diff --git a/baselines/dom.generated.d.ts b/baselines/dom.generated.d.ts
index 7f3689998..6cb51f943 100644
--- a/baselines/dom.generated.d.ts
+++ b/baselines/dom.generated.d.ts
@@ -8312,13 +8312,13 @@ interface IDBCursor {
      * Delete the record pointed at by the cursor with a new value.
      * If successful, request's result will be undefined.
      */
-    delete(): IDBRequest;
+    delete(): IDBRequest<undefined>;
     /**
      * Updated the record pointed at by the cursor with a new value.
      * Throws a "DataError" DOMException if the effective object store uses in-line keys and the key would have changed.
      * If successful, request's result will be the record's key.
      */
-    update(value: any): IDBRequest;
+    update(value: any): IDBRequest<IDBValidKey>;
 }
 
 declare var IDBCursor: {
@@ -8444,40 +8444,40 @@ interface IDBIndex {
      * If successful, request's result will be the
      * count.
      */
-    count(key?: IDBValidKey | IDBKeyRange): IDBRequest;
+    count(key?: IDBValidKey | IDBKeyRange): IDBRequest<number>;
     /**
      * Retrieves the value of the first record matching the
      * given key or key range in query.
      * If successful, request's result will be the value, or undefined if there was no matching record.
      */
-    get(key: IDBValidKey | IDBKeyRange): IDBRequest;
+    get(key: IDBValidKey | IDBKeyRange): IDBRequest<any | undefined>;
     /**
      * Retrieves the values of the records matching the given key or key range in query (up to count if given).
      * If successful, request's result will be an Array of the values.
      */
-    getAll(query?: IDBValidKey | IDBKeyRange, count?: number): IDBRequest;
+    getAll(query?: IDBValidKey | IDBKeyRange, count?: number): IDBRequest<any[]>;
     /**
      * Retrieves the keys of records matching the given key or key range in query (up to count if given).
      * If successful, request's result will be an Array of the keys.
      */
-    getAllKeys(query?: IDBValidKey | IDBKeyRange, count?: number): IDBRequest;
+    getAllKeys(query?: IDBValidKey | IDBKeyRange, count?: number): IDBRequest<IDBValidKey[]>;
     /**
      * Retrieves the key of the first record matching the
      * given key or key range in query.
      * If successful, request's result will be the key, or undefined if there was no matching record.
      */
-    getKey(key: IDBValidKey | IDBKeyRange): IDBRequest;
+    getKey(key: IDBValidKey | IDBKeyRange): IDBRequest<IDBValidKey | undefined>;
     /**
      * Opens a cursor over the records matching query,
      * ordered by direction. If query is null, all records in index are matched.
      * If successful, request's result will be an IDBCursorWithValue, or null if there were no matching records.
      */
-    openCursor(range?: IDBValidKey | IDBKeyRange, direction?: IDBCursorDirection): IDBRequest;
+    openCursor(range?: IDBValidKey | IDBKeyRange, direction?: IDBCursorDirection): IDBRequest<IDBCursorWithValue | null>;
     /**
      * Opens a cursor with key only flag set over the records matching query, ordered by direction. If query is null, all records in index are matched.
      * If successful, request's result will be an IDBCursor, or null if there were no matching records.
      */
-    openKeyCursor(range?: IDBValidKey | IDBKeyRange, direction?: IDBCursorDirection): IDBRequest;
+    openKeyCursor(range?: IDBValidKey | IDBKeyRange, direction?: IDBCursorDirection): IDBRequest<IDBCursor | null>;
 }
 
