Auto merge of #7671 - dtolnay-contrib:singlecharnames, r=xFrednet

Downgrade many_single_char_names to pedantic

As suggested by `@flip1995` in #7666 (comment), by today's standards this lint would be considered `pedantic`.

This is one of the most widely suppressed Clippy lints on crates.io according to https://github.com/dtolnay/noisy-clippy.

In my opinion this lint is just too domain specific for Clippy to have reliable visibility into. Sure there are some cases where the author is just being lazy and could use a kick in the butt, but we're still left with an enormous number of suppressions where single chars are the most appropriate name. For example in the context of colors, a function using `h`, `s`, `l`, `r`, `g`, `b` is 100% sensible and spelling all those out is silly, but it's past the default lint threshold.

---

changelog: Moved [`many_single_char_names`] to `pedantic`

clippy_lints/src/lib.rs

@@ -1137,6 +1137,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         LintId::of(needless_continue::NEEDLESS_CONTINUE),
         LintId::of(needless_for_each::NEEDLESS_FOR_EACH),
         LintId::of(needless_pass_by_value::NEEDLESS_PASS_BY_VALUE),
+        LintId::of(non_expressive_names::MANY_SINGLE_CHAR_NAMES),
         LintId::of(non_expressive_names::SIMILAR_NAMES),
         LintId::of(pass_by_ref_or_value::LARGE_TYPES_PASSED_BY_VALUE),
         LintId::of(pass_by_ref_or_value::TRIVIALLY_COPY_PASS_BY_REF),
@@ -1393,7 +1394,6 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         LintId::of(non_copy_const::BORROW_INTERIOR_MUTABLE_CONST),
         LintId::of(non_copy_const::DECLARE_INTERIOR_MUTABLE_CONST),
         LintId::of(non_expressive_names::JUST_UNDERSCORES_AND_DIGITS),
-        LintId::of(non_expressive_names::MANY_SINGLE_CHAR_NAMES),
         LintId::of(non_octal_unix_permissions::NON_OCTAL_UNIX_PERMISSIONS),
         LintId::of(open_options::NONSENSICAL_OPEN_OPTIONS),
         LintId::of(option_env_unwrap::OPTION_ENV_UNWRAP),
@@ -1567,7 +1567,6 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         LintId::of(non_copy_const::BORROW_INTERIOR_MUTABLE_CONST),
         LintId::of(non_copy_const::DECLARE_INTERIOR_MUTABLE_CONST),
         LintId::of(non_expressive_names::JUST_UNDERSCORES_AND_DIGITS),
-        LintId::of(non_expressive_names::MANY_SINGLE_CHAR_NAMES),
         LintId::of(ptr::CMP_NULL),
         LintId::of(ptr::PTR_ARG),
         LintId::of(ptr_eq::PTR_EQ),

clippy_lints/src/non_expressive_names.rs

@@ -43,7 +43,7 @@ declare_clippy_lint! {
     /// let (a, b, c, d, e, f, g) = (...);
     /// ```
     pub MANY_SINGLE_CHAR_NAMES,
-    style,
+    pedantic,
     "too many single character bindings"
 }
 

clippy_utils/src/hir_utils.rs

@@ -540,7 +540,7 @@ impl<'a, 'tcx> SpanlessHash<'a, 'tcx> {
         std::mem::discriminant(&b.rules).hash(&mut self.s);
     }
 
-    #[allow(clippy::many_single_char_names, clippy::too_many_lines)]
+    #[allow(clippy::too_many_lines)]
     pub fn hash_expr(&mut self, e: &Expr<'_>) {
         let simple_const = self
             .maybe_typeck_results

tests/ui-toml/toml_trivially_copy/test.rs

@@ -2,7 +2,6 @@
 // normalize-stderr-test "\(limit: \d+ byte\)" -> "(limit: N byte)"
 
 #![deny(clippy::trivially_copy_pass_by_ref)]
-#![allow(clippy::many_single_char_names)]
 
