anchor.diff:   */
   
   expr_stmt
  -    : expr              # ExprStmtExpr
  -    | NAME '=' expr     # ExprStmtAssign
  -    ;
  -
  +    : test                # ExprStmtExpr
  +    | NAME '=' test       # ExprStmtAssign
  +    | NAME augassign test # ExprStmtAugmented
  +    ;
  +
  +augassign : '+=' | '-=' | '*=' | '/=' | '%='
  +          | '<<=' | '>>=' | '&=' | '|=' | '^='
  +          ;
   //expr_stmt
  -//    : expr ('=' expr)?;
  +//    : testlist_expr  ( '=' ( testlist_expr ) )*
  +//    ;
  +
   
   flow_stmt
       : return_stmt
  
positive.code:       { self.newLineAction() }
      ;
  
  OPEN_PAREN  : '(' { self.opened += 1 };
  CLOSE_PAREN : ')' { self.opened -= 1 };
  
  
negative.code: factor
      : op='+' factor    # unaryExpr
      | op='-' factor    # unaryExpr
      | '(' test ')'     # parenExpr
      | atom             # atomExpr
      ;
  
  atom
      : NAME
      | funcinvoke
      | number
      | string+
      | NONE
  