 declare var IDBIndex: {
@@ -8556,19 +8556,19 @@ interface IDBObjectStore {
      * Returns the associated transaction.
      */
     readonly transaction: IDBTransaction;
-    add(value: any, key?: IDBValidKey | IDBKeyRange): IDBRequest;
+    add(value: any, key?: IDBValidKey | IDBKeyRange): IDBRequest<IDBValidKey>;
     /**
      * Deletes all records in store.
      * If successful, request's result will
      * be undefined.
      */
-    clear(): IDBRequest;
+    clear(): IDBRequest<undefined>;
     /**
      * Retrieves the number of records matching the
      * given key or key range in query.
      * If successful, request's result will be the count.
      */
-    count(key?: IDBValidKey | IDBKeyRange): IDBRequest;
+    count(key?: IDBValidKey | IDBKeyRange): IDBRequest<number>;
     /**
      * Creates a new index in store with the given name, keyPath and options and returns a new IDBIndex. If the keyPath and options define constraints that cannot be
      * satisfied with the data already in store the upgrade
@@ -8583,7 +8583,7 @@ interface IDBObjectStore {
      * If successful, request's result will
      * be undefined.
      */
-    delete(key: IDBValidKey | IDBKeyRange): IDBRequest;
+    delete(key: IDBValidKey | IDBKeyRange): IDBRequest<undefined>;
     /**
      * Deletes the index in store with the given name.
      * Throws an "InvalidStateError" DOMException if not called within an upgrade
@@ -8595,41 +8595,41 @@ interface IDBObjectStore {
      * given key or key range in query.
      * If successful, request's result will be the value, or undefined if there was no matching record.
      */
-    get(query: IDBValidKey | IDBKeyRange): IDBRequest;
+    get(query: IDBValidKey | IDBKeyRange): IDBRequest<any | undefined>;
     /**
      * Retrieves the values of the records matching the
      * given key or key range in query (up to count if given).
      * If successful, request's result will
      * be an Array of the values.
      */
-    getAll(query?: IDBValidKey | IDBKeyRange, count?: number): IDBRequest;
+    getAll(query?: IDBValidKey | IDBKeyRange, count?: number): IDBRequest<any[]>;
     /**
      * Retrieves the keys of records matching the
      * given key or key range in query (up to count if given).
      * If successful, request's result will
      * be an Array of the keys.
      */
-    getAllKeys(query?: IDBValidKey | IDBKeyRange, count?: number): IDBRequest;
+    getAllKeys(query?: IDBValidKey | IDBKeyRange, count?: number): IDBRequest<IDBValidKey[]>;
     /**
      * Retrieves the key of the first record matching the
      * given key or key range in query.
      * If successful, request's result will be the key, or undefined if there was no matching record.
      */
-    getKey(query: IDBValidKey | IDBKeyRange): IDBRequest;
+    getKey(query: IDBValidKey | IDBKeyRange): IDBRequest<IDBValidKey | undefined>;
     index(name: string): IDBIndex;
     /**
      * Opens a cursor over the records matching query,
      * ordered by direction. If query is null, all records in store are matched.
      * If successful, request's result will be an IDBCursorWithValue pointing at the first matching record, or null if there were no matching records.
      */
-    openCursor(range?: IDBValidKey | IDBKeyRange, direction?: IDBCursorDirection): IDBRequest;
+    openCursor(range?: IDBValidKey | IDBKeyRange, direction?: IDBCursorDirection): IDBRequest<IDBCursorWithValue | null>;
     /**
      * Opens a cursor with key only flag set over the records matching query, ordered by direction. If query is null, all records in store are matched.
      * If successful, request's result will be an IDBCursor pointing at the first matching record, or
      * null if there were no matching records.
      */
-    openKeyCursor(query?: IDBValidKey | IDBKeyRange, direction?: IDBCursorDirection): IDBRequest;
-    put(value: any, key?: IDBValidKey | IDBKeyRange): IDBRequest;
+    openKeyCursor(query?: IDBValidKey | IDBKeyRange, direction?: IDBCursorDirection): IDBRequest<IDBCursor | null>;
+    put(value: any, key?: IDBValidKey | IDBKeyRange): IDBRequest<IDBValidKey>;
 }
 
 declare var IDBObjectStore: {
@@ -8642,7 +8642,7 @@ interface IDBOpenDBRequestEventMap extends IDBRequestEventMap {
     "upgradeneeded": IDBVersionChangeEvent;
 }
 
-interface IDBOpenDBRequest extends IDBRequest {
+interface IDBOpenDBRequest extends IDBRequest<IDBDatabase> {
     onblocked: ((this: IDBOpenDBRequest, ev: Event) => any) | null;
     onupgradeneeded: ((this: IDBOpenDBRequest, ev: IDBVersionChangeEvent) => any) | null;
     addEventListener<K extends keyof IDBOpenDBRequestEventMap>(type: K, listener: (this: IDBOpenDBRequest, ev: IDBOpenDBRequestEventMap[K]) => any, options?: boolean | AddEventListenerOptions): void;
@@ -8661,14 +8661,14 @@ interface IDBRequestEventMap {
     "success": Event;
 }
 
-interface IDBRequest extends EventTarget {
+interface IDBRequest<T = any> extends EventTarget {
     /**
      * When a request is completed, returns the error (a DOMException), or null if the request succeeded. Throws
      * a "InvalidStateError" DOMException if the request is still pending.
      */
     readonly error: DOMException | null;
-    onerror: ((this: IDBRequest, ev: Event) => any) | null;
-    onsuccess: ((this: IDBRequest, ev: Event) => any) | null;
+    onerror: ((this: IDBRequest<T>, ev: Event) => any) | null;
+    onsuccess: ((this: IDBRequest<T>, ev: Event) => any) | null;
     /**
      * Returns "pending" until a request is complete,
      * then returns "done".
@@ -8679,7 +8679,7 @@ interface IDBRequest extends EventTarget {
      * or undefined if the request failed. Throws a
      * "InvalidStateError" DOMException if the request is still pending.
      */
-    readonly result: any;
+    readonly result: T;
     /**
      * Returns the IDBObjectStore, IDBIndex, or IDBCursor the request was made against, or null if is was an open
      * request.
@@ -8690,9 +8690,9 @@ interface IDBRequest extends EventTarget {
      * If this as an open request, then it returns an upgrade transaction while it is running, or null otherwise.
      */
     readonly transaction: IDBTransaction | null;
-    addEventListener<K extends keyof IDBRequestEventMap>(type: K, listener: (this: IDBRequest, ev: IDBRequestEventMap[K]) => any, options?: boolean | AddEventListenerOptions): void;
+    addEventListener<K extends keyof IDBRequestEventMap>(type: K, listener: (this: IDBRequest<T>, ev: IDBRequestEventMap[K]) => any, options?: boolean | AddEventListenerOptions): void;
     addEventListener(type: string, listener: EventListenerOrEventListenerObject, options?: boolean | AddEventListenerOptions): void;
-    removeEventListener<K extends keyof IDBRequestEventMap>(type: K, listener: (this: IDBRequest, ev: IDBRequestEventMap[K]) => any, options?: boolean | EventListenerOptions): void;
+    removeEventListener<K extends keyof IDBRequestEventMap>(type: K, listener: (this: IDBRequest<T>, ev: IDBRequestEventMap[K]) => any, options?: boolean | EventListenerOptions): void;
     removeEventListener(type: string, listener: EventListenerOrEventListenerObject, options?: boolean | EventListenerOptions): void;
 }
 
