diff --git a/libraries/pom.xml b/libraries/pom.xml
index ac138398668..93aee1de9c6 100644
--- a/libraries/pom.xml
+++ b/libraries/pom.xml
@@ -85,6 +85,7 @@
         <!--NB! kotlin-js-library should be built before kotlin-gradle-plugin-->
         <!--because it is used in tests but cannot be added as test-dependency-->
         <!--(kotlin-gradle-plugin module will be recognized as kotlin-js module)-->
+        <module>tools/idl2k</module>
         <module>tools/kotlin-js-library</module>
         <module>tools/kotlin-annotation-processing</module>
         <module>examples/annotation-processor-example</module>
diff --git a/libraries/tools/idl2k/src/main/kotlin/download.kt b/libraries/tools/idl2k/src/main/kotlin/download.kt
index 2347cd9b411..dddb0dab5e4 100644
--- a/libraries/tools/idl2k/src/main/kotlin/download.kt
+++ b/libraries/tools/idl2k/src/main/kotlin/download.kt
@@ -45,13 +45,13 @@ fun main(args: Array<String>) {
         val pkg = e.value.first().second
 
         File(dir, fileName).bufferedWriter().use { w ->
-            w.appendln("namespace ${pkg};")
+            w.appendln("namespace $pkg;")
             w.appendln()
             w.appendln()
 
             e.value.forEach { pair ->
                 val (url) = pair
-                println("Loading ${url}...")
+                println("Loading $url...")
 
                 w.appendln("// Downloaded from $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 7343a127f8f..648800f4d91 100644
--- a/libraries/tools/idl2k/src/main/kotlin/gen.kt
+++ b/libraries/tools/idl2k/src/main/kotlin/gen.kt
@@ -1,8 +1,5 @@
 package org.jetbrains.idl2k
 
-import com.sun.org.apache.bcel.internal.generic.IF_ACMPEQ
-import java.util.*
-
 private fun Operation.getterOrSetter() = this.attributes.map { it.call }.toSet().let { attributes ->
     when {
         "getter" in attributes -> NativeGetterOrSetter.GETTER
@@ -45,7 +42,7 @@ fun generateFunctions(repository: Repository, function: Operation): List<Generat
         val interfaceType = repository.interfaces[parameterType?.type]
         when {
             interfaceType == null -> it
-            interfaceType.operations.size() != 1 -> it
+            interfaceType.operations.size != 1 -> it
             interfaceType.callback -> interfaceType.operations.single().let { callbackFunction ->
                 it.copy(type = FunctionType(callbackFunction.parameters.map { it.copy(type = mapType(repository, it.type)) }, mapType(repository, callbackFunction.returnType), parameterType?.nullable ?: false))
             }
@@ -92,7 +89,7 @@ fun generateTrait(repository: Repository, iface: InterfaceDefinition): GenerateT
             .filterNotNull()
             .filter { resolveDefinitionKind(repository, it) == GenerateDefinitionKind.CLASS }
 
-    assert(superClasses.size() <= 1) { "Type ${iface.name} should have one or zero super classes but found ${superClasses.map { it.name }}" }
+    assert(superClasses.size <= 1) { "Type ${iface.name} should have one or zero super classes but found ${superClasses.map { it.name }}" }
     val superClass = superClasses.singleOrNull()
     val superConstructor = superClass?.findConstructors()?.firstOrNull() ?: EMPTY_CONSTRUCTOR
 
@@ -101,7 +98,7 @@ fun generateTrait(repository: Repository, iface: InterfaceDefinition): GenerateT
     val extensions = repository.externals[iface.name]?.map { repository.interfaces[it] }?.filterNotNull() ?: emptyList()
 
     val primaryConstructor = when {
-        declaredConstructors.size() == 1 -> declaredConstructors.single()
+        declaredConstructors.size == 1 -> declaredConstructors.single()
         declaredConstructors.isEmpty() && entityKind == GenerateDefinitionKind.CLASS -> EMPTY_CONSTRUCTOR
         else -> declaredConstructors.firstOrNull { it.arguments.isEmpty() }
     }
diff --git a/libraries/tools/idl2k/src/main/kotlin/idl.kt b/libraries/tools/idl2k/src/main/kotlin/idl.kt
index dceaa8fae43..cfc349237fa 100644
--- a/libraries/tools/idl2k/src/main/kotlin/idl.kt
+++ b/libraries/tools/idl2k/src/main/kotlin/idl.kt
@@ -87,7 +87,7 @@ class ExtendedAttributeParser(private val namespace: String) : WebIDLBaseVisitor
     override fun defaultResult(): ExtendedAttribute = ExtendedAttribute(name, call, arguments)
 
