add check for not yet implement long expression comparisons

codeGenCpu6502/src/prog8/codegen/cpu6502/IfElseAsmGen.kt

@@ -1492,6 +1492,11 @@ _jump                       jmp  (${target.asmLabel})
         stmt: PtIfElse
     ) {
         // this comparison is not part of an expression but part of an if statement, there's no need to save the previous values of the temp registers
+
+        if(left !is PtNumber && left !is PtIdentifier || right !is PtNumber && right !is PtIdentifier) {
+            TODO("long comparison $operator with expressions - use temporary long variable instead to simplify for now   ${left.position}")
+        }
+
         if(operator=="<" || operator ==">=") {
             assignmentAsmGen.assignExpressionToRegister(right, RegisterOrPair.R14R15_32, left.type.isSigned)
             assignmentAsmGen.assignExpressionToRegister(left, RegisterOrPair.R12R13_32, left.type.isSigned)

docs/source/todo.rst

@@ -9,6 +9,7 @@ TODO
 
 Future Things and Ideas
 ^^^^^^^^^^^^^^^^^^^^^^^
+- implement rest of long comparisons in IfElseAsmGen compareLongValues(): expressions operands that might clobber the R14-R15 registers...
 - struct/ptr: implement the remaining TODOs in PointerAssignmentsGen.
 - struct/ptr: optimize deref in PointerAssignmentsGen: optimize 'forceTemporary' to only use a temporary when the offset is >0
 - struct/ptr: optimize the float copying in assignIndexedPointer() (also word and long?)