fix: unnecessary_filter_map return of Some arg

clippy_lints/src/methods/unnecessary_filter_map.rs

@@ -3,11 +3,12 @@ use clippy_utils::diagnostics::span_lint;
 use clippy_utils::ty::is_copy;
 use clippy_utils::usage::mutated_variables;
 use clippy_utils::visitors::{for_each_expr, Descend};
-use clippy_utils::{is_res_lang_ctor, is_trait_method, path_res, path_to_local_id};
+use clippy_utils::{is_res_lang_ctor, is_trait_method, path_res, path_to_local_id, MaybePath};
 use core::ops::ControlFlow;
 use rustc_hir as hir;
 use rustc_hir::LangItem::{OptionNone, OptionSome};
 use rustc_lint::LateContext;
+use rustc_middle::query::Key;
 use rustc_middle::ty;
 use rustc_span::sym;
 
@@ -17,7 +18,6 @@ pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'tcx>, a
     if !is_trait_method(cx, expr, sym::Iterator) {
         return;
     }
-
     if let hir::ExprKind::Closure(&hir::Closure { body, .. }) = arg.kind {
         let body = cx.tcx.hir().body(body);
         let arg_id = body.params[0].pat.hir_id;
@@ -36,9 +36,20 @@ pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'tcx>, a
                 ControlFlow::Continue(Descend::Yes)
             }
         });
-
         let in_ty = cx.typeck_results().node_type(body.params[0].hir_id);
         let sugg = if !found_filtering {
+            // Check if the closure is .filter_map(|x| Some(x))
+            if name == "filter_map"
+                && let hir::ExprKind::Call(expr, args) = body.value.kind
+            {
+                if is_res_lang_ctor(cx, path_res(cx, expr), OptionSome)
+                    && arg_id.ty_def_id() == args[0].hir_id().ty_def_id()
+                {
+                    if let hir::ExprKind::Path(_) = args[0].kind {
+                        span_lint(cx, UNNECESSARY_FILTER_MAP, arg.span, &format!("{name} is unnecessary"))
+                    }
+                }
+            }
             if name == "filter_map" { "map" } else { "map(..).next()" }
         } else if !found_mapping && !mutates_arg && (!clone_or_copy_needed || is_copy(cx, in_ty)) {
             match cx.typeck_results().expr_ty(body.value).kind() {

tests/ui/unnecessary_filter_map.rs

@@ -1,3 +1,4 @@
+//@no-rustfix
 #![allow(dead_code)]
 
 fn main() {
@@ -21,6 +22,8 @@ fn main() {
     //~^ ERROR: this `.filter_map` can be written more simply using `.map`
 
     let _ = (0..4).filter_map(i32::checked_abs);
+
+    let _ = vec![Some(10), None].into_iter().filter_map(|x| Some(x));
 }
 
 fn filter_map_none_changes_item_type() -> impl Iterator<Item = bool> {

tests/ui/unnecessary_filter_map.stderr

@@ -1,5 +1,5 @@
 error: this `.filter_map` can be written more simply using `.filter`
-  --> tests/ui/unnecessary_filter_map.rs:4:13
+  --> tests/ui/unnecessary_filter_map.rs:5:13
    |
 LL |     let _ = (0..4).filter_map(|x| if x > 1 { Some(x) } else { None });
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -8,7 +8,7 @@ LL |     let _ = (0..4).filter_map(|x| if x > 1 { Some(x) } else { None });
    = help: to override `-D warnings` add `#[allow(clippy::unnecessary_filter_map)]`
 
 error: this `.filter_map` can be written more simply using `.filter`
-  --> tests/ui/unnecessary_filter_map.rs:7:13
+  --> tests/ui/unnecessary_filter_map.rs:8:13
    |
 LL |       let _ = (0..4).filter_map(|x| {
    |  _____________^
@@ -21,7 +21,7 @@ LL | |     });
    | |______^
 
 error: this `.filter_map` can be written more simply using `.filter`
-  --> tests/ui/unnecessary_filter_map.rs:14:13
+  --> tests/ui/unnecessary_filter_map.rs:15:13
    |
 LL |       let _ = (0..4).filter_map(|x| match x {
    |  _____________^
@@ -32,16 +32,37 @@ LL | |     });
    | |______^
 
 error: this `.filter_map` can be written more simply using `.map`
-  --> tests/ui/unnecessary_filter_map.rs:20:13
+  --> tests/ui/unnecessary_filter_map.rs:21:13
    |
 LL |     let _ = (0..4).filter_map(|x| Some(x + 1));
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
+error: filter_map is unnecessary
+  --> tests/ui/unnecessary_filter_map.rs:26:57
+   |
+LL |     let _ = vec![Some(10), None].into_iter().filter_map(|x| Some(x));
+   |                                                         ^^^^^^^^^^^
+
+error: this `.filter_map` can be written more simply using `.map`
+  --> tests/ui/unnecessary_filter_map.rs:26:13
+   |
+LL |     let _ = vec![Some(10), None].into_iter().filter_map(|x| Some(x));
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: redundant closure
+  --> tests/ui/unnecessary_filter_map.rs:26:57
+   |
+LL |     let _ = vec![Some(10), None].into_iter().filter_map(|x| Some(x));
+   |                                                         ^^^^^^^^^^^ help: replace the closure with the function itself: `Some`
+   |
+   = note: `-D clippy::redundant-closure` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(clippy::redundant_closure)]`
+
 error: this `.filter_map` can be written more simply using `.filter`
-  --> tests/ui/unnecessary_filter_map.rs:160:14
+  --> tests/ui/unnecessary_filter_map.rs:163:14
    |
 LL |     let _x = std::iter::once(1).filter_map(|n| (n > 1).then_some(n));
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 5 previous errors
+error: aborting due to 8 previous errors