diff --git a/src/protocol/ast.rs b/src/protocol/ast.rs
index 6f42d75ea68749ad3cc38b3f8e6ff2e935512fd5..c73bcdf4b710390a3a21bc6c0202cf5dd089137f 100644
--- a/src/protocol/ast.rs
+++ b/src/protocol/ast.rs
@@ -1022,7 +1022,7 @@ pub struct MethodSymbolic {
 #[derive(Debug, Clone, serde::Serialize, serde::Deserialize)]
 pub enum Field {
     Length,
-    Symbolic(Identifier),
+    Symbolic(FieldSymbolic),
 }
 impl Field {
     pub fn is_length(&self) -> bool {
@@ -1033,6 +1033,15 @@ impl Field {
     }
 }
 
+#[derive(Debug, Clone, serde::Serialize, serde::Deserialize)]
+pub struct FieldSymbolic {
+    // Phase 1: Parser
+    pub(crate) identifier: Identifier,
+    // Phase 3: Typing
+    pub(crate) definition: Option<DefinitionId>,
+    pub(crate) field_idx: usize,
+}
+
 #[derive(Debug, Clone, Copy, serde::Serialize, serde::Deserialize)]
 pub enum Scope {
     Definition(DefinitionId),