[JS BE] add runtime-function and intrinsics for es6-classes

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsIntrinsics.kt

@@ -151,6 +151,11 @@ class JsIntrinsics(private val irBuiltIns: IrBuiltIns, val context: JsIrBackendC
     val jsAnyToString = getInternalFunction("anyToString")
     val jsCompareTo = getInternalFunction("compareTo")
     val jsEquals = getInternalFunction("equals")
+    val jsConstruct = getInternalFunction("construct")
+    val jsNewTarget = unOp("jsNewTarget")
+    val jsEmptyObject = unOp("emptyObject")
+    val jsOpenInitializerBox = binOp("openInitializerBox")
+    val es6DefaultType = defineEs6DefaultTypeIntrinsic().symbol
 
     val jsImul = getInternalFunction("imul")
 
@@ -324,6 +329,14 @@ class JsIntrinsics(private val irBuiltIns: IrBuiltIns, val context: JsIrBackendC
         }
     }
 
+    private fun defineEs6DefaultTypeIntrinsic(): IrSimpleFunction {
+        return externalPackageFragment.addFunction {
+            name = Name.identifier("DefaultType")
+        }.apply {
+            returnType = addTypeParameter("T", irBuiltIns.anyType).defaultType
+        }
+    }
+
     private fun defineJsBindIntrinsic(): IrSimpleFunction {
         return externalPackageFragment.addFunction {
             name = Name.identifier("\$jsBind\$")

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/JsIntrinsicTransformers.kt

@@ -101,6 +101,36 @@ class JsIntrinsicTransformers(backendContext: JsIrBackendContext) {
                 }
             }
 
+            add(intrinsics.jsNewTarget) { _, _ ->
+                JsNameRef(JsName("target"), JsNameRef(JsName("new")))
+            }
+
+            add(intrinsics.jsOpenInitializerBox) { call, context ->
+                val arguments = translateCallArguments(call, context)
+
+                JsInvocation(
+                    JsNameRef("Object.assign"),
+                    arguments
+                )
+            }
+
+            add(intrinsics.jsEmptyObject) { _, _ ->
+                JsObjectLiteral()
+            }
+
+            add(intrinsics.es6DefaultType) { call, context ->
+                val classifier: IrClassifierSymbol = call.getTypeArgument(0)!!.classifierOrFail
+                val owner = classifier.owner
+
+                when {
+                    owner is IrClass && owner.isEffectivelyExternal() ->
+                        context.getRefForExternalClass(owner)
+
+                    else ->
+                        context.getNameForStaticDeclaration(owner as IrDeclarationWithName).makeRef()
+                }
+            }
+
             addIfNotNull(intrinsics.jsCode) { _, _ -> error("Should not be called") }
 
             add(intrinsics.jsGetContinuation) { _, context: JsGenerationContext ->