1 files changed, 84 insertions, 6 deletions

diff --git a/crates/ra_hir_ty/src/utils.rs b/crates/ra_hir_ty/src/utils.rs
index e4ba890ef..0b1806a84 100644
--- a/crates/ra_hir_ty/src/utils.rs
+++ b/crates/ra_hir_ty/src/utils.rs
@@ -5,14 +5,14 @@ use std::sync::Arc;
 use hir_def::{
     adt::VariantData,
     db::DefDatabase,
+    generics::{GenericParams, TypeParamData},
+    path::Path,
     resolver::{HasResolver, TypeNs},
     type_ref::TypeRef,
-    TraitId, TypeAliasId, VariantId,
+    AssocContainerId, GenericDefId, Lookup, TraitId, TypeAliasId, TypeParamId, VariantId,
 };
-use hir_expand::name::{self, Name};
+use hir_expand::name::{name, Name};
 
-// FIXME: this is wrong, b/c it can't express `trait T: PartialEq<()>`.
-// We should return a `TraitREf` here.
 fn direct_super_traits(db: &impl DefDatabase, trait_: TraitId) -> Vec<TraitId> {
     let resolver = trait_.resolver(db);
     // returning the iterator directly doesn't easily work because of
@@ -23,10 +23,10 @@ fn direct_super_traits(db: &impl DefDatabase, trait_: TraitId) -> Vec<TraitId> {
         .where_predicates
         .iter()
         .filter_map(|pred| match &pred.type_ref {
-            TypeRef::Path(p) if p.as_ident() == Some(&name::SELF_TYPE) => pred.bound.as_path(),
+            TypeRef::Path(p) if p == &Path::from(name![Self]) => pred.bound.as_path(),
             _ => None,
         })
-        .filter_map(|path| match resolver.resolve_path_in_type_ns_fully(db, path) {
+        .filter_map(|path| match resolver.resolve_path_in_type_ns_fully(db, path.mod_path()) {
             Some(TypeNs::TraitId(t)) => Some(t),
             _ => None,
         })
@@ -82,3 +82,81 @@ pub(crate) fn make_mut_slice<T: Clone>(a: &mut Arc<[T]>) -> &mut [T] {
     }
     Arc::get_mut(a).unwrap()
 }
+
+pub(crate) fn generics(db: &impl DefDatabase, def: GenericDefId) -> Generics {
+    let parent_generics = parent_generic_def(db, def).map(|def| Box::new(generics(db, def)));
+    Generics { def, params: db.generic_params(def), parent_generics }
+}
+
+pub(crate) struct Generics {
+    def: GenericDefId,
+    pub(crate) params: Arc<GenericParams>,
+    parent_generics: Option<Box<Generics>>,
+}
+
+impl Generics {
+    pub(crate) fn iter<'a>(&'a self) -> impl Iterator<Item = (u32, &'a TypeParamData)> + 'a {
+        self.parent_generics
+            .as_ref()
+            .into_iter()
+            .flat_map(|it| it.params.types.iter())
+            .chain(self.params.types.iter())
+            .enumerate()
+            .map(|(i, (_local_id, p))| (i as u32, p))
+    }
+
+    pub(crate) fn iter_parent<'a>(&'a self) -> impl Iterator<Item = (u32, &'a TypeParamData)> + 'a {
+        self.parent_generics
+            .as_ref()
+            .into_iter()
+            .flat_map(|it| it.params.types.iter())
+            .enumerate()
+            .map(|(i, (_local_id, p))| (i as u32, p))
+    }
+
+    pub(crate) fn len(&self) -> usize {
+        self.len_split().0
+    }
+    /// (total, parents, child)
+    pub(crate) fn len_split(&self) -> (usize, usize, usize) {
+        let parent = self.parent_generics.as_ref().map_or(0, |p| p.len());
+        let child = self.params.types.len();
+        (parent + child, parent, child)
+    }
+    pub(crate) fn param_idx(&self, param: TypeParamId) -> u32 {
+        self.find_param(param).0
+    }
+    pub(crate) fn param_name(&self, param: TypeParamId) -> Name {
+        self.find_param(param).1.name.clone()
+    }
+    fn find_param(&self, param: TypeParamId) -> (u32, &TypeParamData) {
+        if param.parent == self.def {
+            let (idx, (_local_id, data)) = self
+                .params
+                .types
+                .iter()
+                .enumerate()
+                .find(|(_, (idx, _))| *idx == param.local_id)
+                .unwrap();
+            let (_total, parent_len, _child) = self.len_split();
+            return ((parent_len + idx) as u32, data);
+        }
+        self.parent_generics.as_ref().unwrap().find_param(param)
+    }
+}
+
+fn parent_generic_def(db: &impl DefDatabase, def: GenericDefId) -> Option<GenericDefId> {
+    let container = match def {
+        GenericDefId::FunctionId(it) => it.lookup(db).container,
+        GenericDefId::TypeAliasId(it) => it.lookup(db).container,
+        GenericDefId::ConstId(it) => it.lookup(db).container,
+        GenericDefId::EnumVariantId(it) => return Some(it.parent.into()),
+        GenericDefId::AdtId(_) | GenericDefId::TraitId(_) | GenericDefId::ImplId(_) => return None,
+    };
+
+    match container {
+        AssocContainerId::ImplId(it) => Some(it.into()),
+        AssocContainerId::TraitId(it) => Some(it.into()),
+        AssocContainerId::ContainerId(_) => None,
+    }
+}