diff --git a/baselines/dom.generated.d.ts b/baselines/dom.generated.d.ts
index 7b1cfbc32..265ff3e49 100644
--- a/baselines/dom.generated.d.ts
+++ b/baselines/dom.generated.d.ts
@@ -1953,7 +1953,7 @@ interface ApplicationCacheEventMap {
     "error": Event;
     "noupdate": Event;
     "obsolete": Event;
-    "progress": ProgressEvent;
+    "progress": ProgressEvent<ApplicationCache>;
     "updateready": Event;
 }
 
@@ -1971,7 +1971,7 @@ interface ApplicationCache extends EventTarget {
     /** @deprecated */
     onobsolete: ((this: ApplicationCache, ev: Event) => any) | null;
     /** @deprecated */
-    onprogress: ((this: ApplicationCache, ev: ProgressEvent) => any) | null;
+    onprogress: ((this: ApplicationCache, ev: ProgressEvent<ApplicationCache>) => any) | null;
     /** @deprecated */
     onupdateready: ((this: ApplicationCache, ev: Event) => any) | null;
     /** @deprecated */
@@ -4286,7 +4286,7 @@ interface DocumentEventMap extends GlobalEventHandlersEventMap, DocumentAndEleme
     "fullscreenerror": Event;
     "pointerlockchange": Event;
     "pointerlockerror": Event;
-    "readystatechange": ProgressEvent;
+    "readystatechange": ProgressEvent<Document>;
     "visibilitychange": Event;
 }
 
@@ -4445,7 +4445,7 @@ interface Document extends Node, NonElementParentNode, DocumentOrShadowRoot, Par
      * Fires when the state of the object has changed.
      * @param ev The event
      */
-    onreadystatechange: ((this: Document, ev: ProgressEvent) => any) | null;
+    onreadystatechange: ((this: Document, ev: ProgressEvent<Document>) => any) | null;
     onvisibilitychange: ((this: Document, ev: Event) => any) | null;
     /**
      * Returns document's origin.
@@ -4558,7 +4558,6 @@ interface Document extends Node, NonElementParentNode, DocumentOrShadowRoot, Par
     createEvent(eventInterface: "ErrorEvent"): ErrorEvent;
     createEvent(eventInterface: "Event"): Event;
     createEvent(eventInterface: "Events"): Event;
-    createEvent(eventInterface: "FileReaderProgressEvent"): FileReaderProgressEvent;
     createEvent(eventInterface: "FocusEvent"): FocusEvent;
     createEvent(eventInterface: "FocusNavigationEvent"): FocusNavigationEvent;
     createEvent(eventInterface: "GamepadEvent"): GamepadEvent;
@@ -4808,7 +4807,6 @@ interface DocumentEvent {
     createEvent(eventInterface: "ErrorEvent"): ErrorEvent;
     createEvent(eventInterface: "Event"): Event;
     createEvent(eventInterface: "Events"): Event;
-    createEvent(eventInterface: "FileReaderProgressEvent"): FileReaderProgressEvent;
     createEvent(eventInterface: "FocusEvent"): FocusEvent;
     createEvent(eventInterface: "FocusNavigationEvent"): FocusNavigationEvent;
     createEvent(eventInterface: "GamepadEvent"): GamepadEvent;
@@ -5370,23 +5368,23 @@ declare var FileList: {
 };
 
 interface FileReaderEventMap {
-    "abort": FileReaderProgressEvent;
-    "error": FileReaderProgressEvent;
-    "load": FileReaderProgressEvent;
-    "loadend": FileReaderProgressEvent;
-    "loadstart": FileReaderProgressEvent;
-    "progress": FileReaderProgressEvent;
+    "abort": ProgressEvent<FileReader>;
+    "error": ProgressEvent<FileReader>;
+    "load": ProgressEvent<FileReader>;
+    "loadend": ProgressEvent<FileReader>;
+    "loadstart": ProgressEvent<FileReader>;
+    "progress": ProgressEvent<FileReader>;
 }
 
