Fix translation of delegated functions with default params in JS BE

See KT-17285

compiler/testData/codegen/box/delegation/withDefaultParameters.kt

@@ -0,0 +1,60 @@
+// IGNORE_BACKEND: JVM
+
+var log = ""
+fun log(a: String) {
+    log += a + ";"
+}
+
+interface C {
+    fun foo(x: Int): Unit {
+        log("C.foo($x)")
+    }
+}
+
+interface I {
+    fun foo(x: Int = 1): Unit
+}
+
+class G(c: C) : C by c, I
+class H(c: C) : I, C by c
+
+fun test1() {
+    log = ""
+
+    val g1 = G(object: C {})
+    g1.foo(2)
+    g1.foo()
+    val g2 = G(object: C {
+        override fun foo(x: Int) {
+            log("[2] object:C.foo($x)")
+        }
+    })
+    g2.foo(2)
+    g2.foo()
+}
+
+fun test2() {
+    log = ""
+
+    val h1 = H(object: C {})
+    h1.foo(2)
+    h1.foo()
+    val h2 = H(object: C {
+        override fun foo(x: Int) {
+            log("[2] object:C.foo($x)")
+        }
+    })
+    h2.foo(2)
+    h2.foo()
+}
+
+
+fun box(): String {
+    test1()
+    if (log != "C.foo(2);C.foo(1);[2] object:C.foo(2);[2] object:C.foo(1);") return "fail1: $log"
+
+    test2()
+    if (log != "C.foo(2);C.foo(1);[2] object:C.foo(2);[2] object:C.foo(1);") return "fail2: $log"
+
+    return "OK"
+}

compiler/tests-ir-jvm/tests/org/jetbrains/kotlin/codegen/ir/IrBlackBoxCodegenTestGenerated.java

@@ -7075,6 +7075,18 @@ public class IrBlackBoxCodegenTestGenerated extends AbstractIrBlackBoxCodegenTes
             String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/delegation/kt8154.kt");
             doTest(fileName);
         }
+
+        @TestMetadata("withDefaultParameters.kt")
+        public void testWithDefaultParameters() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/delegation/withDefaultParameters.kt");
+            try {
+                doTest(fileName);
+            }
+            catch (Throwable ignore) {
+                return;
+            }
+            throw new AssertionError("Looks like this test can be unmuted. Remove IGNORE_BACKEND directive for that.");
+        }
     }
 
     @TestMetadata("compiler/testData/codegen/box/destructuringDeclInLambdaParam")

compiler/tests/org/jetbrains/kotlin/codegen/BlackBoxCodegenTestGenerated.java

@@ -7075,6 +7075,18 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
             String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/delegation/kt8154.kt");
             doTest(fileName);
         }
+
+        @TestMetadata("withDefaultParameters.kt")
+        public void testWithDefaultParameters() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/delegation/withDefaultParameters.kt");
+            try {
+                doTest(fileName);
+            }
+            catch (Throwable ignore) {
+                return;
+            }
+            throw new AssertionError("Looks like this test can be unmuted. Remove IGNORE_BACKEND directive for that.");
+        }
     }
 
     @TestMetadata("compiler/testData/codegen/box/destructuringDeclInLambdaParam")

compiler/tests/org/jetbrains/kotlin/codegen/LightAnalysisModeTestGenerated.java

@@ -7048,6 +7048,18 @@ public class LightAnalysisModeTestGenerated extends AbstractLightAnalysisModeTes
     @TestDataPath("$PROJECT_ROOT")
     @RunWith(JUnit3RunnerWithInners.class)
     public static class Delegation extends AbstractLightAnalysisModeTest {
+        @TestMetadata("withDefaultParameters.kt")
+        public void ignoreWithDefaultParameters() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/delegation/withDefaultParameters.kt");
+            try {
+                doTest(fileName);
+            }
+            catch (Throwable ignore) {
+                return;
+            }
+            throw new AssertionError("Looks like this test can be unmuted. Remove IGNORE_BACKEND directive for that.");
+        }
+
         public void testAllFilesPresentInDelegation() throws Exception {
             KotlinTestUtils.assertAllTestsPresentByMetadata(this.getClass(), new File("compiler/testData/codegen/box/delegation"), Pattern.compile("^(.+)\\.kt$"), TargetBackend.JVM, true);
         }

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

@@ -7879,6 +7879,12 @@ public class JsCodegenBoxTestGenerated extends AbstractJsCodegenBoxTest {
             String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/delegation/kt8154.kt");
             doTest(fileName);
         }
+
+        @TestMetadata("withDefaultParameters.kt")
+        public void testWithDefaultParameters() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/delegation/withDefaultParameters.kt");
+            doTest(fileName);
+        }
     }
 
