From a912fc910d04fb01ab719fb41102a3b1acf57ccc Mon Sep 17 00:00:00 2001
From: Antonio Sarosi <sarosiantonio@gmail.com>
Date: Wed, 11 Dec 2024 19:47:47 +0100
Subject: [PATCH] Fix reachable unreachable... XD

---
 .../class/invalid_type_aliases.baml           |  9 +++++
 .../baml-lib/parser-database/src/types/mod.rs |  6 +++-
 .../tests/test_file_manager.rs                | 35 +++++++++++++++++++
 3 files changed, 49 insertions(+), 1 deletion(-)

diff --git a/engine/baml-lib/baml/tests/validation_files/class/invalid_type_aliases.baml b/engine/baml-lib/baml/tests/validation_files/class/invalid_type_aliases.baml
index a8e4a7c3c..0a13664ba 100644
--- a/engine/baml-lib/baml/tests/validation_files/class/invalid_type_aliases.baml
+++ b/engine/baml-lib/baml/tests/validation_files/class/invalid_type_aliases.baml
@@ -8,6 +8,9 @@ type One = int
 // Unexpected keyword.
 typpe Two = float
 
+// Unknown identifier.
+type Three = i
+
 // error: Error validating: Unexpected keyword used in assignment: typpe
 //   -->  class/invalid_type_aliases.baml:9
 //    | 
@@ -20,3 +23,9 @@ typpe Two = float
 //  5 | // Already existing name.
 //  6 | type One = int
 //    | 
+// error: Error validating: Type alias points to unknown identifier `i`
+//   -->  class/invalid_type_aliases.baml:12
+//    | 
+// 11 | // Unknown identifier.
+// 12 | type Three = i
+//    | 
diff --git a/engine/baml-lib/parser-database/src/types/mod.rs b/engine/baml-lib/parser-database/src/types/mod.rs
index 966757b3a..3fe3f46b8 100644
--- a/engine/baml-lib/parser-database/src/types/mod.rs
+++ b/engine/baml-lib/parser-database/src/types/mod.rs
@@ -489,7 +489,11 @@ fn visit_type_alias<'db>(
         match item {
             FieldType::Symbol(_, ident, _) => {
                 let Some(string_id) = ctx.interner.lookup(ident.name()) else {
-                    unreachable!("Visiting alias `{ident}` that does not exist in the interner");
+                    ctx.push_error(DatamodelError::new_validation_error(
+                        &format!("Type alias points to unknown identifier `{ident}`"),
+                        item.span().clone(),
+                    ));
+                    return;
                 };
 
                 let Some(top_id) = ctx.names.tops.get(&string_id) else {
diff --git a/engine/baml-schema-wasm/tests/test_file_manager.rs b/engine/baml-schema-wasm/tests/test_file_manager.rs
index 8de0e0743..ff0f8b1db 100644
--- a/engine/baml-schema-wasm/tests/test_file_manager.rs
+++ b/engine/baml-schema-wasm/tests/test_file_manager.rs
@@ -229,4 +229,39 @@ test Two {
 
         assert!(diagnostics.errors().is_empty());
     }
+
+    #[wasm_bindgen_test]
+    fn test_type_alias() {
+        wasm_logger::init(wasm_logger::Config::new(log::Level::Info));
+        let sample_baml_content = r##"
+            type Foo = i
+        "##;
+        let mut files = HashMap::new();
+        files.insert("error.baml".to_string(), sample_baml_content.to_string());
+        let files_js = to_value(&files).unwrap();
+        let project = WasmProject::new("baml_src", files_js)
+            .map_err(JsValue::from)
+            .unwrap();
+
+        let env_vars = [("OPENAI_API_KEY", "12345")]
+            .iter()
+            .cloned()
+            .collect::<HashMap<_, _>>();
+        let env_vars_js = to_value(&env_vars).unwrap();
+
+        let Err(js_error) = project.runtime(env_vars_js) else {
+            panic!("Expected error, got Ok");
+        };
+
+        assert!(js_error.is_object());
+
+        assert_eq!(
+            js_error,
+            serde_wasm_bindgen::to_value::<HashMap<String, Vec<String>>>(&HashMap::from_iter([(
+                "all_files".to_string(),
+                vec!["error.baml".to_string()]
+            )]))
+            .unwrap()
+        );
+    }
 }