     override fun visitExtendedAttribute(ctx: WebIDLParser.ExtendedAttributeContext): ExtendedAttribute {
-        call = ctx.children.filterIdentifiers().firstOrNull()?.getText() ?: ""
+        call = ctx.children.filterIdentifiers().firstOrNull()?.text ?: ""
 
         visitChildren(ctx)
         return defaultResult()
@@ -101,8 +101,8 @@ class ExtendedAttributeParser(private val namespace: String) : WebIDLBaseVisitor
     override fun visitIdentifierList(ctx: IdentifierListContext): ExtendedAttribute {
         object : WebIDLBaseVisitor<Unit>() {
             override fun visitTerminal(node: TerminalNode) {
-                if (node.getSymbol().getType() == WebIDLLexer.IDENTIFIER_WEBIDL) {
-                    arguments.add(Attribute(node.getText(), AnyType(), true, vararg = false, static = false))
+                if (node.symbol.type == WebIDLLexer.IDENTIFIER_WEBIDL) {
+                    arguments.add(Attribute(node.text, AnyType(), true, vararg = false, static = false))
                 }
             }
         }.visitChildren(ctx)
@@ -134,7 +134,7 @@ class TypeVisitor(val namespace: String) : WebIDLBaseVisitor<Type>() {
     override fun defaultResult() = type
 
     override fun visitNonAnyType(ctx: WebIDLParser.NonAnyTypeContext): Type {
-        type = SimpleType(ctx.getText(), false)
+        type = SimpleType(ctx.text, false)
         return type
     }
 
@@ -144,7 +144,7 @@ class TypeVisitor(val namespace: String) : WebIDLBaseVisitor<Type>() {
     }
 
     override fun visitTypeSuffix(ctx: TypeSuffixContext): Type {
-        when (ctx.getText()?.trim()) {
+        when (ctx.text?.trim()) {
             "?" -> type = type.toNullable()
             "[]" -> type = ArrayType(type, false)
             "[]?" -> type = ArrayType(type, true)
@@ -155,7 +155,7 @@ class TypeVisitor(val namespace: String) : WebIDLBaseVisitor<Type>() {
     }
 
     override fun visitTerminal(node: TerminalNode): Type {
-        type = SimpleType(node.getText(), false)
+        type = SimpleType(node.text, false)
         return type
     }
 }
@@ -169,13 +169,13 @@ class OperationVisitor(private val attributes: List<ExtendedAttribute>, private
     override fun defaultResult() = Operation(name, returnType, parameters, attributes + exts, static)
 
     override fun visitOptionalIdentifier(ctx: OptionalIdentifierContext): Operation {
-        name = ctx.getText()
+        name = ctx.text
         return defaultResult()
     }
 
     override fun visitSpecial(ctx: WebIDLParser.SpecialContext): Operation {
         if (ctx.children != null) {
-            exts.add(ExtendedAttribute(call = ctx.getText(), name = null, arguments = emptyList()))
+            exts.add(ExtendedAttribute(call = ctx.text, name = null, arguments = emptyList()))
         }
 
         return defaultResult()
@@ -211,29 +211,29 @@ class AttributeVisitor(private val readOnly: Boolean = false, private val static
     }
 
     override fun visitOptionalOrRequiredArgument(ctx: WebIDLParser.OptionalOrRequiredArgumentContext): Attribute {
-        if (ctx.children?.any { it is TerminalNode && it.getText() == "optional" } ?: false) {
+        if (ctx.children?.any { it is TerminalNode && it.text == "optional" } ?: false) {
             defaultValue = "noImpl"
         }
         return visitChildren(ctx)
     }
 
