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::source::{snippet_with_applicability, snippet_with_context};
4 use clippy_utils::ty::{is_type_diagnostic_item, peel_mid_ty_refs_is_mutable};
6 can_move_expr_to_closure, in_constant, is_allowed, is_else_clause, is_lang_ctor, match_var, peel_hir_expr_refs,
8 use rustc_ast::util::parser::PREC_POSTFIX;
9 use rustc_errors::Applicability;
10 use rustc_hir::LangItem::{OptionNone, OptionSome};
11 use rustc_hir::{Arm, BindingAnnotation, Block, Expr, ExprKind, MatchSource, Mutability, Pat, PatKind};
12 use rustc_lint::{LateContext, LateLintPass, LintContext};
13 use rustc_middle::lint::in_external_macro;
14 use rustc_session::{declare_lint_pass, declare_tool_lint};
20 declare_clippy_lint! {
21 /// **What it does:** Checks for usages of `match` which could be implemented using `map`
23 /// **Why is this bad?** Using the `map` method is clearer and more concise.
25 /// **Known problems:** None.
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 if let ExprKind::Match(
51 [arm1 @ Arm { guard: None, .. }, arm2 @ Arm { guard: None, .. }],
55 if in_external_macro(cx.sess(), expr.span) || in_constant(cx, expr.hir_id) {
59 let (scrutinee_ty, ty_ref_count, ty_mutability) =
60 peel_mid_ty_refs_is_mutable(cx.typeck_results().expr_ty(scrutinee));
61 if !(is_type_diagnostic_item(cx, scrutinee_ty, sym::option_type)
62 && is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(expr), sym::option_type))
67 let expr_ctxt = expr.span.ctxt();
68 let (some_expr, some_pat, pat_ref_count, is_wild_none) = match (
69 try_parse_pattern(cx, arm1.pat, expr_ctxt),
70 try_parse_pattern(cx, arm2.pat, expr_ctxt),
72 (Some(OptionPat::Wild), Some(OptionPat::Some { pattern, ref_count }))
73 if is_none_expr(cx, arm1.body) =>
75 (arm2.body, pattern, ref_count, true)
77 (Some(OptionPat::None), Some(OptionPat::Some { pattern, ref_count }))
78 if is_none_expr(cx, arm1.body) =>
80 (arm2.body, pattern, ref_count, false)
82 (Some(OptionPat::Some { pattern, ref_count }), Some(OptionPat::Wild))
83 if is_none_expr(cx, arm2.body) =>
85 (arm1.body, pattern, ref_count, true)
87 (Some(OptionPat::Some { pattern, ref_count }), Some(OptionPat::None))
88 if is_none_expr(cx, arm2.body) =>
90 (arm1.body, pattern, ref_count, false)
95 // Top level or patterns aren't allowed in closures.
96 if matches!(some_pat.kind, PatKind::Or(_)) {
100 let some_expr = match get_some_expr(cx, some_expr, expr_ctxt) {
105 // These two lints will go back and forth with each other.
106 if cx.typeck_results().expr_ty(some_expr) == cx.tcx.types.unit
107 && !is_allowed(cx, OPTION_MAP_UNIT_FN, expr.hir_id)
112 // `map` won't perform any adjustments.
113 if !cx.typeck_results().expr_adjustments(some_expr).is_empty() {
117 if !can_move_expr_to_closure(cx, some_expr) {
121 // Determine which binding mode to use.
122 let explicit_ref = some_pat.contains_explicit_ref_binding();
123 let binding_ref = explicit_ref.or_else(|| (ty_ref_count != pat_ref_count).then(|| ty_mutability));
125 let as_ref_str = match binding_ref {
126 Some(Mutability::Mut) => ".as_mut()",
127 Some(Mutability::Not) => ".as_ref()",
131 let mut app = Applicability::MachineApplicable;
133 // Remove address-of expressions from the scrutinee. Either `as_ref` will be called, or
134 // it's being passed by value.