 /** Lets web applications asynchronously read the contents of files (or raw data buffers) stored on the user's computer, using File or Blob objects to specify the file or data to read. */
 interface FileReader extends EventTarget {
     readonly error: DOMException | null;
-    onabort: ((this: FileReader, ev: FileReaderProgressEvent) => any) | null;
-    onerror: ((this: FileReader, ev: FileReaderProgressEvent) => any) | null;
-    onload: ((this: FileReader, ev: FileReaderProgressEvent) => any) | null;
-    onloadend: ((this: FileReader, ev: FileReaderProgressEvent) => any) | null;
-    onloadstart: ((this: FileReader, ev: FileReaderProgressEvent) => any) | null;
-    onprogress: ((this: FileReader, ev: FileReaderProgressEvent) => any) | null;
+    onabort: ((this: FileReader, ev: ProgressEvent<FileReader>) => any) | null;
+    onerror: ((this: FileReader, ev: ProgressEvent<FileReader>) => any) | null;
+    onload: ((this: FileReader, ev: ProgressEvent<FileReader>) => any) | null;
+    onloadend: ((this: FileReader, ev: ProgressEvent<FileReader>) => any) | null;
+    onloadstart: ((this: FileReader, ev: ProgressEvent<FileReader>) => any) | null;
+    onprogress: ((this: FileReader, ev: ProgressEvent<FileReader>) => any) | null;
     readonly readyState: number;
     readonly result: string | ArrayBuffer | null;
     abort(): void;
@@ -5411,10 +5409,6 @@ declare var FileReader: {
     readonly LOADING: number;
 };
 
-interface FileReaderProgressEvent extends ProgressEvent {
-    readonly target: FileReader | null;
-}
-
 /** Focus-related events like focus, blur, focusin, or focusout. */
 interface FocusEvent extends UIEvent {
     readonly relatedTarget: EventTarget;
@@ -11765,9 +11759,10 @@ declare var ProcessingInstruction: {
 };
 
 /** Events measuring progress of an underlying process, like an HTTP request (for an XMLHttpRequest, or the loading of the underlying resource of an <img>, <audio>, <video>, <style> or <link>). */
-interface ProgressEvent extends Event {
+interface ProgressEvent<T extends EventTarget = EventTarget> extends Event {
     readonly lengthComputable: boolean;
     readonly loaded: number;
+    readonly target: T | null;
     readonly total: number;
 }
 
@@ -17246,9 +17241,9 @@ interface WindowEventMap extends GlobalEventHandlersEventMap, WindowEventHandler
     "play": Event;
     "playing": Event;
     "popstate": PopStateEvent;
-    "progress": ProgressEvent;
+    "progress": ProgressEvent<Window>;
     "ratechange": Event;
-    "readystatechange": ProgressEvent;
+    "readystatechange": ProgressEvent<Window>;
     "reset": Event;
     "resize": UIEvent;
     "scroll": Event;
@@ -17332,7 +17327,7 @@ interface Window extends EventTarget, WindowTimers, WindowSessionStorage, Window
     onmspointerup: ((this: Window, ev: Event) => any) | null;
     /** @deprecated */
     onorientationchange: ((this: Window, ev: Event) => any) | null;
-    onreadystatechange: ((this: Window, ev: ProgressEvent) => any) | null;
+    onreadystatechange: ((this: Window, ev: ProgressEvent<Window>) => any) | null;
     onvrdisplayactivate: ((this: Window, ev: Event) => any) | null;
     onvrdisplayblur: ((this: Window, ev: Event) => any) | null;
     onvrdisplayconnect: ((this: Window, ev: Event) => any) | null;
@@ -17684,13 +17679,13 @@ declare var XMLHttpRequest: {
 };
 
 interface XMLHttpRequestEventTargetEventMap {
-    "abort": ProgressEvent;
-    "error": ProgressEvent;
-    "load": ProgressEvent;
-    "loadend": ProgressEvent;
-    "loadstart": ProgressEvent;
-    "progress": ProgressEvent;
-    "timeout": ProgressEvent;
+    "abort": ProgressEvent<XMLHttpRequestEventTarget>;
+    "error": ProgressEvent<XMLHttpRequestEventTarget>;
+    "load": ProgressEvent<XMLHttpRequestEventTarget>;
+    "loadend": ProgressEvent<XMLHttpRequestEventTarget>;
+    "loadstart": ProgressEvent<XMLHttpRequestEventTarget>;
+    "progress": ProgressEvent<XMLHttpRequestEventTarget>;
+    "timeout": ProgressEvent<XMLHttpRequestEventTarget>;
 }
 