     override fun visitAttributeRest(ctx: WebIDLParser.AttributeRestContext): Attribute {
-        name = getNameOrNull(ctx) ?: ctx.children.filter { it is TerminalNode }.filter { it.getText() != ";" }.last().getText()
+        name = getNameOrNull(ctx) ?: ctx.children.filter { it is TerminalNode }.filter { it.text != ";" }.last().text
         return defaultResult()
     }
 
     override fun visitArgumentName(ctx: WebIDLParser.ArgumentNameContext): Attribute {
-        name = getNameOrNull(ctx) ?: ctx.getText()
+        name = getNameOrNull(ctx) ?: ctx.text
         return defaultResult()
     }
 
     override fun visitDefaultValue(ctx: WebIDLParser.DefaultValueContext): Attribute {
-        defaultValue = ctx.getText()
+        defaultValue = ctx.text
         return defaultResult()
     }
 
     override fun visitEllipsis(ctx: WebIDLParser.EllipsisContext): Attribute {
-        vararg = vararg || "..." in ctx.getText()
+        vararg = vararg || "..." in ctx.text
         return defaultResult()
     }
 }
@@ -252,12 +252,12 @@ class ConstantVisitor : WebIDLBaseVisitor<Constant>() {
     }
 
     override fun visitConstType(ctx: WebIDLParser.ConstTypeContext): Constant {
-        type = SimpleType(ctx.getText(), false)
+        type = SimpleType(ctx.text, false)
         return defaultResult()
     }
 
     override fun visitConstValue(ctx: WebIDLParser.ConstValueContext): Constant {
-        value = ctx.getText()
+        value = ctx.text
         return defaultResult()
     }
 }
@@ -363,8 +363,8 @@ class DefinitionVisitor(val extendedAttributes: List<ExtendedAttribute>, val nam
     override fun visitDictionaryMember(ctx: DictionaryMemberContext): Definition {
         val name = ctx.children
                 .filterIdentifiers()
-                .firstOrNull { it.getText() != "" }
-                ?.getText()
+                .firstOrNull { it.text != "" }
+                ?.text
 
         val type = TypeVisitor(namespace).visit(ctx.children.first { it is TypeContext })
         val defaultValue = object : WebIDLBaseVisitor<String?>() {
@@ -373,7 +373,7 @@ class DefinitionVisitor(val extendedAttributes: List<ExtendedAttribute>, val nam
             override fun defaultResult() = value
 
             override fun visitDefaultValue(ctx2: DefaultValueContext): String? {
-                value = ctx2.getText()
+                value = ctx2.text
                 return value
             }
         }.visit(ctx)
@@ -384,9 +384,9 @@ class DefinitionVisitor(val extendedAttributes: List<ExtendedAttribute>, val nam
     }
 
     override fun visitImplementsStatement(ctx: ImplementsStatementContext): Definition {
-        val identifiers = ctx.children.filterIdentifiers().map { it.getText() }
+        val identifiers = ctx.children.filterIdentifiers().map { it.text }
 
-        if (identifiers.size() == 2) {
+        if (identifiers.size == 2) {
             kind = DefinitionKind.EXTENSION_INTERFACE
             name = identifiers[0]
             implements = identifiers[1]
@@ -408,7 +408,7 @@ class DefinitionVisitor(val extendedAttributes: List<ExtendedAttribute>, val nam
 
     override fun visitInheritance(ctx: WebIDLParser.InheritanceContext): Definition {
         if (ctx.children != null) {
-            inherited.addAll(ctx.children.filterIdentifiers().map { it.getText().trim() }.filter { it != "" })
+            inherited.addAll(ctx.children.filterIdentifiers().map { it.text.trim() }.filter { it != "" })
         }
         return defaultResult()
     }
@@ -488,13 +488,13 @@ class ModuleVisitor(val declarations: MutableList<Definition>, var namespace: St
     }
 
     override fun visitNamespaceRest(ctx: NamespaceRestContext) {
-        this.namespace = ctx.getText()
+        this.namespace = ctx.text
     }
 }
 
