1 use crate::{map_unit_fn::OPTION_MAP_UNIT_FN, matches::MATCH_AS_REF};
2 use clippy_utils::diagnostics::span_lint_and_sugg;
3 use clippy_utils::higher::IfLetOrMatch;
4 use clippy_utils::source::{snippet_with_applicability, snippet_with_context};
5 use clippy_utils::ty::{is_type_diagnostic_item, peel_mid_ty_refs_is_mutable};
7 can_move_expr_to_closure, in_constant, is_else_clause, is_lang_ctor, is_lint_allowed, path_to_local_id,
8 peel_hir_expr_refs, peel_hir_expr_while, CaptureKind,
10 use rustc_ast::util::parser::PREC_POSTFIX;
11 use rustc_errors::Applicability;
12 use rustc_hir::LangItem::{OptionNone, OptionSome};
14 def::Res, Arm, BindingAnnotation, Block, Expr, ExprKind, HirId, Mutability, Pat, PatKind, Path, QPath,
16 use rustc_lint::{LateContext, LateLintPass, LintContext};
17 use rustc_middle::lint::in_external_macro;
18 use rustc_session::{declare_lint_pass, declare_tool_lint};
19 use rustc_span::{sym, SyntaxContext};
21 declare_clippy_lint! {
23 /// Checks for usages of `match` which could be implemented using `map`
25 /// ### Why is this bad?
26 /// Using the `map` method is clearer and more concise.
31 /// Some(x) => Some(x + 1),
37 /// Some(0).map(|x| x + 1);
41 "reimplementation of `map`"
44 declare_lint_pass!(ManualMap => [MANUAL_MAP]);
46 impl LateLintPass<'_> for ManualMap {
47 #[allow(clippy::too_many_lines)]
48 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
49 let (scrutinee, then_pat, then_body, else_pat, else_body) = match IfLetOrMatch::parse(cx, expr) {
50 Some(IfLetOrMatch::IfLet(scrutinee, pat, body, Some(r#else))) => (scrutinee, pat, body, None, r#else),
51 Some(IfLetOrMatch::Match(
53 [arm1 @ Arm { guard: None, .. }, arm2 @ Arm { guard: None, .. }],
55 )) => (scrutinee, arm1.pat, arm1.body, Some(arm2.pat), arm2.body),
58 if in_external_macro(cx.sess(), expr.span) || in_constant(cx, expr.hir_id) {
62 let (scrutinee_ty, ty_ref_count, ty_mutability) =
63 peel_mid_ty_refs_is_mutable(cx.typeck_results().expr_ty(scrutinee));
64 if !(is_type_diagnostic_item(cx, scrutinee_ty, sym::option_type)
65 && is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(expr), sym::option_type))
70 let expr_ctxt = expr.span.ctxt();
71 let (some_expr, some_pat, pat_ref_count, is_wild_none) = match (
72 try_parse_pattern(cx, then_pat, expr_ctxt),
73 else_pat.map_or(Some(OptionPat::Wild), |p| try_parse_pattern(cx, p, expr_ctxt)),
75 (Some(OptionPat::Wild), Some(OptionPat::Some { pattern, ref_count })) if is_none_expr(cx, then_body) => {
76 (else_body, pattern, ref_count, true)
78 (Some(OptionPat::None), Some(OptionPat::Some { pattern, ref_count })) if is_none_expr(cx, then_body) => {
79 (else_body, pattern, ref_count, false)
81 (Some(OptionPat::Some { pattern, ref_count }), Some(OptionPat::Wild)) if is_none_expr(cx, else_body) => {
82 (then_body, pattern, ref_count, true)
84 (Some(OptionPat::Some { pattern, ref_count }), Some(OptionPat::None)) if is_none_expr(cx, else_body) => {
85 (then_body, pattern, ref_count, false)
90 // Top level or patterns aren't allowed in closures.
91 if matches!(some_pat.kind, PatKind::Or(_)) {
95 let some_expr = match get_some_expr(cx, some_expr, expr_ctxt) {
100 // These two lints will go back and forth with each other.
101 if cx.typeck_results().expr_ty(some_expr) == cx.tcx.types.unit
102 && !is_lint_allowed(cx, OPTION_MAP_UNIT_FN, expr.hir_id)
107 // `map` won't perform any adjustments.
108 if !cx.typeck_results().expr_adjustments(some_expr).is_empty() {
112 // Determine which binding mode to use.
113 let explicit_ref = some_pat.contains_explicit_ref_binding();
114 let binding_ref = explicit_ref.or_else(|| (ty_ref_count != pat_ref_count).then(|| ty_mutability));
116 let as_ref_str = match binding_ref {
117 Some(Mutability::Mut) => ".as_mut()",
118 Some(Mutability::Not) => ".as_ref()",
122 match can_move_expr_to_closure(cx, some_expr) {
124 // Check if captures the closure will need conflict with borrows made in the scrutinee.
125 // TODO: check all the references made in the scrutinee expression. This will require interacting
126 // with the borrow checker. Currently only `<local>[.<field>]*` is checked for.
