1 use clippy_utils::diagnostics::span_lint_and_sugg;
2 use clippy_utils::sugg::Sugg;
4 can_move_expr_to_closure, eager_or_lazy, higher, in_constant, is_else_clause, is_res_lang_ctor, peel_blocks,
5 peel_hir_expr_while, CaptureKind,
7 use if_chain::if_chain;
8 use rustc_errors::Applicability;
9 use rustc_hir::LangItem::{OptionNone, OptionSome, ResultErr, ResultOk};
11 def::Res, Arm, BindingAnnotation, Expr, ExprKind, MatchSource, Mutability, Pat, PatKind, Path, QPath, UnOp,
13 use rustc_lint::{LateContext, LateLintPass};
14 use rustc_session::{declare_lint_pass, declare_tool_lint};
16 declare_clippy_lint! {
18 /// Lints usage of `if let Some(v) = ... { y } else { x }` and
19 /// `match .. { Some(v) => y, None/_ => x }` which are more
20 /// idiomatically done with `Option::map_or` (if the else bit is a pure
21 /// expression) or `Option::map_or_else` (if the else bit is an impure
24 /// ### Why is this bad?
25 /// Using the dedicated functions of the `Option` type is clearer and
26 /// more concise than an `if let` expression.
28 /// ### Known problems
29 /// This lint uses a deliberately conservative metric for checking
30 /// if the inside of either body contains breaks or continues which will
31 /// cause it to not suggest a fix if either block contains a loop with
32 /// continues or breaks contained within the loop.
36 /// # let optional: Option<u32> = Some(0);
37 /// # fn do_complicated_function() -> u32 { 5 };
38 /// let _ = if let Some(foo) = optional {
43 /// let _ = match optional {
44 /// Some(val) => val + 1,
47 /// let _ = if let Some(foo) = optional {
50 /// let y = do_complicated_function();
58 /// # let optional: Option<u32> = Some(0);
59 /// # fn do_complicated_function() -> u32 { 5 };
60 /// let _ = optional.map_or(5, |foo| foo);
61 /// let _ = optional.map_or(5, |val| val + 1);
62 /// let _ = optional.map_or_else(||{
63 /// let y = do_complicated_function();
67 // FIXME: Before moving this lint out of nursery, the lint name needs to be updated. It now also
68 // covers matches and `Result`.
69 #[clippy::version = "1.47.0"]
70 pub OPTION_IF_LET_ELSE,
72 "reimplementation of Option::map_or"
75 declare_lint_pass!(OptionIfLetElse => [OPTION_IF_LET_ELSE]);
77 /// A struct containing information about occurrences of construct that this lint detects
82 /// if let Some(..) = {..} else {..}
91 struct OptionOccurrence {
98 fn format_option_in_sugg(cx: &LateContext<'_>, cond_expr: &Expr<'_>, as_ref: bool, as_mut: bool) -> String {
101 Sugg::hir_with_macro_callsite(cx, cond_expr, "..").maybe_par(),
112 fn try_get_option_occurrence<'tcx>(
113 cx: &LateContext<'tcx>,
116 if_then: &'tcx Expr<'_>,
117 if_else: &'tcx Expr<'_>,
118 ) -> Option<OptionOccurrence> {
119 let cond_expr = match expr.kind {
120 ExprKind::Unary(UnOp::Deref, inner_expr) | ExprKind::AddrOf(_, _, inner_expr) => inner_expr,
123 let inner_pat = try_get_inner_pat(cx, pat)?;
125 if let PatKind::Binding(bind_annotation, _, id, None) = inner_pat.kind;
126 if let Some(some_captures) = can_move_expr_to_closure(cx, if_then);
127 if let Some(none_captures) = can_move_expr_to_closure(cx, if_else);
130 .filter_map(|(id, &c)| none_captures.get(id).map(|&c2| (c, c2)))
131 .all(|(x, y)| x.is_imm_ref() && y.is_imm_ref());
133 let capture_mut = if bind_annotation == BindingAnnotation::MUT { "mut " } else { "" };
134 let some_body = peel_blocks(if_then);
135 let none_body = peel_blocks(if_else);
136 let method_sugg = if eager_or_lazy::switch_to_eager_eval(cx, none_body) { "map_or" } else { "map_or_else" };
137 let capture_name = id.name.to_ident_string();
138 let (as_ref, as_mut) = match &expr.kind {
139 ExprKind::AddrOf(_, Mutability::Not, _) => (true, false),
140 ExprKind::AddrOf(_, Mutability::Mut, _) => (false, true),
141 _ => (bind_annotation == BindingAnnotation::REF, bind_annotation == BindingAnnotation::REF_MUT),
144 // Check if captures the closure will need conflict with borrows made in the scrutinee.
