diff --git a/js/js.libraries/src/generated/org.khronos.webgl.kt b/js/js.libraries/src/generated/org.khronos.webgl.kt
index e1cfc030044..c2a9129e851 100644
--- a/js/js.libraries/src/generated/org.khronos.webgl.kt
+++ b/js/js.libraries/src/generated/org.khronos.webgl.kt
@@ -15,7 +15,7 @@ import org.w3c.dom.svg.*
 import org.w3c.fetch.*
 import org.w3c.files.*
 import org.w3c.notifications.*
-import org.w3c.time.*
+import org.w3c.performance.*
 import org.w3c.workers.*
 import org.w3c.xhr.*
 
diff --git a/js/js.libraries/src/generated/org.w3c.dom.css.kt b/js/js.libraries/src/generated/org.w3c.dom.css.kt
index 23c0f7a3a0f..8e68a14993e 100644
--- a/js/js.libraries/src/generated/org.w3c.dom.css.kt
+++ b/js/js.libraries/src/generated/org.w3c.dom.css.kt
@@ -15,7 +15,7 @@ import org.w3c.dom.svg.*
 import org.w3c.fetch.*
 import org.w3c.files.*
 import org.w3c.notifications.*
-import org.w3c.time.*
+import org.w3c.performance.*
 import org.w3c.workers.*
 import org.w3c.xhr.*
 
diff --git a/js/js.libraries/src/generated/org.w3c.dom.events.kt b/js/js.libraries/src/generated/org.w3c.dom.events.kt
index 46613fe72c6..c52dfffaf5f 100644
--- a/js/js.libraries/src/generated/org.w3c.dom.events.kt
+++ b/js/js.libraries/src/generated/org.w3c.dom.events.kt
@@ -15,7 +15,7 @@ import org.w3c.dom.svg.*
 import org.w3c.fetch.*
 import org.w3c.files.*
 import org.w3c.notifications.*
-import org.w3c.time.*
+import org.w3c.performance.*
 import org.w3c.workers.*
 import org.w3c.xhr.*
 
diff --git a/js/js.libraries/src/generated/org.w3c.dom.kt b/js/js.libraries/src/generated/org.w3c.dom.kt
index 1cc9167a675..7c7100fce61 100644
--- a/js/js.libraries/src/generated/org.w3c.dom.kt
+++ b/js/js.libraries/src/generated/org.w3c.dom.kt
@@ -15,7 +15,7 @@ import org.w3c.dom.svg.*
 import org.w3c.fetch.*
 import org.w3c.files.*
 import org.w3c.notifications.*
-import org.w3c.time.*
+import org.w3c.performance.*
 import org.w3c.workers.*
 import org.w3c.xhr.*
 
@@ -3026,6 +3026,9 @@ native public trait Window : EventTarget {
     var caches: CacheStorage
         get() = noImpl
         set(value) = noImpl
+    var performance: Performance
+        get() = noImpl
+        set(value) = noImpl
     var window: Window
         get() = noImpl
         set(value) = noImpl
diff --git a/js/js.libraries/src/generated/org.w3c.dom.parsing.kt b/js/js.libraries/src/generated/org.w3c.dom.parsing.kt
index b5a98d497a1..bfe6f1175e0 100644
--- a/js/js.libraries/src/generated/org.w3c.dom.parsing.kt
+++ b/js/js.libraries/src/generated/org.w3c.dom.parsing.kt
@@ -15,7 +15,7 @@ import org.w3c.dom.svg.*
 import org.w3c.fetch.*
 import org.w3c.files.*
 import org.w3c.notifications.*
-import org.w3c.time.*
+import org.w3c.performance.*
 import org.w3c.workers.*
 import org.w3c.xhr.*
 
diff --git a/js/js.libraries/src/generated/org.w3c.dom.svg.kt b/js/js.libraries/src/generated/org.w3c.dom.svg.kt
index 815ebfe6ce6..5376d557cc6 100644
--- a/js/js.libraries/src/generated/org.w3c.dom.svg.kt
+++ b/js/js.libraries/src/generated/org.w3c.dom.svg.kt
@@ -15,7 +15,7 @@ import org.w3c.dom.parsing.*
 import org.w3c.fetch.*
 import org.w3c.files.*
 import org.w3c.notifications.*
-import org.w3c.time.*
+import org.w3c.performance.*
 import org.w3c.workers.*
 import org.w3c.xhr.*
 
