KT-16438 Strange dispatch receiver for descriptors of delegated members

Provide proper dispatch receiver parameter for delegated members.
Use dispatch receiver parameter for delegated members in IR generation
for delegated member body (and check that the receiver has corresponding type).

compiler/frontend/src/org/jetbrains/kotlin/resolve/DelegationResolver.kt

@@ -70,7 +70,14 @@ class DelegationResolver<T : CallableMemberDescriptor> private constructor(
             getDelegatableMembers(delegatedInterfaceType).map { memberDescriptor ->
                 val newModality = if (memberDescriptor.modality == Modality.ABSTRACT) Modality.OPEN else memberDescriptor.modality
                 @Suppress("UNCHECKED_CAST")
-                (memberDescriptor.copy(ownerDescriptor, newModality, Visibilities.INHERITED, DELEGATION, false) as T)
+                memberDescriptor.newCopyBuilder()
+                        .setOwner(ownerDescriptor)
+                        .setDispatchReceiverParameter(ownerDescriptor.thisAsReceiverParameter)
+                        .setModality(newModality)
+                        .setVisibility(Visibilities.INHERITED)
+                        .setKind(DELEGATION)
+                        .setCopyOverrides(false)
+                        .build() as T
             }
 
     private fun checkClashWithOtherDelegatedMember(candidate: T, delegatedMembers: Collection<T>): Boolean {

compiler/ir/ir.psi2ir/src/org/jetbrains/kotlin/psi2ir/generators/ClassGenerator.kt

@@ -168,13 +168,14 @@ class ClassGenerator(val declarationGenerator: DeclarationGenerator) : Generator
     private fun generateDelegateFunctionBody(irDelegate: IrFieldImpl, delegated: FunctionDescriptor, overridden: FunctionDescriptor): IrBlockBodyImpl {
         val startOffset = irDelegate.startOffset
         val endOffset = irDelegate.endOffset
-        val classOwner = delegated.containingDeclaration.assertedCast<ClassDescriptor> { "Class member expected: $delegated" }
+        val dispatchReceiver = delegated.dispatchReceiverParameter ?:
+                               throw AssertionError("Delegated member should have a dispatch receiver: $delegated")
 
         val irBlockBody = IrBlockBodyImpl(startOffset, endOffset)
         val returnType = overridden.returnType!!
         val irCall = IrCallImpl(startOffset, endOffset, returnType, overridden, null)
         irCall.dispatchReceiver = IrGetFieldImpl(startOffset, endOffset, irDelegate.descriptor,
-                                                 IrGetValueImpl(startOffset, endOffset, classOwner.thisAsReceiverParameter)
+                                                 IrGetValueImpl(startOffset, endOffset, dispatchReceiver)
                                                  )
         irCall.extensionReceiver = delegated.extensionReceiverParameter?.let { extensionReceiver ->
             IrGetValueImpl(startOffset, endOffset, extensionReceiver)