new lint: mutable_key_type

CHANGELOG.md

@@ -1108,6 +1108,7 @@ Released 2018-09-13
 [`mut_from_ref`]: https://rust-lang.github.io/rust-clippy/master/index.html#mut_from_ref
 [`mut_mut`]: https://rust-lang.github.io/rust-clippy/master/index.html#mut_mut
 [`mut_range_bound`]: https://rust-lang.github.io/rust-clippy/master/index.html#mut_range_bound
+[`mutable_key_type`]: https://rust-lang.github.io/rust-clippy/master/index.html#mutable_key_type
 [`mutex_atomic`]: https://rust-lang.github.io/rust-clippy/master/index.html#mutex_atomic
 [`mutex_integer`]: https://rust-lang.github.io/rust-clippy/master/index.html#mutex_integer
 [`naive_bytecount`]: https://rust-lang.github.io/rust-clippy/master/index.html#naive_bytecount

README.md

@@ -6,7 +6,7 @@
 
 A collection of lints to catch common mistakes and improve your [Rust](https://github.com/rust-lang/rust) code.
 
-[There are 340 lints included in this crate!](https://rust-lang.github.io/rust-clippy/master/index.html)
+[There are 341 lints included in this crate!](https://rust-lang.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:
 

clippy_lints/src/lib.rs

@@ -240,6 +240,7 @@ pub mod missing_doc;
 pub mod missing_inline;
 pub mod mul_add;
 pub mod multiple_crate_versions;
+pub mod mut_key;
 pub mod mut_mut;
 pub mod mut_reference;
 pub mod mutable_debug_assertion;
@@ -667,6 +668,7 @@ pub fn register_plugins(store: &mut lint::LintStore, sess: &Session, conf: &Conf
  &missing_inline::MISSING_INLINE_IN_PUBLIC_ITEMS,
  &mul_add::MANUAL_MUL_ADD,
  &multiple_crate_versions::MULTIPLE_CRATE_VERSIONS,
+ &mut_key::MUTABLE_KEY_TYPE,
  &mut_mut::MUT_MUT,
  &mut_reference::UNNECESSARY_MUT_PASSED,
  &mutable_debug_assertion::DEBUG_ASSERT_WITH_MUT_CALL,
@@ -939,6 +941,7 @@ pub fn register_plugins(store: &mut lint::LintStore, sess: &Session, conf: &Conf
  store.register_late_pass(|| box trait_bounds::TraitBounds);
  store.register_late_pass(|| box comparison_chain::ComparisonChain);
  store.register_late_pass(|| box mul_add::MulAddCheck);
+ store.register_late_pass(|| box mut_key::MutableKeyType);
  store.register_early_pass(|| box reference::DerefAddrOf);
  store.register_early_pass(|| box reference::RefInDeref);
  store.register_early_pass(|| box double_parens::DoubleParens);
@@ -1223,6 +1226,7 @@ pub fn register_plugins(store: &mut lint::LintStore, sess: &Session, conf: &Conf
  LintId::of(&misc_early::UNNEEDED_FIELD_PATTERN),
  LintId::of(&misc_early::UNNEEDED_WILDCARD_PATTERN),
  LintId::of(&misc_early::ZERO_PREFIXED_LITERAL),
+ LintId::of(&mut_key::MUTABLE_KEY_TYPE),
  LintId::of(&mut_reference::UNNECESSARY_MUT_PASSED),
  LintId::of(&mutable_debug_assertion::DEBUG_ASSERT_WITH_MUT_CALL),
  LintId::of(&mutex_atomic::MUTEX_ATOMIC),
@@ -1532,6 +1536,7 @@ pub fn register_plugins(store: &mut lint::LintStore, sess: &Session, conf: &Conf
  LintId::of(&misc::CMP_NAN),
  LintId::of(&misc::FLOAT_CMP),
  LintId::of(&misc::MODULO_ONE),
+ LintId::of(&mut_key::MUTABLE_KEY_TYPE),
  LintId::of(&mutable_debug_assertion::DEBUG_ASSERT_WITH_MUT_CALL),
  LintId::of(&non_copy_const::BORROW_INTERIOR_MUTABLE_CONST),
  LintId::of(&non_copy_const::DECLARE_INTERIOR_MUTABLE_CONST),