145 // TODO: check all the references made in the scrutinee expression. This will require interacting
146 // with the borrow checker. Currently only `<local>[.<field>]*` is checked for.
147 if as_ref || as_mut {
148 let e = peel_hir_expr_while(cond_expr, |e| match e.kind {
149 ExprKind::Field(e, _) | ExprKind::AddrOf(_, _, e) => Some(e),
152 if let ExprKind::Path(QPath::Resolved(None, Path { res: Res::Local(local_id), .. })) = e.kind {
153 match some_captures.get(local_id)
154 .or_else(|| (method_sugg == "map_or_else").then_some(()).and_then(|_| none_captures.get(local_id)))
156 Some(CaptureKind::Value | CaptureKind::Ref(Mutability::Mut)) => return None,
157 Some(CaptureKind::Ref(Mutability::Not)) if as_mut => return None,
158 Some(CaptureKind::Ref(Mutability::Not)) | None => (),
163 return Some(OptionOccurrence {
164 option: format_option_in_sugg(cx, cond_expr, as_ref, as_mut),
165 method_sugg: method_sugg.to_string(),
166 some_expr: format!("|{capture_mut}{capture_name}| {}", Sugg::hir_with_macro_callsite(cx, some_body, "..")),
167 none_expr: format!("{}{}", if method_sugg == "map_or" { "" } else { "|| " }, Sugg::hir_with_macro_callsite(cx, none_body, "..")),
175 fn try_get_inner_pat<'tcx>(cx: &LateContext<'tcx>, pat: &Pat<'tcx>) -> Option<&'tcx Pat<'tcx>> {
176 if let PatKind::TupleStruct(ref qpath, [inner_pat], ..) = pat.kind {
177 let res = cx.qpath_res(qpath, pat.hir_id);
178 if is_res_lang_ctor(cx, res, OptionSome) || is_res_lang_ctor(cx, res, ResultOk) {
179 return Some(inner_pat);
185 /// If this expression is the option if let/else construct we're detecting, then
186 /// this function returns an `OptionOccurrence` struct with details if
187 /// this construct is found, or None if this construct is not found.
188 fn detect_option_if_let_else<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'tcx>) -> Option<OptionOccurrence> {
189 if let Some(higher::IfLet {
193 if_else: Some(if_else),
194 }) = higher::IfLet::hir(cx, expr)
196 if !is_else_clause(cx.tcx, expr) {
197 return try_get_option_occurrence(cx, let_pat, let_expr, if_then, if_else);
203 fn detect_option_match<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'tcx>) -> Option<OptionOccurrence> {
204 if let ExprKind::Match(ex, arms, MatchSource::Normal) = expr.kind {
205 if let Some((let_pat, if_then, if_else)) = try_convert_match(cx, arms) {
206 return try_get_option_occurrence(cx, let_pat, ex, if_then, if_else);
212 fn try_convert_match<'tcx>(
213 cx: &LateContext<'tcx>,
215 ) -> Option<(&'tcx Pat<'tcx>, &'tcx Expr<'tcx>, &'tcx Expr<'tcx>)> {
216 if let [first_arm, second_arm] = arms
217 && first_arm.guard.is_none()
218 && second_arm.guard.is_none()
220 return if is_none_or_err_arm(cx, second_arm) {
221 Some((first_arm.pat, first_arm.body, second_arm.body))
222 } else if is_none_or_err_arm(cx, first_arm) {
223 Some((second_arm.pat, second_arm.body, first_arm.body))
231 fn is_none_or_err_arm(cx: &LateContext<'_>, arm: &Arm<'_>) -> bool {
233 PatKind::Path(ref qpath) => is_res_lang_ctor(cx, cx.qpath_res(qpath, arm.pat.hir_id), OptionNone),
234 PatKind::TupleStruct(ref qpath, [first_pat], _) => {
235 is_res_lang_ctor(cx, cx.qpath_res(qpath, arm.pat.hir_id), ResultErr)
236 && matches!(first_pat.kind, PatKind::Wild)
238 PatKind::Wild => true,
243 impl<'tcx> LateLintPass<'tcx> for OptionIfLetElse {
244 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &Expr<'tcx>) {
245 // Don't lint macros and constants
246 if expr.span.from_expansion() || in_constant(cx, expr.hir_id) {
250 let detection = detect_option_if_let_else(cx, expr).or_else(|| detect_option_match(cx, expr));
251 if let Some(det) = detection {
256 format!("use Option::{} instead of an if let/else", det.method_sugg).as_str(),
260 det.option, det.method_sugg, det.none_expr, det.some_expr
262 Applicability::MaybeIncorrect,