@@ -17043,4 +17043,4 @@ type VRDisplayEventReason = "mounted" | "navigation" | "requested" | "unmounted"
 type VideoFacingModeEnum = "user" | "environment" | "left" | "right";
 type VisibilityState = "hidden" | "visible" | "prerender";
 type WorkerType = "classic" | "module";
-type XMLHttpRequestResponseType = "" | "arraybuffer" | "blob" | "document" | "json" | "text";
\ No newline at end of file
+type XMLHttpRequestResponseType = "" | "arraybuffer" | "blob" | "document" | "json" | "text";
diff --git a/baselines/webworker.generated.d.ts b/baselines/webworker.generated.d.ts
index 20fc29eea..e061bac6e 100644
--- a/baselines/webworker.generated.d.ts
+++ b/baselines/webworker.generated.d.ts
@@ -1095,13 +1095,13 @@ interface IDBCursor {
      * Delete the record pointed at by the cursor with a new value.
      * If successful, request's result will be undefined.
      */
-    delete(): IDBRequest;
+    delete(): IDBRequest<undefined>;
     /**
      * Updated the record pointed at by the cursor with a new value.
      * Throws a "DataError" DOMException if the effective object store uses in-line keys and the key would have changed.
      * If successful, request's result will be the record's key.
      */
-    update(value: any): IDBRequest;
+    update(value: any): IDBRequest<IDBValidKey>;
 }
 
 declare var IDBCursor: {
@@ -1223,40 +1223,40 @@ interface IDBIndex {
      * If successful, request's result will be the
      * count.
      */
-    count(key?: IDBValidKey | IDBKeyRange): IDBRequest;
+    count(key?: IDBValidKey | IDBKeyRange): IDBRequest<number>;
     /**
      * Retrieves the value of the first record matching the
      * given key or key range in query.
      * If successful, request's result will be the value, or undefined if there was no matching record.
      */
-    get(key: IDBValidKey | IDBKeyRange): IDBRequest;
+    get(key: IDBValidKey | IDBKeyRange): IDBRequest<any | undefined>;
     /**
      * Retrieves the values of the records matching the given key or key range in query (up to count if given).
      * If successful, request's result will be an Array of the values.
      */
-    getAll(query?: IDBValidKey | IDBKeyRange, count?: number): IDBRequest;
+    getAll(query?: IDBValidKey | IDBKeyRange, count?: number): IDBRequest<any[]>;
     /**
      * Retrieves the keys of records matching the given key or key range in query (up to count if given).
      * If successful, request's result will be an Array of the keys.
      */
-    getAllKeys(query?: IDBValidKey | IDBKeyRange, count?: number): IDBRequest;
+    getAllKeys(query?: IDBValidKey | IDBKeyRange, count?: number): IDBRequest<IDBValidKey[]>;
     /**
      * Retrieves the key of the first record matching the
      * given key or key range in query.
      * If successful, request's result will be the key, or undefined if there was no matching record.
      */
-    getKey(key: IDBValidKey | IDBKeyRange): IDBRequest;
+    getKey(key: IDBValidKey | IDBKeyRange): IDBRequest<IDBValidKey | undefined>;
     /**
      * Opens a cursor over the records matching query,
      * ordered by direction. If query is null, all records in index are matched.
      * If successful, request's result will be an IDBCursorWithValue, or null if there were no matching records.
      */
-    openCursor(range?: IDBValidKey | IDBKeyRange, direction?: IDBCursorDirection): IDBRequest;
+    openCursor(range?: IDBValidKey | IDBKeyRange, direction?: IDBCursorDirection): IDBRequest<IDBCursorWithValue | null>;
     /**
      * Opens a cursor with key only flag set over the records matching query, ordered by direction. If query is null, all records in index are matched.
      * If successful, request's result will be an IDBCursor, or null if there were no matching records.
      */
-    openKeyCursor(range?: IDBValidKey | IDBKeyRange, direction?: IDBCursorDirection): IDBRequest;
+    openKeyCursor(range?: IDBValidKey | IDBKeyRange, direction?: IDBCursorDirection): IDBRequest<IDBCursor | null>;
 }
 
