anchor.diff:      ;
   
   else_statement
  -    :   { "else".equals(input.LT(1).getText()) }? ELSE java_statement
  +    :   { "else".equals(_input.LT(1).getText()) }? ELSE java_statement
       ;
   
   switch_block_statement_groups
  
positive.code: // Need to handle the conflicts of BQL keywords and common Java method
  // names supported by BQL.
  java_method
      :   { "contains".equals(input.LT(1).getText()) }? CONTAINS
      |   IDENT
      ;
  
  
negative.code:     ;
  
  boolean_literal
      :   { "true".equals(_input.LT(1).getText()) }? TRUE
      |   { "false".equals(_input.LT(1).getText()) }? FALSE
      ;
  
  selector
  