anchor.diff:  
   scope StmtScope {
       insideTarget;
  +    insideConfig;
   }
   
   
  
positive.code:     | ':' literal  -> ^(BASE_LIST literal)
      ;
  
  configuration_content : '{' assignment_stmt* '}' -> assignment_stmt*;
  
  
  // ---------------------------------------------------------------------------
  
negative.code: 
  program
  scope StmtScope;
  @init {
      $StmtScope::insideTarget = False
      $StmtScope::insideConfig = False
  }
      : introductory_stmt* stmt* EOF -> ^(PROGRAM introductory_stmt* stmt*);
  
  stmt
      : stmt_always_allowed
      | {$StmtScope::insideTarget}?=> stmt_inside_target
      // {$StmtScope::insideConfig}?=> ...nothing extra here...
      | {not $StmtScope::insideTarget and not $StmtScope::insideConfig}?=> stmt_global_scope
      | ';' -> // empty statement
      ;
  
  // statements allowed in any context
  stmt_always_allowed
      : assignment_stmt
      | if_stmt
      ;
  
  // statements only allowed outside target definition:
  stmt_global_scope
      : target_stmt
      | submodule_stmt
      | import_stmt
  