 declare var IDBIndex: {
@@ -1335,19 +1335,19 @@ interface IDBObjectStore {
      * Returns the associated transaction.
      */
     readonly transaction: IDBTransaction;
-    add(value: any, key?: IDBValidKey | IDBKeyRange): IDBRequest;
+    add(value: any, key?: IDBValidKey | IDBKeyRange): IDBRequest<IDBValidKey>;
     /**
      * Deletes all records in store.
      * If successful, request's result will
      * be undefined.
      */
-    clear(): IDBRequest;
+    clear(): IDBRequest<undefined>;
     /**
      * Retrieves the number of records matching the
      * given key or key range in query.
      * If successful, request's result will be the count.
      */
-    count(key?: IDBValidKey | IDBKeyRange): IDBRequest;
+    count(key?: IDBValidKey | IDBKeyRange): IDBRequest<number>;
     /**
      * Creates a new index in store with the given name, keyPath and options and returns a new IDBIndex. If the keyPath and options define constraints that cannot be
      * satisfied with the data already in store the upgrade
@@ -1362,7 +1362,7 @@ interface IDBObjectStore {
      * If successful, request's result will
      * be undefined.
      */
-    delete(key: IDBValidKey | IDBKeyRange): IDBRequest;
+    delete(key: IDBValidKey | IDBKeyRange): IDBRequest<undefined>;
     /**
      * Deletes the index in store with the given name.
      * Throws an "InvalidStateError" DOMException if not called within an upgrade
@@ -1374,41 +1374,41 @@ interface IDBObjectStore {
      * given key or key range in query.
      * If successful, request's result will be the value, or undefined if there was no matching record.
      */
-    get(query: IDBValidKey | IDBKeyRange): IDBRequest;
+    get(query: IDBValidKey | IDBKeyRange): IDBRequest<any | undefined>;
     /**
      * Retrieves the values of the records matching the
      * given key or key range in query (up to count if given).
      * If successful, request's result will
      * be an Array of the values.
      */
-    getAll(query?: IDBValidKey | IDBKeyRange, count?: number): IDBRequest;
+    getAll(query?: IDBValidKey | IDBKeyRange, count?: number): IDBRequest<any[]>;
     /**
      * Retrieves the keys of records matching the
      * given key or key range in query (up to count if given).
      * If successful, request's result will
      * be an Array of the keys.
      */
-    getAllKeys(query?: IDBValidKey | IDBKeyRange, count?: number): IDBRequest;
+    getAllKeys(query?: IDBValidKey | IDBKeyRange, count?: number): IDBRequest<IDBValidKey[]>;
     /**
      * Retrieves the key of the first record matching the
      * given key or key range in query.
      * If successful, request's result will be the key, or undefined if there was no matching record.
      */
-    getKey(query: IDBValidKey | IDBKeyRange): IDBRequest;
+    getKey(query: IDBValidKey | IDBKeyRange): IDBRequest<IDBValidKey | undefined>;
     index(name: string): IDBIndex;
     /**
      * Opens a cursor over the records matching query,
      * ordered by direction. If query is null, all records in store are matched.
      * If successful, request's result will be an IDBCursorWithValue pointing at the first matching record, or null if there were no matching records.
      */
-    openCursor(range?: IDBValidKey | IDBKeyRange, direction?: IDBCursorDirection): IDBRequest;
+    openCursor(range?: IDBValidKey | IDBKeyRange, direction?: IDBCursorDirection): IDBRequest<IDBCursorWithValue | null>;
     /**
      * Opens a cursor with key only flag set over the records matching query, ordered by direction. If query is null, all records in store are matched.
      * If successful, request's result will be an IDBCursor pointing at the first matching record, or
      * null if there were no matching records.
      */
-    openKeyCursor(query?: IDBValidKey | IDBKeyRange, direction?: IDBCursorDirection): IDBRequest;
-    put(value: any, key?: IDBValidKey | IDBKeyRange): IDBRequest;
+    openKeyCursor(query?: IDBValidKey | IDBKeyRange, direction?: IDBCursorDirection): IDBRequest<IDBCursor | null>;
+    put(value: any, key?: IDBValidKey | IDBKeyRange): IDBRequest<IDBValidKey>;
 }
 
 declare var IDBObjectStore: {
@@ -1421,7 +1421,7 @@ interface IDBOpenDBRequestEventMap extends IDBRequestEventMap {
     "upgradeneeded": IDBVersionChangeEvent;
 }
 
-interface IDBOpenDBRequest extends IDBRequest {
+interface IDBOpenDBRequest extends IDBRequest<IDBDatabase> {
     onblocked: ((this: IDBOpenDBRequest, ev: Event) => any) | null;
     onupgradeneeded: ((this: IDBOpenDBRequest, ev: IDBVersionChangeEvent) => any) | null;
     addEventListener<K extends keyof IDBOpenDBRequestEventMap>(type: K, listener: (this: IDBOpenDBRequest, ev: IDBOpenDBRequestEventMap[K]) => any, options?: boolean | AddEventListenerOptions): void;
@@ -1440,14 +1440,14 @@ interface IDBRequestEventMap {
     "success": Event;
 }
 
