2018-05-30 08:15:50 +00:00
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use crate::utils::paths;
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use crate::utils::{is_automatically_derived, is_copy, match_path, span_lint_and_then};
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2018-11-27 20:14:15 +00:00
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use if_chain::if_chain;
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2018-12-29 15:04:45 +00:00
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use rustc::ty::{self, Ty};
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2020-01-06 16:39:50 +00:00
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use rustc_hir::*;
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2020-01-12 06:08:41 +00:00
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use rustc_lint::{LateContext, LateLintPass};
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2020-01-11 11:37:08 +00:00
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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2020-01-04 10:00:00 +00:00
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use rustc_span::source_map::Span;
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2016-01-21 17:19:02 +00:00
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2018-03-28 13:24:26 +00:00
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declare_clippy_lint! {
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2019-03-05 16:50:33 +00:00
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/// **What it does:** Checks for deriving `Hash` but implementing `PartialEq`
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/// explicitly or vice versa.
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///
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/// **Why is this bad?** The implementation of these traits must agree (for
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/// example for use with `HashMap`) so it’s probably a bad idea to use a
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/// default-generated `Hash` implementation with an explicitly defined
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/// `PartialEq`. In particular, the following must hold for any type:
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///
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2019-03-05 22:23:50 +00:00
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/// ```text
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2019-03-05 16:50:33 +00:00
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/// k1 == k2 ⇒ hash(k1) == hash(k2)
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/// ```
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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2019-03-05 22:23:50 +00:00
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/// ```ignore
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2019-03-05 16:50:33 +00:00
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/// #[derive(Hash)]
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/// struct Foo;
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///
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/// impl PartialEq for Foo {
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/// ...
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/// }
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/// ```
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2016-02-15 22:38:09 +00:00
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pub DERIVE_HASH_XOR_EQ,
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2018-03-28 13:24:26 +00:00
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correctness,
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2016-01-21 17:19:02 +00:00
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"deriving `Hash` but implementing `PartialEq` explicitly"
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}
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2018-03-28 13:24:26 +00:00
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declare_clippy_lint! {
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2019-03-05 16:50:33 +00:00
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/// **What it does:** Checks for explicit `Clone` implementations for `Copy`
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/// types.
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///
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/// **Why is this bad?** To avoid surprising behaviour, these traits should
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/// agree and the behaviour of `Copy` cannot be overridden. In almost all
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/// situations a `Copy` type should have a `Clone` implementation that does
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/// nothing more than copy the object, which is what `#[derive(Copy, Clone)]`
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/// gets you.
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///
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/// **Known problems:** Bounds of generic types are sometimes wrong: https://github.com/rust-lang/rust/issues/26925
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///
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/// **Example:**
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2019-08-03 16:42:05 +00:00
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/// ```rust,ignore
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2019-03-05 16:50:33 +00:00
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/// #[derive(Copy)]
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/// struct Foo;
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///
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/// impl Clone for Foo {
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2019-08-03 16:42:05 +00:00
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/// // ..
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2019-03-05 16:50:33 +00:00
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/// }
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/// ```
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2016-01-24 12:56:23 +00:00
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pub EXPL_IMPL_CLONE_ON_COPY,
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2018-03-28 13:24:26 +00:00
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pedantic,
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2016-01-24 12:56:23 +00:00
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"implementing `Clone` explicitly on `Copy` types"
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}
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2019-04-08 20:43:55 +00:00
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declare_lint_pass!(Derive => [EXPL_IMPL_CLONE_ON_COPY, DERIVE_HASH_XOR_EQ]);
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2016-01-21 17:19:02 +00:00
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2016-12-07 12:13:40 +00:00
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Derive {
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2019-12-22 14:42:41 +00:00
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fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item<'_>) {
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2020-01-18 05:14:36 +00:00
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if let ItemKind::Impl {
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of_trait: Some(ref trait_ref),
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..
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} = item.kind
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{
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2019-07-06 03:52:51 +00:00
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let ty = cx.tcx.type_of(cx.tcx.hir().local_def_id(item.hir_id));
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2016-10-30 01:13:41 +00:00
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let is_automatically_derived = is_automatically_derived(&*item.attrs);
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2016-02-15 22:38:09 +00:00
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check_hash_peq(cx, item.span, trait_ref, ty, is_automatically_derived);
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if !is_automatically_derived {
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2016-02-14 19:29:32 +00:00
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check_copy_clone(cx, item, trait_ref, ty);
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2016-01-21 17:19:02 +00:00
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}
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2016-06-05 18:46:27 +00:00
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}
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2016-01-24 12:56:23 +00:00
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}
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}
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2016-01-21 17:19:02 +00:00
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2016-02-15 22:38:09 +00:00
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/// Implementation of the `DERIVE_HASH_XOR_EQ` lint.
