[unnecessary_find_map]: look for then_some

Author: y21

clippy_lints/src/methods/unnecessary_filter_map.rs

@@ -77,6 +77,16 @@ fn check_expression<'tcx>(cx: &LateContext<'tcx>, arg_id: hir::HirId, expr: &'tc
             }
             (true, true)
         },
+        hir::ExprKind::MethodCall(segment, recv, [arg], _) => {
+            if segment.ident.name == sym!(then_some)
+                && cx.typeck_results().expr_ty(recv).is_bool()
+                && path_to_local_id(arg, arg_id)
+            {
+                (false, true)
+            } else {
+                (true, true)
+            }
+        },
         hir::ExprKind::Block(block, _) => block
             .expr
             .as_ref()

tests/ui/unnecessary_find_map.rs

@@ -21,3 +21,7 @@ fn main() {
 fn find_map_none_changes_item_type() -> Option<bool> {
     "".chars().find_map(|_| None)
 }
+
+fn issue11260() {
+    let _x = std::iter::once(1).find_map(|n| (n > 1).then_some(n));
+}

tests/ui/unnecessary_find_map.stderr

@@ -34,5 +34,11 @@ error: this `.find_map` can be written more simply using `.map(..).next()`
 LL |     let _ = (0..4).find_map(|x| Some(x + 1));
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 4 previous errors
+error: this `.find_map` can be written more simply using `.find`
+  --> $DIR/unnecessary_find_map.rs:26:14
+   |
+LL |     let _x = std::iter::once(1).find_map(|n| (n > 1).then_some(n));
+   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 5 previous errors