diff --git a/src/protocol/ast.rs b/src/protocol/ast.rs
index e137985fa110c6e2cea9a0f83be7cedf79aef88d..6ad5f1ca98cfa39f02cad26fa0314df2c6f14413 100644
--- a/src/protocol/ast.rs
+++ b/src/protocol/ast.rs
@@ -1071,6 +1071,36 @@ impl ExpressionInfoVariant {
     }
 }
 
+#[derive(Debug)]
+pub enum ProcedureSource {
+    FuncUserDefined,
+    CompUserDefined,
+    // Builtin functions, available to user
+    FuncGet,
+    FuncPut,
+    FuncFires,
+    FuncCreate,
+    FuncLength,
+    FuncAssert,
+    FuncPrint,
+    // Buitlin functions, not available to user
+    FuncSelectStart,
+    FuncSelectRegisterCasePort,
+    FuncSelectWait,
+    // Builtin components, available to user
+    CompRandomU32, // TODO: Remove, temporary thing
+}
+
+impl ProcedureSource {
+    pub(crate) fn is_builtin(&self) -> bool {
+        match self {
+            ProcedureSource::FuncUserDefined | ProcedureSource::CompUserDefined => false,
+            _ => true,
+        }
+    }
+}
+
+
 /// Generic storage for functions, primitive components and composite
 /// components.
 // Note that we will have function definitions for builtin functions as well. In
@@ -1080,12 +1110,12 @@ pub struct ProcedureDefinition {
     pub this: ProcedureDefinitionId,
     pub defined_in: RootId,
     // Symbol scanning
-    pub builtin: bool,
     pub kind: ProcedureKind,
     pub span: InputSpan,
     pub identifier: Identifier,
     pub poly_vars: Vec<Identifier>,
     // Parser
+    pub source: ProcedureSource,
     pub return_type: Option<ParserType>, // present on functions, not components
     pub parameters: Vec<VariableId>,
     pub scope: ScopeId,
@@ -1101,9 +1131,9 @@ impl ProcedureDefinition {
     ) -> Self {
         Self {
             this, defined_in,
-            builtin: false,
             span,
             kind, identifier, poly_vars,
+            source: ProcedureSource::FuncUserDefined,
             return_type: None,
             parameters: Vec::new(),
             scope: ScopeId::new_invalid(),