Fix false positive in PartialEq implementation

Author: GuillaumeGomez

clippy_lints/src/unconditional_recursion.rs

@@ -102,7 +102,18 @@ impl<'tcx> LateLintPass<'tcx> for UnconditionalRecursion {
             let expr = body.value.peel_blocks();
             let is_bad = match expr.kind {
                 ExprKind::Binary(op, left, right) if op.node == to_check_op => {
-                    is_local(cx, left) && is_local(cx, right)
+                    // First we check both are local variables.
+                    if is_local(cx, left)
+                        && is_local(cx, right)
+                        // Then we check if the left-hand element is of the same type as `self`.
+                        && let Some(left_ty) = cx.typeck_results().expr_ty_opt(left)
+                        && let Some(left_id) = get_ty_def_id(left_ty)
+                        && self_arg == left_id
+                    {
+                        true
+                    } else {
+                        false
+                    }
                 },
                 ExprKind::MethodCall(segment, receiver, &[arg], _) if segment.ident.name == name.name => {
                     if is_local(cx, receiver)