1 files changed, 16 insertions, 5 deletions
diff --git a/src/Language/Fiddle/Ast.hs b/src/Language/Fiddle/Ast.hs
index bb6605e..8680790 100644
--- a/src/Language/Fiddle/Ast.hs
+++ b/src/Language/Fiddle/Ast.hs
@@ -11,6 +11,7 @@ module Language.Fiddle.Ast where
 
 import Data.Functor.Identity
 import Data.Kind (Type)
+import Data.List.NonEmpty
 import Data.Proxy
 import Data.Text (Text)
 import Data.Traversable
@@ -47,6 +48,16 @@ type family ImportType (stage :: Stage) :: SynTreeKind where
   ImportType Stage2 = ImportStatement
   ImportType Stage3 = ImportStatement
 
+-- Type-level constraint to determine if a stage is less than some natural
+-- ordinal. Used to bound parts of the AST in multiple stages.
+type StageLessThan stage (n :: Natural) = (CmpNat (StageNumber stage) n ~ LT)
+
+-- A Name is multiple identifiers separated by dots. It's the way of namespaces
+-- to different packages.
+data Name f a where
+  Name :: NonEmpty (Identifier f a) -> a -> Name f a
+  deriving (Generic, Annotated, Alter, Typeable)
+
 -- [[packed, rust: name="field_name"]]
 data Directive f a where
   Directive :: f (DirectiveBody f a) -> a -> Directive f a
@@ -146,9 +157,11 @@ data FiddleDecl (stage :: Stage) (f :: Type -> Type) a where
     ImportType stage f a ->
     a ->
     FiddleDecl stage f a
+  UsingDecl ::
+    Name f a -> a -> FiddleDecl stage f a
   {- Package Statement. Package Name, Package body -}
   PackageDecl ::
-    Identifier f a ->
+    Name f a ->
     f (PackageBody stage f a) ->
     a ->
     FiddleDecl stage f a
@@ -197,11 +210,9 @@ data ObjType stage f a where
   -- <type>[<expr>]
   ArrayObjType :: ObjType stage f a -> Expression stage f a -> a -> ObjType stage f a
   -- <identifier>
-  ReferencedObjType :: Identifier f a -> a -> ObjType stage f a
+  ReferencedObjType :: Name f a -> a -> ObjType stage f a
   deriving (Typeable)
 
-type StageLessThan stage (n :: Natural) = (CmpNat (StageNumber stage) n ~ LT)
-
 data ObjTypeDecl stage f a where
   {- assert_pos(<expr>) -}
   AssertPosStatement ::
@@ -278,7 +289,7 @@ data RegisterBitsTypeRef stage f a where
     a ->
     RegisterBitsTypeRef stage f a
   {- Reference to a type. -}
-  RegisterBitsReference :: Identifier f a -> a -> RegisterBitsTypeRef stage f a
+  RegisterBitsReference :: Name f a -> a -> RegisterBitsTypeRef stage f a
   {- enum(<expr>) { <body> }
      Anonymous types are only allowed in stage1.
      Stage2 should de-anonymize these type. -}