Change never type to unknown (#4142)

* Distinguish request and response data types

* Change never type to unknown

Using `never` was a workaround I introduced in 3002, because `unknown` wasn’t
supperted by all relevant versions of TypeScript at the time. It is now, and
it is much more correct.

Co-authored-by: Claas Augner <github@caugner.de>
Co-authored-by: Jay <jasonsaayman@gmail.com>

index.d.ts

@@ -81,7 +81,7 @@ export interface AxiosRequestConfig<D = any> {
   signal?: AbortSignal;
 }
 
-export interface AxiosResponse<T = never, D = any>  {
+export interface AxiosResponse<T = unknown, D = any>  {
   data: T;
   status: number;
   statusText: string;
@@ -90,7 +90,7 @@ export interface AxiosResponse<T = never, D = any>  {
   request?: any;
 }
 
-export interface AxiosError<T = never, D = any> extends Error {
+export interface AxiosError<T = unknown, D = any> extends Error {
   config: AxiosRequestConfig<D>;
   code?: string;
   request?: any;
@@ -99,7 +99,7 @@ export interface AxiosError<T = never, D = any> extends Error {
   toJSON: () => object;
 }
 
-export interface AxiosPromise<T = never> extends Promise<AxiosResponse<T>> {
+export interface AxiosPromise<T = unknown> extends Promise<AxiosResponse<T>> {
 }
 
 export interface CancelStatic {
@@ -143,14 +143,14 @@ export class Axios {
     response: AxiosInterceptorManager<AxiosResponse>;
   };
   getUri(config?: AxiosRequestConfig): string;
-  request<T = never, R = AxiosResponse<T>, D = any> (config: AxiosRequestConfig<D>): Promise<R>;
-  get<T = never, R = AxiosResponse<T>, D = any>(url: string, config?: AxiosRequestConfig<D>): Promise<R>;
-  delete<T = never, R = AxiosResponse<T>, D = any>(url: string, config?: AxiosRequestConfig<D>): Promise<R>;
-  head<T = never, R = AxiosResponse<T>, D = any>(url: string, config?: AxiosRequestConfig<D>): Promise<R>;
-  options<T = never, R = AxiosResponse<T>, D = any>(url: string, config?: AxiosRequestConfig<D>): Promise<R>;
-  post<T = never, R = AxiosResponse<T>, D = any>(url: string, data?: D, config?: AxiosRequestConfig<D>): Promise<R>;
-  put<T = never, R = AxiosResponse<T>, D = any>(url: string, data?: D, config?: AxiosRequestConfig<D>): Promise<R>;
-  patch<T = never, R = AxiosResponse<T>, D = any>(url: string, data?: D, config?: AxiosRequestConfig<D>): Promise<R>;
+  request<T = unknown, R = AxiosResponse<T>, D = any> (config: AxiosRequestConfig<D>): Promise<R>;
+  get<T = unknown, R = AxiosResponse<T>, D = any>(url: string, config?: AxiosRequestConfig<D>): Promise<R>;
+  delete<T = unknown, R = AxiosResponse<T>, D = any>(url: string, config?: AxiosRequestConfig<D>): Promise<R>;
+  head<T = unknown, R = AxiosResponse<T>, D = any>(url: string, config?: AxiosRequestConfig<D>): Promise<R>;
+  options<T = unknown, R = AxiosResponse<T>, D = any>(url: string, config?: AxiosRequestConfig<D>): Promise<R>;
+  post<T = unknown, R = AxiosResponse<T>, D = any>(url: string, data?: D, config?: AxiosRequestConfig<D>): Promise<R>;
+  put<T = unknown, R = AxiosResponse<T>, D = any>(url: string, data?: D, config?: AxiosRequestConfig<D>): Promise<R>;
+  patch<T = unknown, R = AxiosResponse<T>, D = any>(url: string, data?: D, config?: AxiosRequestConfig<D>): Promise<R>;
 }
 
 export interface AxiosInstance extends Axios {