clippy_lints/src/mut_key.rs

@@ -0,0 +1,120 @@
+use crate::utils::{match_def_path, paths, span_lint, trait_ref_of_method, walk_ptrs_ty};
+use rustc::declare_lint_pass;
+use rustc::hir;
+use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
+use rustc::ty::{Adt, Dynamic, Opaque, Param, RawPtr, Ref, Ty, TypeAndMut};
+use rustc_session::declare_tool_lint;
+use syntax::source_map::Span;
+
+declare_clippy_lint! {
+ /// **What it does:** Checks for sets/maps with mutable key types.
+ ///
+ /// **Why is this bad?** All of `HashMap`, `HashSet`, `BTreeMap` and
+ /// `BtreeSet` rely on either the hash or the order of keys be unchanging,
+ /// so having types with interior mutability is a bad idea.
+ ///
+ /// **Known problems:** We don't currently account for `Rc` or `Arc`, so
+ /// this may yield false positives.
+ ///
+ /// **Example:**
+ /// ```rust
+ /// use std::cmp::{PartialEq, Eq};
+ /// use std::collections::HashSet;
+ /// use std::hash::{Hash, Hasher};
+ /// use std::sync::atomic::AtomicUsize;
+ ///# #[allow(unused)]
+ ///
+ /// struct Bad(AtomicUsize);
+ /// impl PartialEq for Bad {
+ /// fn eq(&self, rhs: &Self) -> bool {
+ /// ..
+ /// ; unimplemented!();
+ /// }
+ /// }
+ ///
+ /// impl Eq for Bad {}
+ ///
+ /// impl Hash for Bad {
+ /// fn hash<H: Hasher>(&self, h: &mut H) {
+ /// ..
+ /// ; unimplemented!();
+ /// }
+ /// }
+ ///
+ /// fn main() {
+ /// let _: HashSet<Bad> = HashSet::new();
+ /// }
+ /// ```
+ pub MUTABLE_KEY_TYPE,
+ correctness,
+ "Check for mutable Map/Set key type"
+}
+
+declare_lint_pass!(MutableKeyType => [ MUTABLE_KEY_TYPE ]);
+
+impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MutableKeyType {
+ fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx hir::Item<'tcx>) {
+ if let hir::ItemKind::Fn(ref sig, ..) = item.kind {
+ check_sig(cx, item.hir_id, &sig.decl);
+ }
+ }
+
+ fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx hir::ImplItem<'tcx>) {
+ if let hir::ImplItemKind::Method(ref sig, ..) = item.kind {
+ if trait_ref_of_method(cx, item.hir_id).is_none() {
+ check_sig(cx, item.hir_id, &sig.decl);
+ }
+ }
+ }
+
+ fn check_trait_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx hir::TraitItem<'tcx>) {
+ if let hir::TraitItemKind::Method(ref sig, ..) = item.kind {
+ check_sig(cx, item.hir_id, &sig.decl);
+ }
+ }
+
+ fn check_local(&mut self, cx: &LateContext<'_, '_>, local: &hir::Local) {
+ if let hir::PatKind::Wild = local.pat.kind {
+ return;
+ }
+ check_ty(cx, local.span, cx.tables.pat_ty(&*local.pat));
+ }
+}
+
+fn check_sig<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, item_hir_id: hir::HirId, decl: &hir::FnDecl) {
+ let fn_def_id = cx.tcx.hir().local_def_id(item_hir_id);
+ let fn_sig = cx.tcx.fn_sig(fn_def_id);
+ for (hir_ty, ty) in decl.inputs.iter().zip(fn_sig.inputs().skip_binder().iter()) {
+ check_ty(cx, hir_ty.span, ty);
+ }
+ check_ty(
+ cx,
+ decl.output.span(),
+ cx.tcx.erase_late_bound_regions(&fn_sig.output()),
+ );
+}
+
+// We want to lint 1. sets or maps with 2. not immutable key types and 3. no unerased
+// generics (because the compiler cannot ensure immutability for unknown types).
+fn check_ty<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, span: Span, ty: Ty<'tcx>) {
+ let ty = walk_ptrs_ty(ty);
+ if let Adt(def, substs) = ty.kind {
+ if [&paths::HASHMAP, &paths::BTREEMAP, &paths::HASHSET, &paths::BTREESET]
+ .iter()
+ .any(|path| match_def_path(cx, def.did, &**path))
+ {
+ let key_type = substs.type_at(0);
+ if is_concrete_type(key_type) && !key_type.is_freeze(cx.tcx, cx.param_env, span) {
+ span_lint(cx, MUTABLE_KEY_TYPE, span, "mutable key type");
+ }
+ }
+ }
+}
+
+fn is_concrete_type(ty: Ty<'_>) -> bool {
+ match ty.kind {
+ RawPtr(TypeAndMut { ty: inner_ty, .. }) | Ref(_, inner_ty, _) => is_concrete_type(inner_ty),
+ Dynamic(..) | Opaque(..) | Param(..) => false,
+ _ => true,
+ }
+}