-interface IDBRequest extends EventTarget {
+interface IDBRequest<T = any> extends EventTarget {
     /**
      * When a request is completed, returns the error (a DOMException), or null if the request succeeded. Throws
      * a "InvalidStateError" DOMException if the request is still pending.
      */
     readonly error: DOMException | null;
-    onerror: ((this: IDBRequest, ev: Event) => any) | null;
-    onsuccess: ((this: IDBRequest, ev: Event) => any) | null;
+    onerror: ((this: IDBRequest<T>, ev: Event) => any) | null;
+    onsuccess: ((this: IDBRequest<T>, ev: Event) => any) | null;
     /**
      * Returns "pending" until a request is complete,
      * then returns "done".
@@ -1458,7 +1458,7 @@ interface IDBRequest extends EventTarget {
      * or undefined if the request failed. Throws a
      * "InvalidStateError" DOMException if the request is still pending.
      */
-    readonly result: any;
+    readonly result: T;
     /**
      * Returns the IDBObjectStore, IDBIndex, or IDBCursor the request was made against, or null if is was an open
      * request.
@@ -1469,9 +1469,9 @@ interface IDBRequest extends EventTarget {
      * If this as an open request, then it returns an upgrade transaction while it is running, or null otherwise.
      */
     readonly transaction: IDBTransaction | null;
-    addEventListener<K extends keyof IDBRequestEventMap>(type: K, listener: (this: IDBRequest, ev: IDBRequestEventMap[K]) => any, options?: boolean | AddEventListenerOptions): void;
+    addEventListener<K extends keyof IDBRequestEventMap>(type: K, listener: (this: IDBRequest<T>, ev: IDBRequestEventMap[K]) => any, options?: boolean | AddEventListenerOptions): void;
     addEventListener(type: string, listener: EventListenerOrEventListenerObject, options?: boolean | AddEventListenerOptions): void;
-    removeEventListener<K extends keyof IDBRequestEventMap>(type: K, listener: (this: IDBRequest, ev: IDBRequestEventMap[K]) => any, options?: boolean | EventListenerOptions): void;
+    removeEventListener<K extends keyof IDBRequestEventMap>(type: K, listener: (this: IDBRequest<T>, ev: IDBRequestEventMap[K]) => any, options?: boolean | EventListenerOptions): void;
     removeEventListener(type: string, listener: EventListenerOrEventListenerObject, options?: boolean | EventListenerOptions): void;
 }
 
