Move Ty

crates/ra_hir_ty/src/utils.rs

@@ -0,0 +1,84 @@
+//! Helper functions for working with def, which don't need to be a separate
+//! query, but can't be computed directly from `*Data` (ie, which need a `db`).
+use std::sync::Arc;
+
+use hir_def::{
+    adt::VariantData,
+    db::DefDatabase,
+    resolver::{HasResolver, TypeNs},
+    type_ref::TypeRef,
+    TraitId, TypeAliasId, VariantId,
+};
+use hir_expand::name::{self, 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
+    // lifetime problems, but since there usually shouldn't be more than a
+    // few direct traits this should be fine (we could even use some kind of
+    // SmallVec if performance is a concern)
+    db.generic_params(trait_.into())
+        .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(),
+            _ => None,
+        })
+        .filter_map(|path| match resolver.resolve_path_in_type_ns_fully(db, path) {
+            Some(TypeNs::TraitId(t)) => Some(t),
+            _ => None,
+        })
+        .collect()
+}
+
+/// Returns an iterator over the whole super trait hierarchy (including the
+/// trait itself).
+pub(super) fn all_super_traits(db: &impl DefDatabase, trait_: TraitId) -> Vec<TraitId> {
+    // we need to take care a bit here to avoid infinite loops in case of cycles
+    // (i.e. if we have `trait A: B; trait B: A;`)
+    let mut result = vec![trait_];
+    let mut i = 0;
+    while i < result.len() {
+        let t = result[i];
+        // yeah this is quadratic, but trait hierarchies should be flat
+        // enough that this doesn't matter
+        for tt in direct_super_traits(db, t) {
+            if !result.contains(&tt) {
+                result.push(tt);
+            }
+        }
+        i += 1;
+    }
+    result
+}
+
+pub(super) fn associated_type_by_name_including_super_traits(
+    db: &impl DefDatabase,
+    trait_: TraitId,
+    name: &Name,
+) -> Option<TypeAliasId> {
+    all_super_traits(db, trait_)
+        .into_iter()
+        .find_map(|t| db.trait_data(t).associated_type_by_name(name))
+}
+
+pub(super) fn variant_data(db: &impl DefDatabase, var: VariantId) -> Arc<VariantData> {
+    match var {
+        VariantId::StructId(it) => db.struct_data(it).variant_data.clone(),
+        VariantId::UnionId(it) => db.union_data(it).variant_data.clone(),
+        VariantId::EnumVariantId(it) => {
+            db.enum_data(it.parent).variants[it.local_id].variant_data.clone()
+        }
+    }
+}
+
+/// Helper for mutating `Arc<[T]>` (i.e. `Arc::make_mut` for Arc slices).
+/// The underlying values are cloned if there are other strong references.
+pub(crate) fn make_mut_slice<T: Clone>(a: &mut Arc<[T]>) -> &mut [T] {
+    if Arc::get_mut(a).is_none() {
+        *a = a.iter().cloned().collect();
+    }
+    Arc::get_mut(a).unwrap()
+}