diff --git a/js/js.libraries/src/generated/org.w3c.fetch.kt b/js/js.libraries/src/generated/org.w3c.fetch.kt
index 37ffd4d2b5d..6dce9924cda 100644
--- a/js/js.libraries/src/generated/org.w3c.fetch.kt
+++ b/js/js.libraries/src/generated/org.w3c.fetch.kt
@@ -15,7 +15,7 @@ import org.w3c.dom.parsing.*
 import org.w3c.dom.svg.*
 import org.w3c.files.*
 import org.w3c.notifications.*
-import org.w3c.time.*
+import org.w3c.performance.*
 import org.w3c.workers.*
 import org.w3c.xhr.*
 
diff --git a/js/js.libraries/src/generated/org.w3c.files.kt b/js/js.libraries/src/generated/org.w3c.files.kt
index c2cd922f7af..e187a5aff83 100644
--- a/js/js.libraries/src/generated/org.w3c.files.kt
+++ b/js/js.libraries/src/generated/org.w3c.files.kt
@@ -15,7 +15,7 @@ import org.w3c.dom.parsing.*
 import org.w3c.dom.svg.*
 import org.w3c.fetch.*
 import org.w3c.notifications.*
-import org.w3c.time.*
+import org.w3c.performance.*
 import org.w3c.workers.*
 import org.w3c.xhr.*
 
diff --git a/js/js.libraries/src/generated/org.w3c.notifications.kt b/js/js.libraries/src/generated/org.w3c.notifications.kt
index d4596a883ed..16567f337b3 100644
--- a/js/js.libraries/src/generated/org.w3c.notifications.kt
+++ b/js/js.libraries/src/generated/org.w3c.notifications.kt
@@ -15,7 +15,7 @@ import org.w3c.dom.parsing.*
 import org.w3c.dom.svg.*
 import org.w3c.fetch.*
 import org.w3c.files.*
-import org.w3c.time.*
+import org.w3c.performance.*
 import org.w3c.workers.*
 import org.w3c.xhr.*
 
