Auto merge of #5428 - dtolnay:cognitive, r=flip1995

Move cognitive_complexity to nursery

As discussed in #5418 (comment); Clippy's current understanding of cognitive complexity is not good enough yet at analyzing code for understandability to have this lint be enabled by default.

changelog: Remove cognitive_complexity from default set of enabled lints

clippy_lints/src/assign_ops.rs

@@ -77,7 +77,6 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for AssignOps {
             },
             hir::ExprKind::Assign(assignee, e, _) => {
                 if let hir::ExprKind::Binary(op, l, r) = &e.kind {
-                    #[allow(clippy::cognitive_complexity)]
                     let lint = |assignee: &hir::Expr<'_>, rhs: &hir::Expr<'_>| {
                         let ty = cx.tables.expr_ty(assignee);
                         let rty = cx.tables.expr_ty(rhs);

clippy_lints/src/cognitive_complexity.rs

@@ -22,7 +22,7 @@ declare_clippy_lint! {
     ///
     /// **Example:** No. You'll see it when you get the warning.
     pub COGNITIVE_COMPLEXITY,
-    complexity,
+    nursery,
     "functions that should be split up into multiple functions"
 }
 

clippy_lints/src/lib.rs

@@ -1174,7 +1174,6 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         LintId::of(&booleans::LOGIC_BUG),
         LintId::of(&booleans::NONMINIMAL_BOOL),
         LintId::of(&bytecount::NAIVE_BYTECOUNT),
-        LintId::of(&cognitive_complexity::COGNITIVE_COMPLEXITY),
         LintId::of(&collapsible_if::COLLAPSIBLE_IF),
         LintId::of(&comparison_chain::COMPARISON_CHAIN),
         LintId::of(&copies::IFS_SAME_COND),
@@ -1509,7 +1508,6 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         LintId::of(&assign_ops::MISREFACTORED_ASSIGN_OP),
         LintId::of(&attrs::DEPRECATED_CFG_ATTR),
         LintId::of(&booleans::NONMINIMAL_BOOL),
-        LintId::of(&cognitive_complexity::COGNITIVE_COMPLEXITY),
         LintId::of(&double_comparison::DOUBLE_COMPARISONS),
         LintId::of(&double_parens::DOUBLE_PARENS),
         LintId::of(&duration_subsec::DURATION_SUBSEC),
@@ -1678,6 +1676,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
 
     store.register_group(true, "clippy::nursery", Some("clippy_nursery"), vec![
         LintId::of(&attrs::EMPTY_LINE_AFTER_OUTER_ATTR),
+        LintId::of(&cognitive_complexity::COGNITIVE_COMPLEXITY),
         LintId::of(&fallible_impl_from::FALLIBLE_IMPL_FROM),
         LintId::of(&floating_point_arithmetic::IMPRECISE_FLOPS),
         LintId::of(&floating_point_arithmetic::SUBOPTIMAL_FLOPS),

clippy_lints/src/methods/mod.rs

@@ -1317,7 +1317,7 @@ declare_lint_pass!(Methods => [
 ]);
 
 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Methods {
-    #[allow(clippy::cognitive_complexity, clippy::too_many_lines)]
+    #[allow(clippy::too_many_lines)]
     fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr<'_>) {
         if in_macro(expr.span) {
             return;

clippy_lints/src/mutable_debug_assertion.rs

@@ -53,7 +53,6 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for DebugAssertWithMutCall {
 }
 