src/lintlist/mod.rs

@@ -6,7 +6,7 @@ pub use lint::Lint;
 pub use lint::LINT_LEVELS;
 
 // begin lint list, do not remove this comment, it’s used in `update_lints`
-pub const ALL_LINTS: [Lint; 340] = [
+pub const ALL_LINTS: [Lint; 341] = [
  Lint {
  name: "absurd_extreme_comparisons",
  group: "correctness",
@@ -1239,6 +1239,13 @@ pub const ALL_LINTS: [Lint; 340] = [
  deprecation: None,
  module: "loops",
  },
+ Lint {
+ name: "mutable_key_type",
+ group: "correctness",
+ desc: "Check for mutable Map/Set key type",
+ deprecation: None,
+ module: "mut_key",
+ },
  Lint {
  name: "mutex_atomic",
  group: "perf",

tests/ui/mut_key.rs

@@ -0,0 +1,37 @@
+use std::collections::{HashMap, HashSet};
+use std::hash::{Hash, Hasher};
+use std::sync::atomic::{AtomicUsize, Ordering::Relaxed};
+
+struct Key(AtomicUsize);
+
+impl Clone for Key {
+ fn clone(&self) -> Self {
+ Key(AtomicUsize::new(self.0.load(Relaxed)))
+ }
+}
+
+impl PartialEq for Key {
+ fn eq(&self, other: &Self) -> bool {
+ self.0.load(Relaxed) == other.0.load(Relaxed)
+ }
+}
+
+impl Eq for Key {}
+
+impl Hash for Key {
+ fn hash<H: Hasher>(&self, h: &mut H) {
+ self.0.load(Relaxed).hash(h);
+ }
+}
+
+fn should_not_take_this_arg(m: &mut HashMap<Key, usize>, _n: usize) -> HashSet<Key> {
+ let _other: HashMap<Key, bool> = HashMap::new();
+ m.keys().cloned().collect()
+}
+
+fn this_is_ok(m: &mut HashMap<usize, Key>) {}
+
+fn main() {
+ let _ = should_not_take_this_arg(&mut HashMap::new(), 1);
+ this_is_ok(&mut HashMap::new());
+}

tests/ui/mut_key.stderr

@@ -0,0 +1,22 @@
+error: mutable key type
+ --> $DIR/mut_key.rs:27:32
+ |
+LL | fn should_not_take_this_arg(m: &mut HashMap<Key, usize>, _n: usize) -> HashSet<Key> {
+ | ^^^^^^^^^^^^^^^^^^^^^^^^
+ |
+ = note: `#[deny(clippy::mutable_key_type)]` on by default
+
+error: mutable key type
+ --> $DIR/mut_key.rs:27:72
+ |
+LL | fn should_not_take_this_arg(m: &mut HashMap<Key, usize>, _n: usize) -> HashSet<Key> {
+ | ^^^^^^^^^^^^
+
+error: mutable key type
+ --> $DIR/mut_key.rs:28:5
+ |
+LL | let _other: HashMap<Key, bool> = HashMap::new();
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 3 previous errors
+