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_else_clause, is_lang_ctor, is_lint_allowed, path_to_local_id,
9 use rustc_ast::util::parser::PREC_POSTFIX;
10 use rustc_errors::Applicability;
11 use rustc_hir::LangItem::{OptionNone, OptionSome};
12 use rustc_hir::{Arm, BindingAnnotation, Block, Expr, ExprKind, HirId, MatchSource, Mutability, Pat, PatKind};
13 use rustc_lint::{LateContext, LateLintPass, LintContext};
14 use rustc_middle::lint::in_external_macro;
15 use rustc_session::{declare_lint_pass, declare_tool_lint};
16 use rustc_span::{sym, SyntaxContext};
18 declare_clippy_lint! {
20 /// Checks for usages of `match` which could be implemented using `map`
22 /// ### Why is this bad?
23 /// Using the `map` method is clearer and more concise.
28 /// Some(x) => Some(x + 1),
34 /// Some(0).map(|x| x + 1);
38 "reimplementation of `map`"
41 declare_lint_pass!(ManualMap => [MANUAL_MAP]);
43 impl LateLintPass<'_> for ManualMap {
44 #[allow(clippy::too_many_lines)]
45 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
46 if let ExprKind::Match(
48 [arm1 @ Arm { guard: None, .. }, arm2 @ Arm { guard: None, .. }],
52 if in_external_macro(cx.sess(), expr.span) || in_constant(cx, expr.hir_id) {
56 let (scrutinee_ty, ty_ref_count, ty_mutability) =
57 peel_mid_ty_refs_is_mutable(cx.typeck_results().expr_ty(scrutinee));
58 if !(is_type_diagnostic_item(cx, scrutinee_ty, sym::option_type)
59 && is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(expr), sym::option_type))
64 let expr_ctxt = expr.span.ctxt();
65 let (some_expr, some_pat, pat_ref_count, is_wild_none) = match (
66 try_parse_pattern(cx, arm1.pat, expr_ctxt),
67 try_parse_pattern(cx, arm2.pat, expr_ctxt),
69 (Some(OptionPat::Wild), Some(OptionPat::Some { pattern, ref_count }))
70 if is_none_expr(cx, arm1.body) =>
72 (arm2.body, pattern, ref_count, true)
74 (Some(OptionPat::None), Some(OptionPat::Some { pattern, ref_count }))
75 if is_none_expr(cx, arm1.body) =>
77 (arm2.body, pattern, ref_count, false)
79 (Some(OptionPat::Some { pattern, ref_count }), Some(OptionPat::Wild))
80 if is_none_expr(cx, arm2.body) =>
82 (arm1.body, pattern, ref_count, true)
84 (Some(OptionPat::Some { pattern, ref_count }), Some(OptionPat::None))
85 if is_none_expr(cx, arm2.body) =>
87 (arm1.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, expr_ctxt) {
102 // These two lints will go back and forth with each other.
103 if cx.typeck_results().expr_ty(some_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).is_empty() {
114 if !can_move_expr_to_closure(cx, some_expr) {
118 // Determine which binding mode to use.
119 let explicit_ref = some_pat.contains_explicit_ref_binding();
120 let binding_ref = explicit_ref.or_else(|| (ty_ref_count != pat_ref_count).then(|| ty_mutability));
122 let as_ref_str = match binding_ref {
123 Some(Mutability::Mut) => ".as_mut()",
124 Some(Mutability::Not) => ".as_ref()",
128 let mut app = Applicability::MachineApplicable;
130 // Remove address-of expressions from the scrutinee. Either `as_ref` will be called, or
131 // it's being passed by value.
