collections/string-operator.cfa:317:1 error: Cannot choose between 2 alternatives for expression
Applying untyped:
  Name: printf
...to:
  Constant Expression ("%c\n": array of char with dimension of Constant Expression (4: unsigned long int)
  ... with resolved type:
    unsigned long int)
  ... with resolved type:
    array of char with dimension of Constant Expression (4: unsigned long int)
    ... with resolved type:
      unsigned long int
  Applying untyped:
    Name: ?+?
  ...to:
    Constant Expression ('a': char)
    ... with resolved type:
      char
    Constant Expression ('b': char)
    ... with resolved type:
      char

 Alternatives are:
Cost ( 1, 0, 0, 1, 0, 0, 0, 0 ): Application of
      Variable Expression: printf: extern function
      ... with parameters
        restrict pointer to const char
        and a variable number of other arguments
      ... returning
        signed int

      ... with resolved type:
        pointer to function
        ... with parameters
          restrict pointer to const char
          and a variable number of other arguments
        ... returning
          signed int

      ... to arguments
      Generated Cast of:
        Constant Expression ("%c\n": pointer to char)
        ... with resolved type:
          pointer to char
      ... to:
        restrict pointer to const char
      ... with resolved type:
        restrict pointer to const char
      Application of
        Variable Expression: ?+?: function
        ... with parameters
          char
          char
        ... returning
          char

        ... with resolved type:
          pointer to function
          ... with parameters
            char
            char
          ... returning
            char

        ... to arguments
        Constant Expression ('a': char)
        ... with resolved type:
          char
        Constant Expression ('b': char)
        ... with resolved type:
          char

      ... with resolved type:
        char

    ... with resolved type:
      signed int
  (types:
    signed int
  )
  Environment:

Cost ( 1, 0, 0, 1, 0, 0, 0, 0 ): Application of
      Variable Expression: printf: extern function
      ... with parameters
        restrict pointer to const char
        and a variable number of other arguments
      ... returning
        signed int

      ... with resolved type:
        pointer to function
        ... with parameters
          restrict pointer to const char
          and a variable number of other arguments
        ... returning
          signed int

      ... to arguments
      Generated Cast of:
        Constant Expression ("%c\n": pointer to char)
        ... with resolved type:
          pointer to char
      ... to:
        restrict pointer to const char
      ... with resolved type:
        restrict pointer to const char
      Application of
        Variable Expression: ?+?: function
        ... with parameters
          char
          char
        ... returning
          instance of struct string with body

        ... with resolved type:
          pointer to function
          ... with parameters
            char
            char
          ... returning
            instance of struct string with body

        ... to arguments
        Constant Expression ('a': char)
        ... with resolved type:
          char
        Constant Expression ('b': char)
        ... with resolved type:
          char

      ... with resolved type:
        instance of struct string with body

    ... with resolved type:
      signed int
  (types:
    signed int
  )
  Environment: