JS: don't remove imports only used for fake overrides (KT-31007 fixed)

js/js.ast/src/org/jetbrains/kotlin/js/backend/ast/JsClassModel.kt

@@ -18,6 +18,6 @@ package org.jetbrains.kotlin.js.backend.ast
 
 class JsClassModel(val name: JsName, val superName: JsName?) {
     val interfaces: MutableSet<JsName> = mutableSetOf()
-    val preDeclarationBlock = JsGlobalBlock()
+    val preDeclarationBlock = JsGlobalBlock() // TODO only used in IR backend => hide from current backend
     val postDeclarationBlock = JsGlobalBlock()
 }

js/js.inliner/src/org/jetbrains/kotlin/js/inline/InliningScope.kt

@@ -140,6 +140,9 @@ class ImportIntoFragmentInliningScope private constructor(
         get() = JsBlock(
             JsBlock(fragment.inlinedLocalDeclarations.values.toList()),
             fragment.declarationBlock,
+            JsBlock(fragment.classes.values.flatMap {
+                listOf(it.preDeclarationBlock, it.postDeclarationBlock)
+            }),
             fragment.exportBlock,
             JsExpressionStatement(JsFunction(JsDynamicScope, fragment.initializerBlock, ""))
         ).also { block ->

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

@@ -5316,6 +5316,11 @@ public class IrBoxJsTestGenerated extends AbstractIrBoxJsTest {
             runTest("js/js.translator/testData/box/multiModule/moduleAndVariableNameClash.kt");
         }
 
+        @TestMetadata("privateInterfaceMethodInheritance.kt")
+        public void testPrivateInterfaceMethodInheritance() throws Exception {
+            runTest("js/js.translator/testData/box/multiModule/privateInterfaceMethodInheritance.kt");
+        }
+
         @TestMetadata("privateInterfaceNameClash.kt")
         public void testPrivateInterfaceNameClash() throws Exception {
             runTest("js/js.translator/testData/box/multiModule/privateInterfaceNameClash.kt");

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

@@ -5321,6 +5321,11 @@ public class BoxJsTestGenerated extends AbstractBoxJsTest {
             runTest("js/js.translator/testData/box/multiModule/moduleAndVariableNameClash.kt");
         }
 
+        @TestMetadata("privateInterfaceMethodInheritance.kt")
+        public void testPrivateInterfaceMethodInheritance() throws Exception {
+            runTest("js/js.translator/testData/box/multiModule/privateInterfaceMethodInheritance.kt");
+        }
+
         @TestMetadata("privateInterfaceNameClash.kt")
         public void testPrivateInterfaceNameClash() throws Exception {
             runTest("js/js.translator/testData/box/multiModule/privateInterfaceNameClash.kt");

js/js.translator/testData/box/multiModule/privateInterfaceMethodInheritance.kt

@@ -0,0 +1,25 @@
+// EXPECTED_REACHABLE_NODES: 1280
+// IGNORE_BACKEND: JS_IR
+// MODULE: lib
+// FILE: lib.kt
+package lib
+
+interface A {
+    private fun foo() = "OK"
+
+    fun bar() = foo()
+}
+
+open class AProxy: A
+
+// MODULE: main(lib)
+// FILE: main.kt
+package main
+
+// KT-31007
+import lib.AProxy
+
+// Important bit: don't inherit A directly
+class B : AProxy()
+
+fun box(): String = B().bar()