allow when with byte 1,2,3 for word variables without having to cast the values to word explicitly

compiler/src/prog8/compiler/astprocessing/TypecastsAdder.kt

@@ -375,6 +375,21 @@ class TypecastsAdder(val program: Program, val options: CompilationOptions, val
         return noModifications
     }
 
+    override fun after(whenChoice: WhenChoice, parent: Node): Iterable<IAstModification> {
+        if((parent as When).condition.inferType(program).isWords) {
+            val values = whenChoice.values
+            values?.toTypedArray()?.withIndex()?.forEach { (index, value) ->
+                val num = value.constValue(program)
+                if(num!=null && num.type in ByteDatatypes) {
+                    val wordNum = NumericLiteral(if(num.type==DataType.UBYTE) DataType.UWORD else DataType.WORD, num.number, num.position)
+                    wordNum.parent = num.parent
+                    values[index] = wordNum
+                }
+            }
+        }
+        return noModifications
+    }
+
     private fun addTypecastOrCastedValueModification(
         modifications: MutableList<IAstModification>,
         expressionToCast: Expression,

compiler/test/TestTypecasts.kt

@@ -1001,4 +1001,19 @@ main  {
         compileText(VMTarget(), false, text, writeAssembly = true) shouldNotBe null
         compileText(VMTarget(), true, text, writeAssembly = true) shouldNotBe null
     }
+
+    test("byte when choices silently converted to word for convenience") {
+        var text="""
+main {
+  sub start() {
+    uword z = 3
+    when z {
+        1-> z++
+        2-> z++
+        else -> z++
+    }
+  }
+}"""
+        compileText(C64Target(), false, text, writeAssembly = false) shouldNotBe null
+    }
 })

compiler/test/ast/TestProg8Parser.kt

@@ -311,7 +311,7 @@ class TestProg8Parser: FunSpec( {
                     sub start() {
                         ubyte foo = 42
                         ubyte bar
-                        when (foo) {
+                        when foo {
                             23 -> bar = 'x'
                             42 -> bar = 'y'
                             else -> bar = 'z'