Reimplement the `map_clone` lint from scratch

This commit is contained in:
Oliver Schneider 2018-10-02 15:13:43 +02:00
parent 057243f16b
commit b36bb0a68d
6 changed files with 136 additions and 3 deletions

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@ -688,8 +688,6 @@ All notable changes to this project will be documented in this file.
[`float_arithmetic`]: https://rust-lang-nursery.github.io/rust-clippy/master/index.html#float_arithmetic
[`float_cmp`]: https://rust-lang-nursery.github.io/rust-clippy/master/index.html#float_cmp
[`float_cmp_const`]: https://rust-lang-nursery.github.io/rust-clippy/master/index.html#float_cmp_const
[`fn_to_numeric_cast`]: https://rust-lang-nursery.github.io/rust-clippy/master/index.html#fn_to_numeric_cast
[`fn_to_numeric_cast_with_truncation`]: https://rust-lang-nursery.github.io/rust-clippy/master/index.html#fn_to_numeric_cast_with_truncation
[`for_kv_map`]: https://rust-lang-nursery.github.io/rust-clippy/master/index.html#for_kv_map
[`for_loop_over_option`]: https://rust-lang-nursery.github.io/rust-clippy/master/index.html#for_loop_over_option
[`for_loop_over_result`]: https://rust-lang-nursery.github.io/rust-clippy/master/index.html#for_loop_over_result

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@ -9,7 +9,7 @@ We are currently in the process of discussing Clippy 1.0 via the RFC process in
A collection of lints to catch common mistakes and improve your [Rust](https://github.com/rust-lang/rust) code.
[There are 279 lints included in this crate!](https://rust-lang-nursery.github.io/rust-clippy/master/index.html)
[There are 277 lints included in this crate!](https://rust-lang-nursery.github.io/rust-clippy/master/index.html)
We have a bunch of lint categories to allow you to choose how much Clippy is supposed to ~~annoy~~ help you:

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@ -129,6 +129,7 @@ pub mod let_if_seq;
pub mod lifetimes;
pub mod literal_representation;
pub mod loops;
pub mod map_clone;
pub mod map_unit_fn;
pub mod matches;
pub mod mem_forget;
@ -327,6 +328,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry<'_>, conf: &Conf) {
reg.register_late_lint_pass(box strings::StringAdd);
reg.register_early_lint_pass(box returns::ReturnPass);
reg.register_late_lint_pass(box methods::Pass);
reg.register_late_lint_pass(box map_clone::Pass);
reg.register_late_lint_pass(box shadow::Pass);
reg.register_late_lint_pass(box types::LetPass);
reg.register_late_lint_pass(box types::UnitCmp);
@ -583,6 +585,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry<'_>, conf: &Conf) {
loops::WHILE_IMMUTABLE_CONDITION,
loops::WHILE_LET_LOOP,
loops::WHILE_LET_ON_ITERATOR,
map_clone::MAP_CLONE,
map_unit_fn::OPTION_MAP_UNIT_FN,
map_unit_fn::RESULT_MAP_UNIT_FN,
matches::MATCH_AS_REF,
@ -742,6 +745,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry<'_>, conf: &Conf) {
loops::FOR_KV_MAP,
loops::NEEDLESS_RANGE_LOOP,
loops::WHILE_LET_ON_ITERATOR,
map_clone::MAP_CLONE,
matches::MATCH_BOOL,
matches::MATCH_OVERLAPPING_ARM,
matches::MATCH_REF_PATS,

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@ -0,0 +1,100 @@
use crate::rustc::hir;
use crate::rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
use crate::rustc::{declare_tool_lint, lint_array};
use crate::syntax::source_map::Span;
use crate::utils::paths;
use crate::utils::{
in_macro, match_trait_method, match_type,
remove_blocks, snippet,
span_lint_and_sugg,
};
use if_chain::if_chain;
use crate::syntax::ast::Ident;
#[derive(Clone)]
pub struct Pass;
/// **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();
/// ```
declare_clippy_lint! {
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)
}
}
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 {
lint(cx, e.span, args[0].span, name, closure_expr);
},
hir::PatKind::Binding(hir::BindingAnnotation::Unannotated, _, name, None) => match closure_expr.node {
hir::ExprKind::Unary(hir::UnOp::UnDeref, ref inner) => lint(cx, e.span, args[0].span, name, inner),
hir::ExprKind::MethodCall(ref method, _, ref obj) => if method.ident.as_str() == "clone" {
if match_trait_method(cx, closure_expr, &paths::CLONE_TRAIT) {
lint(cx, e.span, args[0].span, name, &obj[0]);
}
}
_ => {},
},
_ => {},
}
}
}
}
}
fn lint(cx: &LateContext<'_, '_>, replace: Span, root: Span, name: Ident, path: &hir::Expr) {
if let hir::ExprKind::Path(hir::QPath::Resolved(None, ref path)) = path.node {
if path.segments.len() == 1 && path.segments[0].ident == name {
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(cx, root, "..")),
)
}
}
}

9
tests/ui/map_clone.rs Normal file
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@ -0,0 +1,9 @@
#![feature(tool_lints)]
#![warn(clippy::all, clippy::pedantic)]
#![allow(clippy::missing_docs_in_private_items)]
fn main() {
let _: Vec<i8> = vec![5_i8; 6].iter().map(|x| *x).collect();
let _: Vec<String> = vec![String::new()].iter().map(|x| x.clone()).collect();
let _: Vec<u32> = vec![42, 43].iter().map(|&x| x).collect();
}

22
tests/ui/map_clone.stderr Normal file
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@ -0,0 +1,22 @@
error: You are using an explicit closure for cloning elements
--> $DIR/map_clone.rs:6:22
|
6 | let _: Vec<i8> = vec![5_i8; 6].iter().map(|x| *x).collect();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: Consider calling the dedicated `cloned` method: `vec![5_i8; 6].iter().cloned()`
|
= note: `-D clippy::map-clone` implied by `-D warnings`
error: You are using an explicit closure for cloning elements
--> $DIR/map_clone.rs:7:26
|
7 | let _: Vec<String> = vec![String::new()].iter().map(|x| x.clone()).collect();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: Consider calling the dedicated `cloned` method: `vec![String::new()].iter().cloned()`
error: You are using an explicit closure for cloning elements
--> $DIR/map_clone.rs:8:23
|
8 | let _: Vec<u32> = vec![42, 43].iter().map(|&x| x).collect();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: Consider calling the dedicated `cloned` method: `vec![42, 43].iter().cloned()`
error: aborting due to 3 previous errors