iter 23.1.2: load_workspace auto-injects prelude module

crates/ail/src/main.rs

@@ -1140,6 +1140,19 @@ fn workspace_error_to_diagnostic(
                 "type": type_repr,
             })),
         ),
+        // Iter 23.1: the user named a module `prelude`, which the
+        // loader reserves for the auto-injected prelude module.
+        W::ReservedModuleName { name } => Some(
+            ailang_check::Diagnostic::error(
+                "reserved-module-name",
+                format!(
+                    "module name {name:?} is reserved (auto-injected by the loader)"
+                ),
+            )
+            .with_ctx(serde_json::json!({
+                "module": name,
+            })),
+        ),
     }
 }