JVM KT-49613 don't generate indy reference to protected constructor

compiler/ir/backend.jvm/lower/src/org/jetbrains/kotlin/backend/jvm/lower/TypeOperatorLowering.kt

@@ -270,7 +270,7 @@ private class TypeOperatorLowering(private val context: JvmBackendContext) : Fil
         targetRef: IrFunctionReference
     ): IrCall {
         fun fail(message: String): Nothing =
-            throw AssertionError("$message, irFunRef:\n${targetRef.dump()}")
+            throw AssertionError("$message, targetRef:\n${targetRef.dump()}")
 
         val dynamicCallArguments = ArrayList<IrExpression>()
 

compiler/ir/backend.jvm/lower/src/org/jetbrains/kotlin/backend/jvm/lower/indy/LambdaMetafactoryArguments.kt

@@ -91,9 +91,8 @@ internal class LambdaMetafactoryArgumentsBuilder(
         if (implFun.isInline)
             return null
 
-        if (implFun is IrConstructor && DescriptorVisibilities.isPrivate(implFun.visibility)) {
+        if (isConstructorRequiringAccessor(implFun)) {
             // Kotlin generates constructor accessors differently from Java.
-            // TODO more precise accessibility check (see SyntheticAccessorLowering::isAccessible)
             return null
         }
 
@@ -138,6 +137,15 @@ internal class LambdaMetafactoryArgumentsBuilder(
         return getLambdaMetafactoryArgsOrNullInner(reference, samMethod, samType, implFun)
     }
 
+    private fun isConstructorRequiringAccessor(implFun: IrFunction): Boolean {
+        if (implFun !is IrConstructor) return false
+        // We don't do exact accessibility check here:
+        // constructor will be called by a class generated by LambdaMetafactory at runtime.
+        val visibility = implFun.visibility
+        return visibility == DescriptorVisibilities.PROTECTED ||
+                DescriptorVisibilities.isPrivate(visibility)
+    }
+
     private val javaIoSerializableFqn =
         FqName("java.io").child(Name.identifier("Serializable"))
 

compiler/testData/codegen/box/invokedynamic/sam/functionRefToJavaInterface/kt49613.kt

@@ -0,0 +1,28 @@
+// TARGET_BACKEND: JVM
+// JVM_TARGET: 1.8
+// SAM_CONVERSIONS: INDY
+// FILE: kt49613.kt
+
+interface GetStep {
+    fun get(): Any
+}
+
+class Outer protected constructor(val ok: Any) {
+    constructor(): this("xxx")
+
+    val obj = object : GetStep {
+        override fun get() = Step(::Outer)
+    }
+}
+
+fun box(): String {
+    val s = Outer().obj.get() as Step
+    val t = s.step("OK") as Outer
+    return t.ok as String
+}
+
+// FILE: Step.java
+
+public interface Step {
+    Object step(String string);
+}