132 let scrutinee = peel_hir_expr_refs(scrutinee).0;
133 let (scrutinee_str, _) = snippet_with_context(cx, scrutinee.span, expr_ctxt, "..", &mut app);
135 if scrutinee.span.ctxt() == expr.span.ctxt() && scrutinee.precedence().order() < PREC_POSTFIX {
136 format!("({})", scrutinee_str)
141 let body_str = if let PatKind::Binding(annotation, id, some_binding, None) = some_pat.kind {
142 match can_pass_as_func(cx, id, some_expr) {
143 Some(func) if func.span.ctxt() == some_expr.span.ctxt() => {
144 snippet_with_applicability(cx, func.span, "..", &mut app).into_owned()
147 if path_to_local_id(some_expr, id)
148 && !is_lint_allowed(cx, MATCH_AS_REF, expr.hir_id)
149 && binding_ref.is_some()
154 // `ref` and `ref mut` annotations were handled earlier.
155 let annotation = if matches!(annotation, BindingAnnotation::Mutable) {
164 snippet_with_context(cx, some_expr.span, expr_ctxt, "..", &mut app).0
168 } else if !is_wild_none && explicit_ref.is_none() {
169 // TODO: handle explicit reference annotations.
172 snippet_with_context(cx, some_pat.span, expr_ctxt, "..", &mut app).0,
173 snippet_with_context(cx, some_expr.span, expr_ctxt, "..", &mut app).0
176 // Refutable bindings and mixed reference annotations can't be handled by `map`.
184 "manual implementation of `Option::map`",
186 if matches!(match_kind, MatchSource::IfLetDesugar { .. }) && is_else_clause(cx.tcx, expr) {
187 format!("{{ {}{}.map({}) }}", scrutinee_str, as_ref_str, body_str)
189 format!("{}{}.map({})", scrutinee_str, as_ref_str, body_str)
197 // Checks whether the expression could be passed as a function, or whether a closure is needed.
198 // Returns the function to be passed to `map` if it exists.
199 fn can_pass_as_func(cx: &LateContext<'tcx>, binding: HirId, expr: &'tcx Expr<'_>) -> Option<&'tcx Expr<'tcx>> {
201 ExprKind::Call(func, [arg])
202 if path_to_local_id(arg, binding) && cx.typeck_results().expr_adjustments(arg).is_empty() =>
214 // The pattern contained in the `Some` tuple.
215 pattern: &'a Pat<'a>,
216 // The number of references before the `Some` tuple.
217 // e.g. `&&Some(_)` has a ref count of 2.
222 // Try to parse into a recognized `Option` pattern.
223 // i.e. `_`, `None`, `Some(..)`, or a reference to any of those.
224 fn try_parse_pattern(cx: &LateContext<'tcx>, pat: &'tcx Pat<'_>, ctxt: SyntaxContext) -> Option<OptionPat<'tcx>> {
225 fn f(cx: &LateContext<'tcx>, pat: &'tcx Pat<'_>, ref_count: usize, ctxt: SyntaxContext) -> Option<OptionPat<'tcx>> {
227 PatKind::Wild => Some(OptionPat::Wild),
228 PatKind::Ref(pat, _) => f(cx, pat, ref_count + 1, ctxt),
229 PatKind::Path(ref qpath) if is_lang_ctor(cx, qpath, OptionNone) => Some(OptionPat::None),
230 PatKind::TupleStruct(ref qpath, [pattern], _)
231 if is_lang_ctor(cx, qpath, OptionSome) && pat.span.ctxt() == ctxt =>
233 Some(OptionPat::Some { pattern, ref_count })
241 // Checks for an expression wrapped by the `Some` constructor. Returns the contained expression.
242 fn get_some_expr(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, ctxt: SyntaxContext) -> Option<&'tcx Expr<'tcx>> {
243 // TODO: Allow more complex expressions.
247 kind: ExprKind::Path(ref qpath),
251 ) if ctxt == expr.span.ctxt() && is_lang_ctor(cx, qpath, OptionSome) => Some(arg),
259 ) => get_some_expr(cx, expr, ctxt),
264 // Checks for the `None` value.
265 fn is_none_expr(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> bool {
267 ExprKind::Path(ref qpath) => is_lang_ctor(cx, qpath, OptionNone),
275 ) => is_none_expr(cx, expr),