feat: make file handling more robust (#5057)

src/global.d.ts

@@ -35,6 +35,8 @@ type Mutable<T> = {
   -readonly [P in keyof T]: T[P];
 };
 
+type ValueOf<T> = T[keyof T];
+
 type Merge<M, N> = Omit<M, keyof N> & N;
 
 /** utility type to assert that the second type is a subtype of the first type.