@@ -2727,4 +2727,4 @@ type ServiceWorkerState = "installing" | "installed" | "activating" | "activated
 type ServiceWorkerUpdateViaCache = "imports" | "all" | "none";
 type VisibilityState = "hidden" | "visible" | "prerender";
 type WorkerType = "classic" | "module";
-type XMLHttpRequestResponseType = "" | "arraybuffer" | "blob" | "document" | "json" | "text";
\ No newline at end of file
+type XMLHttpRequestResponseType = "" | "arraybuffer" | "blob" | "document" | "json" | "text";
diff --git a/inputfiles/addedTypes.json b/inputfiles/addedTypes.json
index 96bf70afe..c80268aaf 100644
--- a/inputfiles/addedTypes.json
+++ b/inputfiles/addedTypes.json
@@ -715,6 +715,7 @@
             },
             "IDBOpenDBRequest": {
                 "name": "IDBOpenDBRequest",
+                "extends": "IDBRequest<IDBDatabase>",
                 "events": {
                     "event": [
                         {
diff --git a/inputfiles/overridingTypes.json b/inputfiles/overridingTypes.json
index 7705ee0d7..a17e92980 100644
--- a/inputfiles/overridingTypes.json
+++ b/inputfiles/overridingTypes.json
@@ -224,7 +224,10 @@
                     }
                 },
                 "type-parameters": [
-                    "T = any"
+                    {
+                        "name": "T",
+                        "default": "any"
+                    }
                 ],
                 "constructor": {
                     "override-signatures": [
@@ -454,61 +457,67 @@
                         "openCursor": {
                             "name": "openCursor",
                             "override-signatures": [
-                                "openCursor(range?: IDBValidKey | IDBKeyRange, direction?: IDBCursorDirection): IDBRequest"
+                                "openCursor(range?: IDBValidKey | IDBKeyRange, direction?: IDBCursorDirection): IDBRequest<IDBCursorWithValue | null>"
                             ]
                         },
                         "openKeyCursor": {
                             "name": "openKeyCursor",
                             "override-signatures": [
-                                "openKeyCursor(query?: IDBValidKey | IDBKeyRange, direction?: IDBCursorDirection): IDBRequest"
+                                "openKeyCursor(query?: IDBValidKey | IDBKeyRange, direction?: IDBCursorDirection): IDBRequest<IDBCursor | null>"
                             ]
                         },
                         "add": {
                             "name": "add",
                             "override-signatures": [
-                                "add(value: any, key?: IDBValidKey | IDBKeyRange): IDBRequest"
+                                "add(value: any, key?: IDBValidKey | IDBKeyRange): IDBRequest<IDBValidKey>"
+                            ]
+                        },
+                        "clear": {
+                            "name": "clear",
+                            "override-signatures": [
+                                "clear(): IDBRequest<undefined>"
                             ]
                         },
                         "count": {
                             "name": "count",
                             "override-signatures": [
-                                "count(key?: IDBValidKey | IDBKeyRange): IDBRequest"
+                                "count(key?: IDBValidKey | IDBKeyRange): IDBRequest<number>"
                             ]
                         },
                         "delete": {
                             "name": "delete",
                             "override-signatures": [
-                                "delete(key: IDBValidKey | IDBKeyRange): IDBRequest"
+                                "delete(key: IDBValidKey | IDBKeyRange): IDBRequest<undefined>"
                             ]
                         },
                         "put": {
                             "name": "put",
                             "override-signatures": [
-                                "put(value: any, key?: IDBValidKey | IDBKeyRange): IDBRequest"
+                                "put(value: any, key?: IDBValidKey | IDBKeyRange): IDBRequest<IDBValidKey>"
                             ]
                         },
                         "get": {
                             "name": "get",
                             "override-signatures": [
-                                "get(query: IDBValidKey | IDBKeyRange): IDBRequest"
+                                "get(query: IDBValidKey | IDBKeyRange): IDBRequest<any | undefined>"
                             ]
                         },
                         "getAll": {
                             "name": "getAll",
                             "override-signatures": [
-                                "getAll(query?: IDBValidKey | IDBKeyRange, count?: number): IDBRequest"
+                                "getAll(query?: IDBValidKey | IDBKeyRange, count?: number): IDBRequest<any[]>"
                             ]
                         },
                         "getAllKeys": {
                             "name": "getAllKeys",
                             "override-signatures": [
-                                "getAllKeys(query?: IDBValidKey | IDBKeyRange, count?: number): IDBRequest"
+                                "getAllKeys(query?: IDBValidKey | IDBKeyRange, count?: number): IDBRequest<IDBValidKey[]>"
                             ]
                         },
                         "getKey": {
                             "name": "getKey",
                             "override-signatures": [
-                                "getKey(query: IDBValidKey | IDBKeyRange): IDBRequest"
+                                "getKey(query: IDBValidKey | IDBKeyRange): IDBRequest<IDBValidKey | undefined>"
                             ]
                         }
                     }
@@ -554,43 +563,43 @@
                         "openCursor": {
                             "name": "openCursor",
                             "override-signatures": [
-                                "openCursor(range?: IDBValidKey | IDBKeyRange, direction?: IDBCursorDirection): IDBRequest"
+                                "openCursor(range?: IDBValidKey | IDBKeyRange, direction?: IDBCursorDirection): IDBRequest<IDBCursorWithValue | null>"
                             ]
                         },
                         "openKeyCursor": {
                             "name": "openKeyCursor",
                             "override-signatures": [
-                                "openKeyCursor(range?: IDBValidKey | IDBKeyRange, direction?: IDBCursorDirection): IDBRequest"
+                                "openKeyCursor(range?: IDBValidKey | IDBKeyRange, direction?: IDBCursorDirection): IDBRequest<IDBCursor | null>"
                             ]
                         },
                         "count": {
                             "name": "count",
                             "override-signatures": [
-                                "count(key?: IDBValidKey | IDBKeyRange): IDBRequest"
+                                "count(key?: IDBValidKey | IDBKeyRange): IDBRequest<number>"
                             ]
                         },
                         "get": {
                             "name": "get",
                             "override-signatures": [
-                                "get(key: IDBValidKey | IDBKeyRange): IDBRequest"
+                                "get(key: IDBValidKey | IDBKeyRange): IDBRequest<any | undefined>"
                             ]
                         },
                         "getAll": {
                             "name": "getAll",
                             "override-signatures": [
-                                "getAll(query?: IDBValidKey | IDBKeyRange, count?: number): IDBRequest"
+                                "getAll(query?: IDBValidKey | IDBKeyRange, count?: number): IDBRequest<any[]>"
                             ]
                         },
                         "getAllKeys": {
                             "name": "getAllKeys",
                             "override-signatures": [
-                                "getAllKeys(query?: IDBValidKey | IDBKeyRange, count?: number): IDBRequest"
+                                "getAllKeys(query?: IDBValidKey | IDBKeyRange, count?: number): IDBRequest<IDBValidKey[]>"
                             ]
                         },
                         "getKey": {
                             "name": "getKey",
                             "override-signatures": [
-                                "getKey(key: IDBValidKey | IDBKeyRange): IDBRequest"
+                                "getKey(key: IDBValidKey | IDBKeyRange): IDBRequest<IDBValidKey | undefined>"
                             ]
                         }
                     }
@@ -1183,6 +1192,16 @@
                             "override-signatures": [
                                 "continuePrimaryKey(key: IDBValidKey | IDBKeyRange, primaryKey: IDBValidKey | IDBKeyRange): void"
                             ]
+                        },
+                        "delete": {
+                            "override-signatures": [
+                                "delete(): IDBRequest<undefined>"
+                            ]
+                        },
+                        "update": {
+                            "override-signatures": [
+                                "update(value: any): IDBRequest<IDBValidKey>"
+                            ]
                         }
                     }
                 }
@@ -1200,9 +1219,19 @@
                             "name": "source",
                             "nullable": false,
                             "override-type": "IDBObjectStore | IDBIndex | IDBCursor"
+                        },
+                        "result": {
+                            "name": "result",
+                            "override-type": "T"
                         }
                     }
-                }
+                },
+                "type-parameters": [
+                    {
+                        "name": "T",
+                        "default": "any"
+                    }
+                ]
             },
             "IDBTransaction": {
                 "name": "IDBTransaction",
@@ -2315,7 +2344,10 @@
                     }
                 },
                 "type-parameters": [
-                    "T = any"
+                    {
+                        "name": "T",
+                        "default": "any"
+                    }
                 ]
             },
             "AesGcmParams": {
diff --git a/package-lock.json b/package-lock.json
index 26c791cf6..81aab6dd8 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -307,6 +307,11 @@
       "resolved": "https://registry.npmjs.org/delayed-stream/-/delayed-stream-1.0.0.tgz",
       "integrity": "sha1-3zrhmayt+31ECqrgsp4icrJOxhk="
     },
+    "diff": {
+      "version": "1.4.0",
+      "resolved": "https://registry.npmjs.org/diff/-/diff-1.4.0.tgz",
+      "integrity": "sha1-fyjS657nsVqX79ic5j3P2qPMur8="
+    },
     "domexception": {
       "version": "1.0.1",
       "resolved": "https://registry.npmjs.org/domexception/-/domexception-1.0.1.tgz",
@@ -1385,6 +1390,14 @@
       "resolved": "https://registry.npmjs.org/preserve/-/preserve-0.2.0.tgz",
       "integrity": "sha1-gV7R9uvGWSb4ZbMQwHE7yzMVzks="
     },
+    "print-diff": {
+      "version": "0.1.1",
+      "resolved": "https://registry.npmjs.org/print-diff/-/print-diff-0.1.1.tgz",
+      "integrity": "sha512-dp36GezMEivgKH/zcLB4eBhJmQM3ewAa1UAqEPXMzU69NQ5wCP8puVBZlDFyt1WEtR5k2UC+3ahg+T5BfmRVGw==",
+      "requires": {
+        "diff": "^1.2.1"
+      }
+    },
     "process-nextick-args": {
       "version": "2.0.0",
       "resolved": "https://registry.npmjs.org/process-nextick-args/-/process-nextick-args-2.0.0.tgz",
diff --git a/package.json b/package.json
index 7210c6db7..6ba0eafef 100644
--- a/package.json
+++ b/package.json
@@ -15,6 +15,7 @@
     "cpx": "^1.5.0",
     "jsdom": "^11.11.0",
     "node-fetch": "^2.1.1",
+    "print-diff": "^0.1.1",
     "typescript": "next",
     "webidl2": "^13.0.2"
   }
diff --git a/src/emitter.ts b/src/emitter.ts
index 5b2fe7c90..809bb7d73 100644
--- a/src/emitter.ts
+++ b/src/emitter.ts
@@ -82,11 +82,9 @@ function createTextWriter(newLine: string) {
         stack = [];
     }
 
