Add a lint for maps with zero-sized values

Co-authored-by: Eduardo Broto <ebroto@tutanota.com>
This commit is contained in:
Korrat 2020-10-24 16:48:10 +02:00
parent a2d99259a4
commit f77f1db35b
7 changed files with 437 additions and 0 deletions

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@ -2171,5 +2171,6 @@ Released 2018-09-13
[`zero_divided_by_zero`]: https://rust-lang.github.io/rust-clippy/master/index.html#zero_divided_by_zero
[`zero_prefixed_literal`]: https://rust-lang.github.io/rust-clippy/master/index.html#zero_prefixed_literal
[`zero_ptr`]: https://rust-lang.github.io/rust-clippy/master/index.html#zero_ptr
[`zero_sized_map_values`]: https://rust-lang.github.io/rust-clippy/master/index.html#zero_sized_map_values
[`zst_offset`]: https://rust-lang.github.io/rust-clippy/master/index.html#zst_offset
<!-- end autogenerated links to lint list -->

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@ -345,6 +345,7 @@ mod wildcard_dependencies;
mod wildcard_imports;
mod write;
mod zero_div_zero;
mod zero_sized_map_values;
// end lints modules, do not remove this comment, its used in `update_lints`
pub use crate::utils::conf::Conf;
@ -944,6 +945,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
&write::WRITE_LITERAL,
&write::WRITE_WITH_NEWLINE,
&zero_div_zero::ZERO_DIVIDED_BY_ZERO,
&zero_sized_map_values::ZERO_SIZED_MAP_VALUES,
]);
// end register lints, do not remove this comment, its used in `update_lints`
@ -1204,6 +1206,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
store.register_late_pass(|| box undropped_manually_drops::UndroppedManuallyDrops);
store.register_late_pass(|| box strings::StrToString);
store.register_late_pass(|| box strings::StringToString);
store.register_late_pass(|| box zero_sized_map_values::ZeroSizedMapValues);
store.register_group(true, "clippy::restriction", Some("clippy_restriction"), vec![
LintId::of(&arithmetic::FLOAT_ARITHMETIC),
@ -1336,6 +1339,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
LintId::of(&unused_self::UNUSED_SELF),
LintId::of(&wildcard_imports::ENUM_GLOB_USE),
LintId::of(&wildcard_imports::WILDCARD_IMPORTS),
LintId::of(&zero_sized_map_values::ZERO_SIZED_MAP_VALUES),
]);
#[cfg(feature = "internal-lints")]

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@ -0,0 +1,82 @@
use if_chain::if_chain;
use rustc_hir::{self as hir, HirId, ItemKind, Node};
use rustc_lint::{LateContext, LateLintPass};
use rustc_middle::ty::{Adt, Ty};
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_target::abi::LayoutOf as _;
use rustc_typeck::hir_ty_to_ty;
use crate::utils::{is_type_diagnostic_item, match_type, paths, span_lint_and_help};
declare_clippy_lint! {
/// **What it does:** Checks for maps with zero-sized value types anywhere in the code.
///
/// **Why is this bad?** Since there is only a single value for a zero-sized type, a map
/// containing zero sized values is effectively a set. Using a set in that case improves
/// readability and communicates intent more clearly.
///
/// **Known problems:**
/// * A zero-sized type cannot be recovered later if it contains private fields.
/// * This lints the signature of public items
///
/// **Example:**
///
/// ```rust
/// # use std::collections::HashMap;
/// fn unique_words(text: &str) -> HashMap<&str, ()> {
/// todo!();
/// }
/// ```
/// Use instead:
/// ```rust
/// # use std::collections::HashSet;
/// fn unique_words(text: &str) -> HashSet<&str> {
/// todo!();
/// }
/// ```
pub ZERO_SIZED_MAP_VALUES,
pedantic,
"usage of map with zero-sized value type"
}
declare_lint_pass!(ZeroSizedMapValues => [ZERO_SIZED_MAP_VALUES]);
impl LateLintPass<'_> for ZeroSizedMapValues {
fn check_ty(&mut self, cx: &LateContext<'_>, hir_ty: &hir::Ty<'_>) {
if_chain! {
if !hir_ty.span.from_expansion();
if !in_trait_impl(cx, hir_ty.hir_id);
let ty = ty_from_hir_ty(cx, hir_ty);
if is_type_diagnostic_item(cx, ty, sym!(hashmap_type)) || match_type(cx, ty, &paths::BTREEMAP);
if let Adt(_, ref substs) = ty.kind();
let ty = substs.type_at(1);
if let Ok(layout) = cx.layout_of(ty);
if layout.is_zst();
then {
span_lint_and_help(cx, ZERO_SIZED_MAP_VALUES, hir_ty.span, "map with zero-sized value type", None, "consider using a set instead");
}
}
}
}
fn in_trait_impl(cx: &LateContext<'_>, hir_id: HirId) -> bool {
let parent_id = cx.tcx.hir().get_parent_item(hir_id);
if let Some(Node::Item(item)) = cx.tcx.hir().find(cx.tcx.hir().get_parent_item(parent_id)) {
if let ItemKind::Impl { of_trait: Some(_), .. } = item.kind {
return true;
}
}
false
}
fn ty_from_hir_ty<'tcx>(cx: &LateContext<'tcx>, hir_ty: &hir::Ty<'_>) -> Ty<'tcx> {
cx.maybe_typeck_results()
.and_then(|results| {
if results.hir_owner == hir_ty.hir_id.owner {
results.node_type_opt(hir_ty.hir_id)
} else {
None
}
})
.unwrap_or_else(|| hir_ty_to_ty(cx.tcx, hir_ty))
}