 //HACK(hellow554): remove this when #4694 is implemented
-#[allow(clippy::cognitive_complexity)]
 fn extract_call<'a, 'tcx>(cx: &'a LateContext<'a, 'tcx>, e: &'tcx Expr<'_>) -> Option<Span> {
     if_chain! {
         if let ExprKind::Block(ref block, _) = e.kind;

clippy_lints/src/types.rs

@@ -315,7 +315,6 @@ impl Types {
     /// The parameter `is_local` distinguishes the context of the type; types from
     /// local bindings should only be checked for the `BORROWED_BOX` lint.
     #[allow(clippy::too_many_lines)]
-    #[allow(clippy::cognitive_complexity)]
     fn check_ty(&mut self, cx: &LateContext<'_, '_>, hir_ty: &hir::Ty<'_>, is_local: bool) {
         if hir_ty.span.from_expansion() {
             return;

src/lintlist/mod.rs

@@ -250,7 +250,7 @@ pub static ref ALL_LINTS: Vec<Lint> = vec![
     },
     Lint {
         name: "cognitive_complexity",
-        group: "complexity",
+        group: "nursery",
         desc: "functions that should be split up into multiple functions",
         deprecation: None,
         module: "cognitive_complexity",

tests/ui/collapsible_else_if.fixed

@@ -1,5 +1,5 @@
 // run-rustfix
-#![allow(clippy::cognitive_complexity, clippy::assertions_on_constants)]
+#![allow(clippy::assertions_on_constants)]
 
 #[rustfmt::skip]
 #[warn(clippy::collapsible_if)]

tests/ui/collapsible_else_if.rs

@@ -1,5 +1,5 @@
 // run-rustfix
-#![allow(clippy::cognitive_complexity, clippy::assertions_on_constants)]
+#![allow(clippy::assertions_on_constants)]
 
 #[rustfmt::skip]
 #[warn(clippy::collapsible_if)]

tests/ui/collapsible_if.fixed

@@ -1,5 +1,5 @@
 // run-rustfix
-#![allow(clippy::cognitive_complexity, clippy::assertions_on_constants)]
+#![allow(clippy::assertions_on_constants)]
 
 #[rustfmt::skip]
 #[warn(clippy::collapsible_if)]

tests/ui/collapsible_if.rs

@@ -1,5 +1,5 @@
 // run-rustfix
-#![allow(clippy::cognitive_complexity, clippy::assertions_on_constants)]
+#![allow(clippy::assertions_on_constants)]
 
 #[rustfmt::skip]
 #[warn(clippy::collapsible_if)]

tests/ui/debug_assert_with_mut_call.rs

@@ -2,7 +2,7 @@
 #![feature(custom_inner_attributes)]
 #![rustfmt::skip]
 #![warn(clippy::debug_assert_with_mut_call)]
-#![allow(clippy::cognitive_complexity, clippy::redundant_closure_call)]
+#![allow(clippy::redundant_closure_call)]
 
 struct S;
 

tests/ui/for_loop_fixable.fixed

@@ -28,7 +28,6 @@ impl Unrelated {
     clippy::linkedlist,
     clippy::shadow_unrelated,
     clippy::unnecessary_mut_passed,
-    clippy::cognitive_complexity,
     clippy::similar_names
 )]
 #[allow(clippy::many_single_char_names, unused_variables)]

tests/ui/for_loop_fixable.rs

@@ -28,7 +28,6 @@ impl Unrelated {
     clippy::linkedlist,
     clippy::shadow_unrelated,
     clippy::unnecessary_mut_passed,
-    clippy::cognitive_complexity,
     clippy::similar_names
 )]
 #[allow(clippy::many_single_char_names, unused_variables)]

tests/ui/for_loop_fixable.stderr

@@ -1,5 +1,5 @@
 error: this range is empty so this for loop will never run
-  --> $DIR/for_loop_fixable.rs:39:14
+  --> $DIR/for_loop_fixable.rs:38:14
    |
 LL |     for i in 10..0 {
    |              ^^^^^
@@ -11,7 +11,7 @@ LL |     for i in (0..10).rev() {
    |              ^^^^^^^^^^^^^
 
 error: this range is empty so this for loop will never run
-  --> $DIR/for_loop_fixable.rs:43:14
+  --> $DIR/for_loop_fixable.rs:42:14
    |
 LL |     for i in 10..=0 {
    |              ^^^^^^
@@ -22,7 +22,7 @@ LL |     for i in (0..=10).rev() {
    |              ^^^^^^^^^^^^^^
 
