[IR] Reworked adapted references building + test

As a side effect, this fixes https://youtrack.jetbrains.com/issue/KT-43887

(cherry picked from commit 387c09e7aed7666f5a178b2ac342fb17ed3cdda3)

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

@@ -213,30 +213,8 @@ internal class FunctionReferenceLowering(val context: Context): FileLoweringPass
 
         private val samSuperClass = samSuperType?.let { it.classOrNull ?: error("Expected a class but was: ${it.render()}") }
 
-        private val adapteeCall: IrFunctionAccessExpression? =
-                // TODO: Copied from JVM.
-                if (referencedFunction.origin == IrDeclarationOrigin.ADAPTER_FOR_CALLABLE_REFERENCE) {
-                    // The body of a callable reference adapter contains either only a call, or an IMPLICIT_COERCION_TO_UNIT type operator
-                    // applied to a call. That call's target is the original function which we need to get owner/name/signature.
-                    val call = when (val statement = referencedFunction.body!!.statements.single()) {
-                        is IrTypeOperatorCall -> {
-                            assert(statement.operator == IrTypeOperator.IMPLICIT_COERCION_TO_UNIT) {
-                                "Unexpected type operator in ADAPTER_FOR_CALLABLE_REFERENCE: ${referencedFunction.render()}"
-                            }
-                            statement.argument
-                        }
-                        is IrReturn -> statement.value
-                        else -> statement
-                    }
-                    if (call !is IrFunctionAccessExpression) {
-                        throw UnsupportedOperationException("Unknown structure of ADAPTER_FOR_CALLABLE_REFERENCE: ${referencedFunction.render()}")
-                    }
-                    call
-                } else {
-                    null
-                }
+        private val adaptedReferenceOriginalTarget: IrFunction? = functionReference.reflectionTarget?.owner
 
-        private val adaptedReferenceOriginalTarget: IrFunction? = adapteeCall?.symbol?.owner
         private val functionReferenceTarget = adaptedReferenceOriginalTarget ?: referencedFunction
 
         private val functionReferenceClass: IrClass =
@@ -404,13 +382,21 @@ internal class FunctionReferenceLowering(val context: Context): FileLoweringPass
         }
 
         private fun hasVarargMappedToElement(): Boolean {
-            if (adapteeCall == null) return false
-            for (i in 0 until adapteeCall.valueArgumentsCount) {
-                val arg = adapteeCall.getValueArgument(i) ?: continue
-                if (arg !is IrVararg) continue
-                for (varargElement in arg.elements) {
-                    if (varargElement is IrGetValue) return true
+            if (adaptedReferenceOriginalTarget == null) return false
+            val originalParameters = adaptedReferenceOriginalTarget.allParameters
+            val adaptedParameters = functionReference.symbol.owner.allParameters
+            var index = 0
+            // TODO: There should be similar code somewhere in the resolve.
+            while (index < originalParameters.size && index < adaptedParameters.size) {
+                val originalParameter = originalParameters[index]
+                val adaptedParameter = adaptedParameters[index]
+                if (originalParameter.defaultValue != null) return false
+                if (originalParameter.isVararg) {
+                    if (originalParameter.varargElementType!!.erasureForTypeOperation()
+                            == adaptedParameter.type.erasureForTypeOperation())
+                        return true
                 }
+                ++index
             }
             return false
         }

kotlin-native/backend.native/tests/build.gradle

@@ -2779,6 +2779,10 @@ task funInterface_nonTrivialProjectionInSuperType(type: KonanLocalTest) {
     source = "codegen/funInterface/nonTrivialProjectionInSuperType.kt"
 }
 
+task funInterface_kt43887(type: KonanLocalTest) {
+    source = "codegen/funInterface/kt43887.kt"
+}
+
 task objectExpression1(type: KonanLocalTest) {
     goldValue = "aabb\n"
     source = "codegen/objectExpression/expr1.kt"

kotlin-native/backend.native/tests/codegen/funInterface/kt43887.kt

@@ -0,0 +1,38 @@
+/*
+ * Copyright 2010-2021 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license
+ * that can be found in the LICENSE file.
+ */
+
+package codegen.funInterface.kt43887
+
+import kotlin.test.*
+
+import kotlinx.cinterop.*
+typealias heap_t = IntVar
+fun heap_create(size: Long): CPointer<heap_t>? = null
+fun heap_alloc(heap: CPointer<heap_t>?, size: ULong): CPointer<*>? = null
+fun heap_free(heap: CPointer<heap_t>?, ptr: CPointer<*>?): CPointer<BooleanVar>? = null
+inline fun Heap(size: Long): CPointer<heap_t>? {
+    return heap_create(size)
+}
+inline fun <reified T : CVariable> CPointer<heap_t>?.use(f: (CPointer<T>) -> Unit) {
+    alloc<T>()
+            ?.also(f)
+            ?.also(::free)
+}
+inline fun <reified T : CVariable> CPointer<heap_t>?.alloc(): CPointer<T>? {
+    return heap_alloc(this, sizeOf<T>().toULong())?.reinterpret()
+}
+inline fun CPointer<heap_t>?.free(ptr: CPointer<*>?): Boolean {
+    return heap_free(this, ptr)?.pointed?.value ?: false
+}
+
+@Test
+fun runTest(): Unit = memScoped {
+    val heap = Heap(1024)
+
+    heap.use<IntVar> { ptr ->
+        ptr.pointed.value = 40
+        //println("PTR ${ptr.pointed}")
+    }
+}