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@ -0,0 +1,68 @@
#![warn(clippy::zero_sized_map_values)]
use std::collections::BTreeMap;
const CONST_OK: Option<BTreeMap<String, usize>> = None;
const CONST_NOT_OK: Option<BTreeMap<String, ()>> = None;
static STATIC_OK: Option<BTreeMap<String, usize>> = None;
static STATIC_NOT_OK: Option<BTreeMap<String, ()>> = None;
type OkMap = BTreeMap<String, usize>;
type NotOkMap = BTreeMap<String, ()>;
enum TestEnum {
Ok(BTreeMap<String, usize>),
NotOk(BTreeMap<String, ()>),
}
struct Test {
ok: BTreeMap<String, usize>,
not_ok: BTreeMap<String, ()>,
also_not_ok: Vec<BTreeMap<usize, ()>>,
}
trait TestTrait {
type Output;
fn produce_output() -> Self::Output;
fn weird_map(&self, map: BTreeMap<usize, ()>);
}
impl Test {
fn ok(&self) -> BTreeMap<String, usize> {
todo!()
}
fn not_ok(&self) -> BTreeMap<String, ()> {
todo!()
}
}
impl TestTrait for Test {
type Output = BTreeMap<String, ()>;
fn produce_output() -> Self::Output {
todo!();
}
fn weird_map(&self, map: BTreeMap<usize, ()>) {
todo!();
}
}
fn test(map: BTreeMap<String, ()>, key: &str) -> BTreeMap<String, ()> {
todo!();
}
fn test2(map: BTreeMap<String, usize>, key: &str) -> BTreeMap<String, usize> {
todo!();
}
fn main() {
let _: BTreeMap<String, ()> = BTreeMap::new();
let _: BTreeMap<String, usize> = BTreeMap::new();
let _: BTreeMap<_, _> = std::iter::empty::<(String, ())>().collect();
}

