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, type_is_unsafe_function};
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, BlockCheckMode, Expr, ExprKind, HirId, Mutability, Pat, PatKind, Path,
17 use rustc_lint::{LateContext, LateLintPass, LintContext};
18 use rustc_middle::lint::in_external_macro;
19 use rustc_session::{declare_lint_pass, declare_tool_lint};
20 use rustc_span::{sym, SyntaxContext};
22 declare_clippy_lint! {
24 /// Checks for usages of `match` which could be implemented using `map`
26 /// ### Why is this bad?
27 /// Using the `map` method is clearer and more concise.
32 /// Some(x) => Some(x + 1),
38 /// Some(0).map(|x| x + 1);
40 #[clippy::version = "1.52.0"]
43 "reimplementation of `map`"
46 declare_lint_pass!(ManualMap => [MANUAL_MAP]);
48 impl LateLintPass<'_> for ManualMap {
49 #[allow(clippy::too_many_lines)]
50 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
51 let (scrutinee, then_pat, then_body, else_pat, else_body) = match IfLetOrMatch::parse(cx, expr) {
52 Some(IfLetOrMatch::IfLet(scrutinee, pat, body, Some(r#else))) => (scrutinee, pat, body, None, r#else),
53 Some(IfLetOrMatch::Match(
55 [arm1 @ Arm { guard: None, .. }, arm2 @ Arm { guard: None, .. }],
57 )) => (scrutinee, arm1.pat, arm1.body, Some(arm2.pat), arm2.body),
60 if in_external_macro(cx.sess(), expr.span) || in_constant(cx, expr.hir_id) {
64 let (scrutinee_ty, ty_ref_count, ty_mutability) =
65 peel_mid_ty_refs_is_mutable(cx.typeck_results().expr_ty(scrutinee));
66 if !(is_type_diagnostic_item(cx, scrutinee_ty, sym::Option)
67 && is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(expr), sym::Option))
72 let expr_ctxt = expr.span.ctxt();
73 let (some_expr, some_pat, pat_ref_count, is_wild_none) = match (
74 try_parse_pattern(cx, then_pat, expr_ctxt),
75 else_pat.map_or(Some(OptionPat::Wild), |p| try_parse_pattern(cx, p, expr_ctxt)),
77 (Some(OptionPat::Wild), Some(OptionPat::Some { pattern, ref_count })) if is_none_expr(cx, then_body) => {
78 (else_body, pattern, ref_count, true)
80 (Some(OptionPat::None), Some(OptionPat::Some { pattern, ref_count })) if is_none_expr(cx, then_body) => {
81 (else_body, pattern, ref_count, false)
83 (Some(OptionPat::Some { pattern, ref_count }), Some(OptionPat::Wild)) if is_none_expr(cx, else_body) => {
84 (then_body, pattern, ref_count, true)
86 (Some(OptionPat::Some { pattern, ref_count }), Some(OptionPat::None)) if is_none_expr(cx, else_body) => {
87 (then_body, pattern, ref_count, false)
92 // Top level or patterns aren't allowed in closures.
93 if matches!(some_pat.kind, PatKind::Or(_)) {
97 let some_expr = match get_some_expr(cx, some_expr, false, expr_ctxt) {
102 // These two lints will go back and forth with each other.
103 if cx.typeck_results().expr_ty(some_expr.expr) == cx.tcx.types.unit
104 && !is_lint_allowed(cx, OPTION_MAP_UNIT_FN, expr.hir_id)
109 // `map` won't perform any adjustments.
110 if !cx.typeck_results().expr_adjustments(some_expr.expr).is_empty() {
114 // Determine which binding mode to use.
115 let explicit_ref = some_pat.contains_explicit_ref_binding();
116 let binding_ref = explicit_ref.or_else(|| (ty_ref_count != pat_ref_count).then(|| ty_mutability));
118 let as_ref_str = match binding_ref {
119 Some(Mutability::Mut) => ".as_mut()",
120 Some(Mutability::Not) => ".as_ref()",
124 match can_move_expr_to_closure(cx, some_expr.expr) {
126 // Check if captures the closure will need conflict with borrows made in the scrutinee.
127 // TODO: check all the references made in the scrutinee expression. This will require interacting
128 // with the borrow checker. Currently only `<local>[.<field>]*` is checked for.
129 if let Some(binding_ref_mutability) = binding_ref {
130 let e = peel_hir_expr_while(scrutinee, |e| match e.kind {
131 ExprKind::Field(e, _) | ExprKind::AddrOf(_, _, e) => Some(e),
134 if let ExprKind::Path(QPath::Resolved(None, Path { res: Res::Local(l), .. })) = e.kind {
135 match captures.get(l) {
136 Some(CaptureKind::Value | CaptureKind::Ref(Mutability::Mut)) => return,
137 Some(CaptureKind::Ref(Mutability::Not)) if binding_ref_mutability == Mutability::Mut => {
140 Some(CaptureKind::Ref(Mutability::Not)) | None => (),
148 let mut app = Applicability::MachineApplicable;
150 // Remove address-of expressions from the scrutinee. Either `as_ref` will be called, or
151 // it's being passed by value.