diff --git a/js/js.libraries/src/generated/org.w3c.performance.kt b/js/js.libraries/src/generated/org.w3c.performance.kt
new file mode 100644
index 00000000000..c66a6e36697
--- /dev/null
+++ b/js/js.libraries/src/generated/org.w3c.performance.kt
@@ -0,0 +1,113 @@
+/*
+ * Generated file
+ * DO NOT EDIT
+ * 
+ * See libraries/tools/idl2k for details
+ */
+
+package org.w3c.performance
+
+import org.khronos.webgl.*
+import org.w3c.dom.*
+import org.w3c.dom.css.*
+import org.w3c.dom.events.*
+import org.w3c.dom.parsing.*
+import org.w3c.dom.svg.*
+import org.w3c.fetch.*
+import org.w3c.files.*
+import org.w3c.notifications.*
+import org.w3c.workers.*
+import org.w3c.xhr.*
+
+native public trait Performance {
+    var timing: PerformanceTiming
+        get() = noImpl
+        set(value) = noImpl
+    var navigation: PerformanceNavigation
+        get() = noImpl
+        set(value) = noImpl
+    fun now(): Double = noImpl
+}
+
+native public trait PerformanceTiming {
+    var navigationStart: Long
+        get() = noImpl
+        set(value) = noImpl
+    var unloadEventStart: Long
+        get() = noImpl
+        set(value) = noImpl
+    var unloadEventEnd: Long
+        get() = noImpl
+        set(value) = noImpl
+    var redirectStart: Long
+        get() = noImpl
+        set(value) = noImpl
+    var redirectEnd: Long
+        get() = noImpl
+        set(value) = noImpl
+    var fetchStart: Long
+        get() = noImpl
+        set(value) = noImpl
+    var domainLookupStart: Long
+        get() = noImpl
+        set(value) = noImpl
+    var domainLookupEnd: Long
+        get() = noImpl
+        set(value) = noImpl
+    var connectStart: Long
+        get() = noImpl
+        set(value) = noImpl
+    var connectEnd: Long
+        get() = noImpl
+        set(value) = noImpl
+    var secureConnectionStart: Long
+        get() = noImpl
+        set(value) = noImpl
+    var requestStart: Long
+        get() = noImpl
+        set(value) = noImpl
+    var responseStart: Long
+        get() = noImpl
+        set(value) = noImpl
+    var responseEnd: Long
+        get() = noImpl
+        set(value) = noImpl
+    var domLoading: Long
+        get() = noImpl
+        set(value) = noImpl
+    var domInteractive: Long
+        get() = noImpl
+        set(value) = noImpl
+    var domContentLoadedEventStart: Long
+        get() = noImpl
+        set(value) = noImpl
+    var domContentLoadedEventEnd: Long
+        get() = noImpl
+        set(value) = noImpl
+    var domComplete: Long
+        get() = noImpl
+        set(value) = noImpl
+    var loadEventStart: Long
+        get() = noImpl
+        set(value) = noImpl
+    var loadEventEnd: Long
+        get() = noImpl
+        set(value) = noImpl
+}
+
+native public trait PerformanceNavigation {
+    var type: Short
+        get() = noImpl
+        set(value) = noImpl
+    var redirectCount: Short
+        get() = noImpl
+        set(value) = noImpl
+
+    companion object {
+        val TYPE_NAVIGATE: Short = 0
+        val TYPE_RELOAD: Short = 1
+        val TYPE_BACK_FORWARD: Short = 2
+        val TYPE_RESERVED: Short = 255
+    }
+}
+
diff --git a/js/js.libraries/src/generated/org.w3c.time.kt b/js/js.libraries/src/generated/org.w3c.time.kt
deleted file mode 100644
index 33a7217239b..00000000000
--- a/js/js.libraries/src/generated/org.w3c.time.kt
+++ /dev/null
@@ -1,25 +0,0 @@
-/*
- * Generated file
- * DO NOT EDIT
- * 
- * See libraries/tools/idl2k for details
- */
-
-package org.w3c.time
-
-import org.khronos.webgl.*
-import org.w3c.dom.*
-import org.w3c.dom.css.*
-import org.w3c.dom.events.*
-import org.w3c.dom.parsing.*
-import org.w3c.dom.svg.*
-import org.w3c.fetch.*
-import org.w3c.files.*
-import org.w3c.notifications.*
-import org.w3c.workers.*
-import org.w3c.xhr.*
-
-native public trait Performance {
-    fun now(): Double = noImpl
-}
-
diff --git a/js/js.libraries/src/generated/org.w3c.workers.kt b/js/js.libraries/src/generated/org.w3c.workers.kt
index e853b74eebf..2b66b906257 100644
--- a/js/js.libraries/src/generated/org.w3c.workers.kt
+++ b/js/js.libraries/src/generated/org.w3c.workers.kt
@@ -16,7 +16,7 @@ import org.w3c.dom.svg.*
 import org.w3c.fetch.*
 import org.w3c.files.*
 import org.w3c.notifications.*
-import org.w3c.time.*
+import org.w3c.performance.*
 import org.w3c.xhr.*
 
 native public trait ServiceWorkerRegistration : EventTarget {
diff --git a/js/js.libraries/src/generated/org.w3c.xhr.kt b/js/js.libraries/src/generated/org.w3c.xhr.kt
index 3166aaea5d4..8d704008935 100644
--- a/js/js.libraries/src/generated/org.w3c.xhr.kt
+++ b/js/js.libraries/src/generated/org.w3c.xhr.kt
@@ -16,7 +16,7 @@ import org.w3c.dom.svg.*
 import org.w3c.fetch.*
 import org.w3c.files.*
 import org.w3c.notifications.*
-import org.w3c.time.*
+import org.w3c.performance.*
 import org.w3c.workers.*
 