 interface XMLHttpRequestEventTarget extends EventTarget {
@@ -18328,7 +18323,7 @@ declare var onmspointerover: ((this: Window, ev: Event) => any) | null;
 declare var onmspointerup: ((this: Window, ev: Event) => any) | null;
 /** @deprecated */
 declare var onorientationchange: ((this: Window, ev: Event) => any) | null;
-declare var onreadystatechange: ((this: Window, ev: ProgressEvent) => any) | null;
+declare var onreadystatechange: ((this: Window, ev: ProgressEvent<Window>) => any) | null;
 declare var onvrdisplayactivate: ((this: Window, ev: Event) => any) | null;
 declare var onvrdisplayblur: ((this: Window, ev: Event) => any) | null;
 declare var onvrdisplayconnect: ((this: Window, ev: Event) => any) | null;
diff --git a/baselines/webworker.generated.d.ts b/baselines/webworker.generated.d.ts
index 8115f73c6..c208bdccb 100644
--- a/baselines/webworker.generated.d.ts
+++ b/baselines/webworker.generated.d.ts
@@ -1525,23 +1525,23 @@ declare var FileList: {
 };
 
 interface FileReaderEventMap {
-    "abort": FileReaderProgressEvent;
-    "error": FileReaderProgressEvent;
-    "load": FileReaderProgressEvent;
-    "loadend": FileReaderProgressEvent;
-    "loadstart": FileReaderProgressEvent;
-    "progress": FileReaderProgressEvent;
+    "abort": ProgressEvent<FileReader>;
+    "error": ProgressEvent<FileReader>;
+    "load": ProgressEvent<FileReader>;
+    "loadend": ProgressEvent<FileReader>;
+    "loadstart": ProgressEvent<FileReader>;
+    "progress": ProgressEvent<FileReader>;
 }
 
 /** Lets web applications asynchronously read the contents of files (or raw data buffers) stored on the user's computer, using File or Blob objects to specify the file or data to read. */
 interface FileReader extends EventTarget {
     readonly error: DOMException | null;
-    onabort: ((this: FileReader, ev: FileReaderProgressEvent) => any) | null;
-    onerror: ((this: FileReader, ev: FileReaderProgressEvent) => any) | null;
-    onload: ((this: FileReader, ev: FileReaderProgressEvent) => any) | null;
-    onloadend: ((this: FileReader, ev: FileReaderProgressEvent) => any) | null;
-    onloadstart: ((this: FileReader, ev: FileReaderProgressEvent) => any) | null;
-    onprogress: ((this: FileReader, ev: FileReaderProgressEvent) => any) | null;
+    onabort: ((this: FileReader, ev: ProgressEvent<FileReader>) => any) | null;
+    onerror: ((this: FileReader, ev: ProgressEvent<FileReader>) => any) | null;
+    onload: ((this: FileReader, ev: ProgressEvent<FileReader>) => any) | null;
+    onloadend: ((this: FileReader, ev: ProgressEvent<FileReader>) => any) | null;
+    onloadstart: ((this: FileReader, ev: ProgressEvent<FileReader>) => any) | null;
+    onprogress: ((this: FileReader, ev: ProgressEvent<FileReader>) => any) | null;
     readonly readyState: number;
     readonly result: string | ArrayBuffer | null;
     abort(): void;
@@ -1566,10 +1566,6 @@ declare var FileReader: {
     readonly LOADING: number;
 };
 
-interface FileReaderProgressEvent extends ProgressEvent {
-    readonly target: FileReader | null;
-}
-
 /** Allows to read File or Blob objects in a synchronous way. */
 interface FileReaderSync {
     readAsArrayBuffer(blob: Blob): ArrayBuffer;
@@ -2587,9 +2583,10 @@ declare var Permissions: {
 };
 
