better error message

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

@@ -1039,7 +1039,10 @@ internal class AstChecker(private val program: Program,
         val targetStatement = target.targetStatement(program.namespace)
         if(targetStatement is Label || targetStatement is Subroutine || targetStatement is BuiltinFunctionStatementPlaceholder)
             return targetStatement
-        errors.err("undefined function or subroutine: ${target.nameInSource.joinToString(".")}", statement.position)
+        else if(targetStatement==null)
+            errors.err("undefined function or subroutine: ${target.nameInSource.joinToString(".")}", statement.position)
+        else
+            errors.err("cannot call that: ${target.nameInSource.joinToString(".")}", statement.position)
         return null
     }
 

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

@@ -22,6 +22,9 @@ internal class AstIdentifiersChecker(private val program: Program, private val e
     }
 
     override fun visit(block: Block) {
+        if(block.name in CompilationTarget.machine.opcodeNames)
+            errors.err("can't use a cpu opcode name as a symbol: '${block.name}'", block.position)
+
         val existing = blocks[block.name]
         if(existing!=null)
             nameError(block.name, block.position, existing)

examples/test.p8

@@ -10,28 +10,10 @@ main {
     sub start() {
 
         byte nop2
-
         nop2=4
-        nop2++
-        foo.xxx()
 
-    derp:
-        goto main.nop2
-        main.nop2()
-    }
-
-    sub nop2 () {
-        c64.CHROUT('\n')
+        ; nop2()  ; better error
+        nop2()
     }
 }
 
-foo {
-
-    sub xxx() {
-
-    bar:
-        goto bar
-    }
-
-
-}