compiler error for duplicate when choice labels

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

@@ -1141,12 +1141,18 @@ internal class AstChecker(private val program: Program,
         val conditionType = whenStatement.condition.inferType(program).typeOrElse(DataType.STRUCT)
         if(conditionType !in IntegerDatatypes)
             errors.err("when condition must be an integer value", whenStatement.position)
-        val choiceValues = whenStatement.choiceValues(program)
-        val occurringValues = choiceValues.map {it.first}
-        val tally = choiceValues.associate { it.second to occurringValues.count { ov->it.first==ov} }
-        tally.filter { it.value>1 }.forEach {
-            errors.err("choice value occurs multiple times", it.key.position)
+        val tally = mutableSetOf<Int>()
+        for((choices, choiceNode) in whenStatement.choiceValues(program)) {
+            if(choices!=null) {
+                for (c in choices) {
+                    if(c in tally)
+                        errors.err("choice value already occurs earlier", choiceNode.position)
+                    else
+                        tally.add(c)
+                }
+            }
         }
+
         if(whenStatement.choices.isEmpty())
             errors.err("empty when statement", whenStatement.position)
 

docs/source/todo.rst

@@ -2,8 +2,6 @@
 TODO
 ====
 
-- compiler error for double when labels
-
 - add sound to the cx16 tehtriz
 
 - add const arrays and cost strings

examples/test.p8

@@ -6,14 +6,19 @@ main {
 
 ;   $1F9C0 - $1F9FF 	PSG registers
 
-    sub init(uword addr, ubyte length) {
-        @(addr+length) = $ea
-    }
-
     sub start() {
 
-        init($4000, 0)
-        txt.print_uwhex(@($4000), true)
+        ubyte xx=33
+        when xx {
+            1 -> {
+            }
+            2 -> {
+            }
+            else -> {
+            }
+            else -> {
+            }
+        }
 
 ;        uword freq = 1181
 ;        cx16.vpoke(1, $f9c0, lsb(freq))