[JS BE] es6: save instance after superCall

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/EnumClassLowering.kt

@@ -362,7 +362,13 @@ class EnumEntryInstancesBodyLowering(val context: JsIrBackendContext) : BodyLowe
             val enum = entryClass.parentAsClass
             if (enum.goodEnum) {
                 val entry = enum.declarations.filterIsInstance<IrEnumEntry>().find { it.correspondingClass === entryClass }!!
-                (irBody as IrBlockBody).statements.add(0, context.createIrBuilder(container.symbol).run {
+
+                //In ES6 using `this` before superCall is unavailable, so
+                //need to find superCall and put `instance = this` after it
+                val index = (irBody as IrBlockBody).statements
+                    .indexOfFirst { it is IrTypeOperatorCall && it.argument is IrDelegatingConstructorCall } + 1
+
+                (irBody as IrBlockBody).statements.add(index, context.createIrBuilder(container.symbol).run {
                     irSetField(null, entry.correspondingField!!, irGet(entryClass.thisReceiver!!))
                 })
             }

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/ObjectLowering.kt

@@ -18,16 +18,10 @@ import org.jetbrains.kotlin.ir.backend.js.ir.JsIrBuilder
 import org.jetbrains.kotlin.ir.builders.*
 import org.jetbrains.kotlin.ir.builders.declarations.buildField
 import org.jetbrains.kotlin.ir.declarations.*
-import org.jetbrains.kotlin.ir.expressions.IrBlockBody
-import org.jetbrains.kotlin.ir.expressions.IrBody
-import org.jetbrains.kotlin.ir.expressions.IrExpression
-import org.jetbrains.kotlin.ir.expressions.IrGetObjectValue
+import org.jetbrains.kotlin.ir.expressions.*
 import org.jetbrains.kotlin.ir.expressions.impl.IrBlockBodyImpl
 import org.jetbrains.kotlin.ir.types.makeNullable
-import org.jetbrains.kotlin.ir.util.defaultType
-import org.jetbrains.kotlin.ir.util.isEffectivelyExternal
-import org.jetbrains.kotlin.ir.util.parentAsClass
-import org.jetbrains.kotlin.ir.util.primaryConstructor
+import org.jetbrains.kotlin.ir.util.*
 import org.jetbrains.kotlin.ir.visitors.IrElementTransformerVoid
 import org.jetbrains.kotlin.ir.visitors.transformChildrenVoid
 import org.jetbrains.kotlin.name.Name
@@ -87,7 +81,18 @@ class ObjectUsageLowering(
                 val initInstanceField = context.createIrBuilder(container.symbol).buildStatement(UNDEFINED_OFFSET, UNDEFINED_OFFSET) {
                     irSetField(null, instanceField, irGet(irClass.thisReceiver!!))
                 }
-                (irBody as IrBlockBody).statements.add(0, initInstanceField)
+                if (context.es6mode) {
+                    //find `superCall` and put after
+                    (irBody as IrBlockBody).statements.transformFlat {
+                        if (it is IrDelegatingConstructorCall) listOf(it, initInstanceField)
+                        else if (it is IrVariable && it.origin === ES6_THIS_VARIABLE_ORIGIN) {
+                            initInstanceField.value = JsIrBuilder.buildGetValue(it.symbol)
+                            listOf(it, initInstanceField)
+                        } else null
+                    }
+                } else {
+                    (irBody as IrBlockBody).statements.add(0, initInstanceField)
+                }
             }
         }