 native public trait XMLHttpRequestEventTarget : EventTarget {
diff --git a/libraries/idl/org.w3c.performance.idl b/libraries/idl/org.w3c.performance.idl
new file mode 100644
index 00000000000..7d59736168e
--- /dev/null
+++ b/libraries/idl/org.w3c.performance.idl
@@ -0,0 +1,47 @@
+namespace org.w3c.performance;
+
+
+typedef double DOMHighResTimeStamp;
+partial interface Performance {
+  DOMHighResTimeStamp now();
+};
+interface PerformanceTiming {
+  readonly attribute unsigned long long navigationStart;
+  readonly attribute unsigned long long unloadEventStart;
+  readonly attribute unsigned long long unloadEventEnd;
+  readonly attribute unsigned long long redirectStart;
+  readonly attribute unsigned long long redirectEnd;
+  readonly attribute unsigned long long fetchStart;
+  readonly attribute unsigned long long domainLookupStart;
+  readonly attribute unsigned long long domainLookupEnd;
+  readonly attribute unsigned long long connectStart;
+  readonly attribute unsigned long long connectEnd;
+  readonly attribute unsigned long long secureConnectionStart;
+  readonly attribute unsigned long long requestStart;
+  readonly attribute unsigned long long responseStart;
+  readonly attribute unsigned long long responseEnd;
+  readonly attribute unsigned long long domLoading;
+  readonly attribute unsigned long long domInteractive;
+  readonly attribute unsigned long long domContentLoadedEventStart;
+  readonly attribute unsigned long long domContentLoadedEventEnd;
+  readonly attribute unsigned long long domComplete;
+  readonly attribute unsigned long long loadEventStart;
+  readonly attribute unsigned long long loadEventEnd;
+};
+interface PerformanceNavigation {
+  const unsigned short TYPE_NAVIGATE = 0;
+  const unsigned short TYPE_RELOAD = 1;
+  const unsigned short TYPE_BACK_FORWARD = 2;
+  const unsigned short TYPE_RESERVED = 255;
+  readonly attribute unsigned short type;
+  readonly attribute unsigned short redirectCount;
+};
+interface Performance {
+  readonly attribute PerformanceTiming timing;
+  readonly attribute PerformanceNavigation navigation;
+};
+
+partial interface Window {
+  [Replaceable] readonly attribute Performance performance;
+};
+
diff --git a/libraries/idl/org.w3c.time.idl b/libraries/idl/org.w3c.time.idl
deleted file mode 100644
index b510b849ce3..00000000000
--- a/libraries/idl/org.w3c.time.idl
+++ /dev/null
@@ -1,8 +0,0 @@
-namespace org.w3c.time;
-
-
-typedef double DOMHighResTimeStamp;
-partial interface Performance {
-  DOMHighResTimeStamp now();
-};
-
diff --git a/libraries/tools/idl2k/src/main/kotlin/download.kt b/libraries/tools/idl2k/src/main/kotlin/download.kt
index 459724f8fb3..e402b01bd2d 100644
--- a/libraries/tools/idl2k/src/main/kotlin/download.kt
+++ b/libraries/tools/idl2k/src/main/kotlin/download.kt
@@ -23,26 +23,31 @@ import java.io.File
 import java.net.URL
 