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@ -0,0 +1,107 @@
error: map with zero-sized value type
--> $DIR/zero_sized_btreemap_values.rs:5:28
|
LL | const CONST_NOT_OK: Option<BTreeMap<String, ()>> = None;
| ^^^^^^^^^^^^^^^^^^^^
|
= note: `-D clippy::zero-sized-map-values` implied by `-D warnings`
= help: consider using a set instead
error: map with zero-sized value type
--> $DIR/zero_sized_btreemap_values.rs:8:30
|
LL | static STATIC_NOT_OK: Option<BTreeMap<String, ()>> = None;
| ^^^^^^^^^^^^^^^^^^^^
|
= help: consider using a set instead
error: map with zero-sized value type
--> $DIR/zero_sized_btreemap_values.rs:11:17
|
LL | type NotOkMap = BTreeMap<String, ()>;
| ^^^^^^^^^^^^^^^^^^^^
|
= help: consider using a set instead
error: map with zero-sized value type
--> $DIR/zero_sized_btreemap_values.rs:15:11
|
LL | NotOk(BTreeMap<String, ()>),
| ^^^^^^^^^^^^^^^^^^^^
|
= help: consider using a set instead
error: map with zero-sized value type
--> $DIR/zero_sized_btreemap_values.rs:20:13
|
LL | not_ok: BTreeMap<String, ()>,
| ^^^^^^^^^^^^^^^^^^^^
|
= help: consider using a set instead
error: map with zero-sized value type
--> $DIR/zero_sized_btreemap_values.rs:22:22
|
LL | also_not_ok: Vec<BTreeMap<usize, ()>>,
| ^^^^^^^^^^^^^^^^^^^
|
= help: consider using a set instead
error: map with zero-sized value type
--> $DIR/zero_sized_btreemap_values.rs:30:30
|
LL | fn weird_map(&self, map: BTreeMap<usize, ()>);
| ^^^^^^^^^^^^^^^^^^^
|
= help: consider using a set instead
error: map with zero-sized value type
--> $DIR/zero_sized_btreemap_values.rs:38:25
|
LL | fn not_ok(&self) -> BTreeMap<String, ()> {
| ^^^^^^^^^^^^^^^^^^^^
|
= help: consider using a set instead
error: map with zero-sized value type
--> $DIR/zero_sized_btreemap_values.rs:55:14
|
LL | fn test(map: BTreeMap<String, ()>, key: &str) -> BTreeMap<String, ()> {
| ^^^^^^^^^^^^^^^^^^^^
|
= help: consider using a set instead
error: map with zero-sized value type
--> $DIR/zero_sized_btreemap_values.rs:55:50
|
LL | fn test(map: BTreeMap<String, ()>, key: &str) -> BTreeMap<String, ()> {
| ^^^^^^^^^^^^^^^^^^^^
|
= help: consider using a set instead
error: map with zero-sized value type
--> $DIR/zero_sized_btreemap_values.rs:64:35
|
LL | let _: BTreeMap<String, ()> = BTreeMap::new();
| ^^^^^^^^^^^^^
|
= help: consider using a set instead
error: map with zero-sized value type
--> $DIR/zero_sized_btreemap_values.rs:64:12
|
LL | let _: BTreeMap<String, ()> = BTreeMap::new();
| ^^^^^^^^^^^^^^^^^^^^
|
= help: consider using a set instead
error: map with zero-sized value type
--> $DIR/zero_sized_btreemap_values.rs:67:12
|
LL | let _: BTreeMap<_, _> = std::iter::empty::<(String, ())>().collect();
| ^^^^^^^^^^^^^^
|
= help: consider using a set instead
error: aborting due to 13 previous errors

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@ -0,0 +1,68 @@
#![warn(clippy::zero_sized_map_values)]
use std::collections::HashMap;
const CONST_OK: Option<HashMap<String, usize>> = None;
const CONST_NOT_OK: Option<HashMap<String, ()>> = None;
static STATIC_OK: Option<HashMap<String, usize>> = None;
static STATIC_NOT_OK: Option<HashMap<String, ()>> = None;
type OkMap = HashMap<String, usize>;
type NotOkMap = HashMap<String, ()>;
enum TestEnum {
Ok(HashMap<String, usize>),
NotOk(HashMap<String, ()>),
}
struct Test {
ok: HashMap<String, usize>,
not_ok: HashMap<String, ()>,
also_not_ok: Vec<HashMap<usize, ()>>,
}
trait TestTrait {
type Output;
fn produce_output() -> Self::Output;
fn weird_map(&self, map: HashMap<usize, ()>);
}
impl Test {
fn ok(&self) -> HashMap<String, usize> {
todo!()
}
fn not_ok(&self) -> HashMap<String, ()> {
todo!()
}
}
impl TestTrait for Test {
type Output = HashMap<String, ()>;
fn produce_output() -> Self::Output {
todo!();
}
fn weird_map(&self, map: HashMap<usize, ()>) {
todo!();
}
}
fn test(map: HashMap<String, ()>, key: &str) -> HashMap<String, ()> {
todo!();
}
fn test2(map: HashMap<String, usize>, key: &str) -> HashMap<String, usize> {
todo!();
}
fn main() {
let _: HashMap<String, ()> = HashMap::new();
let _: HashMap<String, usize> = HashMap::new();
let _: HashMap<_, _> = std::iter::empty::<(String, ())>().collect();
}

