fix(types): type structural sharing as unknown (#6888)

docs/framework/react/reference/useQuery.md

@@ -152,7 +152,7 @@ const {
   - If set, this value will be used as the placeholder data for this particular query observer while the query is still in the `pending` state.
   - `placeholderData` is **not persisted** to the cache
   - If you provide a function for `placeholderData`, as a first argument you will receive previously watched query data if available, and the second argument will be the complete previousQuery instance.
-- `structuralSharing: boolean | (<T>(oldData: T | undefined, newData: T) => T)`
+- `structuralSharing: boolean | (oldData: unknown | undefined, newData: unknown) => unknown)`
   - Optional
   - Defaults to `true`
   - If set to `false`, structural sharing between query results will be disabled.

packages/query-core/src/types.ts

@@ -164,7 +164,9 @@ export interface QueryOptions<
    * Set this to a function which accepts the old and new data and returns resolved data of the same type to implement custom structural sharing logic.
    * Defaults to `true`.
    */
-  structuralSharing?: boolean | (<T>(oldData: T | undefined, newData: T) => T)
+  structuralSharing?:
+    | boolean
+    | ((oldData: unknown | undefined, newData: unknown) => unknown)
   _defaulted?: boolean
   /**
    * Additional payload to be stored on each query.

packages/query-core/src/utils.ts

@@ -319,7 +319,7 @@ export function replaceData<
   TOptions extends QueryOptions<any, any, any, any>,
 >(prevData: TData | undefined, data: TData, options: TOptions): TData {
   if (typeof options.structuralSharing === 'function') {
-    return options.structuralSharing(prevData, data)
+    return options.structuralSharing(prevData, data) as TData
   } else if (options.structuralSharing !== false) {
     // Structurally share data between prev and new data if needed
     return replaceEqualDeep(prevData, data)