 val urls = listOf(
-//        "http://heycam.github.io/webidl/" to "org.w3c.webidl"
         "https://raw.githubusercontent.com/whatwg/html-mirror/master/source" to "org.w3c.dom",
         "https://html.spec.whatwg.org/" to "org.w3c.dom",
         "https://raw.githubusercontent.com/whatwg/dom/master/dom.html" to "org.w3c.dom",
-        "http://www.w3.org/TR/uievents/" to "org.w3c.dom.events",
         "https://dvcs.w3.org/hg/editing/raw-file/tip/editing.html" to "org.w3c.dom",
         "http://www.w3.org/TR/animation-timing/" to "org.w3c.dom",
-        "http://www.w3.org/TR/hr-time/" to "org.w3c.time",
-        "https://raw.githubusercontent.com/whatwg/xhr/master/Overview.src.html" to "org.w3c.xhr",
-        "https://raw.githubusercontent.com/w3c/FileAPI/gh-pages/index.html" to "org.w3c.files",
-        "https://raw.githubusercontent.com/whatwg/notifications/master/notifications.html" to "org.w3c.notifications",
-        "https://raw.githubusercontent.com/whatwg/fullscreen/master/Overview.src.html" to "org.w3c.fullscreen",
-        "http://www.w3.org/TR/DOM-Parsing/" to "org.w3c.dom.parsing",
-        "http://slightlyoff.github.io/ServiceWorker/spec/service_worker/index.html" to "org.w3c.workers",
-        "https://raw.githubusercontent.com/whatwg/fetch/master/Overview.src.html" to "org.w3c.fetch",
-        "http://www.w3.org/TR/vibration/" to "org.w3c.vibration",
+        "http://www.w3.org/TR/uievents/" to "org.w3c.dom.events",
         "http://dev.w3.org/csswg/cssom/" to "org.w3c.dom.css",
+        "http://www.w3.org/TR/DOM-Parsing/" to "org.w3c.dom.parsing",
+
         "http://web.archive.org/web/20150317051602/http://www.w3.org/TR/SVG11/single-page.html" to "org.w3c.dom.svg",
         "https://www.khronos.org/registry/webgl/specs/latest/1.0/webgl.idl" to "org.khronos.webgl",
-        "https://www.khronos.org/registry/typedarray/specs/latest/typedarray.idl" to "org.khronos.webgl"
+        "https://www.khronos.org/registry/typedarray/specs/latest/typedarray.idl" to "org.khronos.webgl",
+
+        "https://raw.githubusercontent.com/whatwg/xhr/master/Overview.src.html" to "org.w3c.xhr",
+        "https://raw.githubusercontent.com/whatwg/fetch/master/Overview.src.html" to "org.w3c.fetch",
+        "https://raw.githubusercontent.com/w3c/FileAPI/gh-pages/index.html" to "org.w3c.files",
+
+        "https://raw.githubusercontent.com/whatwg/notifications/master/notifications.html" to "org.w3c.notifications",
+        "https://raw.githubusercontent.com/whatwg/fullscreen/master/Overview.src.html" to "org.w3c.fullscreen",
+        "http://www.w3.org/TR/vibration/" to "org.w3c.vibration",
+
+        "http://www.w3.org/TR/hr-time/" to "org.w3c.performance",
+        "http://www.w3.org/TR/2012/REC-navigation-timing-20121217/" to "org.w3c.performance",
+
+        "http://slightlyoff.github.io/ServiceWorker/spec/service_worker/index.html" to "org.w3c.workers"
 )
 
 fun main(args: Array<String>) {
@@ -61,7 +66,7 @@ fun main(args: Array<String>) {
             w.appendln()
 
             e.value.forEach { pair ->
-                val (url, _) = pair
+                val (url) = pair
                 println("Loading ${url}...")
 
                 if (url.endsWith(".idl")) {
diff --git a/libraries/tools/idl2k/src/main/kotlin/gen.kt b/libraries/tools/idl2k/src/main/kotlin/gen.kt
index ef278d300e1..1e63a20f1b7 100644
--- a/libraries/tools/idl2k/src/main/kotlin/gen.kt
+++ b/libraries/tools/idl2k/src/main/kotlin/gen.kt
@@ -174,7 +174,7 @@ fun generateUnions(ifaces: List<GenerateTraitOrClass>, typedefs: Iterable<Typede
             typedefsToBeGenerated.flatMap { typedef -> typedef.value.memberTypes.map { unionMember -> unionMember to typedef.name } }.toMultiMap()
 
     return GenerateUnionTypes(
-            typeNamesToUnions = typeNamesToUnions,
+            typeNamesToUnionsMap = typeNamesToUnions,
             anonymousUnionsMap = anonymousUnionsMap,
             typedefsMarkersMap = typedefsMarkersMap
     )
diff --git a/libraries/tools/idl2k/src/main/kotlin/idl.kt b/libraries/tools/idl2k/src/main/kotlin/idl.kt
index 787ed73ccdf..789fecc37cb 100644
--- a/libraries/tools/idl2k/src/main/kotlin/idl.kt
+++ b/libraries/tools/idl2k/src/main/kotlin/idl.kt
@@ -259,7 +259,7 @@ class ConstantVisitor : WebIDLBaseVisitor<Constant>() {
 }
 
