Merge #892

892: Type aliases r=matklad a=flodiebold

This implements type aliases (i.e. `type` definitions).

There's just one snag: handling recursion. E.g. `type Foo = Foo` makes type inference panic with a query cycle. I think the best way to handle this would be if Salsa provided the ability to catch cycle errors? It seems that there's some work underway to support this [here](https://github.com/salsa-rs/salsa/issues/6) and [here](https://github.com/salsa-rs/salsa/pull/147). Should we wait for this? I don't see a good way to handle this without help from Salsa.

Co-authored-by: Florian Diebold <[email protected]>

1 files changed, 4 insertions, 1 deletions

diff --git a/crates/ra_hir/src/db.rs b/crates/ra_hir/src/db.rs
index fc0ee068c..b8bd82f0c 100644
--- a/crates/ra_hir/src/db.rs
+++ b/crates/ra_hir/src/db.rs
@@ -15,7 +15,7 @@ use crate::{
     adt::{StructData, EnumData},
     impl_block::{ModuleImplBlocks, ImplSourceMap},
     generics::{GenericParams, GenericDef},
-    ids::SourceFileItemId, nameres::Namespace
+    ids::SourceFileItemId, nameres::Namespace, type_ref::TypeRef, code_model_api::Type
 };
 
 #[salsa::query_group(PersistentHirDatabaseStorage)]
@@ -77,6 +77,9 @@ pub trait PersistentHirDatabase: SourceDatabase + AsRef<HirInterner> {
 
     #[salsa::invoke(crate::FnSignature::fn_signature_query)]
     fn fn_signature(&self, func: Function) -> Arc<FnSignature>;
+
+    #[salsa::invoke(crate::type_alias::type_alias_ref_query)]
+    fn type_alias_ref(&self, typ: Type) -> Arc<TypeRef>;
 }
 
 #[salsa::query_group(HirDatabaseStorage)]