-    function writeLine() {
-        if (!lineStart) {
-            output += newLine;
-            lineStart = true;
-        }
+    function endLine() {
+        output += newLine;
+        lineStart = true;
     }
 
     reset();
@@ -98,8 +96,9 @@ function createTextWriter(newLine: string) {
         increaseIndent() { indent++; },
         decreaseIndent() { indent--; },
 
+        endLine: endLine,
         print: write,
-        printLine(c: string) { writeLine(); write(c); },
+        printLine(c: string) { write(c); endLine(); },
 
         clearStack() { stack = []; },
         stackIsEmpty() { return stack.length === 0; },
@@ -226,7 +225,8 @@ export function emitWebIDl(webidl: Browser.WebIdl, flavor: Flavor) {
             return ehParents;
         }
 
-        const parentWithEventHandler = allInterfacesMap[i.extends] && getParentEventHandler(allInterfacesMap[i.extends]) || [];
+        const iExtends = i.extends && i.extends.replace(/<.*>$/, '');
+        const parentWithEventHandler = allInterfacesMap[iExtends] && getParentEventHandler(allInterfacesMap[iExtends]) || [];
         const mixinsWithEventHandler = flatMap(i.implements || [], i => getParentEventHandler(allInterfacesMap[i]));
 
         return distinct(parentWithEventHandler.concat(mixinsWithEventHandler));
@@ -356,6 +356,15 @@ export function emitWebIDl(webidl: Browser.WebIdl, flavor: Flavor) {
         return obj.nullable ? makeNullable(resolvedType) : resolvedType;
     }
 
+    function nameWithForwardedTypes (i: Browser.Interface) {
+        const typeParameters = i["type-parameters"];
+
+        if (!typeParameters) return i.name;
+        if (!typeParameters.length) return i.name;
+
+        return `${i.name}<${typeParameters.map(t => t.name)}>`;
+    }
+
     function emitConstant(c: Browser.Constant) {
         printer.printLine(`readonly ${c.name}: ${convertDomTypeToTsType(c)};`);
     }
@@ -377,7 +386,11 @@ export function emitWebIDl(webidl: Browser.WebIdl, flavor: Flavor) {
     }
 
     function processInterfaceType(i: Browser.Interface | Browser.Dictionary, name: string) {
-        return i["type-parameters"] ? name + "<" + i["type-parameters"]!.join(", ") + ">" : name;
+        function typeParameterWithDefault (type: Browser.TypeParameter) {
+            return type.default ? type.name + " = " + type.default : type.name
+        }
+
+        return i["type-parameters"] ? name + "<" + i["type-parameters"]!.map(typeParameterWithDefault).join(", ") + ">" : name;
     }
 