-private fun List<ParseTree>?.filterIdentifiers(): List<ParseTree> = this?.filter { it is TerminalNode && it.getSymbol().getType() == WebIDLLexer.IDENTIFIER_WEBIDL } ?: emptyList()
-private fun getName(ctx: ParserRuleContext) = ctx.children.filterIdentifiers().first().getText()
-private fun getNameOrNull(ctx: ParserRuleContext) = ctx.children.filterIdentifiers().firstOrNull()?.getText()
+private fun List<ParseTree>?.filterIdentifiers(): List<ParseTree> = this?.filter { it is TerminalNode && it.symbol.type == WebIDLLexer.IDENTIFIER_WEBIDL } ?: emptyList()
+private fun getName(ctx: ParserRuleContext) = ctx.children.filterIdentifiers().first().text
+private fun getNameOrNull(ctx: ParserRuleContext) = ctx.children.filterIdentifiers().firstOrNull()?.text
 
 fun parseIDL(reader: CharStream): Repository {
     val ll = WebIDLLexer(reader)
diff --git a/libraries/tools/idl2k/src/main/kotlin/main.kt b/libraries/tools/idl2k/src/main/kotlin/main.kt
index 4385e4ec362..a3c981a7994 100644
--- a/libraries/tools/idl2k/src/main/kotlin/main.kt
+++ b/libraries/tools/idl2k/src/main/kotlin/main.kt
@@ -2,20 +2,19 @@ package org.jetbrains.idl2k
 
 import org.antlr.v4.runtime.ANTLRFileStream
 import java.io.File
-import java.io.StringReader
 import java.util.*
 
 fun main(args: Array<String>) {
     val outDir = File("../../../js/js.libraries/src/generated")
     val srcDir = File("../../idl")
     if (!srcDir.exists()) {
-        System.err?.println("Directory ${srcDir.getAbsolutePath()} doesn't exist")
+        System.err?.println("Directory ${srcDir.absolutePath} doesn't exist")
         System.exit(1)
         return
     }
 
-    val repositoryPre = srcDir.walkTopDown().filter { it.isDirectory() || it.extension == "idl" }.asSequence().filter { it.isFile() }.toList().sortBy { it.getAbsolutePath() }.fold(Repository(emptyMap(), emptyMap(), emptyMap(), emptyMap())) { acc, e ->
-        val fileRepository = parseIDL(ANTLRFileStream(e.getAbsolutePath(), "UTF-8"))
+    val repositoryPre = srcDir.walkTopDown().filter { it.isDirectory || it.extension == "idl" }.asSequence().filter { it.isFile }.toList().sortedBy { it.absolutePath }.fold(Repository(emptyMap(), emptyMap(), emptyMap(), emptyMap())) { acc, e ->
+        val fileRepository = parseIDL(ANTLRFileStream(e.absolutePath, "UTF-8"))
 
         Repository(
                 interfaces = acc.interfaces.mergeReduce(fileRepository.interfaces, ::merge),
@@ -37,7 +36,7 @@ fun main(args: Array<String>) {
         }
     }
     val unions = generateUnions(definitions, repository.typeDefs.values())
-    val allPackages = definitions.map { it.namespace }.distinct().sort()
+    val allPackages = definitions.map { it.namespace }.distinct().sorted()
 
     outDir.deleteRecursively()
     outDir.mkdirs()
@@ -52,11 +51,11 @@ fun main(args: Array<String>) {
             w.appendln(" */")
 
             w.appendln()
-            w.appendln("package ${pkg}")
+            w.appendln("package $pkg")
             w.appendln()
 
             allPackages.filter { it != pkg }.forEach { import ->
-                w.appendln("import ${import}.*")
+                w.appendln("import $import.*")
             }
             w.appendln()
 
@@ -65,10 +64,10 @@ fun main(args: Array<String>) {
     }
 }
 
-private fun <K, V> Map<K, List<V>>.reduceValues(reduce: (V, V) -> V = { a, b -> b }): Map<K, V> = mapValues { it.value.reduce(reduce) }
+internal fun <K, V> Map<K, List<V>>.reduceValues(reduce: (V, V) -> V = { a, b -> b }): Map<K, V> = mapValues { it.value.reduce(reduce) }
 
