mirror of
https://github.com/rust-lang/rust-clippy
synced 2024-12-23 03:23:33 +00:00
160 lines
6.2 KiB
Rust
160 lines
6.2 KiB
Rust
use clippy_utils::diagnostics::span_lint_and_sugg;
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use clippy_utils::is_trait_method;
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use clippy_utils::remove_blocks;
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use clippy_utils::source::snippet_with_applicability;
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use clippy_utils::ty::{is_copy, is_type_diagnostic_item};
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use if_chain::if_chain;
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use rustc_errors::Applicability;
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use rustc_hir as hir;
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_middle::mir::Mutability;
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use rustc_middle::ty;
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use rustc_middle::ty::adjustment::Adjust;
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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use rustc_span::symbol::Ident;
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use rustc_span::{sym, Span};
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declare_clippy_lint! {
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/// **What it does:** Checks for usage of `map(|x| x.clone())` or
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/// dereferencing closures for `Copy` types, on `Iterator` or `Option`,
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/// and suggests `cloned()` or `copied()` instead
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///
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/// **Why is this bad?** Readability, this can be written more concisely
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///
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/// **Known problems:** None
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///
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/// **Example:**
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///
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/// ```rust
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/// let x = vec![42, 43];
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/// let y = x.iter();
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/// let z = y.map(|i| *i);
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/// ```
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///
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/// The correct use would be:
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///
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/// ```rust
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/// let x = vec![42, 43];
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/// let y = x.iter();
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/// let z = y.cloned();
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/// ```
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pub MAP_CLONE,
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style,
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"using `iterator.map(|x| x.clone())`, or dereferencing closures for `Copy` types"
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}
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declare_lint_pass!(MapClone => [MAP_CLONE]);
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impl<'tcx> LateLintPass<'tcx> for MapClone {
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fn check_expr(&mut self, cx: &LateContext<'_>, e: &hir::Expr<'_>) {
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if e.span.from_expansion() {
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return;
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}
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if_chain! {
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if let hir::ExprKind::MethodCall(method, _, args, _) = e.kind;
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if args.len() == 2;
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if method.ident.name == sym::map;
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let ty = cx.typeck_results().expr_ty(&args[0]);
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if is_type_diagnostic_item(cx, ty, sym::option_type) || is_trait_method(cx, e, sym::Iterator);
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if let hir::ExprKind::Closure(_, _, body_id, _, _) = args[1].kind;
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then {
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let closure_body = cx.tcx.hir().body(body_id);
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let closure_expr = remove_blocks(&closure_body.value);
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match closure_body.params[0].pat.kind {
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hir::PatKind::Ref(inner, hir::Mutability::Not) => if let hir::PatKind::Binding(
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hir::BindingAnnotation::Unannotated, .., name, None
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) = inner.kind {
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if ident_eq(name, closure_expr) {
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lint(cx, e.span, args[0].span, true);
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}
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},
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hir::PatKind::Binding(hir::BindingAnnotation::Unannotated, .., name, None) => {
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match closure_expr.kind {
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hir::ExprKind::Unary(hir::UnOp::Deref, inner) => {
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if ident_eq(name, inner) {
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if let ty::Ref(.., Mutability::Not) = cx.typeck_results().expr_ty(inner).kind() {
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lint(cx, e.span, args[0].span, true);
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}
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}
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},
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hir::ExprKind::MethodCall(method, _, [obj], _) => if_chain! {
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if ident_eq(name, obj) && method.ident.name == sym::clone;
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if let Some(fn_id) = cx.typeck_results().type_dependent_def_id(closure_expr.hir_id);
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if let Some(trait_id) = cx.tcx.trait_of_item(fn_id);
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if cx.tcx.lang_items().clone_trait().map_or(false, |id| id == trait_id);
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// no autoderefs
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if !cx.typeck_results().expr_adjustments(obj).iter()
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.any(|a| matches!(a.kind, Adjust::Deref(Some(..))));
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then {
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let obj_ty = cx.typeck_results().expr_ty(obj);
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if let ty::Ref(_, ty, mutability) = obj_ty.kind() {
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if matches!(mutability, Mutability::Not) {
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let copy = is_copy(cx, ty);
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lint(cx, e.span, args[0].span, copy);
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}
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} else {
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lint_needless_cloning(cx, e.span, args[0].span);
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}
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}
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},
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_ => {},
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}
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},
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_ => {},
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}
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}
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}
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}
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}
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fn ident_eq(name: Ident, path: &hir::Expr<'_>) -> bool {
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if let hir::ExprKind::Path(hir::QPath::Resolved(None, path)) = path.kind {
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path.segments.len() == 1 && path.segments[0].ident == name
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} else {
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false
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}
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}
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fn lint_needless_cloning(cx: &LateContext<'_>, root: Span, receiver: Span) {
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span_lint_and_sugg(
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cx,
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MAP_CLONE,
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root.trim_start(receiver).unwrap(),
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"you are needlessly cloning iterator elements",
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"remove the `map` call",
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String::new(),
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Applicability::MachineApplicable,
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)
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}
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fn lint(cx: &LateContext<'_>, replace: Span, root: Span, copied: bool) {
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let mut applicability = Applicability::MachineApplicable;
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if copied {
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span_lint_and_sugg(
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cx,
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MAP_CLONE,
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replace,
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"you are using an explicit closure for copying elements",
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"consider calling the dedicated `copied` method",
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format!(
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"{}.copied()",
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snippet_with_applicability(cx, root, "..", &mut applicability)
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),
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applicability,
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)
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} else {
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span_lint_and_sugg(
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cx,
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MAP_CLONE,
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replace,
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"you are using an explicit closure for cloning elements",
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"consider calling the dedicated `cloned` method",
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format!(
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"{}.cloned()",
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snippet_with_applicability(cx, root, "..", &mut applicability)
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),
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applicability,
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)
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}
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}
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