     /// Emit overloads for the createElement method
@@ -536,7 +549,7 @@ export function emitWebIDl(webidl: Browser.WebIdl, flavor: Flavor) {
 
     function emitEventHandlerThis(prefix: string, i: Browser.Interface) {
         if (prefix === "") {
-            return `this: ${i.name}, `;
+            return `this: ${nameWithForwardedTypes(i)}, `;
         }
         else {
             return pollutor ? `this: ${pollutor.name}, ` : "";
@@ -723,7 +736,7 @@ export function emitWebIDl(webidl: Browser.WebIdl, flavor: Flavor) {
         return;
 
         function emitTypedEventHandler(prefix: string, addOrRemove: string, iParent: Browser.Interface, optionsType: string) {
-            printer.printLine(`${prefix}${addOrRemove}EventListener<K extends keyof ${iParent.name}EventMap>(type: K, listener: (this: ${i.name}, ev: ${iParent.name}EventMap[K]) => any, options?: boolean | ${optionsType}): void;`);
+            printer.printLine(`${prefix}${addOrRemove}EventListener<K extends keyof ${iParent.name}EventMap>(type: K, listener: (this: ${nameWithForwardedTypes(i)}, ev: ${iParent.name}EventMap[K]) => any, options?: boolean | ${optionsType}): void;`);
         }
 
         function tryEmitTypedEventHandlerForInterface(addOrRemove: string, optionsType: string) {
@@ -811,7 +824,7 @@ export function emitWebIDl(webidl: Browser.WebIdl, flavor: Flavor) {
             printer.printLineToStack(`interface ${processInterfaceType(i, i.name)} extends ${processedIName} {`);
         }
 
-        printer.printLine(`interface ${processInterfaceType(i, processedIName)}`);
+        printer.print(`interface ${processInterfaceType(i, processedIName)}`);
 
         const finalExtends = distinct([i.extends || "Object"].concat(i.implements || [])
             .filter(i => i !== "Object")
@@ -821,6 +834,7 @@ export function emitWebIDl(webidl: Browser.WebIdl, flavor: Flavor) {
             printer.print(` extends ${finalExtends.join(", ")}`);
         }
         printer.print(" {");
+        printer.endLine();
     }
 
     /// To decide if a given method is an indexer and should be emited
@@ -881,12 +895,13 @@ export function emitWebIDl(webidl: Browser.WebIdl, flavor: Flavor) {
         const ehParentCount = iNameToEhParents[i.name] && iNameToEhParents[i.name].length;
 
         if (hasEventHandlers || ehParentCount > 1) {
-            printer.printLine(`interface ${i.name}EventMap`);
+            printer.print(`interface ${i.name}EventMap`);
             if (ehParentCount) {
                 const extend = iNameToEhParents[i.name].map(i => i.name + "EventMap");
                 printer.print(` extends ${extend.join(", ")}`);
             }
             printer.print(" {");
+            printer.endLine();
             printer.increaseIndent();
             iNameToEhList[i.name]
                 .sort(compareName)
@@ -1170,6 +1185,7 @@ export function emitWebIDl(webidl: Browser.WebIdl, flavor: Flavor) {
         if (subtypes) {
             const iteratorExtends = getIteratorExtends(i.iterator, subtypes);
             const name = extendConflictsBaseTypes[i.name] ? `${i.name}Base` : i.name;
+            printer.printLine("");
             printer.printLine(`interface ${name} ${iteratorExtends}{`);
             printer.increaseIndent();
             if (!iteratorExtends) {
@@ -1180,7 +1196,6 @@ export function emitWebIDl(webidl: Browser.WebIdl, flavor: Flavor) {
             }
             printer.decreaseIndent();
             printer.printLine("}");
-            printer.printLine("");
         }
     }
 
@@ -1189,7 +1204,6 @@ export function emitWebIDl(webidl: Browser.WebIdl, flavor: Flavor) {
         printer.printLine("/////////////////////////////");
         printer.printLine("/// DOM Iterable APIs");
         printer.printLine("/////////////////////////////");
-        printer.printLine("");
 
         allInterfaces
             .sort(compareName)
diff --git a/src/test.ts b/src/test.ts
index b6efa9cf0..21e725b25 100644
--- a/src/test.ts
+++ b/src/test.ts
@@ -1,6 +1,7 @@
 import * as fs from "fs";
 import * as path from "path";
 import child_process from "child_process";
+import printDiff = require("print-diff");
 
 const __SOURCE_DIRECTORY__ = __dirname;
 const baselineFolder = path.join(__SOURCE_DIRECTORY__, "../", "baselines");
@@ -17,6 +18,7 @@ function compareToBaselines() {
         const generated = normalizeLineEndings(fs.readFileSync(path.join(outputFolder, file)).toString());
         if (baseline !== generated) {
             console.error(`Test failed: '${file}' is different from baseline file.`);
+            printDiff(generated, baseline);
             return false;
         }
     }
diff --git a/src/types.d.ts b/src/types.d.ts
index 54128103c..0d1543b11 100644
--- a/src/types.d.ts
+++ b/src/types.d.ts
@@ -138,6 +138,11 @@ export interface Element {
     specs?: string;
 }
 
+export interface TypeParameter {
+    name: string;
+    default?: string;
+}
+
 export interface Interface {
     name: string;
     extends: string;
@@ -173,7 +178,7 @@ export interface Interface {
     "primary-global"?: string;
     "no-interface-object"?: 1;
     global?: string;
-    "type-parameters"?: string[];
+    "type-parameters"?: TypeParameter[];
     "override-index-signatures"?: string[];
     specs?: string;
     iterable?: "value" | "pair" | "pair-iterator";
@@ -207,7 +212,7 @@ export interface Dictionary {
         member: Record<string, Member>;
     }
     specs?: string;
-    "type-parameters"?: string[];
+    "type-parameters"?: TypeParameter[];
 }
 
 export interface WebIdl {