-private fun <K, V> Map<K, V>.mergeReduce(other: Map<K, V>, reduce: (V, V) -> V = { a, b -> b }): Map<K, V> {
-    val result = LinkedHashMap<K, V>(this.size() + other.size())
+internal fun <K, V> Map<K, V>.mergeReduce(other: Map<K, V>, reduce: (V, V) -> V = { a, b -> b }): Map<K, V> {
+    val result = LinkedHashMap<K, V>(this.size + other.size)
     result.putAll(this)
     other.forEach { e ->
         val existing = result[e.key]
@@ -84,8 +83,8 @@ private fun <K, V> Map<K, V>.mergeReduce(other: Map<K, V>, reduce: (V, V) -> V =
     return result
 }
 
-private fun <K, V> Map<K, List<V>>.merge(other: Map<K, List<V>>): Map<K, List<V>> {
-    val result = LinkedHashMap<K, MutableList<V>>(size() + other.size())
+internal fun <K, V> Map<K, List<V>>.merge(other: Map<K, List<V>>): Map<K, List<V>> {
+    val result = LinkedHashMap<K, MutableList<V>>(size + other.size)
     this.forEach {
         result[it.key] = ArrayList(it.value)
     }
diff --git a/libraries/tools/idl2k/src/main/kotlin/render.kt b/libraries/tools/idl2k/src/main/kotlin/render.kt
index d8b00ea515b..c5ce1148cb2 100644
--- a/libraries/tools/idl2k/src/main/kotlin/render.kt
+++ b/libraries/tools/idl2k/src/main/kotlin/render.kt
@@ -92,7 +92,7 @@ private fun List<GenerateAttribute>.hasNoVars() = none { it.isVar }
 
 private fun GenerateAttribute.isCommented(parent: String) = "$parent.$name" in commentOutDeclarations || "$parent.$name: ${type.render()}" in commentOutDeclarations
 private fun GenerateFunction.isCommented(parent: String) =
-        "$parent.$name" in commentOutDeclarations || "$parent.$name(${arguments.size()})" in commentOutDeclarations
+        "$parent.$name" in commentOutDeclarations || "$parent.$name(${arguments.size})" in commentOutDeclarations
 private fun GenerateAttribute.isRequiredFunctionArgument(owner: String, functionName: String) = "$owner.$functionName.$name" in requiredArguments
 private fun GenerateFunction.fixRequiredArguments(parent: String) = copy(arguments = arguments.map { arg -> arg.copy(initializer = if (arg.isRequiredFunctionArgument(parent, name)) null else arg.initializer) })
 
diff --git a/libraries/tools/idl2k/src/main/kotlin/typeMappings.kt b/libraries/tools/idl2k/src/main/kotlin/typeMappings.kt
index 2cd20009c58..fabe8011c45 100644
--- a/libraries/tools/idl2k/src/main/kotlin/typeMappings.kt
+++ b/libraries/tools/idl2k/src/main/kotlin/typeMappings.kt
@@ -69,7 +69,7 @@ fun Type.dynamicIfUnknownType(allTypes: Set<String>, standardTypes: Set<Type> =
 
 private fun Type.dynamicIfAnyType(): Type = if (this is AnyType && this.nullable) DynamicType else this
 
-private fun mapType(repository: Repository, type: Type): Type = when (type) {
+internal fun mapType(repository: Repository, type: Type): Type = when (type) {
     is SimpleType -> {
         val typeName = type.type
         when {
@@ -101,7 +101,7 @@ private fun mapTypedef(repository: Repository, type: SimpleType): Type {
     val typedef = repository.typeDefs[type.type]!!
 
     return when {
-        typedef.types is UnionType && typedef.types.memberTypes.size() == 1 -> mapType(repository, typedef.types.memberTypes.single().withNullability(type.nullable))
+        typedef.types is UnionType && typedef.types.memberTypes.size == 1 -> mapType(repository, typedef.types.memberTypes.single().withNullability(type.nullable))
         typedef.types is UnionType -> SimpleType(typedef.name, type.nullable)
         else -> mapType(repository, typedef.types.withNullability(type.nullable))
     }
@@ -109,7 +109,7 @@ private fun mapTypedef(repository: Repository, type: SimpleType): Type {
 
 private fun GenerateFunction?.allTypes() = if (this != null) sequenceOf(returnType) + arguments.asSequence().map { it.type } else emptySequence()
 
