add this in your module.ts,
declarations: [ AppComponent , VariantComponentDirective ]
if VariantComponentDirective is in another module, you need to export it there thus you can use it outside, add :
exports: [ VariantComponentDirective ]

add this in your module.ts,

declarations: [ AppComponent , ConfirmComponent ] if ConfirmComponent is in another module, you need to export it there thus you can use it outside, add :
exports: [ ConfirmComponent ]