fix: add test case, use a better conditional expression.

clippy_lints/src/non_canonical_impls.rs

@@ -1,10 +1,11 @@
 use clippy_utils::diagnostics::{span_lint_and_sugg, span_lint_and_then};
 use clippy_utils::ty::implements_trait;
-use clippy_utils::{is_res_lang_ctor, last_path_segment, path_res, std_or_core};
+use clippy_utils::{is_from_proc_macro, is_res_lang_ctor, last_path_segment, path_res, std_or_core};
 use rustc_errors::Applicability;
 use rustc_hir::def_id::LocalDefId;
 use rustc_hir::{Expr, ExprKind, ImplItem, ImplItemKind, LangItem, Node, UnOp};
-use rustc_lint::{LateContext, LateLintPass};
+use rustc_lint::{LateContext, LateLintPass, LintContext};
+use rustc_middle::lint::in_external_macro;
 use rustc_middle::ty::EarlyBinder;
 use rustc_session::declare_lint_pass;
 use rustc_span::sym;
@@ -111,7 +112,7 @@
 
 impl LateLintPass<'_> for NonCanonicalImpls {
     #[expect(clippy::too_many_lines)]
-    fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &ImplItem<'_>) {
+    fn check_impl_item<'tcx>(&mut self, cx: &LateContext<'tcx>, impl_item: &ImplItem<'tcx>) {
         let Node::Item(item) = cx.tcx.parent_hir_node(impl_item.hir_id()) else {
             return;
         };
@@ -128,9 +129,7 @@ fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &ImplItem<'_>) {
         let ExprKind::Block(block, ..) = body.value.kind else {
             return;
         };
-        if let Some(expr) = block.expr
-            && expr.span.from_expansion()
-        {
+        if in_external_macro(cx.sess(), block.span) || is_from_proc_macro(cx, impl_item) {
             return;
         }
 

tests/ui/auxiliary/proc_macro_derive.rs

@@ -176,8 +176,7 @@ pub fn non_canonical_clone_derive(_: TokenStream) -> TokenStream {
         struct NonCanonicalClone;
         impl Clone for NonCanonicalClone {
             fn clone(&self) -> Self {
-                let a = *self;
-                a
+                todo!()
             }
         }
         impl Copy for NonCanonicalClone {}

tests/ui/non_canonical_clone_impl.fixed

@@ -3,6 +3,9 @@
 #![allow(clippy::assigning_clones)]
 #![no_main]
 
+extern crate proc_macros;
+use proc_macros::with_span;
+
 // lint
 
 struct A(u32);
@@ -100,3 +103,15 @@ impl<A: std::fmt::Debug + Copy + Clone> Copy for Uwu<A> {}
 // should skip proc macros, see https://github.com/rust-lang/rust-clippy/issues/12788
 #[derive(proc_macro_derive::NonCanonicalClone)]
 pub struct G;
+
+with_span!(
+    span
+
+    #[derive(Copy)]
+    struct H;
+    impl Clone for H {
+        fn clone(&self) -> Self {
+            todo!()
+        }
+    }
+);

tests/ui/non_canonical_clone_impl.rs

@@ -3,6 +3,9 @@
 #![allow(clippy::assigning_clones)]
 #![no_main]
 
+extern crate proc_macros;
+use proc_macros::with_span;
+
 // lint
 
 struct A(u32);
@@ -110,3 +113,15 @@ impl<A: std::fmt::Debug + Copy + Clone> Copy for Uwu<A> {}
 // should skip proc macros, see https://github.com/rust-lang/rust-clippy/issues/12788
 #[derive(proc_macro_derive::NonCanonicalClone)]
 pub struct G;
+
+with_span!(
+    span
+
+    #[derive(Copy)]
+    struct H;
+    impl Clone for H {
+        fn clone(&self) -> Self {
+            todo!()
+        }
+    }
+);

tests/ui/non_canonical_clone_impl.stderr

@@ -1,5 +1,5 @@
 error: non-canonical implementation of `clone` on a `Copy` type
-  --> tests/ui/non_canonical_clone_impl.rs:11:29
+  --> tests/ui/non_canonical_clone_impl.rs:14:29
    |
 LL |       fn clone(&self) -> Self {
    |  _____________________________^
@@ -11,7 +11,7 @@ LL | |     }
    = help: to override `-D warnings` add `#[allow(clippy::non_canonical_clone_impl)]`
 
 error: unnecessary implementation of `clone_from` on a `Copy` type
-  --> tests/ui/non_canonical_clone_impl.rs:15:5
+  --> tests/ui/non_canonical_clone_impl.rs:18:5
    |
 LL | /     fn clone_from(&mut self, source: &Self) {
 LL | |         source.clone();
@@ -20,7 +20,7 @@ LL | |     }
    | |_____^ help: remove it
 
 error: non-canonical implementation of `clone` on a `Copy` type
-  --> tests/ui/non_canonical_clone_impl.rs:82:29
+  --> tests/ui/non_canonical_clone_impl.rs:85:29
    |
 LL |       fn clone(&self) -> Self {
    |  _____________________________^
@@ -29,7 +29,7 @@ LL | |     }
    | |_____^ help: change this to: `{ *self }`
 
 error: unnecessary implementation of `clone_from` on a `Copy` type
-  --> tests/ui/non_canonical_clone_impl.rs:86:5
+  --> tests/ui/non_canonical_clone_impl.rs:89:5
    |
 LL | /     fn clone_from(&mut self, source: &Self) {
 LL | |         source.clone();