Adjust Registry createType return detection (#3844)

* Adjust Registry createType return detection

* type as 'OtherType' cast removal

* Use createClass via registry

packages/api-derive/src/democracy/dispatchQueue.ts

@@ -86,7 +86,7 @@ function queryScheduler (api: ApiInterfaceRx): Observable<DeriveDispatch[]> {
               const id = scheduled.maybeId.unwrap().toHex();
 
               if (id.startsWith(DEMOCRACY_ID)) {
-                const [, index] = api.registry.createType('(u64, ReferendumIndex)' as any, id) as ITuple<[u64, ReferendumIndex]>;
+                const [, index] = api.registry.createType<ITuple<[u64, ReferendumIndex]>>('(u64, ReferendumIndex)', id);
                 const imageHash = scheduled.call.args[0] as Hash;
 
                 result.push({ at, imageHash, index });

packages/api-derive/src/index.spec.ts

@@ -14,10 +14,7 @@ import { TypeRegistry } from '@polkadot/types/create';
 import { ExactDerive } from '.';
 
 const testFunction = (api: ApiRx): any => {
-  return <
-    Section extends keyof ExactDerive,
-    Method extends keyof (typeof api.derive[Section])
-  >(section: Section, method: Method, inputs: any[]): void => {
+  return <S extends keyof ExactDerive, M extends keyof (typeof api.derive[S])>(section: S, method: M, inputs: any[]): void => {
     describe(`derive.${section}.${method}`, (): void => {
       it('should be a function', (): void => {
         expect(typeof api.derive[section][method]).toBe('function');
@@ -96,7 +93,7 @@ describe('derive', (): void => {
     testFunction(api)('balances', 'fees', ['a', 'b']);
 
     // new
-    testFunction(api)('custom' as any, 'test', [1, 2, 3]);
+    testFunction(api)('custom', 'test', [1, 2, 3]);
 
     // existing
     testFunction(api)('chain', 'bestNumber', []);