Error: two or more data types in declaration of 'x'

I'm compiling a C++ program which and I get the error "two or more data types in declaration" at the line below. Here is the code:

#include <iostream>
#include <string>
#include <sstream>
#include <stdlib.h>
List SplitInflix(const string infix)
{
List tokenlist;
string word= "";
char x;
for (char x : infix)
    {
    switch (x)
    {
    case '(':
        if (word != "")
        {
            Token* token = new Token(word);
            tokenlist.append(token);
            word = "";
            Token * token1 = new Token(LEFT);
            tokenlist.append(token1);
        }
        else
        {
            Token * token = new Token(LEFT);
            tokenlist.append(token);
        }
        break;
    ...
}
return tokenlist;
}

I get the error:

error: two or more data types in declaration of 'x'

There's more coding but it's too long and I think it's not related to the error.

How do I fix it. Thanks!