Don't lint with map_clone if current type is Option or Result and method call is as_ref.

Author: GuillaumeGomez

clippy_lints/src/methods/map_clone.rs

@@ -15,22 +15,29 @@ use rustc_span::{sym, Span};
 
 use super::MAP_CLONE;
 
-fn should_run_lint(cx: &LateContext<'_>, method_id: DefId) -> bool {
+fn should_run_lint(cx: &LateContext<'_>, e: &hir::Expr<'_>, method_id: DefId) -> bool {
     if is_diag_trait_item(cx, method_id, sym::Iterator) {
         return true;
     }
     if !cx.tcx.impl_of_method(method_id).map_or(false, |id| {
-        is_type_diagnostic_item(cx, cx.tcx.type_of(id).instantiate_identity(), sym::Option)
-            || is_type_diagnostic_item(cx, cx.tcx.type_of(id).instantiate_identity(), sym::Result)
+        let identity = cx.tcx.type_of(id).instantiate_identity();
+        is_type_diagnostic_item(cx, identity, sym::Option) || is_type_diagnostic_item(cx, identity, sym::Result)
     }) {
         return false;
     }
+    // We check if the previous method call is `as_ref`.
+    if let hir::ExprKind::MethodCall(path1, receiver, _, _) = &e.kind
+        && let hir::ExprKind::MethodCall(path2, _, _, _) = &receiver.kind
+    {
+        return path2.ident.name != sym::as_ref || path1.ident.name != sym::map;
+    }
+
     return true;
 }
 
 pub(super) fn check(cx: &LateContext<'_>, e: &hir::Expr<'_>, recv: &hir::Expr<'_>, arg: &hir::Expr<'_>, msrv: &Msrv) {
     if let Some(method_id) = cx.typeck_results().type_dependent_def_id(e.hir_id)
-        && should_run_lint(cx, method_id)
+        && should_run_lint(cx, e, method_id)
     {
         match arg.kind {
             hir::ExprKind::Closure(&hir::Closure { body, .. }) => {