improve error message for non-numeric when choice values

compiler/src/prog8/compiler/astprocessing/AstChecker.kt

@@ -1663,7 +1663,7 @@ internal class AstChecker(private val program: Program,
             val constvalues = whenChoice.values!!.map { it.constValue(program) to it.position }
             for((constvalue, pos) in constvalues) {
                 when {
-                    constvalue == null -> errors.err("choice value must be a constant", pos)
+                    constvalue == null -> errors.err("choice values must be constant numbers", pos)
                     !constvalue.type.isIntegerOrBool -> errors.err("choice value must be a byte or word", pos)
                     !(conditionType issimpletype constvalue.type) -> {
                         if(conditionType.isKnown) {

docs/source/todo.rst

@@ -12,6 +12,7 @@ TODO
 Future Things and Ideas
 ^^^^^^^^^^^^^^^^^^^^^^^
 
+- allow integer range as when choice? because 1,2,3,4,5 is already allowed, so perhaps 1 to 5 should be allowed too? However, [1,2,3,4,5] usually is the desugared equivalent of 1 to 5 and choice values can't be arrays.
 - const values should always either be of type long or float, this is how they were usually treated in const expression evaluation already anyway
 - Kotlin: can we use inline value classes in certain spots?
 - add float support to the configurable compiler targets