 /** Events measuring progress of an underlying process, like an HTTP request (for an XMLHttpRequest, or the loading of the underlying resource of an <img>, <audio>, <video>, <style> or <link>). */
-interface ProgressEvent extends Event {
+interface ProgressEvent<T extends EventTarget = EventTarget> extends Event {
     readonly lengthComputable: boolean;
     readonly loaded: number;
+    readonly target: T | null;
     readonly total: number;
 }
 
@@ -4513,13 +4510,13 @@ declare var XMLHttpRequest: {
 };
 
 interface XMLHttpRequestEventTargetEventMap {
-    "abort": ProgressEvent;
-    "error": ProgressEvent;
-    "load": ProgressEvent;
-    "loadend": ProgressEvent;
-    "loadstart": ProgressEvent;
-    "progress": ProgressEvent;
-    "timeout": ProgressEvent;
+    "abort": ProgressEvent<XMLHttpRequestEventTarget>;
+    "error": ProgressEvent<XMLHttpRequestEventTarget>;
+    "load": ProgressEvent<XMLHttpRequestEventTarget>;
+    "loadend": ProgressEvent<XMLHttpRequestEventTarget>;
+    "loadstart": ProgressEvent<XMLHttpRequestEventTarget>;
+    "progress": ProgressEvent<XMLHttpRequestEventTarget>;
+    "timeout": ProgressEvent<XMLHttpRequestEventTarget>;
 }
 
 interface XMLHttpRequestEventTarget extends EventTarget {
diff --git a/inputfiles/addedTypes.json b/inputfiles/addedTypes.json
index 40fa45518..9b3fac023 100644
--- a/inputfiles/addedTypes.json
+++ b/inputfiles/addedTypes.json
@@ -599,8 +599,14 @@
                     }
                 }
             },
-            "NodeListOf<TNode extends Node>": {
-                "name": "NodeListOf<TNode extends Node>",
+            "NodeListOf": {
+                "name": "NodeListOf",
+                "type-parameters": [
+                    {
+                        "name": "TNode",
+                        "extends": "Node"
+                    }
+                ],
                 "exposed": "Window",
                 "extends": "NodeList",
                 "properties": {
@@ -634,8 +640,14 @@
                     ]
                 }
             },
-            "HTMLCollectionOf<T extends Element>": {
-                "name": "HTMLCollectionOf<T extends Element>",
+            "HTMLCollectionOf": {
+                "name": "HTMLCollectionOf",
+                "type-parameters": [
+                    {
+                        "name": "T",
+                        "extends": "Element"
+                    }
+                ],
                 "exposed": "Window",
                 "extends": "HTMLCollection",
                 "methods": {
@@ -2175,17 +2187,21 @@
                     }
                 }
             },
-            "FileReaderProgressEvent": {
-                "name": "FileReaderProgressEvent",
-                "extends": "ProgressEvent",
-                "no-interface-object": 1,
+            "ProgressEvent": {
+                "type-parameters": [
+                    {
+                        "name": "T",
+                        "extends": "EventTarget",
+                        "default": "EventTarget"
+                    }
+                ],
                 "properties": {
                     "property": {
                         "target": {
                             "name": "target",
                             "read-only": 1,
                             "nullable": 1,
-                            "type": "FileReader"
+                            "override-type": "T"
                         }
                     }
                 }
diff --git a/inputfiles/comments.json b/inputfiles/comments.json
index 227279498..4fcf6ef5d 100644
--- a/inputfiles/comments.json
+++ b/inputfiles/comments.json
@@ -177,7 +177,7 @@
                     }
                 }
             },
-            "NodeListOf<TNode extends Node>": {
+            "NodeListOf": {
                 "methods": {
                     "method": {
                         "forEach": {
diff --git a/inputfiles/overridingTypes.json b/inputfiles/overridingTypes.json
index 031b09522..fc5bfe508 100644
--- a/inputfiles/overridingTypes.json
+++ b/inputfiles/overridingTypes.json
@@ -1862,27 +1862,27 @@
                     "event": [
                         {
                             "name": "loadstart",
-                            "type": "FileReaderProgressEvent"
+                            "type": "ProgressEvent"
                         },
                         {
                             "name": "progress",
-                            "type": "FileReaderProgressEvent"
+                            "type": "ProgressEvent"
                         },
                         {
                             "name": "load",
-                            "type": "FileReaderProgressEvent"
+                            "type": "ProgressEvent"
                         },
                         {
                             "name": "abort",
-                            "type": "FileReaderProgressEvent"
+                            "type": "ProgressEvent"
                         },
                         {
                             "name": "error",
-                            "type": "FileReaderProgressEvent"
+                            "type": "ProgressEvent"
                         },
                         {
                             "name": "loadend",
-                            "type": "FileReaderProgressEvent"
+                            "type": "ProgressEvent"
                         }
                     ]
                 }
diff --git a/src/emitter.ts b/src/emitter.ts
index 066a62f9d..46558c1fa 100644
--- a/src/emitter.ts
+++ b/src/emitter.ts
@@ -226,6 +226,10 @@ export function emitWebIdl(webidl: Browser.WebIdl, flavor: Flavor) {
             return ehParents;
         }
 
