fix(KT-49225): remove unnecessery boxing.

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/ExportedDefaultParameterStub.kt

@@ -41,7 +41,7 @@ class ExportedDefaultParameterStub(val context: JsIrBackendContext) : Declaratio
             irIfThenElse(
                 toParameter.type,
                 irEqeqeq(
-                    irGet(toParameter),
+                    irGet(toParameter, context.irBuiltIns.anyNType),
                     irCall(this@ExportedDefaultParameterStub.context.intrinsics.jsUndefined)
                 ),
                 defaultValue.expression,

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/builders/ExpressionHelpers.kt

@@ -128,6 +128,8 @@ fun IrBuilderWithScope.irGet(type: IrType, variable: IrValueSymbol) =
 
 fun IrBuilderWithScope.irGet(variable: IrValueDeclaration) = irGet(variable.type, variable.symbol)
 
+fun IrBuilderWithScope.irGet(variable: IrValueDeclaration, type: IrType) = irGet(type, variable.symbol)
+
 fun IrBuilderWithScope.irSet(variable: IrValueSymbol, value: IrExpression, origin: IrStatementOrigin = IrStatementOrigin.EQ) =
     IrSetValueImpl(startOffset, endOffset, context.irBuiltIns.unitType, variable, value, origin)
 

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

@@ -2110,6 +2110,11 @@ public class IrBoxJsES6TestGenerated extends AbstractIrBoxJsES6Test {
             KtTestUtil.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("js/js.translator/testData/box/export"), Pattern.compile("^([^_](.+))\\.kt$"), null, TargetBackend.JS_IR_ES6, true);
         }
 
+        @TestMetadata("defaultInlineClassConstructorParam.kt")
+        public void testDefaultInlineClassConstructorParam() throws Exception {
+            runTest("js/js.translator/testData/box/export/defaultInlineClassConstructorParam.kt");
+        }
+
         @TestMetadata("exportAllFile.kt")
         public void testExportAllFile() throws Exception {
             runTest("js/js.translator/testData/box/export/exportAllFile.kt");

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

@@ -2105,6 +2105,11 @@ public class IrBoxJsTestGenerated extends AbstractIrBoxJsTest {
             KtTestUtil.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("js/js.translator/testData/box/export"), Pattern.compile("^([^_](.+))\\.kt$"), null, TargetBackend.JS_IR, true);
         }
 
+        @TestMetadata("defaultInlineClassConstructorParam.kt")
+        public void testDefaultInlineClassConstructorParam() throws Exception {
+            runTest("js/js.translator/testData/box/export/defaultInlineClassConstructorParam.kt");
+        }
+
         @TestMetadata("exportAllFile.kt")
         public void testExportAllFile() throws Exception {
             runTest("js/js.translator/testData/box/export/exportAllFile.kt");

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

@@ -1780,6 +1780,11 @@ public class BoxJsTestGenerated extends AbstractBoxJsTest {
             KtTestUtil.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("js/js.translator/testData/box/export"), Pattern.compile("^([^_](.+))\\.kt$"), null, TargetBackend.JS, true);
         }
 
+        @TestMetadata("defaultInlineClassConstructorParam.kt")
+        public void testDefaultInlineClassConstructorParam() throws Exception {
+            runTest("js/js.translator/testData/box/export/defaultInlineClassConstructorParam.kt");
+        }
+
         @TestMetadata("exportAllFile.kt")
         public void testExportAllFile() throws Exception {
             runTest("js/js.translator/testData/box/export/exportAllFile.kt");

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

@@ -0,0 +1,16 @@
+// KT-49225
+// RUN_PLAIN_BOX_FUNCTION
+// IGNORE_BACKEND: JS
+
+// MODULE: lib
+// FILE: lib.kt
+value class Koo(val koo: String = "OK")
+
+@JsExport
+class Bar(val koo: Koo = Koo())
+
+// MODULE: main(lib)
+// FILE: main.js
+function box() {
+    return new main.Bar().koo;
+}