1 files changed, 7 insertions, 1 deletions
diff --git a/src/state/cache/types.ts b/src/state/cache/types.ts
index 8bfcc867c..055f4167e 100644
--- a/src/state/cache/types.ts
+++ b/src/state/cache/types.ts
@@ -1 +1,7 @@
-export type Shadow<T> = T & {isShadowed: true}
+// This isn't a real property, but it prevents T being compatible with Shadow<T>.
+declare const shadowTag: unique symbol
+export type Shadow<T> = T & {[shadowTag]: true}
+
+export function castAsShadow<T>(value: T): Shadow<T> {
+  return value as any as Shadow<T>
+}