 error: this range is empty so this for loop will never run
-  --> $DIR/for_loop_fixable.rs:47:14
+  --> $DIR/for_loop_fixable.rs:46:14
    |
 LL |     for i in MAX_LEN..0 {
    |              ^^^^^^^^^^
@@ -33,7 +33,7 @@ LL |     for i in (0..MAX_LEN).rev() {
    |              ^^^^^^^^^^^^^^^^^^
 
 error: this range is empty so this for loop will never run
-  --> $DIR/for_loop_fixable.rs:72:14
+  --> $DIR/for_loop_fixable.rs:71:14
    |
 LL |     for i in 10..5 + 4 {
    |              ^^^^^^^^^
@@ -44,7 +44,7 @@ LL |     for i in (5 + 4..10).rev() {
    |              ^^^^^^^^^^^^^^^^^
 
 error: this range is empty so this for loop will never run
-  --> $DIR/for_loop_fixable.rs:76:14
+  --> $DIR/for_loop_fixable.rs:75:14
    |
 LL |     for i in (5 + 2)..(3 - 1) {
    |              ^^^^^^^^^^^^^^^^
@@ -55,95 +55,95 @@ LL |     for i in ((3 - 1)..(5 + 2)).rev() {
    |              ^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: it is more concise to loop over references to containers instead of using explicit iteration methods
-  --> $DIR/for_loop_fixable.rs:98:15
+  --> $DIR/for_loop_fixable.rs:97:15
    |
 LL |     for _v in vec.iter() {}
    |               ^^^^^^^^^^ help: to write this more concisely, try: `&vec`
    |
    = note: `-D clippy::explicit-iter-loop` implied by `-D warnings`
 
 error: it is more concise to loop over references to containers instead of using explicit iteration methods
-  --> $DIR/for_loop_fixable.rs:100:15
+  --> $DIR/for_loop_fixable.rs:99:15
    |
 LL |     for _v in vec.iter_mut() {}
    |               ^^^^^^^^^^^^^^ help: to write this more concisely, try: `&mut vec`
 
 error: it is more concise to loop over containers instead of using explicit iteration methods
-  --> $DIR/for_loop_fixable.rs:103:15
+  --> $DIR/for_loop_fixable.rs:102:15
    |
 LL |     for _v in out_vec.into_iter() {}
    |               ^^^^^^^^^^^^^^^^^^^ help: to write this more concisely, try: `out_vec`
    |
    = note: `-D clippy::explicit-into-iter-loop` implied by `-D warnings`
 
 error: it is more concise to loop over references to containers instead of using explicit iteration methods
-  --> $DIR/for_loop_fixable.rs:108:15
+  --> $DIR/for_loop_fixable.rs:107:15
    |
 LL |     for _v in [1, 2, 3].iter() {}
    |               ^^^^^^^^^^^^^^^^ help: to write this more concisely, try: `&[1, 2, 3]`
 
 error: it is more concise to loop over references to containers instead of using explicit iteration methods
-  --> $DIR/for_loop_fixable.rs:112:15
+  --> $DIR/for_loop_fixable.rs:111:15
    |
 LL |     for _v in [0; 32].iter() {}
    |               ^^^^^^^^^^^^^^ help: to write this more concisely, try: `&[0; 32]`
 
 error: it is more concise to loop over references to containers instead of using explicit iteration methods
-  --> $DIR/for_loop_fixable.rs:117:15
+  --> $DIR/for_loop_fixable.rs:116:15
    |
 LL |     for _v in ll.iter() {}
    |               ^^^^^^^^^ help: to write this more concisely, try: `&ll`
 
 error: it is more concise to loop over references to containers instead of using explicit iteration methods
-  --> $DIR/for_loop_fixable.rs:120:15
+  --> $DIR/for_loop_fixable.rs:119:15
    |
 LL |     for _v in vd.iter() {}
    |               ^^^^^^^^^ help: to write this more concisely, try: `&vd`
 
