improve argument/option declaration

src/commonMain/kotlin/com/infendro/cli/command/Command.kt

@@ -1,11 +1,13 @@
 package com.infendro.cli.command
 
+import com.infendro.cli.Dsl
 import com.infendro.cli.command.context.Context
 import com.infendro.cli.command.context.Parser
 import com.infendro.cli.exception.build.*
 import com.infendro.cli.exception.run.CliException
 import com.infendro.cli.util.Regex.COMMAND
 import com.infendro.cli.util.Regex.OPTION
+import kotlin.reflect.KProperty
 
 class Command private constructor(
     val name: String?,
@@ -23,6 +25,7 @@ class Command private constructor(
         println(e.message)
     }
 
+    @Dsl
     class Builder internal constructor(
         private val level: Int,
         private val name: String?,
@@ -68,10 +71,10 @@ class Command private constructor(
             arguments += argument
         }
 
-        fun <T : Argument<*>> T.register() = also(::argument)
-
         fun arguments(vararg arguments: Argument<*>) = arguments.forEach(::argument)
-        fun <T : Argument<*>> Array<T>.register() = also(::arguments)
+
+        operator fun <T : Argument<*>> T.provideDelegate(thisRef: Nothing?, property: KProperty<*>) = also(::argument)
+        operator fun <T : Argument<*>> T.getValue(thisRef: Nothing?, property: KProperty<*>) = this
 
         fun option(option: Option<*>) {
             // validate
@@ -85,10 +88,10 @@ class Command private constructor(
             options += option
         }
 
-        fun <T : Option<*>> T.register() = also(::option)
-
         fun options(vararg options: Option<*>) = options.forEach(::option)
-        fun <T : Option<*>> Array<T>.register() = also(::options)
+
+        operator fun <T : Option<*>> T.provideDelegate(thisRef: Nothing?, property: KProperty<*>) = also(::option)
+        operator fun <T : Option<*>> T.getValue(thisRef: Nothing?, property: KProperty<*>) = this
 
         fun execute(block: Context.() -> Unit) {
             if (::_execute.isInitialized)