compiler checks for conflicting register usage in sub arguments vs target parameter registers

compiler/src/prog8/ast/processing/AstChecker.kt

@@ -1039,6 +1039,28 @@ internal class AstChecker(private val program: Program,
                     if (!argIDt.isKnown)
                         return
                 }
+
+                // check that cx16 virtual registers aren't used as arguments in a conflicting way
+                val params = target.asmParameterRegisters.withIndex().toList()
+                for(arg in args.withIndex()) {
+                    var ident: IdentifierReference? = null
+                    if(arg.value is IdentifierReference)
+                        ident = arg.value as IdentifierReference
+                    else if(arg.value is FunctionCall) {
+                        val fcall = arg.value as FunctionCall
+                        if(fcall.target.nameInSource == listOf("lsb") || fcall.target.nameInSource == listOf("msb"))
+                            ident = fcall.args[0] as? IdentifierReference
+                    }
+                    if(ident!=null && ident.nameInSource[0] == "cx16" && ident.nameInSource[1].startsWith("r")) {
+                        val reg = RegisterOrPair.valueOf(ident.nameInSource[1].toUpperCase())
+                        val same = params.filter { it.value.registerOrPair==reg }
+                        for(s in same) {
+                            if(s.index!=arg.index) {
+                                errors.err("conflicting register $reg used as argument but is also a target register for another parameter", ident.position)
+                            }
+                        }
+                    }
+                }
             }
         }
     }

examples/test.p8

@@ -4,12 +4,6 @@
 main {
 
     sub start() {
-        ubyte bank
-
-        ; TODO give error that a register is used as an argument value and at the same time is a register parameter taking a new value.
-        ;      (note: this is OK if the  register is used as an argument for a register param that is the same register)
-        cx16.vaddr(lsb(cx16.r1), cx16.r0, 0, 1)
-
         txt.print("hello")
     }
 }