[cfe-dev] determine whether a function take reference parameters

[Big~Newbie via cfe-dev]

I want to judge whether a function take reference parameters. the sample code as "void m(int& a){}", the a is referenced! 
I use the following code to access this, but it can't, whats wrong with me?
   FunctionDecl *funDecl = callExpr->getDirectCallee();
   ParmVarDecl* decl = funDecl->getParamDecl(i);//i=0
   if(decl->getType()->isReferenceType()) {// I use this to judge parameter a is referenced, but cannt!!!
           myfile<<"---Ref type:"<<argNames[i]<<endl;
    }
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