mirror of
https://github.com/rust-lang/rust-clippy
synced 2024-12-21 02:23:19 +00:00
9bd4e5469e
Boxes are a bit magic in that they need to use `*` to get an owned value
out of the box. They implement `Deref` but that only returns a
reference. This means an easy way to convert an `Option<Box<T>>` to an
`<Option<T>` is:
```
box_option.map(|b| *b)
```
However, since b36bb0a6 the `map_clone` lint is detecting this as an
attempt to copy the box. Fix by excluding boxes completely from the
deref part of this lint.
Fixes #3274
108 lines
3.8 KiB
Rust
108 lines
3.8 KiB
Rust
// Copyright 2014-2018 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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use crate::rustc::hir;
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use crate::rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
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use crate::rustc::{declare_tool_lint, lint_array};
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use crate::syntax::source_map::Span;
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use crate::utils::paths;
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use crate::utils::{
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in_macro, match_trait_method, match_type,
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remove_blocks, snippet,
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span_lint_and_sugg,
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};
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use if_chain::if_chain;
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use crate::syntax::ast::Ident;
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#[derive(Clone)]
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pub struct Pass;
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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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declare_clippy_lint! {
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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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impl LintPass for Pass {
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fn get_lints(&self) -> LintArray {
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lint_array!(MAP_CLONE)
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}
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}
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
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fn check_expr(&mut self, cx: &LateContext<'_, '_>, e: &hir::Expr) {
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if in_macro(e.span) {
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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.node;
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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].node;
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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.arguments[0].pat.node {
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hir::PatKind::Ref(ref inner, _) => if let hir::PatKind::Binding(hir::BindingAnnotation::Unannotated, _, name, None) = inner.node {
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lint(cx, e.span, args[0].span, name, closure_expr);
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},
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hir::PatKind::Binding(hir::BindingAnnotation::Unannotated, _, name, None) => match closure_expr.node {
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hir::ExprKind::Unary(hir::UnOp::UnDeref, ref inner) if !cx.tables.expr_ty(inner).is_box() => lint(cx, e.span, args[0].span, name, inner),
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hir::ExprKind::MethodCall(ref method, _, ref obj) => if method.ident.as_str() == "clone" && match_trait_method(cx, closure_expr, &paths::CLONE_TRAIT) {
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lint(cx, e.span, args[0].span, name, &obj[0]);
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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 lint(cx: &LateContext<'_, '_>, replace: Span, root: Span, name: Ident, path: &hir::Expr) {
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if let hir::ExprKind::Path(hir::QPath::Resolved(None, ref path)) = path.node {
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if path.segments.len() == 1 && path.segments[0].ident == name {
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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!("{}.cloned()", snippet(cx, root, "..")),
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)
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}
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}
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}
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