| use crate::utils::paths; |
| use crate::utils::{ |
| in_macro, match_trait_method, match_type, remove_blocks, snippet_with_applicability, span_lint_and_sugg, |
| }; |
| use if_chain::if_chain; |
| use rustc::hir; |
| use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass}; |
| use rustc::ty; |
| use rustc::{declare_tool_lint, lint_array}; |
| use rustc_errors::Applicability; |
| use syntax::ast::Ident; |
| use syntax::source_map::Span; |
| |
| #[derive(Clone)] |
| pub struct Pass; |
| |
| declare_clippy_lint! { |
| /// **What it does:** Checks for usage of `iterator.map(|x| x.clone())` and suggests |
| /// `iterator.cloned()` instead |
| /// |
| /// **Why is this bad?** Readability, this can be written more concisely |
| /// |
| /// **Known problems:** None |
| /// |
| /// **Example:** |
| /// |
| /// ```rust |
| /// let x = vec![42, 43]; |
| /// let y = x.iter(); |
| /// let z = y.map(|i| *i); |
| /// ``` |
| /// |
| /// The correct use would be: |
| /// |
| /// ```rust |
| /// let x = vec![42, 43]; |
| /// let y = x.iter(); |
| /// let z = y.cloned(); |
| /// ``` |
| pub MAP_CLONE, |
| style, |
| "using `iterator.map(|x| x.clone())`, or dereferencing closures for `Copy` types" |
| } |
| |
| impl LintPass for Pass { |
| fn get_lints(&self) -> LintArray { |
| lint_array!(MAP_CLONE) |
| } |
| |
| fn name(&self) -> &'static str { |
| "MapClone" |
| } |
| } |
| |
| impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass { |
| fn check_expr(&mut self, cx: &LateContext<'_, '_>, e: &hir::Expr) { |
| if in_macro(e.span) { |
| return; |
| } |
| |
| if_chain! { |
| if let hir::ExprKind::MethodCall(ref method, _, ref args) = e.node; |
| if args.len() == 2; |
| if method.ident.as_str() == "map"; |
| let ty = cx.tables.expr_ty(&args[0]); |
| if match_type(cx, ty, &paths::OPTION) || match_trait_method(cx, e, &paths::ITERATOR); |
| if let hir::ExprKind::Closure(_, _, body_id, _, _) = args[1].node; |
| let closure_body = cx.tcx.hir().body(body_id); |
| let closure_expr = remove_blocks(&closure_body.value); |
| then { |
| match closure_body.arguments[0].pat.node { |
| hir::PatKind::Ref(ref inner, _) => if let hir::PatKind::Binding( |
| hir::BindingAnnotation::Unannotated, .., name, None |
| ) = inner.node { |
| if ident_eq(name, closure_expr) { |
| lint(cx, e.span, args[0].span); |
| } |
| }, |
| hir::PatKind::Binding(hir::BindingAnnotation::Unannotated, .., name, None) => { |
| match closure_expr.node { |
| hir::ExprKind::Unary(hir::UnOp::UnDeref, ref inner) => { |
| if ident_eq(name, inner) && !cx.tables.expr_ty(inner).is_box() { |
| lint(cx, e.span, args[0].span); |
| } |
| }, |
| hir::ExprKind::MethodCall(ref method, _, ref obj) => { |
| if ident_eq(name, &obj[0]) && method.ident.as_str() == "clone" |
| && match_trait_method(cx, closure_expr, &paths::CLONE_TRAIT) { |
| |
| let obj_ty = cx.tables.expr_ty(&obj[0]); |
| if let ty::Ref(..) = obj_ty.sty { |
| lint(cx, e.span, args[0].span); |
| } else { |
| lint_needless_cloning(cx, e.span, args[0].span); |
| } |
| } |
| }, |
| _ => {}, |
| } |
| }, |
| _ => {}, |
| } |
| } |
| } |
| } |
| } |
| |
| fn ident_eq(name: Ident, path: &hir::Expr) -> bool { |
| if let hir::ExprKind::Path(hir::QPath::Resolved(None, ref path)) = path.node { |
| path.segments.len() == 1 && path.segments[0].ident == name |
| } else { |
| false |
| } |
| } |
| |
| fn lint_needless_cloning(cx: &LateContext<'_, '_>, root: Span, receiver: Span) { |
| span_lint_and_sugg( |
| cx, |
| MAP_CLONE, |
| root.trim_start(receiver).unwrap(), |
| "You are needlessly cloning iterator elements", |
| "Remove the map call", |
| String::new(), |
| Applicability::MachineApplicable, |
| ) |
| } |
| |
| fn lint(cx: &LateContext<'_, '_>, replace: Span, root: Span) { |
| let mut applicability = Applicability::MachineApplicable; |
| span_lint_and_sugg( |
| cx, |
| MAP_CLONE, |
| replace, |
| "You are using an explicit closure for cloning elements", |
| "Consider calling the dedicated `cloned` method", |
| format!( |
| "{}.cloned()", |
| snippet_with_applicability(cx, root, "..", &mut applicability) |
| ), |
| applicability, |
| ) |
| } |