[JS IR] Fix name clash between class members defined on prototype

- Fixes [KT-33327]

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/StableNamesCollector.kt

@@ -9,6 +9,7 @@ import org.jetbrains.kotlin.ir.IrElement
 import org.jetbrains.kotlin.ir.declarations.IrConstructor
 import org.jetbrains.kotlin.ir.declarations.IrDeclaration
 import org.jetbrains.kotlin.ir.declarations.IrDeclarationWithName
+import org.jetbrains.kotlin.ir.declarations.IrSimpleFunction
 import org.jetbrains.kotlin.ir.util.isEffectivelyExternal
 import org.jetbrains.kotlin.ir.util.isPropertyAccessor
 import org.jetbrains.kotlin.ir.util.isPropertyField
@@ -35,8 +36,10 @@ class StableNamesCollector : IrElementVisitorVoid {
         if (declaration !is IrDeclarationWithName)
             return
 
+        val isStatic = declaration.hasStaticDispatch()
+
         val scope =
-            if (declaration.hasStaticDispatch())
+            if (isStatic)
                 staticNames
             else
                 memberNames
@@ -45,13 +48,22 @@ class StableNamesCollector : IrElementVisitorVoid {
             if (declaration.isEffectivelyExternal())
                 stableNameForExternalDeclaration(declaration)
             else
-                stableNameForNonExternalDeclaration(declaration)
+                stableNameForNonExternalDeclaration(declaration, isStatic)
 
         scope.addIfNotNull(stableName)
     }
 
-    private fun stableNameForNonExternalDeclaration(declaration: IrDeclarationWithName): String? =
+    private fun stableNameForNonExternalDeclaration(declaration: IrDeclarationWithName, isStatic: Boolean): String? =
-        declaration.getJsName()
+        declaration.getJsName() ?: run {
+            // TODO: since following code affects local variable naming some weird behaviour of js("..") is possible
+            // Remove check once 1. `js` function is re-designed and re-implemented, 2. JsExport is properly implemented
+            if (!isStatic) {
+                // Make sure property defined on prototype has stable name
+                val simpleFunction = declaration as? IrSimpleFunction
+                val property = simpleFunction?.correspondingPropertySymbol?.owner
+                property?.getJsNameOrKotlinName()?.identifier
+            } else null
+        }
 
     private fun stableNameForExternalDeclaration(declaration: IrDeclarationWithName): String? {
         if (declaration.isPropertyAccessor ||

compiler/testData/codegen/box/lazyCodegen/ifElse.kt

@@ -1,6 +1,4 @@
 // IGNORE_BACKEND_FIR: JVM_IR
-// Name clashes
-// IGNORE_BACKEND: JS_IR
 
 class A (val p: String, p1: String, p2: String) {
 

compiler/testData/codegen/box/unit/ifElse.kt

@@ -1,6 +1,4 @@
 // IGNORE_BACKEND_FIR: JVM_IR
-// Name clashes
-// IGNORE_BACKEND: JS_IR
 
 class A (val p: String, p1: String, p2: String) {
 

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

@@ -6514,6 +6514,11 @@ public class IrBoxJsTestGenerated extends AbstractIrBoxJsTest {
             runTest("js/js.translator/testData/box/propertyAccess/propertyAssignment.kt");
         }
 
+        @TestMetadata("publicNameClash.kt")
+        public void testPublicNameClash() throws Exception {
+            runTest("js/js.translator/testData/box/propertyAccess/publicNameClash.kt");
+        }
+
         @TestMetadata("setter.kt")
         public void testSetter() throws Exception {
             runTest("js/js.translator/testData/box/propertyAccess/setter.kt");

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

@@ -6544,6 +6544,11 @@ public class BoxJsTestGenerated extends AbstractBoxJsTest {
             runTest("js/js.translator/testData/box/propertyAccess/propertyAssignment.kt");
         }
 
+        @TestMetadata("publicNameClash.kt")
+        public void testPublicNameClash() throws Exception {
+            runTest("js/js.translator/testData/box/propertyAccess/publicNameClash.kt");
+        }
+
         @TestMetadata("setter.kt")
         public void testSetter() throws Exception {
             runTest("js/js.translator/testData/box/propertyAccess/setter.kt");

js/js.translator/testData/box/inline/thisImplicitlyCaptured.kt

@@ -1,6 +1,3 @@
-// Name clashes
-// IGNORE_BACKEND: JS_IR
-
 // EXPECTED_REACHABLE_NODES: 1295
 package foo
 

js/js.translator/testData/box/propertyAccess/publicNameClash.kt

@@ -0,0 +1,27 @@
+// EXPECTED_REACHABLE_NODES: 1284
+
+// KT-33327
+
+class C {
+    var foo: String = "FAIL1"
+
+    fun foo(foo: String): C {
+        this.foo = foo
+        return this
+    }
+
+    @JsName("_bar")
+    var bar: String = "FAIL2"
+
+    fun bar(bar: String): C {
+        this.bar = bar
+        return this
+    }
+}
+
+fun box(): String {
+    val c = C()
+    c.foo("O").bar("K")
+
+    return c.foo + c.bar
+}