Extend question_mark to cover else if (#16455)

Closes rust-lang/rust-clippy#16429

changelog: [`question_mark`] enhance to cover `else if`

clippy_lints/src/question_mark.rs

@@ -474,7 +474,6 @@ fn check_if_let_some_or_err_and_early_return<'tcx>(cx: &LateContext<'tcx>, expr:
         if_else,
         ..
     }) = higher::IfLet::hir(cx, expr)
-        && !is_else_clause(cx.tcx, expr)
         && let PatKind::TupleStruct(ref path1, [field], ddpos) = let_pat.kind
         && ddpos.as_opt_usize().is_none()
         && let PatKind::Binding(BindingMode(by_ref, _), bind_id, ident, None) = field.kind
@@ -509,10 +508,15 @@ fn check_if_let_some_or_err_and_early_return<'tcx>(cx: &LateContext<'tcx>, expr:
             ByRef::Yes(_, Mutability::Not) => ".as_ref()",
             ByRef::No => "",
         };
-        let sugg = format!(
+
+        let mut sugg = format!(
             "{receiver_str}{method_call_str}?{}",
             if requires_semi { ";" } else { "" }
         );
+        if is_else_clause(cx.tcx, expr) {
+            sugg = format!("{{ {sugg} }}");
+        }
+
         span_lint_and_sugg(
             cx,
             QUESTION_MARK,

tests/ui/question_mark.fixed

@@ -515,3 +515,12 @@ fn wrongly_unmangled_macros() -> Option<i32> {
     test_expr!(42)?;
     test_expr!(42)
 }
+
+fn issue16429(b: i32) -> Option<i32> {
+    let a = Some(5);
+    let _ = if b == 1 {
+        b
+    } else { a? };
+
+    Some(0)
+}

tests/ui/question_mark.rs

@@ -635,3 +635,17 @@ macro_rules! test_expr {
     }
     test_expr!(42)
 }
+
+fn issue16429(b: i32) -> Option<i32> {
+    let a = Some(5);
+    let _ = if b == 1 {
+        b
+    } else if let Some(x) = a {
+        //~^ question_mark
+        x
+    } else {
+        return None;
+    };
+
+    Some(0)
+}

tests/ui/question_mark.stderr

@@ -350,5 +350,17 @@ LL | |         return None;
 LL | |     }
    | |_____^ help: replace it with: `test_expr!(42)?;`
 
-error: aborting due to 37 previous errors
+error: this block may be rewritten with the `?` operator
+  --> tests/ui/question_mark.rs:643:12
+   |
+LL |       } else if let Some(x) = a {
+   |  ____________^
+LL | |
+LL | |         x
+LL | |     } else {
+LL | |         return None;
+LL | |     };
+   | |_____^ help: replace it with: `{ a? }`
+
+error: aborting due to 38 previous errors