-private fun collectUnionTypes(allTypes: Map<String, GenerateTraitOrClass>) =
+internal fun collectUnionTypes(allTypes: Map<String, GenerateTraitOrClass>) =
         allTypes.values().asSequence()
                 .flatMap {
                     it.secondaryConstructors.asSequence().flatMap { it.constructor.allTypes() } +
@@ -129,4 +129,4 @@ private fun guessPackage(types : List<String>, allTypes: Map<String, GenerateTra
         .filterNotNull()
         .filter { it.isNotEmpty() }
         .distinct()
-        .minBy { it.split('.').size() } ?: ""
+        .minBy { it.split('.').size } ?: ""
diff --git a/libraries/tools/idl2k/src/main/kotlin/types.kt b/libraries/tools/idl2k/src/main/kotlin/types.kt
index 41307998173..24ee99b86f6 100644
--- a/libraries/tools/idl2k/src/main/kotlin/types.kt
+++ b/libraries/tools/idl2k/src/main/kotlin/types.kt
@@ -6,7 +6,7 @@ interface Type {
     val nullable: Boolean
     fun render(): String
 
-    protected fun String.withSuffix(): String = if (nullable) "$this?" else this
+    fun String.withSuffix(): String = if (nullable) "$this?" else this
 }
 
 object UnitType : Type {
@@ -33,20 +33,23 @@ data class FunctionType(val parameterTypes : List<Attribute>, val returnType : T
 }
 
 val FunctionType.arity : Int
-    get() = parameterTypes.size()
+    get() = parameterTypes.size
 
-data class UnionType(val namespace: String, types: Collection<Type>, override val nullable: Boolean, val memberTypes: Set<Type> = LinkedHashSet(types.sortBy { it.toString() })) : Type {
+class UnionType(val namespace: String, types: Collection<Type>, override val nullable: Boolean, val memberTypes: Set<Type> = LinkedHashSet(types.sortedBy { it.toString() })) : Type {
     val name = "Union${this.memberTypes.map { it.render() }.joinToString("Or")}"
 
-    fun contains(type: Type) = type in memberTypes
+    operator fun contains(type: Type) = type in memberTypes
     override fun equals(other: Any?): Boolean = other is UnionType && memberTypes == other.memberTypes
     override fun hashCode(): Int = memberTypes.hashCode()
     override fun toString(): String = memberTypes.map { it.toString() }.join(", ", "Union<", ">")
 
     override fun render(): String = name.withSuffix()
+
+    fun copy(namespace: String = this.namespace, types: Collection<Type> = this.memberTypes, nullable: Boolean = this.nullable) =
+            UnionType(namespace, types, nullable)
 }
 
-fun UnionType.toSingleTypeIfPossible() = if (this.memberTypes.size() == 1) this.memberTypes.single().withNullability(nullable) else this
+fun UnionType.toSingleTypeIfPossible() = if (this.memberTypes.size == 1) this.memberTypes.single().withNullability(nullable) else this
 
 data class ArrayType(val memberType: Type, override val nullable: Boolean) : Type {
     override fun render(): String = "Array<${memberType.render()}>".withSuffix()
diff --git a/libraries/tools/idl2k/src/main/kotlin/utils.kt b/libraries/tools/idl2k/src/main/kotlin/utils.kt
index c1cb9daf40b..3f4816a3b41 100644
--- a/libraries/tools/idl2k/src/main/kotlin/utils.kt
+++ b/libraries/tools/idl2k/src/main/kotlin/utils.kt
@@ -2,16 +2,16 @@ package org.jetbrains.idl2k.util
 
 import java.util.*
 
-fun List<List<*>>.mutationsCount() = if (isEmpty()) 0 else fold(1) { acc, e -> acc * e.size() }
+fun List<List<*>>.mutationsCount() = if (isEmpty()) 0 else fold(1) { acc, e -> acc * e.size }
 
 fun <T> List<List<T>>.mutations() : List<List<T>> {
-    val indices = IntArray(size())
-    val sizes = map { it.size() }
+    val indices = IntArray(size)
+    val sizes = map { it.size }
 
     fun next() : Boolean {
         var carry = 1
 
-        for (pos in size() - 1 downTo 0) {
+        for (pos in size - 1 downTo 0) {
             var index = indices[pos]
             val size = sizes[pos]