Don't assume argument type is a type parameter

Author: smoelius

clippy_lints/src/dereference.rs

@@ -980,6 +980,10 @@ fn needless_borrow_impl_arg_position<'tcx>(
         return None;
     }
 
+    if !matches!(child_arg_ty.kind(), ty::Param(_)) {
+        return None;
+    }
+
     // If `child_arg_ty` is a type parameter that appears in more than one place, then substituting
     // it with `T` instead of `&T` could cause a type error.
     if cx

tests/ui/needless_borrow.fixed

@@ -132,6 +132,7 @@ fn main() {
     let _ = std::path::Path::new(".").join(".");
 
     let _ = Box::new(&""); // Don't lint. Type parameter has no trait bounds
+    ref_as_ref_path(&""); // Don't lint. Argument type is not a type parameter
 }
 
 #[allow(clippy::needless_borrowed_reference)]
@@ -163,3 +164,9 @@ fn check_expect_suppression() {
     #[expect(clippy::needless_borrow)]
     let _ = x(&&a);
 }
+
+fn ref_as_ref_path<T: 'static>(_: &'static T)
+where
+    &'static T: AsRef<std::path::Path>,
+{
+}

tests/ui/needless_borrow.rs

@@ -132,6 +132,7 @@ fn main() {
     let _ = std::path::Path::new(".").join(&&".");
 
     let _ = Box::new(&""); // Don't lint. Type parameter has no trait bounds
+    ref_as_ref_path(&""); // Don't lint. Argument type is not a type parameter
 }
 
 #[allow(clippy::needless_borrowed_reference)]
@@ -163,3 +164,9 @@ fn check_expect_suppression() {
     #[expect(clippy::needless_borrow)]
     let _ = x(&&a);
 }
+
+fn ref_as_ref_path<T: 'static>(_: &'static T)
+where
+    &'static T: AsRef<std::path::Path>,
+{
+}