Edit based on review recommendations

Author: surechen

clippy_lints/src/shadow.rs

@@ -1,12 +1,11 @@
 use clippy_utils::diagnostics::span_lint_and_note;
 use clippy_utils::source::snippet;
 use clippy_utils::visitors::is_local_used;
-use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use rustc_data_structures::fx::FxHashMap;
 use rustc_hir::def::Res;
 use rustc_hir::def_id::LocalDefId;
 use rustc_hir::hir_id::ItemLocalId;
-use rustc_hir::intravisit::FnKind;
-use rustc_hir::{Block, Body, BodyOwnerKind, Expr, ExprKind, FnDecl, HirId, IsAsync, Node, Pat, PatKind, QPath, UnOp};
+use rustc_hir::{Block, Body, BodyOwnerKind, Expr, ExprKind, HirId, Node, Pat, PatKind, QPath, UnOp};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::{declare_tool_lint, impl_lint_pass};
 use rustc_span::{Span, Symbol};
@@ -96,7 +95,6 @@ declare_clippy_lint! {
 #[derive(Default)]
 pub(crate) struct Shadow {
     bindings: Vec<FxHashMap<Symbol, Vec<ItemLocalId>>>,
-    skip: Vec<FxHashSet<Symbol>>,
 }
 
 impl_lint_pass!(Shadow => [SHADOW_SAME, SHADOW_REUSE, SHADOW_UNRELATED]);
@@ -107,11 +105,16 @@ impl<'tcx> LateLintPass<'tcx> for Shadow {
             PatKind::Binding(_, hir_id, ident, _) => (hir_id, ident),
             _ => return,
         };
+
+        if pat.span.desugaring_kind().is_some() {
+            return;
+        }
+
         if ident.span.from_expansion() || ident.span.is_dummy() {
             return;
         }
-        let HirId { owner, local_id } = id;
 
+        let HirId { owner, local_id } = id;
         // get (or insert) the list of items for this owner and symbol
         let data = self.bindings.last_mut().unwrap();
         let items_with_name = data.entry(ident.name).or_default();
@@ -123,11 +126,6 @@ impl<'tcx> LateLintPass<'tcx> for Shadow {
                 return;
             }
 
-            if !self.skip.is_empty() && self.skip.last_mut().unwrap().contains(&ident.name) {
-                // skip async function's params
-                return;
-            }
-
             if is_shadow(cx, owner, prev, local_id) {
                 let prev_hir_id = HirId { owner, local_id: prev };
                 lint_shadow(cx, pat, prev_hir_id, ident.span);
@@ -152,58 +150,6 @@ impl<'tcx> LateLintPass<'tcx> for Shadow {
             self.bindings.pop();
         }
     }
-
-    fn check_fn(
-        &mut self,
-        _: &LateContext<'tcx>,
-        kind: FnKind<'tcx>,
-        _: &'tcx FnDecl<'_>,
-        body: &'tcx Body<'_>,
-        _: Span,
-        _: HirId,
-    ) {
-        if_chain! {
-            if let Some(header) = match kind {
-                FnKind::ItemFn(_, _, header, _) => Some(header),
-                FnKind::Method(_, sig, _) => Some(sig.header),
-                FnKind::Closure => None,
-            };
-            if header.asyncness == IsAsync::Async;
-            if !body.params.is_empty();
-            then {
-                self.skip.push(FxHashSet::default());
-                let skip_params = self.skip.last_mut().unwrap();
-                for i in body.params {
-                    if let PatKind::Binding(.., ident, _) = i.pat.kind {
-                       skip_params.insert(ident.name);
-                    }
-                }
-            }
-        }
-    }
-
-    fn check_fn_post(
-        &mut self,
-        _: &LateContext<'tcx>,
-        kind: FnKind<'tcx>,
-        _: &'tcx FnDecl<'_>,
-        body: &'tcx Body<'_>,
-        _: Span,
-        _: HirId,
-    ) {
-        if_chain! {
-            if let Some(header) = match kind {
-                FnKind::ItemFn(_, _, header, _) => Some(header),
-                FnKind::Method(_, sig, _) => Some(sig.header),
-                FnKind::Closure => None,
-            };
-            if header.asyncness == IsAsync::Async;
-            if !body.params.is_empty();
-            then {
-                self.skip.pop();
-            }
-        }
-    }
 }
 
 fn is_shadow(cx: &LateContext<'_>, owner: LocalDefId, first: ItemLocalId, second: ItemLocalId) -> bool {

tests/ui/shadow.stderr

@@ -241,5 +241,17 @@ note: previous binding is here
 LL |     let _ = |[x]: [u32; 1]| {
    |               ^
 
-error: aborting due to 20 previous errors
+error: `_b` shadows a previous, unrelated binding
+  --> $DIR/shadow.rs:85:9
+   |
+LL |     let _b = _a;
+   |         ^^
+   |
+note: previous binding is here
+  --> $DIR/shadow.rs:84:28
+   |
+LL | pub async fn foo2(_a: i32, _b: i64) {
+   |                            ^^
+
+error: aborting due to 21 previous errors