152 let scrutinee = peel_hir_expr_refs(scrutinee).0;
153 let (scrutinee_str, _) = snippet_with_context(cx, scrutinee.span, expr_ctxt, "..", &mut app);
155 if scrutinee.span.ctxt() == expr.span.ctxt() && scrutinee.precedence().order() < PREC_POSTFIX {
156 format!("({})", scrutinee_str)
161 let body_str = if let PatKind::Binding(annotation, id, some_binding, None) = some_pat.kind {
163 if !some_expr.needs_unsafe_block;
164 if let Some(func) = can_pass_as_func(cx, id, some_expr.expr);
165 if func.span.ctxt() == some_expr.expr.span.ctxt();
167 snippet_with_applicability(cx, func.span, "..", &mut app).into_owned()
169 if path_to_local_id(some_expr.expr, id)
170 && !is_lint_allowed(cx, MATCH_AS_REF, expr.hir_id)
171 && binding_ref.is_some()
176 // `ref` and `ref mut` annotations were handled earlier.
177 let annotation = if matches!(annotation, BindingAnnotation::Mutable) {
182 let expr_snip = snippet_with_context(cx, some_expr.expr.span, expr_ctxt, "..", &mut app).0;
183 if some_expr.needs_unsafe_block {
184 format!("|{}{}| unsafe {{ {} }}", annotation, some_binding, expr_snip)
186 format!("|{}{}| {}", annotation, some_binding, expr_snip)
190 } else if !is_wild_none && explicit_ref.is_none() {
191 // TODO: handle explicit reference annotations.
192 let pat_snip = snippet_with_context(cx, some_pat.span, expr_ctxt, "..", &mut app).0;
193 let expr_snip = snippet_with_context(cx, some_expr.expr.span, expr_ctxt, "..", &mut app).0;
194 if some_expr.needs_unsafe_block {
195 format!("|{}| unsafe {{ {} }}", pat_snip, expr_snip)
197 format!("|{}| {}", pat_snip, expr_snip)
200 // Refutable bindings and mixed reference annotations can't be handled by `map`.
208 "manual implementation of `Option::map`",
210 if else_pat.is_none() && is_else_clause(cx.tcx, expr) {
211 format!("{{ {}{}.map({}) }}", scrutinee_str, as_ref_str, body_str)
213 format!("{}{}.map({})", scrutinee_str, as_ref_str, body_str)
220 // Checks whether the expression could be passed as a function, or whether a closure is needed.
221 // Returns the function to be passed to `map` if it exists.
222 fn can_pass_as_func(cx: &LateContext<'tcx>, binding: HirId, expr: &'tcx Expr<'_>) -> Option<&'tcx Expr<'tcx>> {
224 ExprKind::Call(func, [arg])
225 if path_to_local_id(arg, binding)
226 && cx.typeck_results().expr_adjustments(arg).is_empty()
227 && !type_is_unsafe_function(cx, cx.typeck_results().expr_ty(func).peel_refs()) =>
239 // The pattern contained in the `Some` tuple.
240 pattern: &'a Pat<'a>,
241 // The number of references before the `Some` tuple.
242 // e.g. `&&Some(_)` has a ref count of 2.
247 struct SomeExpr<'tcx> {
248 expr: &'tcx Expr<'tcx>,
249 needs_unsafe_block: bool,
252 // Try to parse into a recognized `Option` pattern.
253 // i.e. `_`, `None`, `Some(..)`, or a reference to any of those.
254 fn try_parse_pattern(cx: &LateContext<'tcx>, pat: &'tcx Pat<'_>, ctxt: SyntaxContext) -> Option<OptionPat<'tcx>> {
255 fn f(cx: &LateContext<'tcx>, pat: &'tcx Pat<'_>, ref_count: usize, ctxt: SyntaxContext) -> Option<OptionPat<'tcx>> {
257 PatKind::Wild => Some(OptionPat::Wild),
258 PatKind::Ref(pat, _) => f(cx, pat, ref_count + 1, ctxt),
259 PatKind::Path(ref qpath) if is_lang_ctor(cx, qpath, OptionNone) => Some(OptionPat::None),
260 PatKind::TupleStruct(ref qpath, [pattern], _)
261 if is_lang_ctor(cx, qpath, OptionSome) && pat.span.ctxt() == ctxt =>
263 Some(OptionPat::Some { pattern, ref_count })
271 // Checks for an expression wrapped by the `Some` constructor. Returns the contained expression.
273 cx: &LateContext<'tcx>,
274 expr: &'tcx Expr<'_>,
275 needs_unsafe_block: bool,
277 ) -> Option<SomeExpr<'tcx>> {
278 // TODO: Allow more complex expressions.
282 kind: ExprKind::Path(ref qpath),
286 ) if ctxt == expr.span.ctxt() && is_lang_ctor(cx, qpath, OptionSome) => Some(SomeExpr {
301 needs_unsafe_block || *rules == BlockCheckMode::UnsafeBlock(UnsafeSource::UserProvided),
308 // Checks for the `None` value.
309 fn is_none_expr(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> bool {
311 ExprKind::Path(ref qpath) => is_lang_ctor(cx, qpath, OptionNone),
319 ) => is_none_expr(cx, expr),