     @TestMetadata("compiler/testData/codegen/box/destructuringDeclInLambdaParam")

js/js.translator/src/org/jetbrains/kotlin/js/translate/declaration/ClassModelGenerator.kt

@@ -192,7 +192,8 @@ class ClassModelGenerator(val context: StaticContext) {
             val sourceName = context.getNameForDescriptor(key).ident
             val targetName = context.getNameForDescriptor(value).ident
             if (sourceName != targetName) {
-                model.postDeclarationBlock.statements += generateDelegateCall(descriptor, key, value, JsLiteral.THIS, translationContext)
+                val statement = generateDelegateCall(descriptor, key, value, JsLiteral.THIS, translationContext, false)
+                model.postDeclarationBlock.statements += statement
             }
         }
     }
@@ -228,7 +229,7 @@ class ClassModelGenerator(val context: StaticContext) {
 
         val translationContext = TranslationContext.rootContext(context)
         model.postDeclarationBlock.statements += generateDelegateCall(descriptor, fromDescriptor, toDescriptor, JsLiteral.THIS,
-                                                                      translationContext)
+                                                                      translationContext, false)
     }
 
     private fun copyMethod(

js/js.translator/src/org/jetbrains/kotlin/js/translate/declaration/DelegationTranslator.kt

@@ -196,6 +196,7 @@ class DelegationTranslator(
             delegateName: JsName
     ) {
         val delegateRef = JsNameRef(delegateName, JsLiteral.THIS)
-        context().addDeclarationStatement(generateDelegateCall(classDescriptor, descriptor, overriddenDescriptor, delegateRef, context()))
+        val statement = generateDelegateCall(classDescriptor, descriptor, overriddenDescriptor, delegateRef, context(), true)
+        context().addDeclarationStatement(statement)
     }
 }

js/js.translator/src/org/jetbrains/kotlin/js/translate/utils/utils.kt

@@ -35,6 +35,7 @@ import org.jetbrains.kotlin.js.translate.reference.ReferenceTranslator
 import org.jetbrains.kotlin.js.translate.utils.TranslationUtils.simpleReturnFunction
 import org.jetbrains.kotlin.resolve.BindingContext
 import org.jetbrains.kotlin.resolve.DescriptorUtils
+import org.jetbrains.kotlin.resolve.descriptorUtil.hasOrInheritsParametersWithDefaultValue
 import org.jetbrains.kotlin.types.KotlinType
 
 fun generateDelegateCall(
@@ -42,9 +43,18 @@ fun generateDelegateCall(
         fromDescriptor: FunctionDescriptor,
         toDescriptor: FunctionDescriptor,
         thisObject: JsExpression,
-        context: TranslationContext
+        context: TranslationContext,
+        detectDefaultParameters: Boolean
 ): JsStatement {
-    val overriddenMemberFunctionName = context.getNameForDescriptor(toDescriptor)
+    fun FunctionDescriptor.getNameForFunctionWithPossibleDefaultParam() =
+            if (detectDefaultParameters && hasOrInheritsParametersWithDefaultValue()) {
+                context.scope().declareName(context.getNameForDescriptor(this).ident + Namer.DEFAULT_PARAMETER_IMPLEMENTOR_SUFFIX)
+            }
+            else {
+                context.getNameForDescriptor(this)
+            }
+
+    val overriddenMemberFunctionName = toDescriptor.getNameForFunctionWithPossibleDefaultParam()
     val overriddenMemberFunctionRef = JsNameRef(overriddenMemberFunctionName, thisObject)
 
     val parameters = SmartList<JsParameter>()
@@ -71,10 +81,14 @@ fun generateDelegateCall(
         JsInvocation(overriddenMemberFunctionRef, args)
     }
 
-    val functionObject = simpleReturnFunction(context.getScopeForDescriptor(fromDescriptor), invocation)
+    val functionObject = simpleReturnFunction(context.scope(), invocation)
     functionObject.parameters.addAll(parameters)
 
-    return context.addFunctionToPrototype(classDescriptor, fromDescriptor, functionObject)
+    val fromFunctionName = fromDescriptor.getNameForFunctionWithPossibleDefaultParam()
+
+    val prototypeRef = JsAstUtils.prototypeOf(context.getInnerReference(classDescriptor))
+    val functionRef = JsNameRef(fromFunctionName, prototypeRef)
+    return JsAstUtils.assignment(functionRef, functionObject).makeStmt()
 }
 
 fun <T, S> List<T>.splitToRanges(classifier: (T) -> S): List<Pair<List<T>, S>> {