simplify rollback

src/LetInBlock.tsx

@@ -0,0 +1,22 @@
+import type { EditorState } from "./Editor";
+import type { Dynamic, State2Props } from "./util/extra";
+
+
+export interface LetInBlockState {
+  kind: "let";
+  env: any;
+  name: string;
+  value: EditorState;
+  inner: EditorState;
+  resolved: undefined | Dynamic;
+  rollback?: EditorState;
+}
+
+interface LetInBlockProps extends State2Props<LetInBlockState> {
+  onResolve: (resolved: EditorState) => void;
+}
+
+
+export function LetInBlock({env, name, value, inner, resolved, rollback, onResolve}) {
+  
+}