Auto merge of #7338 - camsteffen:shadow, r=llogic

Re-write shadow lints

changelog: Move shadow_unrelated to restriction
changelog: The shadow lints find a lot more shadows and are not limited to certain patterns

Drastically simplifies the implementation. Catches a lot more cases.

I removed the "initialization happens here" note. It is not helpful IMO.

Closes #318
Fixes #2890
Fixes #6563
Fixes #7588
Fixes #7620

clippy_lints/src/lib.register_pedantic.rs

@@ -81,7 +81,6 @@ store.register_group(true, "clippy::pedantic", Some("clippy_pedantic"), vec![
     LintId::of(redundant_else::REDUNDANT_ELSE),
     LintId::of(ref_option_ref::REF_OPTION_REF),
     LintId::of(semicolon_if_nothing_returned::SEMICOLON_IF_NOTHING_RETURNED),
-    LintId::of(shadow::SHADOW_UNRELATED),
     LintId::of(strings::STRING_ADD_ASSIGN),
     LintId::of(trait_bounds::TRAIT_DUPLICATION_IN_BOUNDS),
     LintId::of(trait_bounds::TYPE_REPETITION_IN_BOUNDS),

clippy_lints/src/lib.register_restriction.rs

@@ -50,6 +50,7 @@ store.register_group(true, "clippy::restriction", Some("clippy_restriction"), ve
     LintId::of(same_name_method::SAME_NAME_METHOD),
     LintId::of(shadow::SHADOW_REUSE),
     LintId::of(shadow::SHADOW_SAME),
+    LintId::of(shadow::SHADOW_UNRELATED),
     LintId::of(strings::STRING_ADD),
     LintId::of(strings::STRING_TO_STRING),
     LintId::of(strings::STR_TO_STRING),

clippy_lints/src/lib.rs

@@ -4,6 +4,7 @@
 #![feature(drain_filter)]
 #![feature(in_band_lifetimes)]
 #![feature(iter_zip)]
+#![feature(iter_map_while)]
 #![feature(once_cell)]
 #![feature(rustc_private)]
 #![feature(stmt_expr_attributes)]
@@ -324,7 +325,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
     store.register_late_pass(|| Box::new(same_name_method::SameNameMethod));
     store.register_late_pass(|| Box::new(map_clone::MapClone));
     store.register_late_pass(|| Box::new(map_err_ignore::MapErrIgnore));
-    store.register_late_pass(|| Box::new(shadow::Shadow));
+    store.register_late_pass(|| Box::new(shadow::Shadow::default()));
     store.register_late_pass(|| Box::new(unit_types::UnitTypes));
     store.register_late_pass(|| Box::new(loops::Loops));
     store.register_late_pass(|| Box::new(main_recursion::MainRecursion::default()));