Fix case for function params

Author: Evan Typanski

clippy_lints/src/manual_rem_euclid.rs

@@ -61,12 +61,23 @@ impl<'tcx> LateLintPass<'tcx> for ManualRemEuclid {
             && op3.node == BinOpKind::Rem
             && let Some((const3, expr3)) = check_for_positive_int_constant(cx, expr2, false)
             && const1 == const2 && const2 == const3
-            // Only apply if we see an explicit type annotation on the local.
             && let Some(hir_id) = path_to_local(expr3)
-            && let Some(Node::Binding(_)) = cx.tcx.hir().find(hir_id)
-            && let Some(Node::Local(local)) = cx.tcx.hir().find(cx.tcx.hir().get_parent_node(hir_id))
-            && let Some(ty) = local.ty
-            && !matches!(ty.kind, TyKind::Infer) {
+            && let Some(Node::Binding(_)) = cx.tcx.hir().find(hir_id) {
+                // Apply only to params or locals with annotated types
+                match cx.tcx.hir().find(cx.tcx.hir().get_parent_node(hir_id)) {
+                    Some(Node::Param(..)) => (),
+                    Some(Node::Local(local)) => {
+                        if let Some(ty) = local.ty {
+                            if matches!(ty.kind, TyKind::Infer) {
+                                return;
+                            }
+                        } else {
+                            return;
+                        }
+                    }
+                    _ => return,
+                };
+
                 let mut app = Applicability::MachineApplicable;
                 let rem_of = snippet_with_applicability(cx, expr3.span, "_", &mut app);
                 span_lint_and_sugg(

tests/ui/manual_rem_euclid.fixed

@@ -26,3 +26,8 @@ fn main() {
     let _: i32 = 4 % ((value % 4) + 4);
     let _: i32 = ((4 % value) + 4) % 4;
 }
+
+// Should lint for params too
+pub fn rem_euclid_4(num: i32) -> i32 {
+    num.rem_euclid(4)
+}

tests/ui/manual_rem_euclid.rs

@@ -26,3 +26,8 @@ fn main() {
     let _: i32 = 4 % ((value % 4) + 4);
     let _: i32 = ((4 % value) + 4) % 4;
 }
+
+// Should lint for params too
+pub fn rem_euclid_4(num: i32) -> i32 {
+    ((num % 4) + 4) % 4
+}

tests/ui/manual_rem_euclid.stderr

@@ -30,5 +30,11 @@ error: manual `rem_euclid` implementation
 LL |     let _: i32 = 1 + (4 + value % 4) % 4;
    |                      ^^^^^^^^^^^^^^^^^^^ help: consider using: `value.rem_euclid(4)`
 
-error: aborting due to 5 previous errors
+error: manual `rem_euclid` implementation
+  --> $DIR/manual_rem_euclid.rs:32:5
+   |
+LL |     ((num % 4) + 4) % 4
+   |     ^^^^^^^^^^^^^^^^^^^ help: consider using: `num.rem_euclid(4)`
+
+error: aborting due to 6 previous errors