E2058 Class, interface and object types only allowed in type section (Delphi)

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Class or object types must always be declared with an explicit type declaration in a type section - unlike record types, they cannot be anonymous.

The main reason for this is that there would be no way you could declare the methods of that type - after all, there is no type name.

program Produce;

var
  MyClass : class
    Field: Integer;
  end;

begin
end.

The example tries to declare a class type within a variable declaration - that is not legal.

program Solve;

type
  TMyClass = class
    Field: Integer;
  end;

var
  MyClass : TMyClass;

begin
end.

The solution is to introduce a type declaration for the class type. Alternatively, you could have changed the class type to a record type.