 class DefinitionVisitor(val extendedAttributes: List<ExtendedAttribute>, val namespace: String, val declarations: MutableList<Definition>) : WebIDLBaseVisitor<Definition>() {
-    private var kind: DefinitionKind = DefinitionKind.INTERFACE
+    private var kind = DefinitionKind.INTERFACE
     private var name = ""
     private val memberAttributes = ArrayList<ExtendedAttribute>()
     private val operations = ArrayList<Operation>()
diff --git a/libraries/tools/idl2k/src/main/kotlin/model.kt b/libraries/tools/idl2k/src/main/kotlin/model.kt
index 3ee788bb0da..0fc70484a28 100644
--- a/libraries/tools/idl2k/src/main/kotlin/model.kt
+++ b/libraries/tools/idl2k/src/main/kotlin/model.kt
@@ -101,7 +101,7 @@ fun InterfaceDefinition?.hasExtendedAttribute(name: String) = this?.findExtended
 fun InterfaceDefinition.findConstructor() = findExtendedAttribute("Constructor")
 
 data class GenerateUnionTypes(
-        val typeNamesToUnions : Map<String, List<String>>,
-        val anonymousUnionsMap : Map<String, GenerateTraitOrClass>,
-        val typedefsMarkersMap : Map<String, GenerateTraitOrClass>
+        val typeNamesToUnionsMap: Map<String, List<String>>,
+        val anonymousUnionsMap: Map<String, GenerateTraitOrClass>,
+        val typedefsMarkersMap: Map<String, GenerateTraitOrClass>
 )
diff --git a/libraries/tools/idl2k/src/main/kotlin/render.kt b/libraries/tools/idl2k/src/main/kotlin/render.kt
index 47cf4a18297..a5794e8c719 100644
--- a/libraries/tools/idl2k/src/main/kotlin/render.kt
+++ b/libraries/tools/idl2k/src/main/kotlin/render.kt
@@ -42,7 +42,7 @@ private fun String.parse() = if (this.startsWith("0x")) BigInteger(this.substrin
 private fun String.replaceWrongConstants(type: String) = if (this == "noImpl" || type == "Int" && parse() > BigInteger.valueOf(Int.MAX_VALUE.toLong())) "noImpl" else this
 private fun String.replaceKeywords() = if (this in keywords) this + "_" else this
 
-private fun Appendable.renderArgumentsDeclaration(allTypes: Set<String>, args: List<GenerateAttribute>, omitDefaults: Boolean) =
+private fun Appendable.renderArgumentsDeclaration(args: List<GenerateAttribute>, omitDefaults: Boolean) =
         args.map {
             StringBuilder {
                 if (it.vararg) {
@@ -60,7 +60,7 @@ private fun Appendable.renderArgumentsDeclaration(allTypes: Set<String>, args: L
 
 private fun renderCall(call: GenerateFunctionCall) = "${call.name.replaceKeywords()}(${call.arguments.map { it.replaceKeywords() }.join(", ")})"
 
-private fun Appendable.renderFunctionDeclaration(allTypes: Set<String>, f: GenerateFunction, override: Boolean) {
+private fun Appendable.renderFunctionDeclaration(f: GenerateFunction, override: Boolean) {
     indent(1)
 
     when (f.nativeGetterOrSetter) {
@@ -76,7 +76,7 @@ private fun Appendable.renderFunctionDeclaration(allTypes: Set<String>, f: Gener
         append("native(\"${f.name}\") ")
     }
     append("fun ${f.name.replaceKeywords()}(")
-    renderArgumentsDeclaration(allTypes, f.arguments, override)
+    renderArgumentsDeclaration(f.arguments, override)
     appendln("): ${f.returnType} = noImpl")
 }
 
@@ -93,7 +93,7 @@ fun Appendable.render(allTypes: Map<String, GenerateTraitOrClass>, typeNamesToUn
     append(iface.name)
     if (iface.constructor != null && iface.constructor.arguments.isNotEmpty()) {
         append("(")
-        renderArgumentsDeclaration(allTypes.keySet(), iface.constructor.arguments.map { it.dynamicIfUnknownType(allTypes.keySet()) }, false)
+        renderArgumentsDeclaration(iface.constructor.arguments.map { it.dynamicIfUnknownType(allTypes.keySet()) }, false)
         append(")")
     }
 