 #[derive(Copy, Clone)]
 struct Foo(u8);

tests/ui-toml/toml_trivially_copy/test.stderr

@@ -1,5 +1,5 @@
 error: this argument (N byte) is passed by reference, but would be more efficient if passed by value (limit: N byte)
-  --> $DIR/test.rs:15:11
+  --> $DIR/test.rs:14:11
    |
 LL | fn bad(x: &u16, y: &Foo) {}
    |           ^^^^ help: consider passing by value instead: `u16`
@@ -11,7 +11,7 @@ LL | #![deny(clippy::trivially_copy_pass_by_ref)]
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: this argument (N byte) is passed by reference, but would be more efficient if passed by value (limit: N byte)
-  --> $DIR/test.rs:15:20
+  --> $DIR/test.rs:14:20
    |
 LL | fn bad(x: &u16, y: &Foo) {}
    |                    ^^^^ help: consider passing by value instead: `Foo`

tests/ui/deref_addrof.fixed

@@ -9,7 +9,7 @@ fn get_reference(n: &usize) -> &usize {
     n
 }
 
-#[allow(clippy::many_single_char_names, clippy::double_parens)]
+#[allow(clippy::double_parens)]
 #[allow(unused_variables, unused_parens)]
 fn main() {
     let a = 10;

tests/ui/deref_addrof.rs

@@ -9,7 +9,7 @@ fn get_reference(n: &usize) -> &usize {
     n
 }
 
-#[allow(clippy::many_single_char_names, clippy::double_parens)]
+#[allow(clippy::double_parens)]
 #[allow(unused_variables, unused_parens)]
 fn main() {
     let a = 10;

tests/ui/eq_op.rs

@@ -2,7 +2,7 @@
 
 #[rustfmt::skip]
 #[warn(clippy::eq_op)]
-#[allow(clippy::identity_op, clippy::double_parens, clippy::many_single_char_names)]
+#[allow(clippy::identity_op, clippy::double_parens)]
 #[allow(clippy::no_effect, unused_variables, clippy::unnecessary_operation, clippy::short_circuit_statement)]
 #[allow(clippy::nonminimal_bool)]
 #[allow(unused)]

tests/ui/eta.fixed

@@ -4,7 +4,6 @@
     unused,
     clippy::no_effect,
     clippy::redundant_closure_call,
-    clippy::many_single_char_names,
     clippy::needless_pass_by_value,
     clippy::option_map_unit_fn
 )]

tests/ui/eta.rs

@@ -4,7 +4,6 @@
     unused,
     clippy::no_effect,
     clippy::redundant_closure_call,
-    clippy::many_single_char_names,
     clippy::needless_pass_by_value,
     clippy::option_map_unit_fn
 )]

tests/ui/eta.stderr

@@ -1,131 +1,131 @@
 error: redundant closure
-  --> $DIR/eta.rs:32:27
+  --> $DIR/eta.rs:31:27
    |
 LL |     let a = Some(1u8).map(|a| foo(a));
    |                           ^^^^^^^^^^ help: replace the closure with the function itself: `foo`
    |
    = note: `-D clippy::redundant-closure` implied by `-D warnings`
 
 error: redundant closure
-  --> $DIR/eta.rs:36:40
+  --> $DIR/eta.rs:35:40
    |
 LL |     let _: Option<Vec<u8>> = true.then(|| vec![]); // special case vec!
    |                                        ^^^^^^^^^ help: replace the closure with `Vec::new`: `std::vec::Vec::new`
 
 error: redundant closure
-  --> $DIR/eta.rs:37:35
+  --> $DIR/eta.rs:36:35
    |
 LL |     let d = Some(1u8).map(|a| foo((|b| foo2(b))(a))); //is adjusted?
    |                                   ^^^^^^^^^^^^^ help: replace the closure with the function itself: `foo2`
 
 error: this expression borrows a reference (`&u8`) that is immediately dereferenced by the compiler
-  --> $DIR/eta.rs:38:21
+  --> $DIR/eta.rs:37:21
    |
 LL |     all(&[1, 2, 3], &&2, |x, y| below(x, y)); //is adjusted
    |                     ^^^ help: change this to: `&2`
    |
    = note: `-D clippy::needless-borrow` implied by `-D warnings`
 
 error: redundant closure
-  --> $DIR/eta.rs:38:26
+  --> $DIR/eta.rs:37:26
    |
 LL |     all(&[1, 2, 3], &&2, |x, y| below(x, y)); //is adjusted
    |                          ^^^^^^^^^^^^^^^^^^ help: replace the closure with the function itself: `below`
 
