I recently changed my project to 1 9 20 Beta2 attempted to s

Question

I recently changed my project to 1 9 20 Beta2 attempted to start `compileProductionExecutableKotlinJs` gradle task and then received this error see comment for full stacktrace ```java lang ClassCastException class org jetbrains kotlin ir declarations impl IrTypeParameterImpl cannot be cast to class org jetbrains kotlin ir declarations IrClass org jetbrains kotlin ir declarations impl IrTypeParameterImpl and org jetbrains kotlin ir declarations IrClass are in unnamed module of loader app ``` it worked perfectly with 1 9 10 any workaround

Andrey Tabakov · Answer

```java lang ClassCastException class org jetbrains kotlin ir declarations impl IrTypeParameterImpl cannot be cast to class org jetbrains kotlin ir declarations IrClass org jetbrains kotlin ir declarations impl IrTypeParameterImpl and org jetbrains kotlin ir declarations IrClass are in unnamed module of loader app at org jetbrains kotlin ir backend js dce JsUsefulDeclarationProcessor$bodyVisitor$1 visitCall JsUsefulDeclarationProcessor kt 74 at org jetbrains kotlin ir backend js dce JsUsefulDeclarationProcessor$bodyVisitor$1 visitCall JsUsefulDeclarationProcessor kt 32 at org jetbrains kotlin ir expressions IrCall accept IrCall kt 26 at org jetbrains kotlin ir expressions IrReturn acceptChildren IrReturn kt 29 at org jetbrains kotlin ir backend js dce UsefulDeclarationProcessor$BodyVisitorBase visitElement UsefulDeclarationProcessor kt 43 at org jetbrains kotlin ir backend js dce UsefulDeclarationProcessor$BodyVisitorBase visitElement UsefulDeclarationProcessor kt 36 at org jetbrains kotlin ir visitors IrElementVisitor$DefaultImpls visitExpression IrElementVisitor kt 156 at org jetbrains kotlin ir backend js dce UsefulDeclarationProcessor$BodyVisitorBase visitExpression UsefulDeclarationProcessor kt 36 at org jetbrains kotlin ir backend js dce UsefulDeclarationProcessor$BodyVisitorBase visitExpression UsefulDeclarationProcessor kt 36 at org jetbrains kotlin ir visitors IrElementVisitor$DefaultImpls visitReturn IrElementVisitor kt 282 at org jetbrains kotlin ir backend js dce UsefulDeclarationProcessor$BodyVisitorBase visitReturn UsefulDeclarationProcessor kt 36 at org jetbrains kotlin ir backend js dce UsefulDeclarationProcessor$BodyVisitorBase visitReturn UsefulDeclarationProcessor kt 36 at org jetbrains kotlin ir expressions IrReturn accept IrReturn kt 26 at org jetbrains kotlin ir expressions IrBlockBody acceptChildren IrBlockBody kt 28 at org jetbrains kotlin ir backend js dce UsefulDeclarationProcessor$BodyVisitorBase visitElement UsefulDeclarationProcessor kt 43 at org jetbrains kotlin ir backend js dce UsefulDeclarationProcessor$BodyVisitorBase visitElement UsefulDeclarationProcessor kt 36 at org jetbrains kotlin ir visitors IrElementVisitor$DefaultImpls visitBody IrElementVisitor kt 159 at org jetbrains kotlin ir backend js dce UsefulDeclarationProcessor$BodyVisitorBase visitBody UsefulDeclarationProcessor kt 36 at org jetbrains kotlin ir backend js dce UsefulDeclarationProcessor$BodyVisitorBase visitBody UsefulDeclarationProcessor kt 36 at org jetbrains kotlin ir visitors IrElementVisitor$DefaultImpls visitBlockBody IrElementVisitor kt 163 at org jetbrains kotlin ir backend js dce UsefulDeclarationProcessor$BodyVisitorBase visitBlockBody UsefulDeclarationProcessor kt 36 at org jetbrains kotlin ir backend js dce UsefulDeclarationProcessor$BodyVisitorBase visitBlockBody UsefulDeclarationProcessor kt 36 at org jetbrains kotlin ir expressions IrBlockBody accept IrBlockBody kt 25 at org jetbrains kotlin ir backend js dce UsefulDeclarationProcessor collectDeclarations UsefulDeclarationProcessor kt 262 at org jetbrains kotlin ir backend js dce DceKt eliminateDeadDeclarations Dce kt 35 at org jetbrains kotlin ir backend js OptimizationsKt optimizeProgramByIr optimizations kt 26 at org jetbrains kotlin ir backend js transformers irToJs IrModuleToJsTransformer makeJsCodeGenerator IrModuleToJsTransformer kt 201 at org jetbrains kotlin cli js K2JsIrCompiler$Ir2JsTransformer makeJsCodeGenerator K2JsIrCompiler kt 130 at org jetbrains kotlin cli js K2JsIrCompiler$Ir2JsTransformer compileAndTransformIrNew K2JsIrCompiler kt 134 at org jetbrains kotlin cli js K2JsIrCompiler doExecute K2JsIrCompiler kt 391 at org jetbrains kotlin cli js K2JSCompiler doExecute K2JSCompiler java 181 at org jetbrains kotlin cli js K2JSCompiler doExecute K2JSCompiler java 72 at org jetbrains kotlin cli common CLICompiler execImpl CLICompiler kt 104 at org jetbrains kotlin cli common CLICompiler execImpl CLICompiler kt 48 at org jetbrains kotlin cli common CLITool exec CLITool kt 101 at org jetbrains kotlin daemon CompileServiceImpl compile CompileServiceImpl kt 1523 ```

Andrey Tabakov · Answer

it fails even with ```js IR browser dceTask this dceOptions devMode = true ```

anton.bannykh · Answer

cc < Artem Kobzar>

Ilya Goncharov [JB] · Answer

BTW `dceTask` is senseless with IR compiler It worked only with legacy compiler For IR you can manage via `development` or `production` task `production` task run with DCE and minification of member names

andylamax · Answer

< Ilya Goncharov JB > does production run with DCE even for `binaries libraries `

Ilya Goncharov [JB] · Answer

< andylamax> Yes DCE works for all `compileProduction KotlinJs`