[IR] Fix synthetic declarations generator to make it produce correct type

- Fix KT-40126
 - Add test

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

@@ -133,7 +133,7 @@ class StandaloneDeclarationGenerator(private val context: GeneratorContext) {
     protected fun generateValueParameterDeclarations(
         irFunction: IrFunction,
         functionDescriptor: FunctionDescriptor,
-        defaultArgumentFactory: IrFunction.(ValueParameterDescriptor) -> IrExpressionBody?
+        defaultArgumentFactory: IrFunction.(IrValueParameter) -> IrExpressionBody?
     ) {
 
         // TODO: KtElements
@@ -150,14 +150,14 @@ class StandaloneDeclarationGenerator(private val context: GeneratorContext) {
         irFunction.valueParameters = functionDescriptor.valueParameters.map { valueParameterDescriptor ->
             val ktParameter = DescriptorToSourceUtils.getSourceFromDescriptor(valueParameterDescriptor) as? KtParameter
             declareParameter(valueParameterDescriptor, ktParameter, irFunction).also {
-                it.defaultValue = irFunction.defaultArgumentFactory(valueParameterDescriptor)
+                it.defaultValue = irFunction.defaultArgumentFactory(it)
             }
         }
     }
 
     fun generateConstructor(
         startOffset: Int, endOffset: Int, origin: IrDeclarationOrigin, descriptor: ClassConstructorDescriptor, symbol: IrConstructorSymbol,
-        defaultArgumentFactory: IrFunction.(ValueParameterDescriptor) -> IrExpressionBody? = { null }
+        defaultArgumentFactory: IrFunction.(IrValueParameter) -> IrExpressionBody? = { null }
     ): IrConstructor {
         val irConstructor = IrConstructorImpl(startOffset, endOffset, origin, symbol, IrUninitializedType, descriptor)
         irConstructor.metadata = MetadataSource.Function(descriptor)
@@ -178,7 +178,7 @@ class StandaloneDeclarationGenerator(private val context: GeneratorContext) {
 
     fun generateSimpleFunction(
         startOffset: Int, endOffset: Int, origin: IrDeclarationOrigin, descriptor: FunctionDescriptor, symbol: IrSimpleFunctionSymbol,
-        defaultArgumentFactory: IrFunction.(ValueParameterDescriptor) -> IrExpressionBody? = { null }
+        defaultArgumentFactory: IrFunction.(IrValueParameter) -> IrExpressionBody? = { null }
     ): IrSimpleFunction {
         val irFunction = IrFunctionImpl(startOffset, endOffset, origin, symbol, IrUninitializedType, descriptor)
         irFunction.metadata = MetadataSource.Function(descriptor)

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

@@ -31,16 +31,15 @@ class SyntheticDeclarationsGenerator(context: GeneratorContext) : DeclarationDes
         return this
     }
 
-    private val errorType = IrErrorTypeImpl(null, emptyList(), Variance.INVARIANT)
+    private fun IrFunction.defaultArgumentFactory(parameter: IrValueParameter): IrExpressionBody? {
-
+        val descriptor = parameter.descriptor as ValueParameterDescriptor
-    private fun IrFunction.defaultArgumentFactory(descriptor: ValueParameterDescriptor): IrExpressionBody? {
         if (!descriptor.declaresDefaultValue()) return null
 
         val description = "Default Argument Value stub for ${descriptor.name}|${descriptor.index}"
-        return IrExpressionBodyImpl(IrErrorExpressionImpl(startOffset, endOffset, errorType, description))
+        return IrExpressionBodyImpl(IrErrorExpressionImpl(startOffset, endOffset, parameter.type, description))
     }
 
-    private val defaultFactoryReference: IrFunction.(ValueParameterDescriptor) -> IrExpressionBody? = { defaultArgumentFactory(it) }
+    private val defaultFactoryReference: IrFunction.(IrValueParameter) -> IrExpressionBody? = { defaultArgumentFactory(it) }
 
     override fun visitPackageFragmentDescriptor(descriptor: PackageFragmentDescriptor, data: IrDeclarationContainer?) {
         error("Unexpected declaration descriptor $descriptor")

compiler/ir/ir.psi2ir/src/org/jetbrains/kotlin/psi2ir/transformations/InsertImplicitCasts.kt