 error: redundant closure
-  --> $DIR/eta.rs:44:27
+  --> $DIR/eta.rs:43:27
    |
 LL |     let e = Some(1u8).map(|a| divergent(a));
    |                           ^^^^^^^^^^^^^^^^ help: replace the closure with the function itself: `divergent`
 
 error: redundant closure
-  --> $DIR/eta.rs:45:27
+  --> $DIR/eta.rs:44:27
    |
 LL |     let e = Some(1u8).map(|a| generic(a));
    |                           ^^^^^^^^^^^^^^ help: replace the closure with the function itself: `generic`
 
 error: redundant closure
-  --> $DIR/eta.rs:91:51
+  --> $DIR/eta.rs:90:51
    |
 LL |     let e = Some(TestStruct { some_ref: &i }).map(|a| a.foo());
    |                                                   ^^^^^^^^^^^ help: replace the closure with the method itself: `TestStruct::foo`
    |
    = note: `-D clippy::redundant-closure-for-method-calls` implied by `-D warnings`
 
 error: redundant closure
-  --> $DIR/eta.rs:92:51
+  --> $DIR/eta.rs:91:51
    |
 LL |     let e = Some(TestStruct { some_ref: &i }).map(|a| a.trait_foo());
    |                                                   ^^^^^^^^^^^^^^^^^ help: replace the closure with the method itself: `TestTrait::trait_foo`
 
 error: redundant closure
-  --> $DIR/eta.rs:94:42
+  --> $DIR/eta.rs:93:42
    |
 LL |     let e = Some(&mut vec![1, 2, 3]).map(|v| v.clear());
    |                                          ^^^^^^^^^^^^^ help: replace the closure with the method itself: `std::vec::Vec::clear`
 
 error: redundant closure
-  --> $DIR/eta.rs:98:29
+  --> $DIR/eta.rs:97:29
    |
 LL |     let e = Some("str").map(|s| s.to_string());
    |                             ^^^^^^^^^^^^^^^^^ help: replace the closure with the method itself: `std::string::ToString::to_string`
 
 error: redundant closure
-  --> $DIR/eta.rs:99:27
+  --> $DIR/eta.rs:98:27
    |
 LL |     let e = Some('a').map(|s| s.to_uppercase());
    |                           ^^^^^^^^^^^^^^^^^^^^ help: replace the closure with the method itself: `char::to_uppercase`
 
 error: redundant closure
-  --> $DIR/eta.rs:101:65
+  --> $DIR/eta.rs:100:65
    |
 LL |     let e: std::vec::Vec<char> = vec!['a', 'b', 'c'].iter().map(|c| c.to_ascii_uppercase()).collect();
    |                                                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace the closure with the method itself: `char::to_ascii_uppercase`
 
 error: redundant closure
-  --> $DIR/eta.rs:164:22
+  --> $DIR/eta.rs:163:22
    |
 LL |     requires_fn_once(|| x());
    |                      ^^^^^^ help: replace the closure with the function itself: `x`
 
 error: redundant closure
-  --> $DIR/eta.rs:171:27
+  --> $DIR/eta.rs:170:27
    |
 LL |     let a = Some(1u8).map(|a| foo_ptr(a));
    |                           ^^^^^^^^^^^^^^ help: replace the closure with the function itself: `foo_ptr`
 
 error: redundant closure
-  --> $DIR/eta.rs:176:27
+  --> $DIR/eta.rs:175:27
    |
 LL |     let a = Some(1u8).map(|a| closure(a));
    |                           ^^^^^^^^^^^^^^ help: replace the closure with the function itself: `closure`
 
 error: redundant closure
-  --> $DIR/eta.rs:208:28
+  --> $DIR/eta.rs:207:28
    |
 LL |     x.into_iter().for_each(|x| add_to_res(x));
    |                            ^^^^^^^^^^^^^^^^^ help: replace the closure with the function itself: `&mut add_to_res`
 
 error: redundant closure
-  --> $DIR/eta.rs:209:28
+  --> $DIR/eta.rs:208:28
    |
 LL |     y.into_iter().for_each(|x| add_to_res(x));
    |                            ^^^^^^^^^^^^^^^^^ help: replace the closure with the function itself: `&mut add_to_res`
 
