補充
判斷是不是dup-declared procedure: 只要procedure name一樣, 就算dup-declared
判斷是不是undeclared procedure: 需要判斷procedure, parameter list,
return type是否一致
in sysio.h:
READ (id1: INTEGER) : INTEGER ;
=> real_number : REAL;
READ(real_number); <- undeclared procedure
btw, parameter list中的ids不要到symbol table上register