Extend result_map_or_into_option lint to handle Result::map_or_else(|_| None, Some)

Author: GuillaumeGomez

clippy_lints/src/methods/mod.rs

@@ -80,6 +80,7 @@ mod read_line_without_trim;
 mod readonly_write_lock;
 mod redundant_as_str;
 mod repeat_once;
+mod result_map_or_else_none;
 mod search_is_some;
 mod seek_from_current;
 mod seek_to_start_instead_of_rewind;
@@ -4291,6 +4292,9 @@ impl Methods {
                     option_map_or_none::check(cx, expr, recv, def, map);
                     manual_ok_or::check(cx, expr, recv, def, map);
                 },
+                ("map_or_else", [_, map]) => {
+                    result_map_or_else_none::check(cx, expr, recv, map);
+                },
                 ("next", []) => {
                     if let Some((name2, recv2, args2, _, _)) = method_call(recv) {
                         match (name2, args2) {

clippy_lints/src/methods/result_map_or_else_none.rs

@@ -0,0 +1,42 @@
+use clippy_utils::diagnostics::span_lint_and_sugg;
+use clippy_utils::source::snippet;
+use clippy_utils::ty::is_type_diagnostic_item;
+use clippy_utils::{is_res_lang_ctor, path_res};
+use rustc_errors::Applicability;
+use rustc_hir as hir;
+use rustc_hir::LangItem::OptionSome;
+use rustc_lint::LateContext;
+use rustc_span::symbol::sym;
+
+use super::RESULT_MAP_OR_INTO_OPTION;
+
+/// lint use of `_.map_or(None, _)` for `Option`s and `Result`s
+pub(super) fn check<'tcx>(
+    cx: &LateContext<'tcx>,
+    expr: &'tcx hir::Expr<'_>,
+    recv: &'tcx hir::Expr<'_>,
+    map_arg: &'tcx hir::Expr<'_>,
+) {
+    let is_result = is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(recv), sym::Result);
+
+    if !is_result {
+        return;
+    }
+
+    let f_arg_is_some = is_res_lang_ctor(cx, path_res(cx, map_arg), OptionSome);
+
+    if f_arg_is_some {
+        // if let hir::ExprKind::Closure(&hir::Closure { body, fn_decl_span, .. }) = map_arg.kind {}
+        let msg = "called `map_or_else(|_| None, Some)` on a `Result` value";
+        let self_snippet = snippet(cx, recv.span, "..");
+        span_lint_and_sugg(
+            cx,
+            RESULT_MAP_OR_INTO_OPTION,
+            expr.span,
+            msg,
+            "try using `ok` instead",
+            format!("{self_snippet}.ok()"),
+            Applicability::MachineApplicable,
+        );
+    }
+}