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@ -0,0 +1,107 @@
error: map with zero-sized value type
--> $DIR/zero_sized_hashmap_values.rs:5:28
|
LL | const CONST_NOT_OK: Option<HashMap<String, ()>> = None;
| ^^^^^^^^^^^^^^^^^^^
|
= note: `-D clippy::zero-sized-map-values` implied by `-D warnings`
= help: consider using a set instead
error: map with zero-sized value type
--> $DIR/zero_sized_hashmap_values.rs:8:30
|
LL | static STATIC_NOT_OK: Option<HashMap<String, ()>> = None;
| ^^^^^^^^^^^^^^^^^^^
|
= help: consider using a set instead
error: map with zero-sized value type
--> $DIR/zero_sized_hashmap_values.rs:11:17
|
LL | type NotOkMap = HashMap<String, ()>;
| ^^^^^^^^^^^^^^^^^^^
|
= help: consider using a set instead
error: map with zero-sized value type
--> $DIR/zero_sized_hashmap_values.rs:15:11
|
LL | NotOk(HashMap<String, ()>),
| ^^^^^^^^^^^^^^^^^^^
|
= help: consider using a set instead
error: map with zero-sized value type
--> $DIR/zero_sized_hashmap_values.rs:20:13
|
LL | not_ok: HashMap<String, ()>,
| ^^^^^^^^^^^^^^^^^^^
|
= help: consider using a set instead
error: map with zero-sized value type
--> $DIR/zero_sized_hashmap_values.rs:22:22
|
LL | also_not_ok: Vec<HashMap<usize, ()>>,
| ^^^^^^^^^^^^^^^^^^
|
= help: consider using a set instead
error: map with zero-sized value type
--> $DIR/zero_sized_hashmap_values.rs:30:30
|
LL | fn weird_map(&self, map: HashMap<usize, ()>);
| ^^^^^^^^^^^^^^^^^^
|
= help: consider using a set instead
error: map with zero-sized value type
--> $DIR/zero_sized_hashmap_values.rs:38:25
|
LL | fn not_ok(&self) -> HashMap<String, ()> {
| ^^^^^^^^^^^^^^^^^^^
|
= help: consider using a set instead
error: map with zero-sized value type
--> $DIR/zero_sized_hashmap_values.rs:55:14
|
LL | fn test(map: HashMap<String, ()>, key: &str) -> HashMap<String, ()> {
| ^^^^^^^^^^^^^^^^^^^
|
= help: consider using a set instead
error: map with zero-sized value type
--> $DIR/zero_sized_hashmap_values.rs:55:49
|
LL | fn test(map: HashMap<String, ()>, key: &str) -> HashMap<String, ()> {
| ^^^^^^^^^^^^^^^^^^^
|
= help: consider using a set instead
error: map with zero-sized value type
--> $DIR/zero_sized_hashmap_values.rs:64:34
|
LL | let _: HashMap<String, ()> = HashMap::new();
| ^^^^^^^^^^^^
|
= help: consider using a set instead
error: map with zero-sized value type
--> $DIR/zero_sized_hashmap_values.rs:64:12
|
LL | let _: HashMap<String, ()> = HashMap::new();
| ^^^^^^^^^^^^^^^^^^^
|
= help: consider using a set instead
error: map with zero-sized value type
--> $DIR/zero_sized_hashmap_values.rs:67:12
|
LL | let _: HashMap<_, _> = std::iter::empty::<(String, ())>().collect();
| ^^^^^^^^^^^^^
|
= help: consider using a set instead
error: aborting due to 13 previous errors