Make Route component extensible

Shouldn't have any impact whatsoever in existing codebases due to default generics

types/react-router/index.d.ts

@@ -71,7 +71,7 @@ export interface RouteProps {
   exact?: boolean;
   strict?: boolean;
 }
-export class Route extends React.Component<RouteProps> { }
+export class Route<T extends RouteProps = RouteProps> extends React.Component<T> { }
 
 export interface RouterProps {
   history: any;

types/react-router/test/InheritingRoute.tsx

@@ -0,0 +1,16 @@
+import * as React from 'react';
+import { Route, RouteProps } from 'react-router';
+
+interface CustomRouteInterface extends RouteProps {
+  aProperty: string;
+  anotherOne: boolean;
+  willItEnd?: number;
+}
+
+// React advocates composition over inheritance, but doesn't prevent us from using it
+export default class CustomRoute extends Route<CustomRouteInterface> {
+  render() {
+    const maybeElement = super.render();
+    return maybeElement && <div className="meaningfulClass">{React.cloneElement(maybeElement, this.props)}</div>;
+  }
+}

types/react-router/tsconfig.json

@@ -33,6 +33,7 @@
     "test/NavigateWithContext.tsx",
     "test/MemoryRouter.tsx",
     "test/Switch.tsx",
+    "test/InheritingRoute.tsx",
     "test/WithRouter.tsx"
   ]
 }