KCL: Improve error messages for var referenced in own definition (#7374)

Jon pointed out that my new error message wasn't showing up in some
cases, and it should store/restore the previous var being defined.

rust/kcl-lib/src/execution/exec_ast.rs

@@ -307,6 +307,7 @@ impl ExecutorContext {
                     // During the evaluation of the variable's RHS, set context that this is all happening inside a variable
                     // declaration, for the given name. This helps improve user-facing error messages.
                     let lhs = variable_declaration.inner.name().to_owned();
+                    let prev_being_declared = exec_state.mod_local.being_declared.clone();
                     exec_state.mod_local.being_declared = Some(lhs);
                     let rhs_result = self
                         .execute_expr(
@@ -318,7 +319,7 @@ impl ExecutorContext {
                         )
                         .await;
                     // Declaration over, so unset this context.
-                    exec_state.mod_local.being_declared = None;
+                    exec_state.mod_local.being_declared = prev_being_declared;
                     let rhs = rhs_result?;
 
                     exec_state
@@ -836,6 +837,17 @@ impl Node<Name> {
         &self,
         exec_state: &'a mut ExecState,
         ctx: &ExecutorContext,
+    ) -> Result<&'a KclValue, KclError> {
+        let being_declared = exec_state.mod_local.being_declared.clone();
+        self.get_result_inner(exec_state, ctx)
+            .await
+            .map_err(|e| var_in_own_ref_err(e, &being_declared))
+    }
+
+    async fn get_result_inner<'a>(
+        &self,
+        exec_state: &'a mut ExecState,
+        ctx: &ExecutorContext,
     ) -> Result<&'a KclValue, KclError> {
         if self.abs_path {
             return Err(KclError::new_semantic(KclErrorDetails::new(

rust/kcl-lib/src/simulation_tests.rs

@@ -3525,3 +3525,24 @@ mod ascription_unknown_type {
         super::execute(TEST_NAME, true).await
     }
 }
+mod var_ref_in_own_def_decl {
+    const TEST_NAME: &str = "var_ref_in_own_def_decl";
+
+    /// Test parsing KCL.
+    #[test]
+    fn parse() {
+        super::parse(TEST_NAME)
+    }
+
+    /// Test that parsing and unparsing KCL produces the original KCL input.
+    #[tokio::test(flavor = "multi_thread")]
+    async fn unparse() {
+        super::unparse(TEST_NAME).await
+    }
+
+    /// Test that KCL is executed correctly.
+    #[tokio::test(flavor = "multi_thread")]
+    async fn kcl_test_execute() {
+        super::execute(TEST_NAME, true).await
+    }
+}