--- /dev/null
+use crate::utils::{in_macro, snippet, snippet_with_applicability, span_lint_and_help, SpanlessHash};
+use if_chain::if_chain;
+use rustc_data_structures::fx::FxHashMap;
+use rustc_errors::Applicability;
+use rustc_hir::{def::Res, GenericBound, Generics, ParamName, Path, QPath, TyKind, WherePredicate};
+use rustc_lint::{LateContext, LateLintPass};
+use rustc_session::{declare_tool_lint, impl_lint_pass};
+use rustc_span::Span;
+
+declare_clippy_lint! {
+ /// **What it does:** This lint warns about unnecessary type repetitions in trait bounds
+ ///
+ /// **Why is this bad?** Repeating the type for every bound makes the code
+ /// less readable than combining the bounds
+ ///
+ /// **Known problems:** None.
+ ///
+ /// **Example:**
+ /// ```rust
+ /// pub fn foo<T>(t: T) where T: Copy, T: Clone {}
+ /// ```
+ ///
+ /// Could be written as:
+ ///
+ /// ```rust
+ /// pub fn foo<T>(t: T) where T: Copy + Clone {}
+ /// ```
+ pub TYPE_REPETITION_IN_BOUNDS,
+ pedantic,
+ "Types are repeated unnecessary in trait bounds use `+` instead of using `T: _, T: _`"
+}
+
+declare_clippy_lint! {
+ /// **What it does:** Checks for cases where generics are being used and multiple
+ /// syntax specifications for trait bounds are used simultaneously.
+ ///
+ /// **Why is this bad?** Duplicate bounds makes the code
+ /// less readable than specifing them only once.
+ ///
+ /// **Known problems:** None.
+ ///
+ /// **Example:**
+ /// ```rust
+ /// fn func<T: Clone + Default>(arg: T) where T: Clone + Default {}
+ /// ```
+ ///
+ /// Could be written as:
+ ///
+ /// ```rust
+ /// fn func<T: Clone + Default>(arg: T) {}
+ /// ```
+ /// or
+ ///
+ /// ```rust
+ /// fn func<T>(arg: T) where T: Clone + Default {}
+ /// ```
+ pub TRAIT_DUPLICATION_IN_BOUNDS,
+ pedantic,
+ "Check if the same trait bounds are specified twice during a function declaration"
+}
+
+#[derive(Copy, Clone)]
+pub struct TraitBounds {
+ max_trait_bounds: u64,
+}
+
+impl TraitBounds {
+ #[must_use]
+ pub fn new(max_trait_bounds: u64) -> Self {
+ Self { max_trait_bounds }
+ }
+}
+
+impl_lint_pass!(TraitBounds => [TYPE_REPETITION_IN_BOUNDS, TRAIT_DUPLICATION_IN_BOUNDS]);
+
+impl<'tcx> LateLintPass<'tcx> for TraitBounds {
+ fn check_generics(&mut self, cx: &LateContext<'tcx>, gen: &'tcx Generics<'_>) {
+ self.check_type_repetition(cx, gen);
+ check_trait_bound_duplication(cx, gen);
+ }
+}
+
+fn get_trait_res_span_from_bound(bound: &GenericBound<'_>) -> Option<(Res, Span)> {
+ if let GenericBound::Trait(t, _) = bound {
+ Some((t.trait_ref.path.res, t.span))
+ } else {
+ None
+ }
+}
+
+impl TraitBounds {
+ fn check_type_repetition(self, cx: &LateContext<'_>, gen: &'_ Generics<'_>) {
+ if in_macro(gen.span) {
+ return;
+ }
+ let hash = |ty| -> u64 {
+ let mut hasher = SpanlessHash::new(cx);
+ hasher.hash_ty(ty);
+ hasher.finish()
+ };
+ let mut map = FxHashMap::default();
+ let mut applicability = Applicability::MaybeIncorrect;
+ for bound in gen.where_clause.predicates {
+ if_chain! {
+ if let WherePredicate::BoundPredicate(ref p) = bound;
+ if p.bounds.len() as u64 <= self.max_trait_bounds;
+ if !in_macro(p.span);
+ let h = hash(&p.bounded_ty);
+ if let Some(ref v) = map.insert(h, p.bounds.iter().collect::<Vec<_>>());
+
+ then {
+ let mut hint_string = format!(
+ "consider combining the bounds: `{}:",
+ snippet(cx, p.bounded_ty.span, "_")
+ );
+ for b in v.iter() {
+ if let GenericBound::Trait(ref poly_trait_ref, _) = b {
+ let path = &poly_trait_ref.trait_ref.path;
+ hint_string.push_str(&format!(
+ " {} +",
+ snippet_with_applicability(cx, path.span, "..", &mut applicability)
+ ));
+ }
+ }
+ for b in p.bounds.iter() {
+ if let GenericBound::Trait(ref poly_trait_ref, _) = b {
+ let path = &poly_trait_ref.trait_ref.path;
+ hint_string.push_str(&format!(
+ " {} +",
+ snippet_with_applicability(cx, path.span, "..", &mut applicability)
+ ));
+ }
+ }
+ hint_string.truncate(hint_string.len() - 2);
+ hint_string.push('`');
+ span_lint_and_help(
+ cx,
+ TYPE_REPETITION_IN_BOUNDS,
+ p.span,
+ "this type has already been used as a bound predicate",
+ None,
+ &hint_string,
+ );
+ }
+ }
+ }
+ }
+}
+
+fn check_trait_bound_duplication(cx: &LateContext<'_>, gen: &'_ Generics<'_>) {
+ if in_macro(gen.span) || gen.params.is_empty() || gen.where_clause.predicates.is_empty() {
+ return;
+ }
+
+ let mut map = FxHashMap::default();
+ for param in gen.params {
+ if let ParamName::Plain(ref ident) = param.name {
+ let res = param
+ .bounds
+ .iter()
+ .filter_map(get_trait_res_span_from_bound)
+ .collect::<Vec<_>>();
+ map.insert(*ident, res);
+ }
+ }
+
+ for predicate in gen.where_clause.predicates {
+ if_chain! {
+ if let WherePredicate::BoundPredicate(ref bound_predicate) = predicate;
+ if !in_macro(bound_predicate.span);
+ if let TyKind::Path(QPath::Resolved(_, Path { ref segments, .. })) = bound_predicate.bounded_ty.kind;
+ if let Some(segment) = segments.first();
+ if let Some(trait_resolutions_direct) = map.get(&segment.ident);
+ then {
+ for (res_where, _) in bound_predicate.bounds.iter().filter_map(get_trait_res_span_from_bound) {
+ if let Some((_, span_direct)) = trait_resolutions_direct
+ .iter()
+ .find(|(res_direct, _)| *res_direct == res_where) {
+ span_lint_and_help(
+ cx,
+ TRAIT_DUPLICATION_IN_BOUNDS,
+ *span_direct,
+ "this trait bound is already specified in the where clause",
+ None,
+ "consider removing this trait bound",
+ );
+ }
+ }
+ }
+ }
+ }
+}
projects / rustc.git / blobdiff