lint on .map(|&x| x.clone())

Author: y21

clippy_lints/src/methods/useless_asref.rs

@@ -1,7 +1,9 @@
 use clippy_utils::diagnostics::span_lint_and_sugg;
 use clippy_utils::source::snippet_with_applicability;
 use clippy_utils::ty::walk_ptrs_ty_depth;
-use clippy_utils::{get_parent_expr, is_diag_trait_item, match_def_path, path_to_local_id, paths, peel_blocks};
+use clippy_utils::{
+    get_parent_expr, is_diag_trait_item, match_def_path, path_to_local_id, paths, peel_blocks, strip_pat_refs,
+};
 use rustc_errors::Applicability;
 use rustc_hir as hir;
 use rustc_lint::LateContext;
@@ -108,26 +110,12 @@ fn check_qpath(cx: &LateContext<'_>, qpath: hir::QPath<'_>, hir_id: hir::HirId)
 
 fn is_calling_clone(cx: &LateContext<'_>, arg: &hir::Expr<'_>) -> bool {
     match arg.kind {
-        hir::ExprKind::Closure(&hir::Closure { body, .. }) => {
+        hir::ExprKind::Closure(&hir::Closure { body, .. })
             // If it's a closure, we need to check what is called.
-            let closure_body = cx.tcx.hir().body(body);
-
-            // |x| ...
-            //  ^
-            let [
-                hir::Param {
-                    pat:
-                        hir::Pat {
-                            kind: hir::PatKind::Binding(_, local_id, ..),
-                            ..
-                        },
-                    ..
-                },
-            ] = closure_body.params
-            else {
-                return false;
-            };
-
+            if let closure_body = cx.tcx.hir().body(body)
+                && let [param] = closure_body.params
+                && let hir::PatKind::Binding(_, local_id, ..) = strip_pat_refs(param.pat).kind =>
+        {
             let closure_expr = peel_blocks(closure_body.value);
             match closure_expr.kind {
                 hir::ExprKind::MethodCall(method, obj, [], _) => {
@@ -139,7 +127,7 @@ fn is_calling_clone(cx: &LateContext<'_>, arg: &hir::Expr<'_>) -> bool {
                         // no autoderefs
                         && !cx.typeck_results().expr_adjustments(obj).iter()
                             .any(|a| matches!(a.kind, Adjust::Deref(Some(..))))
-                        && path_to_local_id(obj, *local_id)
+                        && path_to_local_id(obj, local_id)
                     {
                         true
                     } else {
@@ -148,7 +136,7 @@ fn is_calling_clone(cx: &LateContext<'_>, arg: &hir::Expr<'_>) -> bool {
                 },
                 hir::ExprKind::Call(call, [recv]) => {
                     if let hir::ExprKind::Path(qpath) = call.kind
-                        && path_to_local_id(recv, *local_id)
+                        && path_to_local_id(recv, local_id)
                     {
                         check_qpath(cx, qpath, call.hir_id)
                     } else {

tests/ui/useless_asref.fixed

@@ -171,6 +171,11 @@ mod issue12135 {
         x.field.clone();
         //~^ ERROR: this call to `as_ref.map(...)` does nothing
 
+        // https://github.com/rust-lang/rust-clippy/pull/12136#discussion_r1451565223
+        #[allow(clippy::clone_on_copy)]
+        Some(1).clone();
+        //~^ ERROR: this call to `as_ref.map(...)` does nothing
+
         x.field.as_ref().map(|v| v.method().clone())
     }
 }

tests/ui/useless_asref.rs

@@ -171,6 +171,11 @@ mod issue12135 {
         x.field.as_ref().map(|v| Clone::clone(v));
         //~^ ERROR: this call to `as_ref.map(...)` does nothing
 
+        // https://github.com/rust-lang/rust-clippy/pull/12136#discussion_r1451565223
+        #[allow(clippy::clone_on_copy)]
+        Some(1).as_ref().map(|&x| x.clone());
+        //~^ ERROR: this call to `as_ref.map(...)` does nothing
+
         x.field.as_ref().map(|v| v.method().clone())
     }
 }

tests/ui/useless_asref.stderr

@@ -106,5 +106,11 @@ error: this call to `as_ref.map(...)` does nothing
 LL |         x.field.as_ref().map(|v| Clone::clone(v));
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `x.field.clone()`
 
-error: aborting due to 17 previous errors
+error: this call to `as_ref.map(...)` does nothing
+  --> $DIR/useless_asref.rs:176:9
+   |
+LL |         Some(1).as_ref().map(|&x| x.clone());
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `Some(1).clone()`
+
+error: aborting due to 18 previous errors