fix(query-core): mutation meta typing (TanStack#6680)

* fix QueryMeta type

* reverting previous fix and applied similar behaviour to MutationMeta

* added behaviour details in the documentation

Author: Nicoolandgood

docs/react/typescript.md

@@ -157,11 +157,15 @@ const { error } = useQuery({ queryKey: ['groups'], queryFn: fetchGroups })
 
 ### Registering global Meta
 
-Similarly to registering a [global error type](#registering-a-global-error) you can also register a global `Meta` type. This ensures the optional `meta` field on [queries](./reference/useQuery.md) and [mutations](./reference/useMutation.md) stays consistent and is type-safe.
+Similarly to registering a [global error type](#registering-a-global-error) you can also register a global `Meta` type. This ensures the optional `meta` field on [queries](./reference/useQuery.md) and [mutations](./reference/useMutation.md) stays consistent and is type-safe. Note that the registered type must extend `Record<string, unknown>` so that `meta` remains an object.
 
 ```ts
 import '@tanstack/react-query'
 
+interface MyMeta extends Record<string, unknown> {
+  // Your meta type definition.
+}
+
 declare module '@tanstack/react-query' {
   interface Register {
     queryMeta: MyMeta

packages/query-core/src/types.ts

@@ -688,7 +688,9 @@ export type MutationStatus = 'idle' | 'pending' | 'success' | 'error'
 export type MutationMeta = Register extends {
   mutationMeta: infer TMutationMeta
 }
-  ? TMutationMeta
+  ? TMutationMeta extends Record<string, unknown>
+    ? TMutationMeta
+    : Record<string, unknown>
   : Record<string, unknown>
 
 export type MutationFunction<TData = unknown, TVariables = unknown> = (