Fix clippy::question_mark on let-else with cfg (#15082)

Fixes rust-lang/rust-clippy#13642

changelog: Fix false positive in [`question_mark`] when else branch of
let-else contains `#[cfg]`

clippy_lints/src/question_mark.rs

@@ -142,6 +142,7 @@ fn init_expr_can_use_question_mark(cx: &LateContext<'_>, init_expr: &Expr<'_>) -
         && let Some(ret) = find_let_else_ret_expression(els)
         && let Some(inner_pat) = pat_and_expr_can_be_question_mark(cx, pat, ret)
         && !span_contains_comment(cx.tcx.sess.source_map(), els.span)
+        && !span_contains_cfg(cx, els.span)
     {
         let mut applicability = Applicability::MaybeIncorrect;
         let init_expr_str = Sugg::hir_with_applicability(cx, init_expr, "..", &mut applicability).maybe_paren();

tests/ui/question_mark.fixed

@@ -453,3 +453,15 @@ fn const_in_pattern(x: Option<(i32, i32)>) -> Option<()> {
 
     None
 }
+
+fn issue_13642(x: Option<i32>) -> Option<()> {
+    let Some(x) = x else {
+        #[cfg(false)]
+        panic!();
+
+        #[cfg(true)]
+        return None;
+    };
+
+    None
+}

tests/ui/question_mark.rs

@@ -549,3 +549,15 @@ fn const_in_pattern(x: Option<(i32, i32)>) -> Option<()> {
 
     None
 }
+
+fn issue_13642(x: Option<i32>) -> Option<()> {
+    let Some(x) = x else {
+        #[cfg(false)]
+        panic!();
+
+        #[cfg(true)]
+        return None;
+    };
+
+    None
+}