Is this a constructor problem (referencing deleted function)? (error code C2280)

Question

I have a class ‘Token’ and a class ‘Token_Stream’, as shown in code below. When I try to create an object of class Token_Stream, I get a compile error: (C2280) 'Token_stream::Token_stream(void)': attempting to reference a deleted function

I'm using C++ Visual Studio Community 15.9.1. I am new to "modern" programming and teaching myself C++ from Stroustrup's book PPP C++ 2nd edition. I have read many of the results from searching this site for "c++ attempting to reference a deleted function c2280," but none have helped me solve the problem.

My understanding of constructors is incomplete, despite reading several webpages and book sections about them, but I understand enough (I think) to think this is a constructor problem. I am definitely struggling with the user-defined class that includes a member that is another user-defined class plus member functions.

Code is below. If the declarations of the two member functions of Token_stream would be helpful, let me know and I'll add them.

class Token {
public:
    char kind;
    double value;
    Token(char ch)    // make a Token from a char 
   //- this is a constructor, right?
        :kind(ch), value(0) { } // what do the braces here mean?
    Token(char ch, double val)     // make a Token from a char and a double
        :kind(ch), value(val) { }
};

class Token_stream {
public:
    Token get();
    void putback(Token t);
private:
    bool full{ false };
    Token buffer;   
//  Token_stream() = default;
};

Token_stream ts;    // ERROR C2280 here
// Token_stream::Token_stream(void)': attempting
// to ref. a deleted function

Answer 1

The problem is your Token class. You don't have a default-constructor of Token but you have a member-attribute Token buffer; in Token_stream which will be initialized on instantiation of Token_stream. There is no default constructor for Token. Therefore the compiler can't add an default-constructor for Token_stream.

gcc 8.2 shows the following error/note:

note: 'Token_stream::Token_stream()' is implicitly deleted because the default 
definition would be ill-formed

error: no matching function for call to 'Token::Token()'

This shows the problem with creating a default constructor for Token_stream.

You can simply add a default-constructor for Token and it should work.enter code here