1 use crate::utils::paths;
3 is_copy, is_type_diagnostic_item, match_trait_method, remove_blocks, snippet_with_applicability, span_lint_and_sugg,
5 use if_chain::if_chain;
6 use rustc_errors::Applicability;
8 use rustc_lint::{LateContext, LateLintPass};
9 use rustc_middle::mir::Mutability;
11 use rustc_session::{declare_lint_pass, declare_tool_lint};
12 use rustc_span::symbol::Ident;
15 declare_clippy_lint! {
16 /// **What it does:** Checks for usage of `iterator.map(|x| x.clone())` and suggests
17 /// `iterator.cloned()` instead
19 /// **Why is this bad?** Readability, this can be written more concisely
21 /// **Known problems:** None
26 /// let x = vec![42, 43];
28 /// let z = y.map(|i| *i);
31 /// The correct use would be:
34 /// let x = vec![42, 43];
36 /// let z = y.cloned();
40 "using `iterator.map(|x| x.clone())`, or dereferencing closures for `Copy` types"
43 declare_lint_pass!(MapClone => [MAP_CLONE]);
45 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MapClone {
46 fn check_expr(&mut self, cx: &LateContext<'_, '_>, e: &hir::Expr<'_>) {
47 if e.span.from_expansion() {
52 if let hir::ExprKind::MethodCall(ref method, _, ref args) = e.kind;
54 if method.ident.as_str() == "map";
55 let ty = cx.tables.expr_ty(&args[0]);
56 if is_type_diagnostic_item(cx, ty, sym!(option_type)) || match_trait_method(cx, e, &paths::ITERATOR);
57 if let hir::ExprKind::Closure(_, _, body_id, _, _) = args[1].kind;
58 let closure_body = cx.tcx.hir().body(body_id);
59 let closure_expr = remove_blocks(&closure_body.value);
61 match closure_body.params[0].pat.kind {
62 hir::PatKind::Ref(ref inner, hir::Mutability::Not) => if let hir::PatKind::Binding(
63 hir::BindingAnnotation::Unannotated, .., name, None
65 if ident_eq(name, closure_expr) {
66 lint(cx, e.span, args[0].span, true);
69 hir::PatKind::Binding(hir::BindingAnnotation::Unannotated, .., name, None) => {
70 match closure_expr.kind {
71 hir::ExprKind::Unary(hir::UnOp::UnDeref, ref inner) => {
72 if ident_eq(name, inner) {
73 if let ty::Ref(.., Mutability::Not) = cx.tables.expr_ty(inner).kind {
74 lint(cx, e.span, args[0].span, true);
78 hir::ExprKind::MethodCall(ref method, _, ref obj) => {
79 if ident_eq(name, &obj[0]) && method.ident.as_str() == "clone"
80 && match_trait_method(cx, closure_expr, &paths::CLONE_TRAIT) {
82 let obj_ty = cx.tables.expr_ty(&obj[0]);
83 if let ty::Ref(_, ty, _) = obj_ty.kind {
84 let copy = is_copy(cx, ty);
85 lint(cx, e.span, args[0].span, copy);
87 lint_needless_cloning(cx, e.span, args[0].span);
101 fn ident_eq(name: Ident, path: &hir::Expr<'_>) -> bool {
102 if let hir::ExprKind::Path(hir::QPath::Resolved(None, ref path)) = path.kind {
103 path.segments.len() == 1 && path.segments[0].ident == name
109 fn lint_needless_cloning(cx: &LateContext<'_, '_>, root: Span, receiver: Span) {
113 root.trim_start(receiver).unwrap(),
114 "You are needlessly cloning iterator elements",
115 "Remove the `map` call",
117 Applicability::MachineApplicable,
121 fn lint(cx: &LateContext<'_, '_>, replace: Span, root: Span, copied: bool) {
122 let mut applicability = Applicability::MachineApplicable;
128 "You are using an explicit closure for copying elements",
129 "Consider calling the dedicated `copied` method",
132 snippet_with_applicability(cx, root, "..", &mut applicability)
141 "You are using an explicit closure for cloning elements",
142 "Consider calling the dedicated `cloned` method",
145 snippet_with_applicability(cx, root, "..", &mut applicability)