fix(KT-39423): add support of optional parameters to constructor + fix bug with optional parameters inside functions.

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

@@ -66,7 +66,6 @@ class ExportedDefaultParameterStub(val context: JsIrBackendContext) : Declaratio
                     variables[valueParameter] = it
                 }
             }
-
         }
 
         if (variables.isNotEmpty()) {
@@ -79,7 +78,13 @@ class ExportedDefaultParameterStub(val context: JsIrBackendContext) : Declaratio
         }
 
 
-        return this
+        return also {
+            valueParameters.forEach {
+                if (it.defaultValue != null) {
+                    it.origin = JsLoweredDeclarationOrigin.JS_SHADOWED_DEFAULT_PARAMETER
+                }
+            }
+        }
     }
 
     override fun transformFlat(declaration: IrDeclaration): List<IrDeclaration>? {
@@ -113,8 +118,12 @@ class ExportedDefaultParameterStub(val context: JsIrBackendContext) : Declaratio
         exportedDefaultStubFun.copyParameterDeclarationsFrom(declaration)
         exportedDefaultStubFun.returnType = declaration.returnType.remapTypeParameters(declaration, exportedDefaultStubFun)
         exportedDefaultStubFun.valueParameters.forEach {
+            if (it.defaultValue != null) {
+                it.origin = JsLoweredDeclarationOrigin.JS_SHADOWED_DEFAULT_PARAMETER
+            }
+
             it.defaultValue = null
-            it.origin = JsLoweredDeclarationOrigin.JS_SHADOWED_DEFAULT_PARAMETER
+
         }
 
         declaration.origin = JsLoweredDeclarationOrigin.JS_SHADOWED_EXPORT

js/js.translator/testData/typescript-export/constructors/constructors.d.ts

@@ -33,7 +33,7 @@ declare namespace JS_TESTS {
         static delegateToCreateFromInts(y: number, z: number): DerivedClassWithSecondaryCtor;
     }
     class KotlinGreeter {
-        constructor(greeting: string);
+        constructor(greeting?: string);
         get greeting(): string;
     }
 }

js/js.translator/testData/typescript-export/declarations/declarations.d.ts

@@ -13,7 +13,7 @@ declare namespace JS_TESTS {
         function varargWithOtherParameters(x: string, y: Array<string>, z: string): number;
         function varargWithComplexType(x: Array<(p0: Array<Int32Array>) => Array<Int32Array>>): number;
         function sumNullable(x: Nullable<number>, y: Nullable<number>): number;
-        function defaultParameters(x?: number, y?: string): string;
+        function defaultParameters(a: string, x?: number, y?: string): string;
         function generic1<T>(x: T): T;
         function generic2<T>(x: Nullable<T>): boolean;
         function genericWithConstraint<T extends string>(x: T): T;
@@ -187,5 +187,16 @@ declare namespace JS_TESTS {
                 get value(): number;
             }
         }
+        class KT39423 {
+            constructor(a: string, b?: Nullable<number>);
+            get a(): string;
+            get b(): Nullable<number>;
+            component1(): string;
+            component2(): Nullable<number>;
+            copy(a?: string, b?: Nullable<number>): foo.KT39423;
+            toString(): string;
+            hashCode(): number;
+            equals(other: Nullable<any>): boolean;
+        }
     }
 }

js/js.translator/testData/typescript-export/declarations/declarations.kt

@@ -35,8 +35,8 @@ fun sumNullable(x: Int?, y: Int?): Int =
     (x ?: 0) + (y ?: 0)
 
 @JsExport
-fun defaultParameters(x: Int = 10, y: String = "OK"): String =
-    x.toString() + y
+fun defaultParameters(a: String, x: Int = 10, y: String = "OK"): String =
+    a + x.toString() + y
 
 @JsExport
 fun <T> generic1(x: T): T = x
@@ -250,4 +250,10 @@ class __JsNameTest private constructor() {
 
     @JsName("NestedJsName")
     class __NestJsNameTest(@JsName("value") val __value: Int)
-}
+}
+
+@JsExport
+data class KT39423(
+    val a: String,
+    val b: Int? = null
+)

js/js.translator/testData/typescript-export/declarations/declarations__main.js

@@ -51,7 +51,7 @@ function box() {
     assert(sumNullable(10, null) === 10);
     assert(sumNullable(undefined, 20) === 20);
     assert(sumNullable(1, 2) === 3);
-    assert(defaultParameters(20, "OK") === "20OK");
+    assert(defaultParameters("", 20, "OK") === "20OK");
     assert(generic1("FOO") === "FOO");
     assert(generic1({ x: 10 }).x === 10);
     assert(generic2(null) === true);

js/js.translator/testData/typescript-export/declarations/declarations__main.ts

@@ -54,7 +54,7 @@ function box(): string {
     assert(sumNullable(10, null) === 10);
     assert(sumNullable(undefined, 20) === 20);
     assert(sumNullable(1, 2) === 3);
-    assert(defaultParameters(20, "OK") === "20OK");
+    assert(defaultParameters("", 20, "OK") === "20OK");
     assert(generic1<string>("FOO") === "FOO");
     assert(generic1({x: 10}).x === 10);
     assert(generic2(null) === true);