127 if let Some(binding_ref_mutability) = binding_ref {
128 let e = peel_hir_expr_while(scrutinee, |e| match e.kind {
129 ExprKind::Field(e, _) | ExprKind::AddrOf(_, _, e) => Some(e),
132 if let ExprKind::Path(QPath::Resolved(None, Path { res: Res::Local(l), .. })) = e.kind {
133 match captures.get(l) {
134 Some(CaptureKind::Value | CaptureKind::Ref(Mutability::Mut)) => return,
135 Some(CaptureKind::Ref(Mutability::Not)) if binding_ref_mutability == Mutability::Mut => {
138 Some(CaptureKind::Ref(Mutability::Not)) | None => (),
146 let mut app = Applicability::MachineApplicable;
148 // Remove address-of expressions from the scrutinee. Either `as_ref` will be called, or
149 // it's being passed by value.
150 let scrutinee = peel_hir_expr_refs(scrutinee).0;
151 let (scrutinee_str, _) = snippet_with_context(cx, scrutinee.span, expr_ctxt, "..", &mut app);
153 if scrutinee.span.ctxt() == expr.span.ctxt() && scrutinee.precedence().order() < PREC_POSTFIX {
154 format!("({})", scrutinee_str)
159 let body_str = if let PatKind::Binding(annotation, id, some_binding, None) = some_pat.kind {
160 match can_pass_as_func(cx, id, some_expr) {
161 Some(func) if func.span.ctxt() == some_expr.span.ctxt() => {
162 snippet_with_applicability(cx, func.span, "..", &mut app).into_owned()
165 if path_to_local_id(some_expr, id)
166 && !is_lint_allowed(cx, MATCH_AS_REF, expr.hir_id)
167 && binding_ref.is_some()
172 // `ref` and `ref mut` annotations were handled earlier.
173 let annotation = if matches!(annotation, BindingAnnotation::Mutable) {
182 snippet_with_context(cx, some_expr.span, expr_ctxt, "..", &mut app).0
186 } else if !is_wild_none && explicit_ref.is_none() {
187 // TODO: handle explicit reference annotations.
190 snippet_with_context(cx, some_pat.span, expr_ctxt, "..", &mut app).0,
191 snippet_with_context(cx, some_expr.span, expr_ctxt, "..", &mut app).0
194 // Refutable bindings and mixed reference annotations can't be handled by `map`.
202 "manual implementation of `Option::map`",
204 if else_pat.is_none() && is_else_clause(cx.tcx, expr) {
205 format!("{{ {}{}.map({}) }}", scrutinee_str, as_ref_str, body_str)
207 format!("{}{}.map({})", scrutinee_str, as_ref_str, body_str)
214 // Checks whether the expression could be passed as a function, or whether a closure is needed.
215 // Returns the function to be passed to `map` if it exists.
216 fn can_pass_as_func(cx: &LateContext<'tcx>, binding: HirId, expr: &'tcx Expr<'_>) -> Option<&'tcx Expr<'tcx>> {
218 ExprKind::Call(func, [arg])
219 if path_to_local_id(arg, binding) && cx.typeck_results().expr_adjustments(arg).is_empty() =>
231 // The pattern contained in the `Some` tuple.
232 pattern: &'a Pat<'a>,
233 // The number of references before the `Some` tuple.
234 // e.g. `&&Some(_)` has a ref count of 2.
239 // Try to parse into a recognized `Option` pattern.
240 // i.e. `_`, `None`, `Some(..)`, or a reference to any of those.
241 fn try_parse_pattern(cx: &LateContext<'tcx>, pat: &'tcx Pat<'_>, ctxt: SyntaxContext) -> Option<OptionPat<'tcx>> {
242 fn f(cx: &LateContext<'tcx>, pat: &'tcx Pat<'_>, ref_count: usize, ctxt: SyntaxContext) -> Option<OptionPat<'tcx>> {
244 PatKind::Wild => Some(OptionPat::Wild),
245 PatKind::Ref(pat, _) => f(cx, pat, ref_count + 1, ctxt),
246 PatKind::Path(ref qpath) if is_lang_ctor(cx, qpath, OptionNone) => Some(OptionPat::None),
247 PatKind::TupleStruct(ref qpath, [pattern], _)
248 if is_lang_ctor(cx, qpath, OptionSome) && pat.span.ctxt() == ctxt =>
250 Some(OptionPat::Some { pattern, ref_count })
258 // Checks for an expression wrapped by the `Some` constructor. Returns the contained expression.
259 fn get_some_expr(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, ctxt: SyntaxContext) -> Option<&'tcx Expr<'tcx>> {
260 // TODO: Allow more complex expressions.
264 kind: ExprKind::Path(ref qpath),
268 ) if ctxt == expr.span.ctxt() && is_lang_ctor(cx, qpath, OptionSome) => Some(arg),
276 ) => get_some_expr(cx, expr, ctxt),
281 // Checks for the `None` value.
282 fn is_none_expr(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> bool {
284 ExprKind::Path(ref qpath) => is_lang_ctor(cx, qpath, OptionNone),
292 ) => is_none_expr(cx, expr),