@@ -120,7 +120,7 @@ fun Appendable.render(allTypes: Map<String, GenerateTraitOrClass>, typeNamesToUn
         renderAttributeDeclaration(arg, arg.signature in superSignatures)
     }
     iface.memberFunctions.filter { it !in superFunctions }.map { it.dynamicIfUnknownType(allTypes.keySet()) }.groupBy { it.signature }.reduceValues(::betterFunction).values().forEach {
-        renderFunctionDeclaration(allTypes.keySet(), it, it.signature in superSignatures)
+        renderFunctionDeclaration(it, it.signature in superSignatures)
     }
     if (iface.constants.isNotEmpty()) {
         appendln()
@@ -155,7 +155,7 @@ fun Appendable.render(namespace: String, ifaces: List<GenerateTraitOrClass>, uni
 
     val allTypes = declaredTypes + unions.anonymousUnionsMap + unions.typedefsMarkersMap
     declaredTypes.values().filter { it.namespace == namespace }.forEach {
-        render(allTypes, unions.typeNamesToUnions, it)
+        render(allTypes, unions.typeNamesToUnionsMap, it)
     }
 
     unions.anonymousUnionsMap.values().filter { it.namespace == "" || it.namespace == namespace }.forEach {
diff --git a/libraries/tools/idl2k/src/main/kotlin/typeMappings.kt b/libraries/tools/idl2k/src/main/kotlin/typeMappings.kt
index ffdf48596a0..f39fe5e9ac8 100644
--- a/libraries/tools/idl2k/src/main/kotlin/typeMappings.kt
+++ b/libraries/tools/idl2k/src/main/kotlin/typeMappings.kt
@@ -56,13 +56,14 @@ fun allSuperTypesImpl(roots: List<GenerateTraitOrClass>, all: Map<String, Genera
 }
 
 data class FunctionType(val parameterTypes : List<Attribute>, val returnType : String)
+
 val FunctionType.arity : Int
     get() = parameterTypes.size()
 val FunctionType.text : String
     get() = "(${parameterTypes.map { it.formatFunctionTypePart() }.join(",")}) -> ${returnType}"
 
 fun FunctionType(text : String) : FunctionType {
-    val (parameters, returnType) = text.split("->".toRegex()).map {it.trim()}.filter { it != "" }
+    val (parameters, returnType) = text.split("->".toRegex()).map { it.trim() }.filter { it != "" }
 
     return FunctionType(
             parameterTypes = parameters.removeSurrounding("(", ")").split(',')
@@ -80,14 +81,14 @@ fun String.dynamicIfUnknownType(allTypes: Set<String>, standardTypes: Set<String
     this in standardTypes -> this
     startsWith("Array<") -> "Array<" + removePrefix("Array<").removeSuffix(">").dynamicIfUnknownType(allTypes, standardTypes) + ">"
     startsWith("Union<") -> UnionType("", splitUnionType(this)).name.dynamicIfUnknownType(allTypes, standardTypes).copyNullabilityFrom(this)
-    this != dropNullable() -> dropNullable().dynamicIfUnknownType(allTypes, standardTypes).ensureNullable()
+    isNullable() -> dropNullable().dynamicIfUnknownType(allTypes, standardTypes).ensureNullable()
     contains("->") -> {
-        FunctionType(this).let { function ->
-            function.copy(
-                    returnType = function.returnType.dynamicIfUnknownType(allTypes, standardTypes),
-                    parameterTypes = function.parameterTypes.map { it.copy(type = it.type.dynamicIfUnknownType(allTypes, standardTypes)) }
-            ).text
-        }
+        val function = FunctionType(this)
+
+        function.copy(
+                returnType = function.returnType.dynamicIfUnknownType(allTypes, standardTypes),
+                parameterTypes = function.parameterTypes.map { it.copy(type = it.type.dynamicIfUnknownType(allTypes, standardTypes)) }
+        ).text
     }
     else -> "dynamic"
 }
@@ -103,7 +104,10 @@ private fun mapType(repository: Repository, type: String): String =
         type.startsWith("sequence") -> "Array<dynamic>"
         type in repository.typeDefs -> mapTypedef(repository, type)
         type in repository.enums -> "String"
-        type.contains("->") -> FunctionType(type).let { function ->
+        type.contains("->") -> {
+            val function = FunctionType(type)
+
+            // TODO: Remove takeWhile { !vararg } when we have varargs supported. See KT-3115
             function.copy(
                     returnType = mapType(repository, function.returnType),
                     parameterTypes = function.parameterTypes.takeWhile { !it.vararg }.map { it.copy(type = mapType(repository, it.type)) }