Streamline code and feature gates.

src/api.rs

@@ -1305,16 +1305,15 @@ impl Engine {
         mut ast: AST,
         optimization_level: OptimizationLevel,
     ) -> AST {
-        #[cfg(not(feature = "no_function"))]
-        let lib = ast
-            .lib()
-            .iter_fn()
-            .filter(|(_, _, _, f)| f.is_script())
-            .map(|(_, _, _, f)| f.get_fn_def().clone())
-            .collect();
-
-        #[cfg(feature = "no_function")]
-        let lib = Default::default();
+        let lib = if cfg!(not(feature = "no_function")) {
+            ast.lib()
+                .iter_fn()
+                .filter(|(_, _, _, f)| f.is_script())
+                .map(|(_, _, _, f)| f.get_fn_def().clone())
+                .collect()
+        } else {
+            Default::default()
+        };
 
         let stmt = mem::take(ast.statements_mut());
         optimize_into_ast(self, scope, stmt, lib, optimization_level)