@@ -39,6 +39,7 @@ import org.jetbrains.kotlin.ir.types.impl.originalKotlinType
 import org.jetbrains.kotlin.ir.util.SymbolTable
 import org.jetbrains.kotlin.ir.util.TypeTranslator
 import org.jetbrains.kotlin.ir.util.coerceToUnit
+import org.jetbrains.kotlin.ir.util.render
 import org.jetbrains.kotlin.ir.visitors.IrElementTransformerVoid
 import org.jetbrains.kotlin.ir.visitors.IrElementVisitorVoid
 import org.jetbrains.kotlin.ir.visitors.acceptChildrenVoid
@@ -341,7 +342,7 @@ internal class InsertImplicitCasts(
 
         val notNullableExpectedType = expectedType.makeNotNullable()
 
-        val valueType = this.type.originalKotlinType!!
+        val valueType = this.type.originalKotlinType ?: error("Expecting original kotlin type for IrType ${type.render()}")
 
         return when {
             expectedType.isUnit() ->

js/js.tests/test/org/jetbrains/kotlin/js/test/es6/semantics/IrBoxJsES6TestGenerated.java

@@ -1271,6 +1271,11 @@ public class IrBoxJsES6TestGenerated extends AbstractIrBoxJsES6Test {
             runTest("js/js.translator/testData/box/delegation/delegationExtensionPropertyDelegated.kt");
         }
 
+        @TestMetadata("delegationToExternaInterface.kt")
+        public void testDelegationToExternaInterface() throws Exception {
+            runTest("js/js.translator/testData/box/delegation/delegationToExternaInterface.kt");
+        }
+
         @TestMetadata("jsNamePropertyDelegation.kt")
         public void testJsNamePropertyDelegation() throws Exception {
             runTest("js/js.translator/testData/box/delegation/jsNamePropertyDelegation.kt");

js/js.tests/test/org/jetbrains/kotlin/js/test/ir/semantics/IrBoxJsTestGenerated.java

@@ -1271,6 +1271,11 @@ public class IrBoxJsTestGenerated extends AbstractIrBoxJsTest {
             runTest("js/js.translator/testData/box/delegation/delegationExtensionPropertyDelegated.kt");
         }
 
+        @TestMetadata("delegationToExternaInterface.kt")
+        public void testDelegationToExternaInterface() throws Exception {
+            runTest("js/js.translator/testData/box/delegation/delegationToExternaInterface.kt");
+        }
+
         @TestMetadata("jsNamePropertyDelegation.kt")
         public void testJsNamePropertyDelegation() throws Exception {
             runTest("js/js.translator/testData/box/delegation/jsNamePropertyDelegation.kt");

js/js.tests/test/org/jetbrains/kotlin/js/test/semantics/BoxJsTestGenerated.java

@@ -1271,6 +1271,11 @@ public class BoxJsTestGenerated extends AbstractBoxJsTest {
             runTest("js/js.translator/testData/box/delegation/delegationExtensionPropertyDelegated.kt");
         }
 
+        @TestMetadata("delegationToExternaInterface.kt")
+        public void testDelegationToExternaInterface() throws Exception {
+            runTest("js/js.translator/testData/box/delegation/delegationToExternaInterface.kt");
+        }
+
         @TestMetadata("jsNamePropertyDelegation.kt")
         public void testJsNamePropertyDelegation() throws Exception {
             runTest("js/js.translator/testData/box/delegation/jsNamePropertyDelegation.kt");

js/js.translator/testData/box/delegation/delegationToExternaInterface.kt

@@ -0,0 +1,15 @@
+// EXPECTED_REACHABLE_NODES: 1236
+// KJS_WITH_FULL_RUNTIME
+// KT-40126
+@file:Suppress("EXTERNAL_DELEGATION")
+
+@Suppress("NESTED_CLASS_IN_EXTERNAL_INTERFACE")
+external interface MySymbol {
+    companion object : MySymbolConstructor by definedExternally
+}
+external interface MySymbolConstructor {
+    @nativeInvoke
+    operator fun invoke(description: String = definedExternally): Any
+}
+
+fun box() = "OK"