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2016-12-21 11:14:54 +00:00
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fn check_hash_peq<'a, 'tcx>(
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cx: &LateContext<'a, 'tcx>,
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span: Span,
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2019-12-30 04:02:10 +00:00
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trait_ref: &TraitRef<'_>,
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2017-06-11 02:57:25 +00:00
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ty: Ty<'tcx>,
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2017-08-09 07:30:56 +00:00
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hash_is_automatically_derived: bool,
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2016-12-21 11:14:54 +00:00
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) {
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2017-10-23 19:18:02 +00:00
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if_chain! {
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2019-05-17 21:53:54 +00:00
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if match_path(&trait_ref.path, &paths::HASH);
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2017-10-23 19:18:02 +00:00
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if let Some(peq_trait_def_id) = cx.tcx.lang_items().eq_trait();
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2019-11-01 19:12:08 +00:00
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if !&trait_ref.trait_def_id().is_local();
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2017-10-23 19:18:02 +00:00
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then {
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// Look for the PartialEq implementations for `ty`
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cx.tcx.for_each_relevant_impl(peq_trait_def_id, ty, |impl_id| {
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let peq_is_automatically_derived = is_automatically_derived(&cx.tcx.get_attrs(impl_id));
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2017-11-04 19:55:56 +00:00
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2017-10-23 19:18:02 +00:00
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if peq_is_automatically_derived == hash_is_automatically_derived {
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return;
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}
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2017-11-04 19:55:56 +00:00
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2017-10-23 19:18:02 +00:00
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let trait_ref = cx.tcx.impl_trait_ref(impl_id).expect("must be a trait implementation");
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2017-11-04 19:55:56 +00:00
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2017-10-23 19:18:02 +00:00
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// Only care about `impl PartialEq<Foo> for Foo`
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// For `impl PartialEq<B> for A, input_types is [A, B]
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if trait_ref.substs.type_at(1) == ty {
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let mess = if peq_is_automatically_derived {
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"you are implementing `Hash` explicitly but have derived `PartialEq`"
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} else {
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"you are deriving `Hash` but have implemented `PartialEq` explicitly"
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};
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2017-11-04 19:55:56 +00:00
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2017-10-23 19:18:02 +00:00
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span_lint_and_then(
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cx, DERIVE_HASH_XOR_EQ, span,
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mess,
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|db| {
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2019-06-18 09:15:47 +00:00
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if let Some(node_id) = cx.tcx.hir().as_local_hir_id(impl_id) {
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2017-10-23 19:18:02 +00:00
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db.span_note(
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2018-12-08 00:56:03 +00:00
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cx.tcx.hir().span(node_id),
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2017-10-23 19:18:02 +00:00
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"`PartialEq` implemented here"
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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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2016-01-24 12:56:23 +00:00
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}
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2016-01-21 17:19:02 +00:00
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2016-01-24 12:56:23 +00:00
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/// Implementation of the `EXPL_IMPL_CLONE_ON_COPY` lint.
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2019-12-30 04:02:10 +00:00
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fn check_copy_clone<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, item: &Item<'_>, trait_ref: &TraitRef<'_>, ty: Ty<'tcx>) {
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2019-05-17 21:53:54 +00:00
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if match_path(&trait_ref.path, &paths::CLONE_TRAIT) {
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2017-06-11 02:34:47 +00:00
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if !is_copy(cx, ty) {
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2017-04-28 15:03:18 +00:00
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return;
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2016-01-24 12:56:23 +00:00
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}
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2016-01-21 17:19:02 +00:00
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2019-09-26 09:03:36 +00:00
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match ty.kind {
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2018-08-22 21:34:52 +00:00
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ty::Adt(def, _) if def.is_union() => return,
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2016-08-28 17:43:55 +00:00
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// Some types are not Clone by default but could be cloned “by hand” if necessary
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2018-11-27 20:14:15 +00:00
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ty::Adt(def, substs) => {
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for variant in &def.variants {
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for field in &variant.fields {
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2019-09-26 09:03:36 +00:00
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if let ty::FnDef(..) = field.ty(cx.tcx, substs).kind {
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2018-01-11 09:28:42 +00:00
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return;
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}
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}
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2018-11-27 20:14:15 +00:00
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for subst in substs {
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2019-09-26 16:34:43 +00:00
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if let ty::subst::GenericArgKind::Type(subst) = subst.unpack() {
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2019-09-26 09:03:36 +00:00
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if let ty::Param(_) = subst.kind {
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2018-11-27 20:14:15 +00:00
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return;
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}
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}
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}
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2018-01-11 09:28:42 +00:00
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}
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2016-12-20 17:21:30 +00:00
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},
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2016-01-24 12:56:23 +00:00
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_ => (),
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}
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2017-09-05 09:33:04 +00:00
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span_lint_and_then(
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cx,
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EXPL_IMPL_CLONE_ON_COPY,
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item.span,
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"you are implementing `Clone` explicitly on a `Copy` type",
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2017-11-04 19:55:56 +00:00
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|db| {
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db.span_note(item.span, "consider deriving `Clone` or removing `Copy`");
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},
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2017-09-05 09:33:04 +00:00
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);
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2016-01-24 12:56:23 +00:00
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}
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}
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