fix(clone_on_ref_ptr): only name the generic type if possible

clippy_lints/src/methods/clone_on_ref_ptr.rs

@@ -3,7 +3,7 @@ use clippy_utils::source::snippet_with_context;
 use rustc_errors::Applicability;
 use rustc_hir as hir;
 use rustc_lint::LateContext;
-use rustc_middle::ty;
+use rustc_middle::ty::{self, IsSuggestable};
 use rustc_span::symbol::{Symbol, sym};
 
 use super::CLONE_ON_REF_PTR;
@@ -15,12 +15,10 @@ pub(super) fn check(
     receiver: &hir::Expr<'_>,
     args: &[hir::Expr<'_>],
 ) {
-    if !(args.is_empty() && method_name == sym::clone) {
-        return;
-    }
-    let obj_ty = cx.typeck_results().expr_ty(receiver).peel_refs();
-
-    if let ty::Adt(adt, subst) = obj_ty.kind()
+    if method_name == sym::clone
+        && args.is_empty()
+        && let obj_ty = cx.typeck_results().expr_ty(receiver).peel_refs()
+        && let ty::Adt(adt, subst) = obj_ty.kind()
         && let Some(name) = cx.tcx.get_diagnostic_name(adt.did())
     {
         let caller_type = match name {
@@ -39,12 +37,22 @@ pub(super) fn check(
                 // Sometimes unnecessary ::<_> after Rc/Arc/Weak
                 let mut app = Applicability::Unspecified;
                 let snippet = snippet_with_context(cx, receiver.span, expr.span.ctxt(), "..", &mut app).0;
-                diag.span_suggestion(
-                    expr.span,
-                    "try",
-                    format!("{caller_type}::<{}>::clone(&{snippet})", subst.type_at(0)),
-                    app,
-                );
+                let generic = subst.type_at(0);
+                if generic.is_suggestable(cx.tcx, true) {
+                    diag.span_suggestion(
+                        expr.span,
+                        "try",
+                        format!("{caller_type}::<{generic}>::clone(&{snippet})"),
+                        app,
+                    );
+                } else {
+                    diag.span_suggestion(
+                        expr.span,
+                        "try",
+                        format!("{caller_type}::</* generic */>::clone(&{snippet})"),
+                        Applicability::HasPlaceholders,
+                    );
+                }
             },
         );
     }

tests/ui/clone_on_copy.fixed

@@ -1,25 +1,16 @@
+#![warn(clippy::clone_on_copy)]
 #![allow(
-    unused,
     clippy::redundant_clone,
     clippy::deref_addrof,
     clippy::no_effect,
     clippy::unnecessary_operation,
-    clippy::vec_init_then_push,
     clippy::toplevel_ref_arg,
     clippy::needless_borrow
 )]
 
 use std::cell::RefCell;
-use std::rc::{self, Rc};
-use std::sync::{self, Arc};
 
-fn main() {}
-
-fn is_ascii(ch: char) -> bool {
-    ch.is_ascii()
-}
-
-fn clone_on_copy() -> Option<(i32)> {
+fn main() {
     42;
     //~^ clone_on_copy
 
@@ -65,20 +56,66 @@ fn clone_on_copy() -> Option<(i32)> {
     let x = 42;
     let ref y = x.clone(); // ok, binds by reference
     let ref mut y = x.clone(); // ok, binds by reference
+}
+
+mod issue3052 {
+    struct A;
+    struct B;
+    struct C;
+    struct D;
+    #[derive(Copy, Clone)]
+    struct E;
+
+    macro_rules! impl_deref {
+        ($src:ident, $dst:ident) => {
+            impl std::ops::Deref for $src {
+                type Target = $dst;
+                fn deref(&self) -> &Self::Target {
+                    &$dst
+                }
+            }
+        };
+    }
+
+    impl_deref!(A, B);
+    impl_deref!(B, C);
+    impl_deref!(C, D);
+    impl std::ops::Deref for D {
+        type Target = &'static E;
+        fn deref(&self) -> &Self::Target {
+            &&E
+        }
+    }
+
+    fn go1() {
+        let a = A;
+        let _: E = *****a;
+        //~^ clone_on_copy
+
+        let _: E = *****a;
+    }
+}
+
+fn issue4348() {
+    fn is_ascii(ch: char) -> bool {
+        ch.is_ascii()
+    }
 
-    // Issue #4348
     let mut x = 43;
     let _ = &x.clone(); // ok, getting a ref
     'a'.clone().make_ascii_uppercase(); // ok, clone and then mutate
     is_ascii('z');
     //~^ clone_on_copy
+}
 
-    // Issue #5436
+#[expect(clippy::vec_init_then_push)]
+fn issue5436() {
     let mut vec = Vec::new();
     vec.push(42);
     //~^ clone_on_copy
+}
 
-    //  Issue #9277
+fn issue9277() -> Option<i32> {
     let opt: &Option<i32> = &None;
     let value = (*opt)?; // operator precedence needed (*opt)?
     //

tests/ui/clone_on_copy.rs

@@ -1,25 +1,16 @@
+#![warn(clippy::clone_on_copy)]
 #![allow(
-    unused,
     clippy::redundant_clone,
     clippy::deref_addrof,
     clippy::no_effect,
     clippy::unnecessary_operation,
-    clippy::vec_init_then_push,
     clippy::toplevel_ref_arg,
     clippy::needless_borrow
 )]
 
 use std::cell::RefCell;
-use std::rc::{self, Rc};
-use std::sync::{self, Arc};
 
