Fix #2004

Fix delegation to constructor of the same class in Objective-C subclasses

backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/llvm/IrToBitcode.kt

@@ -2583,7 +2583,8 @@ internal class CodeGeneratorVisitor(val context: Context, val lifetimes: Map<IrE
         val constructedClass = functionGenerationContext.constructedClass!!
         val thisPtr = currentCodeContext.genGetValue(constructedClass.thisReceiver!!)
 
-        if (constructedClass.isObjCClass()) {
+        if (descriptor.constructedClass.isExternalObjCClass()) {
+            assert(args.isEmpty())
             return codegen.theUnitInstanceRef.llvm
         }
 

backend.native/tests/interop/objc/smoke.kt

@@ -45,6 +45,10 @@ fun run() {
     pair.swap()
     println("${pair.first}, ${pair.second}")
 
+    val defaultPair = MutablePairImpl()
+    assertEquals(defaultPair.first(), 123)
+    assertEquals(defaultPair.second(), 321)
+
     // equals and hashCode (virtually):
     val map = mapOf(foo to pair, pair to foo)
 
@@ -105,6 +109,8 @@ class MutablePairImpl(first: Int, second: Int) : NSObject(), MutablePairProtocol
     override fun update(index: Int, sub: Int) {
         elements[index] -= sub
     }
+
+    constructor() : this(123, 321)
 }
 
 fun testTypeOps() {