[JS, Frontend] Add test with extension member in external interface

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

@@ -3307,6 +3307,11 @@ public class IrBoxJsES6TestGenerated extends AbstractIrBoxJsES6Test {
             runTest("js/js.translator/testData/box/extensionFunction/implicitReceiverInExtension.kt");
         }
 
+        @TestMetadata("inExternalInterface.kt")
+        public void testInExternalInterface() throws Exception {
+            runTest("js/js.translator/testData/box/extensionFunction/inExternalInterface.kt");
+        }
+
         @TestMetadata("intExtension.kt")
         public void testIntExtension() throws Exception {
             runTest("js/js.translator/testData/box/extensionFunction/intExtension.kt");

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

@@ -3307,6 +3307,11 @@ public class IrBoxJsTestGenerated extends AbstractIrBoxJsTest {
             runTest("js/js.translator/testData/box/extensionFunction/implicitReceiverInExtension.kt");
         }
 
+        @TestMetadata("inExternalInterface.kt")
+        public void testInExternalInterface() throws Exception {
+            runTest("js/js.translator/testData/box/extensionFunction/inExternalInterface.kt");
+        }
+
         @TestMetadata("intExtension.kt")
         public void testIntExtension() throws Exception {
             runTest("js/js.translator/testData/box/extensionFunction/intExtension.kt");

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

@@ -3322,6 +3322,11 @@ public class BoxJsTestGenerated extends AbstractBoxJsTest {
             runTest("js/js.translator/testData/box/extensionFunction/implicitReceiverInExtension.kt");
         }
 
+        @TestMetadata("inExternalInterface.kt")
+        public void testInExternalInterface() throws Exception {
+            runTest("js/js.translator/testData/box/extensionFunction/inExternalInterface.kt");
+        }
+
         @TestMetadata("intExtension.kt")
         public void testIntExtension() throws Exception {
             runTest("js/js.translator/testData/box/extensionFunction/intExtension.kt");

js/js.translator/testData/box/extensionFunction/inExternalInterface.kt

@@ -0,0 +1,9 @@
+// !LANGUAGE: +JsEnableExtensionFunctionInExternals
+
+external interface Foo {
+    fun foo(): String.() -> Unit
+}
+
+fun box(): String {
+    return "OK"
+}