $DIR/default_numeric_fallback_i32.rs:104:21
|
LL | generic_arg(1);
| ^ help: consider adding suffix: `1_i32`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_i32.rs:106:32
--> $DIR/default_numeric_fallback_i32.rs:107:32
|
LL | let x: _ = generic_arg(1);
| ^ help: consider adding suffix: `1_i32`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_i32.rs:124:28
--> $DIR/default_numeric_fallback_i32.rs:125:28
|
LL | GenericStruct { x: 1 };
| ^ help: consider adding suffix: `1_i32`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_i32.rs:127:36
--> $DIR/default_numeric_fallback_i32.rs:128:36
|
LL | let _ = GenericStruct { x: 1 };
| ^ help: consider adding suffix: `1_i32`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_i32.rs:145:24
--> $DIR/default_numeric_fallback_i32.rs:146:24
|
LL | GenericEnum::X(1);
| ^ help: consider adding suffix: `1_i32`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_i32.rs:165:23
--> $DIR/default_numeric_fallback_i32.rs:166:23
|
LL | s.generic_arg(1);
| ^ help: consider adding suffix: `1_i32`
error: default numeric fallback might occur
--> $DIR/default_numeric_fallback_i32.rs:172:21
--> $DIR/default_numeric_fallback_i32.rs:173:21
|
LL | let x = 22;
| ^^ help: consider adding suffix: `22_i32`

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@ -0,0 +1,19 @@
#![allow(unused)]
#![warn(clippy::let_with_type_underscore)]
#![allow(clippy::let_unit_value)]
fn func() -> &'static str {
""
}
fn main() {
// Will lint
let x: _ = 1;
let _: _ = 2;
let x: _ = func();
let x = 1; // Will not lint, Rust inferres this to an integer before Clippy
let x = func();
let x: Vec<_> = Vec::<u32>::new();
let x: [_; 1] = [1];
}

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@ -0,0 +1,39 @@
error: variable declared with type underscore
--> $DIR/let_with_type_underscore.rs:11:5
|
LL | let x: _ = 1;
| ^^^^^^^^^^^^^
|
help: remove the explicit type `_` declaration
--> $DIR/let_with_type_underscore.rs:11:10
|
LL | let x: _ = 1;
| ^^^
= note: `-D clippy::let-with-type-underscore` implied by `-D warnings`
error: variable declared with type underscore
--> $DIR/let_with_type_underscore.rs:12:5
|
LL | let _: _ = 2;
| ^^^^^^^^^^^^^
|
help: remove the explicit type `_` declaration
--> $DIR/let_with_type_underscore.rs:12:10
|
LL | let _: _ = 2;
| ^^^
error: variable declared with type underscore
--> $DIR/let_with_type_underscore.rs:13:5
|
LL | let x: _ = func();
| ^^^^^^^^^^^^^^^^^^
|
help: remove the explicit type `_` declaration
--> $DIR/let_with_type_underscore.rs:13:10
|
LL | let x: _ = func();
| ^^^
error: aborting due to 3 previous errors

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@ -2,6 +2,7 @@
// aux-build:macro_rules.rs
#![warn(clippy::manual_rem_euclid)]
#![allow(clippy::let_with_type_underscore)]
#[macro_use]
extern crate macro_rules;

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@ -2,6 +2,7 @@
// aux-build:macro_rules.rs
#![warn(clippy::manual_rem_euclid)]
#![allow(clippy::let_with_type_underscore)]
#[macro_use]
extern crate macro_rules;

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@ -1,5 +1,5 @@
error: manual `rem_euclid` implementation
--> $DIR/manual_rem_euclid.rs:19:18
--> $DIR/manual_rem_euclid.rs:20:18
|
LL | let _: i32 = ((value % 4) + 4) % 4;
| ^^^^^^^^^^^^^^^^^^^^^ help: consider using: `value.rem_euclid(4)`
@ -7,31 +7,31 @@ LL | let _: i32 = ((value % 4) + 4) % 4;
= note: `-D clippy::manual-rem-euclid` implied by `-D warnings`
error: manual `rem_euclid` implementation
--> $DIR/manual_rem_euclid.rs:20:18
--> $DIR/manual_rem_euclid.rs:21:18
|
LL | let _: i32 = (4 + (value % 4)) % 4;
| ^^^^^^^^^^^^^^^^^^^^^ help: consider using: `value.rem_euclid(4)`
error: manual `rem_euclid` implementation
--> $DIR/manual_rem_euclid.rs:21:18
--> $DIR/manual_rem_euclid.rs:22:18
|
LL | let _: i32 = (value % 4 + 4) % 4;
| ^^^^^^^^^^^^^^^^^^^ help: consider using: `value.rem_euclid(4)`
error: manual `rem_euclid` implementation
--> $DIR/manual_rem_euclid.rs:22:18
--> $DIR/manual_rem_euclid.rs:23:18
|
LL | let _: i32 = (4 + value % 4) % 4;
| ^^^^^^^^^^^^^^^^^^^ help: consider using: `value.rem_euclid(4)`
error: manual `rem_euclid` implementation
--> $DIR/manual_rem_euclid.rs:23:22
--> $DIR/manual_rem_euclid.rs:24:22
|
LL | let _: i32 = 1 + (4 + value % 4) % 4;
| ^^^^^^^^^^^^^^^^^^^ help: consider using: `value.rem_euclid(4)`
error: manual `rem_euclid` implementation
--> $DIR/manual_rem_euclid.rs:12:22
--> $DIR/manual_rem_euclid.rs:13:22
|
LL | let _: i32 = ((value % 4) + 4) % 4;
| ^^^^^^^^^^^^^^^^^^^^^ help: consider using: `value.rem_euclid(4)`
@ -42,25 +42,25 @@ LL | internal_rem_euclid!();
= note: this error originates in the macro `internal_rem_euclid` (in Nightly builds, run with -Z macro-backtrace for more info)
error: manual `rem_euclid` implementation
--> $DIR/manual_rem_euclid.rs:49:5
--> $DIR/manual_rem_euclid.rs:50:5
|
LL | ((num % 4) + 4) % 4
| ^^^^^^^^^^^^^^^^^^^ help: consider using: `num.rem_euclid(4)`
error: manual `rem_euclid` implementation
--> $DIR/manual_rem_euclid.rs:54:5
--> $DIR/manual_rem_euclid.rs:55:5
|
LL | ((num % 4) + 4) % 4
| ^^^^^^^^^^^^^^^^^^^ help: consider using: `num.rem_euclid(4)`
error: manual `rem_euclid` implementation
--> $DIR/manual_rem_euclid.rs:66:18
--> $DIR/manual_rem_euclid.rs:67:18
|
LL | let _: i32 = ((x % 4) + 4) % 4;
| ^^^^^^^^^^^^^^^^^ help: consider using: `x.rem_euclid(4)`
error: manual `rem_euclid` implementation
--> $DIR/manual_rem_euclid.rs:79:18
--> $DIR/manual_rem_euclid.rs:80:18
|
LL | let _: i32 = ((x % 4) + 4) % 4;
| ^^^^^^^^^^^^^^^^^ help: consider using: `x.rem_euclid(4)`