1 // Copyright 2014-2018 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution.
4 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
5 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
6 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
7 // option. This file may not be copied, modified, or distributed
8 // except according to those terms.
10 use crate::rustc::hir;
11 use crate::rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
12 use crate::rustc::{declare_tool_lint, lint_array};
13 use crate::rustc_errors::Applicability;
14 use crate::syntax::ast::Ident;
15 use crate::syntax::source_map::Span;
16 use crate::utils::paths;
18 in_macro, match_trait_method, match_type, remove_blocks, snippet_with_applicability, span_lint_and_sugg,
20 use if_chain::if_chain;
25 /// **What it does:** Checks for usage of `iterator.map(|x| x.clone())` and suggests
26 /// `iterator.cloned()` instead
28 /// **Why is this bad?** Readability, this can be written more concisely
30 /// **Known problems:** Sometimes `.cloned()` requires stricter trait
31 /// bound than `.map(|e| e.clone())` (which works because of the coercion).
32 /// See [#498](https://github.com/rust-lang-nursery/rust-clippy/issues/498).
37 /// let x = vec![42, 43];
39 /// let z = y.map(|i| *i);
42 /// The correct use would be:
45 /// let x = vec![42, 43];
47 /// let z = y.cloned();
49 declare_clippy_lint! {
52 "using `iterator.map(|x| x.clone())`, or dereferencing closures for `Copy` types"
55 impl LintPass for Pass {
56 fn get_lints(&self) -> LintArray {
57 lint_array!(MAP_CLONE)
61 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
62 fn check_expr(&mut self, cx: &LateContext<'_, '_>, e: &hir::Expr) {
68 if let hir::ExprKind::MethodCall(ref method, _, ref args) = e.node;
70 if method.ident.as_str() == "map";
71 let ty = cx.tables.expr_ty(&args[0]);
72 if match_type(cx, ty, &paths::OPTION) || match_trait_method(cx, e, &paths::ITERATOR);
73 if let hir::ExprKind::Closure(_, _, body_id, _, _) = args[1].node;
74 let closure_body = cx.tcx.hir().body(body_id);
75 let closure_expr = remove_blocks(&closure_body.value);
77 match closure_body.arguments[0].pat.node {
78 hir::PatKind::Ref(ref inner, _) => if let hir::PatKind::Binding(
79 hir::BindingAnnotation::Unannotated, _, name, None
81 lint(cx, e.span, args[0].span, name, closure_expr);
83 hir::PatKind::Binding(hir::BindingAnnotation::Unannotated, _, name, None) => {
84 match closure_expr.node {
85 hir::ExprKind::Unary(hir::UnOp::UnDeref, ref inner) => {
86 if !cx.tables.expr_ty(inner).is_box() {
87 lint(cx, e.span, args[0].span, name, inner);
90 hir::ExprKind::MethodCall(ref method, _, ref obj) => {
91 if method.ident.as_str() == "clone"
92 && match_trait_method(cx, closure_expr, &paths::CLONE_TRAIT) {
93 lint(cx, e.span, args[0].span, name, &obj[0]);
106 fn lint(cx: &LateContext<'_, '_>, replace: Span, root: Span, name: Ident, path: &hir::Expr) {
107 if let hir::ExprKind::Path(hir::QPath::Resolved(None, ref path)) = path.node {
108 if path.segments.len() == 1 && path.segments[0].ident == name {
109 let mut applicability = Applicability::MachineApplicable;
114 "You are using an explicit closure for cloning elements",
115 "Consider calling the dedicated `cloned` method",
118 snippet_with_applicability(cx, root, "..", &mut applicability)