+        if (!i.name) {
+            throw new Error("Unexpected nameless object: " + JSON.stringify(i));
+        }
+
         const iExtends = i.extends && i.extends.replace(/<.*>$/, '');
         const parentWithEventHandler = allInterfacesMap[iExtends] && getParentEventHandler(allInterfacesMap[iExtends]) || [];
         const mixinsWithEventHandler = flatMap(i.implements || [], i => getParentEventHandler(allInterfacesMap[i]));
@@ -245,19 +249,26 @@ export function emitWebIdl(webidl: Browser.WebIdl, flavor: Flavor) {
     }
 
     function getEventTypeInInterface(eName: string, i: Browser.Interface) {
+        function getGenericEventType(baseName: string) {
+            if (baseName === "ProgressEvent" && !i.mixin) {
+                return `${baseName}<${i.name}>`;
+            }
+            return baseName;
+        }
+
         if (i.events) {
             const event = i.events.event.find(e => e.name === eName);
             if (event && event.type) {
-                return event.type;
+                return getGenericEventType(event.type);
             }
         }
         if (i["attributeless-events"]) {
             const event = i["attributeless-events"].event.find(e => e.name === eName);
             if (event && event.type) {
-                return event.type;
+                return getGenericEventType(event.type);
             }
         }
-        return eNameToEType[eName] || "Event";
+        return getGenericEventType(eNameToEType[eName]) || "Event";
     }
 
     /// Determine if interface1 depends on interface2
@@ -391,14 +402,17 @@ export function emitWebIdl(webidl: Browser.WebIdl, flavor: Flavor) {
             expectedParamType.every((pt, idx) => convertDomTypeToTsType(m.signature[0].param![idx]) === pt);
     }
 
-    function processInterfaceType(i: Browser.Interface | Browser.Dictionary | Browser.CallbackFunction, name: string) {
+    function getNameWithTypeParameter(i: Browser.Interface | Browser.Dictionary | Browser.CallbackFunction, name: string) {
         function typeParameterWithDefault(type: Browser.TypeParameter) {
-            return `${type.name}`
-                + (type.extends ? ` extends ${type.extends}` : ``)
-                + (type.default ? ` = ${type.default}` : ``)
+            return type.name
+                + (type.extends ? ` extends ${type.extends}` : "")
+                + (type.default ? ` = ${type.default}` : "");
         }
 
-        return i["type-parameters"] ? name + "<" + i["type-parameters"]!.map(typeParameterWithDefault).join(", ") + ">" : name;
+        if (!i["type-parameters"]) {
+            return name;
+        }
+        return `${name}<${i["type-parameters"]!.map(typeParameterWithDefault).join(", ")}>`;
     }
 
