Support trait bounds with type parameters.

Author: Allen Hsu

clippy_lints/src/trait_bounds.rs

@@ -8,8 +8,8 @@ use rustc_data_structures::unhash::UnhashMap;
 use rustc_errors::Applicability;
 use rustc_hir::def::Res;
 use rustc_hir::{
-    GenericBound, Generics, Item, ItemKind, Node, ParamName, Path, PathSegment, QPath, TraitItem, Ty, TyKind,
-    WherePredicate,
+    GenericArg, GenericBound, Generics, Item, ItemKind, Node, ParamName, Path, PathSegment, QPath, TraitItem, Ty,
+    TyKind, WherePredicate,
 };
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::{declare_tool_lint, impl_lint_pass};
@@ -289,44 +289,11 @@ fn check_trait_bound_duplication(cx: &LateContext<'_>, gen: &'_ Generics<'_>) {
     }
 }
 
-fn check_bounds_or_where_duplication(cx: &LateContext<'_>, gen: &'_ Generics<'_>) {
-    fn rollup_traits(cx: &LateContext<'_>, bounds: &[GenericBound<'_>], msg: &str) {
-        let mut map = FxHashMap::default();
-        let mut repeated_spans = false;
-        for bound in bounds.iter().filter_map(get_trait_info_from_bound) {
-            let (definition, _, span_direct) = bound;
-            if map.insert(definition, span_direct).is_some() {
-                repeated_spans = true;
-            }
-        }
-
-        if_chain! {
-            if repeated_spans;
-            if let Some(first_trait) = bounds.get(0);
-            if let Some(last_trait) = bounds.iter().last();
-            then {
-                let all_trait_span = first_trait.span().to(last_trait.span());
-
-                let mut traits = map.values()
-                    .filter_map(|span| snippet_opt(cx, *span))
-                    .collect::<Vec<_>>();
-                traits.sort_unstable();
-                let traits = traits.join(" + ");
-
-                span_lint_and_sugg(
-                    cx,
-                    REPEATED_WHERE_CLAUSE_OR_TRAIT_BOUND,
-                    all_trait_span,
-                    msg,
-                    "try",
-                    traits,
-                    Applicability::MachineApplicable
-                    );
-            }
-        }
-    }
+#[derive(PartialEq, Eq, Hash, Debug)]
+struct ComparableBound(Res, Vec<Res>, Vec<ComparableBound>);
 
-    if gen.span.from_expansion() || (gen.params.is_empty() && gen.where_clause.predicates.is_empty()) {
+fn check_bounds_or_where_duplication(cx: &LateContext<'_>, gen: &'_ Generics<'_>) {
+    if gen.span.from_expansion() {
         return;
     }
 
@@ -355,3 +322,76 @@ fn get_trait_info_from_bound<'a>(bound: &'a GenericBound<'_>) -> Option<(Res, &'
         None
     }
 }
+
+fn try_into_comparable_bound(bound: &GenericBound<'_>) -> Option<ComparableBound> {
+    if let GenericBound::Trait(t, _) = bound {
+        Some(ComparableBound(
+            t.trait_ref.path.res,
+            t.trait_ref
+                .path
+                .segments
+                .iter()
+                .filter_map(|segment| {
+                    // get trait bound type arguments
+                    Some(segment.args?.args.iter().filter_map(|arg| {
+                        if_chain! {
+                            if let GenericArg::Type(ty) = arg;
+                            if let TyKind::Path(QPath::Resolved(_, path)) = ty.kind;
+                            then { return Some(path.res) }
+                        }
+                        None
+                    }))
+                })
+                .flatten()
+                .collect(),
+            t.bound_generic_params
+                .iter()
+                .flat_map(|param| param.bounds.iter().filter_map(try_into_comparable_bound))
+                .collect(),
+        ))
+    } else {
+        None
+    }
+}
+
+fn rollup_traits(cx: &LateContext<'_>, bounds: &[GenericBound<'_>], msg: &str) {
+    let mut map = FxHashMap::default();
+    let mut repeated_spans = false;
+    for bound in bounds.iter().filter_map(|bound| {
+        if let GenericBound::Trait(t, _) = bound {
+            Some((try_into_comparable_bound(bound)?, t.span))
+        } else {
+            None
+        }
+    }) {
+        let (comparable_bound, span_direct) = bound;
+        if map.insert(comparable_bound, span_direct).is_some() {
+            repeated_spans = true;
+        }
+    }
+
+    if_chain! {
+        if repeated_spans;
+        if let Some(first_trait) = bounds.get(0);
+        if let Some(last_trait) = bounds.iter().last();
+        then {
+            let all_trait_span = first_trait.span().to(last_trait.span());
+
+            let mut traits = map.values()
+                .filter_map(|span| snippet_opt(cx, *span))
+                .collect::<Vec<_>>();
+            traits.sort_unstable();
+            let traits = traits.join(" + ");
+
+            span_lint_and_sugg(
+                cx,
+                REPEATED_WHERE_CLAUSE_OR_TRAIT_BOUND,
+                all_trait_span,
+                msg,
+                "try",
+                traits,
+                Applicability::MachineApplicable
+                );
+        }
+    }
+}

tests/ui/repeated_where_clause_or_trait_bound.fixed

@@ -92,4 +92,14 @@ where
 
 fn no_error_separate_arg_bounds(program: impl AsRef<()>, dir: impl AsRef<()>, args: &[impl AsRef<()>]) {}
 
+trait GenericTrait<T> {}
+
+fn good_generic<T: GenericTrait<u64> + GenericTrait<u32>>(arg0: T) {
+    unimplemented!();
+}
+
+fn bad_generic<T: GenericTrait<u32> + GenericTrait<u64>>(arg0: T) {
+    unimplemented!();
+}
+
 fn main() {}

tests/ui/repeated_where_clause_or_trait_bound.rs

@@ -92,4 +92,14 @@ where
 
 fn no_error_separate_arg_bounds(program: impl AsRef<()>, dir: impl AsRef<()>, args: &[impl AsRef<()>]) {}
 
+trait GenericTrait<T> {}
+
+fn good_generic<T: GenericTrait<u64> + GenericTrait<u32>>(arg0: T) {
+    unimplemented!();
+}
+
+fn bad_generic<T: GenericTrait<u64> + GenericTrait<u32> + GenericTrait<u64>>(arg0: T) {
+    unimplemented!();
+}
+
 fn main() {}

tests/ui/repeated_where_clause_or_trait_bound.stderr

@@ -34,5 +34,11 @@ error: this where clause contains repeated elements
 LL |         T: Clone + Clone + Clone + Copy,
    |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `Clone + Copy`
 
-error: aborting due to 5 previous errors
+error: this trait bound contains repeated elements
+  --> $DIR/repeated_where_clause_or_trait_bound.rs:101:19
+   |
+LL | fn bad_generic<T: GenericTrait<u64> + GenericTrait<u32> + GenericTrait<u64>>(arg0: T) {
+   |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `GenericTrait<u32> + GenericTrait<u64>`
+
+error: aborting due to 6 previous errors