150 lines
5.3 KiB
Rust
150 lines
5.3 KiB
Rust
use crate::utils::paths;
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use crate::utils::{
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is_copy, match_trait_method, match_type, remove_blocks, snippet_with_applicability, span_lint_and_sugg,
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};
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use if_chain::if_chain;
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use rustc::lint::{LateContext, LateLintPass};
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use rustc::ty;
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use rustc_errors::Applicability;
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use rustc_hir as hir;
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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use rustc_span::source_map::Span;
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use syntax::ast::Ident;
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declare_clippy_lint! {
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/// **What it does:** Checks for usage of `iterator.map(|x| x.clone())` and suggests
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/// `iterator.cloned()` 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<'a, 'tcx> LateLintPass<'a, '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(ref method, _, ref args) = e.kind;
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if args.len() == 2;
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if method.ident.as_str() == "map";
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let ty = cx.tables.expr_ty(&args[0]);
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if match_type(cx, ty, &paths::OPTION) || match_trait_method(cx, e, &paths::ITERATOR);
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if let hir::ExprKind::Closure(_, _, body_id, _, _) = args[1].kind;
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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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then {
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match closure_body.params[0].pat.kind {
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hir::PatKind::Ref(ref inner, _) => 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::UnDeref, ref inner) => {
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if ident_eq(name, inner) {
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if let ty::Ref(..) = cx.tables.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(ref method, _, ref obj) => {
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if ident_eq(name, &obj[0]) && method.ident.as_str() == "clone"
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&& match_trait_method(cx, closure_expr, &paths::CLONE_TRAIT) {
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let obj_ty = cx.tables.expr_ty(&obj[0]);
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if let ty::Ref(_, ty, _) = obj_ty.kind {
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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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} 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, ref 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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