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use clippy_utils::diagnostics::span_lint_and_help;
use clippy_utils::is_lint_allowed;
use clippy_utils::macros::span_is_local;
use rustc_hir::def_id::DefIdMap;
use rustc_hir::{Impl, Item, ItemKind};
use rustc_lint::{LateContext, LateLintPass};
use rustc_middle::ty::AssocItem;
use rustc_session::{declare_lint_pass, declare_tool_lint};
declare_clippy_lint! {
/// ### What it does
/// Checks if a provided method is used implicitly by a trait
/// implementation. A usage example would be a wrapper where every method
/// should perform some operation before delegating to the inner type's
/// implemenation.
///
/// This lint should typically be enabled on a specific trait `impl` item
/// rather than globally.
///
/// ### Why is this bad?
/// Indicates that a method is missing.
///
/// ### Example
/// ```rust
/// trait Trait {
/// fn required();
///
/// fn provided() {}
/// }
///
/// # struct Type;
/// #[warn(clippy::missing_trait_methods)]
/// impl Trait for Type {
/// fn required() { /* ... */ }
/// }
/// ```
/// Use instead:
/// ```rust
/// trait Trait {
/// fn required();
///
/// fn provided() {}
/// }
///
/// # struct Type;
/// #[warn(clippy::missing_trait_methods)]
/// impl Trait for Type {
/// fn required() { /* ... */ }
///
/// fn provided() { /* ... */ }
/// }
/// ```
#[clippy::version = "1.66.0"]
pub MISSING_TRAIT_METHODS,
restriction,
"trait implementation uses default provided method"
}
declare_lint_pass!(MissingTraitMethods => [MISSING_TRAIT_METHODS]);
impl<'tcx> LateLintPass<'tcx> for MissingTraitMethods {
fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'tcx>) {
if !is_lint_allowed(cx, MISSING_TRAIT_METHODS, item.hir_id())
&& span_is_local(item.span)
&& let ItemKind::Impl(Impl {
items,
of_trait: Some(trait_ref),
..
}) = item.kind
&& let Some(trait_id) = trait_ref.trait_def_id()
{
let mut provided: DefIdMap<&AssocItem> = cx
.tcx
.provided_trait_methods(trait_id)
.map(|assoc| (assoc.def_id, assoc))
.collect();
for impl_item in *items {
if let Some(def_id) = impl_item.trait_item_def_id {
provided.remove(&def_id);
}
}
cx.tcx.with_stable_hashing_context(|hcx| {
for assoc in provided.values_sorted(&hcx, true) {
let source_map = cx.tcx.sess.source_map();
let definition_span = source_map.guess_head_span(cx.tcx.def_span(assoc.def_id));
span_lint_and_help(
cx,
MISSING_TRAIT_METHODS,
source_map.guess_head_span(item.span),
&format!("missing trait method provided by default: `{}`", assoc.name),
Some(definition_span),
"implement the method",
);
}
})
}
}
}
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