fix: fake override on interfaces.

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/JsClassGenerator.kt

@@ -141,7 +141,7 @@ class JsClassGenerator(private val irClass: IrClass, val context: JsGenerationCo
                 // so we need regenerate `defineProperty` with setter.
                 // P.S. If the overridden property is owned by an interface - we should generate defineProperty
                 // for overridden property in the first class which override those properties
-                val hasOverriddenExportedInterfaceProperties = overriddenSymbols.any { it.owner.parentClassOrNull.isExportedInterface() }
+                val hasOverriddenExportedInterfaceProperties = overriddenSymbols.any { it.owner.isDefinedInsideExportedInterface() }
                         && !overriddenSymbols.any { it.owner.parentClassOrNull.isExportedClass() }
 
                 val getterOverridesExternal = property.getter?.overridesExternal() == true
@@ -212,6 +212,11 @@ class JsClassGenerator(private val irClass: IrClass, val context: JsGenerationCo
         return if (modality == Modality.FINAL) accessorRef() else generateFunc()
     }
 
+    private fun IrSimpleFunction.isDefinedInsideExportedInterface(): Boolean {
+        return (!isFakeOverride && parentClassOrNull.isExportedInterface()) ||
+                overriddenSymbols.any { it.owner.isDefinedInsideExportedInterface() }
+    }
+
     private fun IrSimpleFunction?.shouldExportAccessor(): Boolean {
         if (this == null) return false
 

js/js.translator/testData/box/export/exportInterface.kt

@@ -5,22 +5,34 @@
 // MODULE: export_interface
 // FILE: lib.kt
 
+interface ParentI {
+   val str: String
+}
+
 @JsExport
-interface I {
+interface I : ParentI {
     val value: Int
     var variable: Int
     fun foo(): String
 }
 
-open class NotExportedClass(override var value: Int) : I {
+interface ExtendedI: I {
+    fun bar(): Int
+}
+
+open class NotExportedClass(override var value: Int) : ExtendedI {
     override var variable: Int = value
     override open fun foo(): String = "Not Exported"
+    override val str: String = "test 1"
+    override open fun bar(): Int = 42
 }
 
 @JsExport
-class ExportedClass(override val value: Int) : I {
+class ExportedClass(override val value: Int) : ExtendedI {
     override var variable: Int = value
     override fun foo(): String = "Exported"
+    override val str: String = "test 2"
+    override open fun bar(): Int = 43
 }
 
 @JsExport
@@ -75,5 +87,11 @@ function box() {
     if (consume(another) !== "Value is 42, variable is 102 and result is 'Another One Exported'") return "Fail: methods or fields of AnotherOne was mangled"
     if (consume(notExported) !== "Value is 3, variable is 103 and result is 'Not Exported'") return "Fail: methods or fields of NotExported was mangled"
 
+    if (notExported.str !== undefined) return "Fail: str should not exist inside NotExportedClass"
+    if (exported.str !== undefined) return "Fail: str should not exist inside ExportedClass"
+
+    if (notExported.bar !== undefined) return "Fail: bar should not exist inside NotExportedClass"
+    if (exported.bar !== undefined) return "Fail: bar should not exist inside ExportedClass"
+
     return "OK"
 }