fix: LocalEnv::merge to also merge the bindings vector (#596)

* Fix LocalEnv::merge and merge bindings

* added a unit test

src/compiler/state.rs

@@ -88,6 +88,8 @@ impl LocalEnv {
         for (ident, other_details) in other.bindings {
             if let Some(self_details) = self.bindings.get_mut(&ident) {
                 *self_details = self_details.clone().merge(other_details);
+            } else {
+                self.bindings.insert(ident, other_details);
             }
         }
         self

src/compiler/target.rs

@@ -278,7 +278,10 @@ mod value_target_impl {
 mod tests {
     #![allow(clippy::print_stdout)] // tests
 
-    use crate::owned_value_path;
+    use crate::{
+        compiler::{parser::Ident, state::LocalEnv, type_def::Details, TypeDef},
+        owned_value_path,
+    };
 
     use super::*;
     use crate::value;
@@ -530,4 +533,28 @@ mod tests {
             );
         }
     }
+
+    #[test]
+    fn merge_multiple_local_env() {
+        let mut a = LocalEnv::default();
+        a.insert_variable(
+            Ident("foo".into()),
+            Details {
+                type_def: TypeDef::any(),
+                value: None,
+            },
+        );
+
+        let mut b = LocalEnv::default();
+        b.insert_variable(
+            Ident("bar".into()),
+            Details {
+                type_def: TypeDef::any(),
+                value: None,
+            },
+        );
+
+        let merged = a.merge(b);
+        assert_eq!(merged.bindings.len(), 2);
+    }
 }