added footgun warning when calling labels as subroutine

compiler/src/prog8/compiler/astprocessing/AstChecker.kt

@@ -1522,8 +1522,11 @@ internal class AstChecker(private val program: Program,
             }
         }
 
-        if(target is Label && args.isNotEmpty())
-            errors.err("cannot use arguments when calling a label", position)
+        if (target is Label) {
+            errors.warn("\uD83D\uDCA3 footgun: calling label as subroutine (JSR) is tricky", position)
+            if (args.isNotEmpty())
+                errors.err("cannot use arguments when calling a label", position)
+        }
 
         if(target is Subroutine) {
             if(target.isAsmSubroutine) {

docs/source/programming.rst

@@ -63,10 +63,11 @@ Subroutine
 
 Label
     This is a named position in your code where you can jump to from another place.
-    You can jump to it with a jump statement elsewhere. It is also possible to use a
-    subroutine call to a label (but without parameters and return value).
     A label is an identifier followed by a colon ``:``. It's ok to put the next statement on
     the same line, immediately after the label.
+    You can jump to it with a goto statement. It is also possible to use a
+    subroutine call to a label (but without parameters and return value), however 🦶🔫 footgun warning:
+    doing that is tricky because it makes for weird control flow and interferes with defers.
 
 Scope
     Also known as 'namespace', this is a named box around the symbols defined in it.

examples/test.p8

@@ -3,6 +3,7 @@
 
 main {
   sub start() {
+    defer txt.print("defer\n")
     txt.print("1\n")
     label()
     txt.print("2\n")