Auto merge of #8804 - Jarcho:in_recursion, r=Alexendoo

Rework `only_used_in_recursion`

fixes #8782
fixes #8629
fixes #8560
fixes #8556

This is a complete rewrite of the lint. This loses some capabilities of the old implementation. Namely the ability to track through tuple and slice patterns, as well as the ability to trace through assignments.

The two reported bugs are fixed with this. One was caused by using the name of the method rather than resolving to the `DefId` of the called method. The second was cause by using the existence of a cycle in the dependency graph to determine whether the parameter was used in recursion even though there were other ways to create a cycle in the graph.

Implementation wise this switches from using a visitor to walking up the tree from every use of each parameter until it has been determined the parameter is used for something other than recursion. This is likely to perform better as it avoids walking the entire function a second time, and it is unlikely to walk up the HIR tree very much. Some cases would perform worse though.

cc `@buttercrab`

changelog: Scale back `only_used_in_recursion` to fix false positives
changelog: Move `only_used_in_recursion` back to `complexity`

Author: bors

clippy_lints/src/lib.register_all.rs

@@ -252,6 +252,7 @@ store.register_group(true, "clippy::all", Some("clippy_all"), vec![
     LintId::of(non_expressive_names::JUST_UNDERSCORES_AND_DIGITS),
     LintId::of(non_octal_unix_permissions::NON_OCTAL_UNIX_PERMISSIONS),
     LintId::of(octal_escapes::OCTAL_ESCAPES),
+    LintId::of(only_used_in_recursion::ONLY_USED_IN_RECURSION),
     LintId::of(operators::ABSURD_EXTREME_COMPARISONS),
     LintId::of(operators::ASSIGN_OP_PATTERN),
     LintId::of(operators::BAD_BIT_MASK),

clippy_lints/src/lib.register_complexity.rs

@@ -72,6 +72,7 @@ store.register_group(true, "clippy::complexity", Some("clippy_complexity"), vec!
     LintId::of(neg_cmp_op_on_partial_ord::NEG_CMP_OP_ON_PARTIAL_ORD),
     LintId::of(no_effect::NO_EFFECT),
     LintId::of(no_effect::UNNECESSARY_OPERATION),
+    LintId::of(only_used_in_recursion::ONLY_USED_IN_RECURSION),
     LintId::of(operators::DOUBLE_COMPARISONS),
     LintId::of(operators::DURATION_SUBSEC),
     LintId::of(operators::IDENTITY_OP),

clippy_lints/src/lib.register_nursery.rs

@@ -24,7 +24,6 @@ store.register_group(true, "clippy::nursery", Some("clippy_nursery"), vec![
     LintId::of(mutex_atomic::MUTEX_INTEGER),
     LintId::of(non_send_fields_in_send_ty::NON_SEND_FIELDS_IN_SEND_TY),
     LintId::of(nonstandard_macro_braces::NONSTANDARD_MACRO_BRACES),
-    LintId::of(only_used_in_recursion::ONLY_USED_IN_RECURSION),
     LintId::of(option_if_let_else::OPTION_IF_LET_ELSE),
     LintId::of(redundant_pub_crate::REDUNDANT_PUB_CRATE),
     LintId::of(regex::TRIVIAL_REGEX),

clippy_lints/src/lib.rs

@@ -860,7 +860,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
     store.register_late_pass(move || Box::new(manual_bits::ManualBits::new(msrv)));
     store.register_late_pass(|| Box::new(default_union_representation::DefaultUnionRepresentation));
     store.register_early_pass(|| Box::new(doc_link_with_quotes::DocLinkWithQuotes));
-    store.register_late_pass(|| Box::new(only_used_in_recursion::OnlyUsedInRecursion));
+    store.register_late_pass(|| Box::new(only_used_in_recursion::OnlyUsedInRecursion::default()));
     let allow_dbg_in_tests = conf.allow_dbg_in_tests;
     store.register_late_pass(move || Box::new(dbg_macro::DbgMacro::new(allow_dbg_in_tests)));
     let cargo_ignore_publish = conf.cargo_ignore_publish;