     /// Emit overloads for the createElement method
@@ -530,7 +544,7 @@ export function emitWebIdl(webidl: Browser.WebIdl, flavor: Flavor) {
     }
 
     function emitCallBackFunction(cb: Browser.CallbackFunction) {
-        printer.printLine(`interface ${processInterfaceType(cb, cb.name)} {`);
+        printer.printLine(`interface ${getNameWithTypeParameter(cb, cb.name)} {`);
         printer.increaseIndent();
         emitSignatures(cb, "", "", printer.printLine);
         printer.decreaseIndent();
@@ -694,7 +708,7 @@ export function emitWebIdl(webidl: Browser.WebIdl, flavor: Flavor) {
         const value = subtype[subtype.length - 1];
         const key = subtype.length > 1 ? subtype[0] :
             i.iterator.kind === "iterable" ? "number" : value;
-        const name = i.name.replace(/ extends \w+/, "");
+        const name = i["type-parameters"] ? `${i.name}<${i["type-parameters"]!.map(p => p.name).join(", ")}>` : i.name;
         printer.printLine(`forEach(callbackfn: (value: ${value}, key: ${key}, parent: ${name}) => void, thisArg?: any): void;`);
     }
 
@@ -821,14 +835,14 @@ export function emitWebIdl(webidl: Browser.WebIdl, flavor: Flavor) {
         const processedIName = processIName(i.name);
 
         if (processedIName !== i.name) {
-            printer.printLineToStack(`interface ${processInterfaceType(i, i.name)} extends ${processedIName} {`);
+            printer.printLineToStack(`interface ${getNameWithTypeParameter(i, i.name)} extends ${processedIName} {`);
         }
 
         if (i.comment) {
             printer.printLine(`/** ${i.comment} */`);
         }
 
-        printer.print(`interface ${processInterfaceType(i, processedIName)}`);
+        printer.print(`interface ${getNameWithTypeParameter(i, processedIName)}`);
 
         const finalExtends = distinct([i.extends || "Object"].concat(i.implements || [])
             .filter(i => i !== "Object")
@@ -1044,10 +1058,10 @@ export function emitWebIdl(webidl: Browser.WebIdl, flavor: Flavor) {
 
     function emitDictionary(dict: Browser.Dictionary) {
         if (!dict.extends || dict.extends === "Object") {
-            printer.printLine(`interface ${processInterfaceType(dict, dict.name)} {`);
+            printer.printLine(`interface ${getNameWithTypeParameter(dict, dict.name)} {`);
         }
         else {
-            printer.printLine(`interface ${processInterfaceType(dict, dict.name)} extends ${dict.extends} {`);
+            printer.printLine(`interface ${getNameWithTypeParameter(dict, dict.name)} extends ${dict.extends} {`);
         }
         printer.increaseIndent();
         if (dict.members) {
@@ -1223,7 +1237,7 @@ export function emitWebIdl(webidl: Browser.WebIdl, flavor: Flavor) {
         const subtypes = getIteratorSubtypes();
         if (subtypes) {
             const iteratorExtends = getIteratorExtends(i.iterator, subtypes);
-            const name = extendConflictsBaseTypes[i.name] ? `${i.name}Base` : i.name;
+            const name = getNameWithTypeParameter(i, extendConflictsBaseTypes[i.name] ? `${i.name}Base` : i.name);
             printer.printLine("");
             printer.printLine(`interface ${name} ${iteratorExtends}{`);
             printer.increaseIndent();
diff --git a/src/types.d.ts b/src/types.d.ts
index 018326ccb..ed3c118b8 100644
--- a/src/types.d.ts
+++ b/src/types.d.ts
@@ -150,6 +150,7 @@ export interface TypeParameter {
 
 export interface Interface {
     name: string;
+    mixin?: boolean;
     extends: string;
     comment?: string;
     constants?: {
diff --git a/src/widlprocess.ts b/src/widlprocess.ts
index dda75c7af..06a8f93ee 100644
--- a/src/widlprocess.ts
+++ b/src/widlprocess.ts
@@ -91,6 +91,7 @@ function convertInterface(i: webidl2.InterfaceType, commentMap: Record<string, s
 
 function convertInterfaceMixin(i: webidl2.InterfaceMixinType, commentMap: Record<string, string>) {
     const result = convertInterfaceCommon(i, commentMap);
+    result.mixin = true;
     result['no-interface-object'] = 1;
     return result;
 }