Allow steps to be nested under google.maps.DirectionsLeg (#37963)

types/googlemaps/googlemaps-tests.ts

@@ -793,3 +793,31 @@ const directionsWaypointLocationPlace: google.maps.DirectionsWaypoint = {
 const directionsWaypointStopover: google.maps.DirectionsWaypoint = {
     stopover: true,
 };
+
+/***** google.maps.DirectionsService *****/
+let directionsService = new google.maps.DirectionsService();
+
+directionsService.route({
+    avoidFerries: true,
+    avoidHighways: true,
+    avoidTolls: true,
+    destination: 'destination',
+    origin: 'origin',
+    provideRouteAlternatives: true,
+    transitOptions: {
+        arrivalTime: new Date(),
+        departureTime: new Date(),
+        modes: [
+            google.maps.TransitMode.BUS,
+            google.maps.TransitMode.RAIL
+        ],
+        routingPreference: google.maps.TransitRoutePreference.FEWER_TRANSFERS
+    },
+    travelMode: google.maps.TravelMode.TRANSIT,
+    unitSystem: google.maps.UnitSystem.IMPERIAL
+}, (result: google.maps.DirectionsResult, status: google.maps.DirectionsStatus) => {
+    const routes = result.routes; // $ExpectType DirectionsRoute[]
+    const legs = routes[0].legs; // $ExpectType DirectionsLeg[]
+    const steps = legs[0].steps; // $ExpectType DirectionsStep[]
+    steps[0].steps; // $ExpectType BaseDirectionsStep[]
+});

types/googlemaps/index.d.ts

@@ -1977,18 +1977,24 @@ declare namespace google.maps {
         via_waypoints: LatLng[];
     }
 
-    interface DirectionsStep {
+    interface BaseDirectionsStep {
         distance: Distance;
         duration: Duration;
         end_location: LatLng;
         instructions: string;
         path: LatLng[];
         start_location: LatLng;
-        steps: DirectionsStep;
         transit: TransitDetails;
         travel_mode: TravelMode;
     }
 
+    interface DirectionsStep extends BaseDirectionsStep {
+        /**
+         * This field will only be available if travel_mode is set to TRANSIT.
+         */
+        steps: BaseDirectionsStep[];
+    }
+
     interface Distance {
         text: string;
         value: number;