Interop, backend: refactor and reorder interop lowering

* Do not break type compatibility when lowering interop intrinsics.
* Place interop lowering before callable reference lowering.
* Add other improvements to interop implementation.

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

@@ -6,6 +6,7 @@ import org.jetbrains.kotlin.incremental.components.NoLookupLocation
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.resolve.scopes.MemberScope
+import org.jetbrains.kotlin.types.TypeUtils
 
 private val cPointerName = "CPointer"
 private val nativePointedName = "NativePointed"
@@ -37,12 +38,26 @@ internal class InteropBuiltIns(builtIns: KonanBuiltIns) {
 
     val cPointerRawValue = cPointer.unsubstitutedMemberScope.getContributedVariables("rawValue").single()
 
+    val cPointerGetRawValue = packageScope.getContributedFunctions("getRawValue").single {
+        val extensionReceiverParameter = it.extensionReceiverParameter
+        extensionReceiverParameter != null &&
+                TypeUtils.getClassDescriptor(extensionReceiverParameter.type) == cPointer
+    }
+
     val nativePointedRawPtrGetter =
             nativePointed.unsubstitutedMemberScope.getContributedVariables("rawPtr").single().getter!!
 
+    val nativePointedGetRawPointer = packageScope.getContributedFunctions("getRawPointer").single {
+        val extensionReceiverParameter = it.extensionReceiverParameter
+        extensionReceiverParameter != null &&
+                TypeUtils.getClassDescriptor(extensionReceiverParameter.type) == nativePointed
+    }
+
     val memberAt = packageScope.getContributedFunctions("memberAt").single()
 
-    val interpretPointed = packageScope.getContributedFunctions("interpretPointed").single()
+    val interpretNullablePointed = packageScope.getContributedFunctions("interpretNullablePointed").single()
+
+    val interpretCPointer = packageScope.getContributedFunctions("interpretCPointer").single()
 
     val arrayGetByIntIndex = packageScope.getContributedFunctions("get").single {
         KotlinBuiltIns.isInt(it.valueParameters.single().type)

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

@@ -48,6 +48,9 @@ internal class KonanLower(val context: Context) {
         phaser.phase(KonanPhase.LOWER_INNER_CLASSES) {
             InnerClassLowering(context).runOnFilePostfix(irFile)
         }
+        phaser.phase(KonanPhase.LOWER_INTEROP) {
+            InteropLowering(context).lower(irFile)
+        }
         phaser.phase(KonanPhase.LOWER_CALLABLES) {
             CallableReferenceLowering(context).runOnFilePostfix(irFile)
         }
@@ -62,8 +65,5 @@ internal class KonanLower(val context: Context) {
         phaser.phase(KonanPhase.AUTOBOX) {
             Autoboxing(context).lower(irFile)
         }
-        phaser.phase(KonanPhase.LOWER_INTEROP) {
-            InteropLowering(context).lower(irFile)
-        }
     }
 }

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

@@ -1661,6 +1661,9 @@ internal class CodeGeneratorVisitor(val context: Context) : IrElementVisitorVoid
         val interop = context.interopBuiltIns
 
         return when (descriptor) {
+            interop.interpretNullablePointed, interop.interpretCPointer,
+            interop.nativePointedGetRawPointer, interop.cPointerGetRawValue -> args.single()
+
             in interop.readPrimitive -> {
                 val pointerType = pointerType(codegen.getLLVMType(descriptor.returnType!!))
                 val rawPointer = args.last()

backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/lower/InteropLowering.kt

@@ -148,20 +148,25 @@ private class InteropTransformer(val context: Context) : IrBuildingTransformer(c
         if (descriptor is ClassConstructorDescriptor) {
             val type = descriptor.constructedClass.defaultType
             if (type.isRepresentedAs(ValueType.C_POINTER) || type.isRepresentedAs(ValueType.NATIVE_POINTED)) {
-                return expression.getValueArgument(0)!!
+                throw Error("Native interop types constructors must not be called directly")
             }
         }
 
         if (descriptor == interop.nativePointedRawPtrGetter ||
                 OverridingUtil.overrides(descriptor, interop.nativePointedRawPtrGetter)) {
 
-            return expression.dispatchReceiver!!
+            // Replace by the intrinsic call to be handled by code generator:
+            return builder.irCall(interop.nativePointedGetRawPointer).apply {
+                extensionReceiver = expression.dispatchReceiver
+            }
         }
 
         return when (descriptor) {
-            interop.cPointerRawValue.getter -> expression.dispatchReceiver!!
-
-            interop.interpretPointed -> expression.getValueArgument(0)!!
+            interop.cPointerRawValue.getter ->
+                // Replace by the intrinsic call to be handled by code generator:
+                builder.irCall(interop.cPointerGetRawValue).apply {
+                    extensionReceiver = expression.dispatchReceiver
+                }
 
             interop.arrayGetByIntIndex, interop.arrayGetByLongIndex -> {
                 val array = expression.extensionReceiver!!