-fn main() {}
-
-fn is_ascii(ch: char) -> bool {
-    ch.is_ascii()
-}
-
-fn clone_on_copy() -> Option<(i32)> {
+fn main() {
     42.clone();
     //~^ clone_on_copy
 
@@ -65,20 +56,66 @@ fn clone_on_copy() -> Option<(i32)> {
     let x = 42;
     let ref y = x.clone(); // ok, binds by reference
     let ref mut y = x.clone(); // ok, binds by reference
+}
+
+mod issue3052 {
+    struct A;
+    struct B;
+    struct C;
+    struct D;
+    #[derive(Copy, Clone)]
+    struct E;
+
+    macro_rules! impl_deref {
+        ($src:ident, $dst:ident) => {
+            impl std::ops::Deref for $src {
+                type Target = $dst;
+                fn deref(&self) -> &Self::Target {
+                    &$dst
+                }
+            }
+        };
+    }
+
+    impl_deref!(A, B);
+    impl_deref!(B, C);
+    impl_deref!(C, D);
+    impl std::ops::Deref for D {
+        type Target = &'static E;
+        fn deref(&self) -> &Self::Target {
+            &&E
+        }
+    }
+
+    fn go1() {
+        let a = A;
+        let _: E = a.clone();
+        //~^ clone_on_copy
+
+        let _: E = *****a;
+    }
+}
+
+fn issue4348() {
+    fn is_ascii(ch: char) -> bool {
+        ch.is_ascii()
+    }
 
-    // Issue #4348
     let mut x = 43;
     let _ = &x.clone(); // ok, getting a ref
     'a'.clone().make_ascii_uppercase(); // ok, clone and then mutate
     is_ascii('z'.clone());
     //~^ clone_on_copy
+}
 
-    // Issue #5436
+#[expect(clippy::vec_init_then_push)]
+fn issue5436() {
     let mut vec = Vec::new();
     vec.push(42.clone());
     //~^ clone_on_copy
+}
 
-    //  Issue #9277
+fn issue9277() -> Option<i32> {
     let opt: &Option<i32> = &None;
     let value = opt.clone()?; // operator precedence needed (*opt)?
     //

tests/ui/clone_on_copy.stderr

@@ -1,5 +1,5 @@
 error: using `clone` on type `i32` which implements the `Copy` trait
-  --> tests/ui/clone_on_copy.rs:23:5
+  --> tests/ui/clone_on_copy.rs:14:5
    |
 LL |     42.clone();
    |     ^^^^^^^^^^ help: try removing the `clone` call: `42`
@@ -8,52 +8,58 @@ LL |     42.clone();
    = help: to override `-D warnings` add `#[allow(clippy::clone_on_copy)]`
 
 error: using `clone` on type `i32` which implements the `Copy` trait
-  --> tests/ui/clone_on_copy.rs:28:5
+  --> tests/ui/clone_on_copy.rs:19:5
    |
 LL |     (&42).clone();
    |     ^^^^^^^^^^^^^ help: try dereferencing it: `*(&42)`
 
 error: using `clone` on type `i32` which implements the `Copy` trait
-  --> tests/ui/clone_on_copy.rs:32:5
+  --> tests/ui/clone_on_copy.rs:23:5
    |
 LL |     rc.borrow().clone();
    |     ^^^^^^^^^^^^^^^^^^^ help: try dereferencing it: `*rc.borrow()`
 
 error: using `clone` on type `u32` which implements the `Copy` trait
-  --> tests/ui/clone_on_copy.rs:36:5
+  --> tests/ui/clone_on_copy.rs:27:5
    |
 LL |     x.clone().rotate_left(1);
    |     ^^^^^^^^^ help: try removing the `clone` call: `x`
 
 error: using `clone` on type `i32` which implements the `Copy` trait
-  --> tests/ui/clone_on_copy.rs:51:5
+  --> tests/ui/clone_on_copy.rs:42:5
    |
 LL |     m!(42).clone();
    |     ^^^^^^^^^^^^^^ help: try removing the `clone` call: `m!(42)`
 
 error: using `clone` on type `[u32; 2]` which implements the `Copy` trait
-  --> tests/ui/clone_on_copy.rs:62:5
+  --> tests/ui/clone_on_copy.rs:53:5
    |
 LL |     x.clone()[0];
    |     ^^^^^^^^^ help: try dereferencing it: `(*x)`
 
+error: using `clone` on type `E` which implements the `Copy` trait
+  --> tests/ui/clone_on_copy.rs:92:20
+   |
+LL |         let _: E = a.clone();
+   |                    ^^^^^^^^^ help: try dereferencing it: `*****a`
+
 error: using `clone` on type `char` which implements the `Copy` trait
-  --> tests/ui/clone_on_copy.rs:73:14
+  --> tests/ui/clone_on_copy.rs:107:14
    |
 LL |     is_ascii('z'.clone());
    |              ^^^^^^^^^^^ help: try removing the `clone` call: `'z'`
 
 error: using `clone` on type `i32` which implements the `Copy` trait
-  --> tests/ui/clone_on_copy.rs:78:14
+  --> tests/ui/clone_on_copy.rs:114:14
    |
 LL |     vec.push(42.clone());
    |              ^^^^^^^^^^ help: try removing the `clone` call: `42`
 
 error: using `clone` on type `Option<i32>` which implements the `Copy` trait
-  --> tests/ui/clone_on_copy.rs:83:17
+  --> tests/ui/clone_on_copy.rs:120:17
    |
 LL |     let value = opt.clone()?; // operator precedence needed (*opt)?
    |                 ^^^^^^^^^^^ help: try dereferencing it: `(*opt)`
 
-error: aborting due to 9 previous errors
+error: aborting due to 10 previous errors