[JS IR] Use separate origin for class reference to preserve constructors

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/Dce.kt

@@ -10,6 +10,7 @@ import org.jetbrains.kotlin.ir.IrElement
 import org.jetbrains.kotlin.ir.UNDEFINED_OFFSET
 import org.jetbrains.kotlin.ir.backend.js.export.isExported
 import org.jetbrains.kotlin.ir.backend.js.ir.JsIrBuilder
+import org.jetbrains.kotlin.ir.backend.js.lower.ClassReferenceLowering
 import org.jetbrains.kotlin.ir.backend.js.utils.*
 import org.jetbrains.kotlin.ir.declarations.*
 import org.jetbrains.kotlin.ir.expressions.*
@@ -385,6 +386,13 @@ fun usefulDeclarations(roots: Iterable<IrDeclaration>, context: JsIrBackendConte
                             val ref = expression.getTypeArgument(0)!!.classifierOrFail.owner as IrDeclaration
                             ref.enqueue("intrinsic: jsClass")
                             referencedJsClasses += ref
+                            if (expression.origin == ClassReferenceLowering.Companion.CLASS_REFERENCE) {
+                                (ref as IrClass)
+                                    .constructors
+                                    .forEach {
+                                        it.enqueue("intrinsic: jsClass constructor")
+                                    }
+                            }
                         }
                         context.intrinsics.jsGetKClassFromExpression -> {
                             val ref = expression.getTypeArgument(0)?.classOrNull ?: context.irBuiltIns.anyClass

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/ir/IrBuilder.kt

@@ -21,7 +21,12 @@ object JsIrBuilder {
     object SYNTHESIZED_STATEMENT : IrStatementOriginImpl("SYNTHESIZED_STATEMENT")
     object SYNTHESIZED_DECLARATION : IrDeclarationOriginImpl("SYNTHESIZED_DECLARATION")
 
-    fun buildCall(target: IrSimpleFunctionSymbol, type: IrType? = null, typeArguments: List<IrType>? = null): IrCall {
+    fun buildCall(
+        target: IrSimpleFunctionSymbol,
+        type: IrType? = null,
+        typeArguments: List<IrType>? = null,
+        origin: IrStatementOrigin = SYNTHESIZED_STATEMENT
+    ): IrCall {
         val owner = target.owner
         return IrCallImpl(
             UNDEFINED_OFFSET,
@@ -30,7 +35,7 @@ object JsIrBuilder {
             target,
             typeArgumentsCount = owner.typeParameters.size,
             valueArgumentsCount = owner.valueParameters.size,
-            origin = SYNTHESIZED_STATEMENT
+            origin = origin
         ).apply {
             typeArguments?.let {
                 assert(typeArguments.size == typeArgumentsCount)

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

@@ -127,7 +127,11 @@ class ClassReferenceLowering(val context: JsIrBackendContext) : BodyLoweringPass
     }
 
     private fun callJsClass(type: IrType) =
-        JsIrBuilder.buildCall(intrinsics.jsClass, typeArguments = listOf(type))
+        JsIrBuilder.buildCall(
+            intrinsics.jsClass,
+            typeArguments = listOf(type),
+            origin = CLASS_REFERENCE
+        )
 
     private fun buildCall(name: IrSimpleFunctionSymbol, vararg args: IrExpression): IrExpression =
         JsIrBuilder.buildCall(name).apply {
@@ -252,5 +256,9 @@ class ClassReferenceLowering(val context: JsIrBackendContext) : BodyLoweringPass
                 }
         })
     }
+
+    companion object {
+        object CLASS_REFERENCE : IrStatementOriginImpl("CLASS_REFERENCE")
+    }
 }