restored proper compiler error when trying to modify a constant

compiler/src/prog8/optimizer/ConstantFolding.kt

@@ -167,6 +167,15 @@ class ConstantFolding(private val program: Program) : IAstModifyingVisitor {
      * replace identifiers that refer to const value, with the value itself (if it's a simple type)
      */
     override fun visit(identifier: IdentifierReference): Expression {
+        // don't replace when it's an assignment target or loop variable
+        if(identifier.parent is AssignTarget)
+            return identifier
+        var forloop = identifier.parent as? ForLoop
+        if(forloop==null)
+            forloop = identifier.parent.parent as? ForLoop
+        if(forloop!=null && identifier===forloop.loopVar)
+            return identifier
+
         return try {
             val cval = identifier.constValue(program) ?: return identifier
             return when {

examples/tehtriz.p8

@@ -9,9 +9,6 @@
 ;
 ; @todo show ghost?
 
-
-; TODO FIX COMPILATION ERROR  can't change class of loopvar
-
 main {
 
     const ubyte boardOffsetX = 14
@@ -354,8 +351,8 @@ waitkey:
     sub drawNextBlock() {
         const ubyte nextBlockXpos = 29
         const ubyte nextBlockYpos = 5
-        const ubyte x = 33
-        for x in nextBlockXpos+3 to nextBlockXpos step -1 {     ; TODO error because const
+        ubyte x
+        for x in nextBlockXpos+3 to nextBlockXpos step -1 {
             c64scr.setcc(x, nextBlockYpos, ' ', 0)
             c64scr.setcc(x, nextBlockYpos+1, ' ', 0)
         }

examples/test.p8

@@ -6,19 +6,18 @@ main {
 
     sub start() {
 
-        ubyte i
+        const ubyte i = 33
 
-        for i in [1,3,5,99] {
-            c64scr.print_ub(i)
-            c64.CHROUT(',')
+        i=33
+        i++
+        const ubyte q=33
+        for q in [1,3,5,99] {
+            A=i
         }
-        c64.CHROUT('\n')
 
-        for A in [1,3,5,99] {
-            c64scr.print_ub(A)
-            c64.CHROUT(',')
+        while q<10 {
+            q++
         }
-        c64.CHROUT('\n')
 
     }
 }

examples/testarrays.p8

@@ -2,10 +2,6 @@
 %zeropage basicsafe
 %option enable_floats
 
-; TODO complete asm code generation for all lines in this
-
-
-
 main {
 
     sub start() {
@@ -34,8 +30,6 @@ main {
         float fl
 
         ; read array
-        @($d020) = ub
-
         A=s1[2]
         ub=s1[2]
         ub=s2[2]

examples/testforloops.p8

@@ -17,7 +17,7 @@ main {
         }
         c64.CHROUT('\n')
 
-        for A in [1,3,5,99] {           ; TODO FIX COMPILER ERROR array should have been moved to the heap
+        for A in [1,3,5,99] {
             c64scr.print_ub(A)
             c64.CHROUT(',')
         }