 error: redundant closure
-  --> $DIR/eta.rs:210:28
+  --> $DIR/eta.rs:209:28
    |
 LL |     z.into_iter().for_each(|x| add_to_res(x));
    |                            ^^^^^^^^^^^^^^^^^ help: replace the closure with the function itself: `add_to_res`
 
 error: redundant closure
-  --> $DIR/eta.rs:217:21
+  --> $DIR/eta.rs:216:21
    |
 LL |         Some(1).map(|n| closure(n));
    |                     ^^^^^^^^^^^^^^ help: replace the closure with the function itself: `&mut closure`
 
 error: redundant closure
-  --> $DIR/eta.rs:236:21
+  --> $DIR/eta.rs:235:21
    |
 LL |     map_str_to_path(|s| s.as_ref());
    |                     ^^^^^^^^^^^^^^ help: replace the closure with the method itself: `std::convert::AsRef::as_ref`

tests/ui/eval_order_dependence.rs

@@ -4,7 +4,6 @@
 #[allow(
     unused_assignments,
     unused_variables,
-    clippy::many_single_char_names,
     clippy::no_effect,
     dead_code,
     clippy::blacklisted_name

tests/ui/eval_order_dependence.stderr

@@ -1,48 +1,48 @@
 error: unsequenced read of `x`
-  --> $DIR/eval_order_dependence.rs:17:9
+  --> $DIR/eval_order_dependence.rs:16:9
    |
 LL |     } + x;
    |         ^
    |
    = note: `-D clippy::eval-order-dependence` implied by `-D warnings`
 note: whether read occurs before this write depends on evaluation order
-  --> $DIR/eval_order_dependence.rs:15:9
+  --> $DIR/eval_order_dependence.rs:14:9
    |
 LL |         x = 1;
    |         ^^^^^
 
 error: unsequenced read of `x`
-  --> $DIR/eval_order_dependence.rs:20:5
+  --> $DIR/eval_order_dependence.rs:19:5
    |
 LL |     x += {
    |     ^
    |
 note: whether read occurs before this write depends on evaluation order
-  --> $DIR/eval_order_dependence.rs:21:9
+  --> $DIR/eval_order_dependence.rs:20:9
    |
 LL |         x = 20;
    |         ^^^^^^
 
 error: unsequenced read of `x`
-  --> $DIR/eval_order_dependence.rs:33:12
+  --> $DIR/eval_order_dependence.rs:32:12
    |
 LL |         a: x,
    |            ^
    |
 note: whether read occurs before this write depends on evaluation order
-  --> $DIR/eval_order_dependence.rs:35:13
+  --> $DIR/eval_order_dependence.rs:34:13
    |
 LL |             x = 6;
    |             ^^^^^
 
 error: unsequenced read of `x`
-  --> $DIR/eval_order_dependence.rs:42:9
+  --> $DIR/eval_order_dependence.rs:41:9
    |
 LL |         x += {
    |         ^
    |
 note: whether read occurs before this write depends on evaluation order
-  --> $DIR/eval_order_dependence.rs:43:13
+  --> $DIR/eval_order_dependence.rs:42:13
    |
 LL |             x = 20;
    |             ^^^^^^

tests/ui/explicit_deref_methods.fixed

@@ -1,6 +1,6 @@
 // run-rustfix
 
-#![allow(unused_variables, clippy::many_single_char_names, clippy::clone_double_ref)]
+#![allow(unused_variables, clippy::clone_double_ref)]
 #![warn(clippy::explicit_deref_methods)]
 
 use std::ops::{Deref, DerefMut};

tests/ui/explicit_deref_methods.rs

@@ -1,6 +1,6 @@
 // run-rustfix
 
-#![allow(unused_variables, clippy::many_single_char_names, clippy::clone_double_ref)]
+#![allow(unused_variables, clippy::clone_double_ref)]
 #![warn(clippy::explicit_deref_methods)]
 
 use std::ops::{Deref, DerefMut};

tests/ui/float_cmp.rs

@@ -4,8 +4,7 @@
     clippy::no_effect,
     clippy::op_ref,
     clippy::unnecessary_operation,
-    clippy::cast_lossless,
-    clippy::many_single_char_names
+    clippy::cast_lossless
 )]
 
 use std::ops::Add;