135 let scrutinee = peel_hir_expr_refs(scrutinee).0;
136 let (scrutinee_str, _) = snippet_with_context(cx, scrutinee.span, expr_ctxt, "..", &mut app);
138 if scrutinee.span.ctxt() == expr.span.ctxt() && scrutinee.precedence().order() < PREC_POSTFIX {
139 format!("({})", scrutinee_str)
144 let body_str = if let PatKind::Binding(annotation, _, some_binding, None) = some_pat.kind {
145 match can_pass_as_func(cx, some_binding, some_expr) {
146 Some(func) if func.span.ctxt() == some_expr.span.ctxt() => {
147 snippet_with_applicability(cx, func.span, "..", &mut app).into_owned()
150 if match_var(some_expr, some_binding.name)
151 && !is_allowed(cx, MATCH_AS_REF, expr.hir_id)
152 && binding_ref.is_some()
157 // `ref` and `ref mut` annotations were handled earlier.
158 let annotation = if matches!(annotation, BindingAnnotation::Mutable) {
167 snippet_with_context(cx, some_expr.span, expr_ctxt, "..", &mut app).0
171 } else if !is_wild_none && explicit_ref.is_none() {
172 // TODO: handle explicit reference annotations.
175 snippet_with_context(cx, some_pat.span, expr_ctxt, "..", &mut app).0,
176 snippet_with_context(cx, some_expr.span, expr_ctxt, "..", &mut app).0
179 // Refutable bindings and mixed reference annotations can't be handled by `map`.
187 "manual implementation of `Option::map`",
189 if matches!(match_kind, MatchSource::IfLetDesugar { .. }) && is_else_clause(cx.tcx, expr) {
190 format!("{{ {}{}.map({}) }}", scrutinee_str, as_ref_str, body_str)
192 format!("{}{}.map({})", scrutinee_str, as_ref_str, body_str)
200 // Checks whether the expression could be passed as a function, or whether a closure is needed.
201 // Returns the function to be passed to `map` if it exists.
202 fn can_pass_as_func(cx: &LateContext<'tcx>, binding: Ident, expr: &'tcx Expr<'_>) -> Option<&'tcx Expr<'tcx>> {
204 ExprKind::Call(func, [arg])
205 if match_var(arg, binding.name) && cx.typeck_results().expr_adjustments(arg).is_empty() =>
217 // The pattern contained in the `Some` tuple.
218 pattern: &'a Pat<'a>,
219 // The number of references before the `Some` tuple.
220 // e.g. `&&Some(_)` has a ref count of 2.
225 // Try to parse into a recognized `Option` pattern.
226 // i.e. `_`, `None`, `Some(..)`, or a reference to any of those.
227 fn try_parse_pattern(cx: &LateContext<'tcx>, pat: &'tcx Pat<'_>, ctxt: SyntaxContext) -> Option<OptionPat<'tcx>> {
228 fn f(cx: &LateContext<'tcx>, pat: &'tcx Pat<'_>, ref_count: usize, ctxt: SyntaxContext) -> Option<OptionPat<'tcx>> {
230 PatKind::Wild => Some(OptionPat::Wild),
231 PatKind::Ref(pat, _) => f(cx, pat, ref_count + 1, ctxt),
232 PatKind::Path(ref qpath) if is_lang_ctor(cx, qpath, OptionNone) => Some(OptionPat::None),
233 PatKind::TupleStruct(ref qpath, [pattern], _)
234 if is_lang_ctor(cx, qpath, OptionSome) && pat.span.ctxt() == ctxt =>
236 Some(OptionPat::Some { pattern, ref_count })
244 // Checks for an expression wrapped by the `Some` constructor. Returns the contained expression.
245 fn get_some_expr(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, ctxt: SyntaxContext) -> Option<&'tcx Expr<'tcx>> {
246 // TODO: Allow more complex expressions.
250 kind: ExprKind::Path(ref qpath),
254 ) if ctxt == expr.span.ctxt() && is_lang_ctor(cx, qpath, OptionSome) => Some(arg),
262 ) => get_some_expr(cx, expr, ctxt),
267 // Checks for the `None` value.
268 fn is_none_expr(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> bool {
270 ExprKind::Path(ref qpath) => is_lang_ctor(cx, qpath, OptionNone),
278 ) => is_none_expr(cx, expr),