1 use clippy_utils::diagnostics::span_lint_and_sugg;
2 use clippy_utils::is_lang_ctor;
3 use clippy_utils::source::snippet;
4 use if_chain::if_chain;
5 use rustc_errors::Applicability;
6 use rustc_hir::LangItem::{OptionSome, ResultOk};
7 use rustc_hir::{Body, Expr, ExprKind, LangItem, MatchSource, QPath};
8 use rustc_lint::{LateContext, LateLintPass};
9 use rustc_middle::ty::TyS;
10 use rustc_session::{declare_lint_pass, declare_tool_lint};
12 declare_clippy_lint! {
14 /// Suggests alternatives for useless applications of `?` in terminating expressions
16 /// ### Why is this bad?
17 /// There's no reason to use `?` to short-circuit when execution of the body will end there anyway.
22 /// magic: Option<usize>,
25 /// fn f(to: TO) -> Option<usize> {
30 /// magic: Result<usize, bool>,
33 /// fn g(tr: Result<TR, bool>) -> Result<usize, bool> {
34 /// tr.and_then(|t| Ok(t.magic?))
41 /// magic: Option<usize>,
44 /// fn f(to: TO) -> Option<usize> {
49 /// magic: Result<usize, bool>,
52 /// fn g(tr: Result<TR, bool>) -> Result<usize, bool> {
53 /// tr.and_then(|t| t.magic)
56 #[clippy::version = "1.51.0"]
57 pub NEEDLESS_QUESTION_MARK,
59 "Suggest `value.inner_option` instead of `Some(value.inner_option?)`. The same goes for `Result<T, E>`."
62 declare_lint_pass!(NeedlessQuestionMark => [NEEDLESS_QUESTION_MARK]);
64 impl LateLintPass<'_> for NeedlessQuestionMark {
66 * The question mark operator is compatible with both Result<T, E> and Option<T>,
67 * from Rust 1.13 and 1.22 respectively.
72 * Expressions that look like this:
73 * Some(option?), Ok(result?)
76 * Last expression of a body
78 * A body's value (single line closure)
80 * What do we not match:
81 * Implicit calls to `from(..)` on the error value
84 fn check_expr(&mut self, cx: &LateContext<'_>, expr: &'_ Expr<'_>) {
85 if let ExprKind::Ret(Some(e)) = expr.kind {
90 fn check_body(&mut self, cx: &LateContext<'_>, body: &'_ Body<'_>) {
91 check(cx, body.value.peel_blocks());
95 fn check(cx: &LateContext<'_>, expr: &Expr<'_>) {
97 if let ExprKind::Call(path, [arg]) = &expr.kind;
98 if let ExprKind::Path(ref qpath) = &path.kind;
99 let sugg_remove = if is_lang_ctor(cx, qpath, OptionSome) {
101 } else if is_lang_ctor(cx, qpath, ResultOk) {
106 if let ExprKind::Match(inner_expr_with_q, _, MatchSource::TryDesugar) = &arg.kind;
107 if let ExprKind::Call(called, [inner_expr]) = &inner_expr_with_q.kind;
108 if let ExprKind::Path(QPath::LangItem(LangItem::TryTraitBranch, ..)) = &called.kind;
109 if expr.span.ctxt() == inner_expr.span.ctxt();
110 let expr_ty = cx.typeck_results().expr_ty(expr);
111 let inner_ty = cx.typeck_results().expr_ty(inner_expr);
112 if TyS::same_type(expr_ty, inner_ty);
116 NEEDLESS_QUESTION_MARK,
118 "question mark operator is useless here",
119 &format!("try removing question mark and `{}`", sugg_remove),
120 format!("{}", snippet(cx, inner_expr.span, r#""...""#)),
121 Applicability::MachineApplicable,