Auto merge of #12136 - y21:issue12135, r=Jarcho

[`useless_asref`]: check that the clone receiver is the parameter

Fixes #12135

There was no check for the receiver of the `clone` call in the map closure. This makes sure that it's a path to the parameter.

changelog: [`useless_asref`]: check that the clone receiver is the closure parameter

4 files changed, 110 insertions, 6 deletions

diff --git a/clippy_lints/src/methods/useless_asref.rs b/clippy_lints/src/methods/useless_asref.rs
index 66727e5a29d..514015af045 100644
--- a/clippy_lints/src/methods/useless_asref.rs
+++ b/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, 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;
@@ -108,9 +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);
+            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, [], _) => {
@@ -122,14 +127,17 @@ 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)
                     {
                         true
                     } else {
                         false
                     }
                 },
-                hir::ExprKind::Call(call, [_]) => {
-                    if let hir::ExprKind::Path(qpath) = call.kind {
+                hir::ExprKind::Call(call, [recv]) => {
+                    if let hir::ExprKind::Path(qpath) = call.kind
+                        && path_to_local_id(recv, local_id)
+                    {
                         check_qpath(cx, qpath, call.hir_id)
                     } else {
                         false
diff --git a/tests/ui/useless_asref.fixed b/tests/ui/useless_asref.fixed
index 88b95095bc0..c98f2928e03 100644
--- a/tests/ui/useless_asref.fixed
+++ b/tests/ui/useless_asref.fixed
@@ -144,6 +144,42 @@ fn foo() {
     //~^ ERROR: this call to `as_ref.map(...)` does nothing
 }
 
+mod issue12135 {
+    pub struct Struct {
+        field: Option<InnerStruct>,
+    }
+
+    #[derive(Clone)]
+    pub struct Foo;
+
+    #[derive(Clone)]
+    struct InnerStruct {
+        x: Foo,
+    }
+
+    impl InnerStruct {
+        fn method(&self) -> &Foo {
+            &self.x
+        }
+    }
+
+    pub fn f(x: &Struct) -> Option<Foo> {
+        x.field.clone();
+        //~^ ERROR: this call to `as_ref.map(...)` does nothing
+        x.field.clone();
+        //~^ ERROR: this call to `as_ref.map(...)` does nothing
+        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())
+    }
+}
+
 fn main() {
     not_ok();
     ok();
diff --git a/tests/ui/useless_asref.rs b/tests/ui/useless_asref.rs
index 504dc1f5cbf..f9d603f116d 100644
--- a/tests/ui/useless_asref.rs
+++ b/tests/ui/useless_asref.rs
@@ -144,6 +144,42 @@ fn foo() {
     //~^ ERROR: this call to `as_ref.map(...)` does nothing
 }
 
+mod issue12135 {
+    pub struct Struct {
+        field: Option<InnerStruct>,
+    }
+
+    #[derive(Clone)]
+    pub struct Foo;
+
+    #[derive(Clone)]
+    struct InnerStruct {
+        x: Foo,
+    }
+
+    impl InnerStruct {
+        fn method(&self) -> &Foo {
+            &self.x
+        }
+    }
+
+    pub fn f(x: &Struct) -> Option<Foo> {
+        x.field.as_ref().map(|v| v.clone());
+        //~^ ERROR: this call to `as_ref.map(...)` does nothing
+        x.field.as_ref().map(Clone::clone);
+        //~^ ERROR: this call to `as_ref.map(...)` does nothing
+        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())
+    }
+}
+
 fn main() {
     not_ok();
     ok();
diff --git a/tests/ui/useless_asref.stderr b/tests/ui/useless_asref.stderr
index deb5d90f2f6..e158df2664d 100644
--- a/tests/ui/useless_asref.stderr
+++ b/tests/ui/useless_asref.stderr
@@ -88,5 +88,29 @@ error: this call to `as_ref.map(...)` does nothing
 LL |     let z = x.as_ref().map(|z| String::clone(z));
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `x.clone()`
 
-error: aborting due to 14 previous errors
+error: this call to `as_ref.map(...)` does nothing
+  --> $DIR/useless_asref.rs:167:9
+   |
+LL |         x.field.as_ref().map(|v| v.clone());
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `x.field.clone()`
+
+error: this call to `as_ref.map(...)` does nothing
+  --> $DIR/useless_asref.rs:169:9
+   |
+LL |         x.field.as_ref().map(Clone::clone);
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `x.field.clone()`
+
+error: this call to `as_ref.map(...)` does nothing
+  --> $DIR/useless_asref.rs:171:9
+   |
+LL |         x.field.as_ref().map(|v| Clone::clone(v));
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `x.field.clone()`
+
+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