“Does not name a type” error in class

Question

I'm writing a program for my class which involves using a class inside of a struct. When defining the struct (named polynomial) 'Polynomial does not name a type'. It triggers on the first line of the default constructor:

Polynomial::Polynomial(){
    coefs = vector<Fraction>();
}

Specifically the error occurs on the "Polynomial::Polynomial(){" line.

All other examples I've found for this error include using class B inside class A before class B is declared. The only member of Polynomial is a vector of class Fractions. I have tried forward declaration of class Fractions and vector is included. This is probably a rookie mistake as I am still very new to C++ classes (this being my first one) so any help would be appreciated.

The relevant portion of the polynomial header file is:

// data members
vector<Fraction> coefs;

// methods
Polynomial() = default;

Answer 1

polynomial.cpp needs to include it's header:

#include "polynomial.h"

There is no implicit association between the source (.cpp file) and the header (.h) file in C++. You must include the header for the name Polynomial to be understood.