only stub default constructor when compiling against .java source files

compiler/frontend.java/src/org/jetbrains/kotlin/load/java/structure/impl/JavaClassImpl.kt

@@ -100,6 +100,8 @@ class JavaClassImpl(psiClass: PsiClass) : JavaClassifierImpl<PsiClass>(psiClass)
             return constructors(psi.constructors.filter { method -> method.isConstructor })
         }
 
+    override fun hasDefaultConstructor() = !isInterface && constructors.isEmpty()
+
     override val isAbstract: Boolean
         get() = JavaElementUtil.isAbstract(this)
 

compiler/frontend.java/src/org/jetbrains/kotlin/load/java/structure/impl/classFiles/BinaryJavaClass.kt

@@ -47,6 +47,7 @@ class BinaryJavaClass(
     override val methods = arrayListOf<JavaMethod>()
     override val fields = arrayListOf<JavaField>()
     override val constructors = arrayListOf<JavaConstructor>()
+    override fun hasDefaultConstructor() = false // never: all constructors explicit in bytecode
 
     override val annotationsByFqName by buildLazyValueForMap()