From 2817c5fc14cbf44b07fae0d7fe9cec4c321b4705 Mon Sep 17 00:00:00 2001
From: Guillaume Gomez <guillaume1.gomez@gmail.com>
Date: Mon, 20 Nov 2023 14:54:20 +0100
Subject: [PATCH] Extend `result_map_or_into_option` lint to handle
 `Result::map_or_else(|_| None, Some)`

---
 clippy_lints/src/methods/mod.rs               |  4 ++
 .../src/methods/result_map_or_else_none.rs    | 46 +++++++++++++++++++
 2 files changed, 50 insertions(+)
 create mode 100644 clippy_lints/src/methods/result_map_or_else_none.rs

diff --git a/clippy_lints/src/methods/mod.rs b/clippy_lints/src/methods/mod.rs
index 82cd3ac0486d..71de77acfc1d 100644
--- a/clippy_lints/src/methods/mod.rs
+++ b/clippy_lints/src/methods/mod.rs
@@ -81,6 +81,7 @@ 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;
@@ -4335,6 +4336,9 @@ impl Methods {
                     option_map_or_none::check(cx, expr, recv, def, map);
                     manual_ok_or::check(cx, expr, recv, def, map);
                 },
+                ("map_or_else", [def, map]) => {
+                    result_map_or_else_none::check(cx, expr, recv, def, map);
+                },
                 ("next", []) => {
                     if let Some((name2, recv2, args2, _, _)) = method_call(recv) {
                         match (name2, args2) {
diff --git a/clippy_lints/src/methods/result_map_or_else_none.rs b/clippy_lints/src/methods/result_map_or_else_none.rs
new file mode 100644
index 000000000000..b0e3ca367b45
--- /dev/null
+++ b/clippy_lints/src/methods/result_map_or_else_none.rs
@@ -0,0 +1,46 @@
+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, peel_blocks};
+use rustc_errors::Applicability;
+use rustc_hir as hir;
+use rustc_hir::LangItem::{OptionNone, OptionSome};
+use rustc_lint::LateContext;
+use rustc_span::symbol::sym;
+
+use super::RESULT_MAP_OR_INTO_OPTION;
+
+/// lint use of `_.map_or_else(|_| None, Some)` for `Result`s
+pub(super) fn check<'tcx>(
+    cx: &LateContext<'tcx>,
+    expr: &'tcx hir::Expr<'_>,
+    recv: &'tcx hir::Expr<'_>,
+    def_arg: &'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
+        && let hir::ExprKind::Closure(&hir::Closure { body, .. }) = def_arg.kind
+        && let body = cx.tcx.hir().body(body)
+        && is_res_lang_ctor(cx, path_res(cx, peel_blocks(body.value)), OptionNone)
+    {
+        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,
+        );
+    }
+}