 error: it is more concise to loop over references to containers instead of using explicit iteration methods
-  --> $DIR/for_loop_fixable.rs:123:15
+  --> $DIR/for_loop_fixable.rs:122:15
    |
 LL |     for _v in bh.iter() {}
    |               ^^^^^^^^^ help: to write this more concisely, try: `&bh`
 
 error: it is more concise to loop over references to containers instead of using explicit iteration methods
-  --> $DIR/for_loop_fixable.rs:126:15
+  --> $DIR/for_loop_fixable.rs:125:15
    |
 LL |     for _v in hm.iter() {}
    |               ^^^^^^^^^ help: to write this more concisely, try: `&hm`
 
 error: it is more concise to loop over references to containers instead of using explicit iteration methods
-  --> $DIR/for_loop_fixable.rs:129:15
+  --> $DIR/for_loop_fixable.rs:128:15
    |
 LL |     for _v in bt.iter() {}
    |               ^^^^^^^^^ help: to write this more concisely, try: `&bt`
 
 error: it is more concise to loop over references to containers instead of using explicit iteration methods
-  --> $DIR/for_loop_fixable.rs:132:15
+  --> $DIR/for_loop_fixable.rs:131:15
    |
 LL |     for _v in hs.iter() {}
    |               ^^^^^^^^^ help: to write this more concisely, try: `&hs`
 
 error: it is more concise to loop over references to containers instead of using explicit iteration methods
-  --> $DIR/for_loop_fixable.rs:135:15
+  --> $DIR/for_loop_fixable.rs:134:15
    |
 LL |     for _v in bs.iter() {}
    |               ^^^^^^^^^ help: to write this more concisely, try: `&bs`
 
 error: it is more concise to loop over containers instead of using explicit iteration methods
-  --> $DIR/for_loop_fixable.rs:310:18
+  --> $DIR/for_loop_fixable.rs:309:18
    |
 LL |         for i in iterator.into_iter() {
    |                  ^^^^^^^^^^^^^^^^^^^^ help: to write this more concisely, try: `iterator`
 
 error: it is more concise to loop over references to containers instead of using explicit iteration methods
-  --> $DIR/for_loop_fixable.rs:330:18
+  --> $DIR/for_loop_fixable.rs:329:18
    |
 LL |         for _ in t.into_iter() {}
    |                  ^^^^^^^^^^^^^ help: to write this more concisely, try: `&t`
 
 error: it is more concise to loop over containers instead of using explicit iteration methods
-  --> $DIR/for_loop_fixable.rs:332:18
+  --> $DIR/for_loop_fixable.rs:331:18
    |
 LL |         for _ in r.into_iter() {}
    |                  ^^^^^^^^^^^^^ help: to write this more concisely, try: `r`

tests/ui/for_loop_unfixable.rs

@@ -12,7 +12,6 @@
     clippy::linkedlist,
     clippy::shadow_unrelated,
     clippy::unnecessary_mut_passed,
-    clippy::cognitive_complexity,
     clippy::similar_names,
     unused,
     dead_code

tests/ui/for_loop_unfixable.stderr

@@ -1,5 +1,5 @@
 error[E0425]: cannot find function `f` in this scope
-  --> $DIR/for_loop_unfixable.rs:37:12
+  --> $DIR/for_loop_unfixable.rs:36:12
    |
 LL |         if f(&vec[i], &vec[i]) {
    |            ^ help: a local variable with a similar name exists: `i`

tests/ui/if_same_then_else2.rs

@@ -1,7 +1,6 @@
 #![warn(clippy::if_same_then_else)]
 #![allow(
     clippy::blacklisted_name,
-    clippy::cognitive_complexity,
     clippy::collapsible_if,
     clippy::ifs_same_cond,
     clippy::needless_return