fix(types): widen types for structuralSharing

fixes #5806

Author: TkDodo

docs/react/reference/useQuery.md

@@ -155,7 +155,7 @@ 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 | ((oldData: TData | undefined, newData: TData) => TData)`
+- `structuralSharing: boolean | (<T>(oldData: T | undefined, newData: T) => T)`
   - Optional
   - Defaults to `true`
   - If set to `false`, structural sharing between query results will be disabled.

packages/query-core/src/types.ts

@@ -152,9 +152,7 @@ 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
-    | ((oldData: TData | undefined, newData: TData) => TData)
+  structuralSharing?: boolean | (<T>(oldData: T | undefined, newData: T) => T)
   _defaulted?: boolean
   /**
    * Additional payload to be stored on each query.

packages/react-query/src/__tests__/useQuery.types.test.tsx

@@ -155,4 +155,24 @@ describe('initialData', () => {
       })
     })
   })
+
+  describe('structuralSharing', () => {
+    it('should restrict to same types', () => {
+      doNotExecute(() => {
+        const structuralSharing = (
+          _oldData: number | string | undefined,
+          newData: number | string,
+        ) => {
+          return newData
+        }
+
+        useQuery({
+          queryKey: ['key'],
+          queryFn: () => 5,
+          select: String,
+          structuralSharing,
+        })
+      })
+    })
+  })
 })