Lifetime parameters for enumeration in structure

I don't understand why I am getting an error with this type of structure

enum Cell <'a> {
    Str(&'a str),
    Double(&'a f32),
}

struct MyCellRep<'a> {
    value: &'a Cell,
    ptr: *const u8,
}

impl MyCellRep{
    fn new_from_str(s: &str) {
        MyCellRep { value: Cell::Str(&s), ptr: new_sCell(CString::new(&s)) }
    }

    fn new_from_double(d: &f32) {
        MyCellRep { value: Cell::Double(&d), ptr: new_dCell(&d) }
    }
}

      

        
        
        
      

    

I am getting the error

14:22 error: wrong number of lifetime parameters: expected 1, found 0 [E0107]
src\lib.rs:14     value : & 'a Cell ,

      

        
        
        
      

    

So I tried and

struct MyCellRep<'a> {
    value: &'a Cell + 'a,
    ptr: *const u8,
}

      

        
        
        
      

    

but got

14:22 error: expected a path on the left-hand side of `+`, not `&'a Cell`

      

        
        
        
      

    

I suppose I Cell

should have a lifetime MyCellRep

, Cell::Str

and Cell::Double

should at least have a lifetime Cell

.

In the end what I had to do was just say

let x = MyCellRef::new_from_str("foo");
let y = MyCellRef::new_from_double(123.0);

      

        
        
        
      

    

Update I would like to add by changing the definition of the cell, the rest of the code should also change to the following for anyone else looking for answers.

pub enum Cell<'a> {
    Str(&'a str),
    Double(&'a f32),
}


struct MyCellRep<'a> {
    value: Cell<'a>, // Ref to enum 
    ptr: *const u8, // Pointer to c struct
}

impl<'a>  MyCellRep<'a> {
    fn from_str(s: &'a str) -> DbaxCell<'a> {
        MyCellRep { value: Cell::Str(&s) , ptr: unsafe { new_sCell(CString::new(s).unwrap()) } }
    }

    fn from_double(d: &'a f32) -> DbaxCell {
        MyCellRep{ value: Cell::Double(&d) , ptr: unsafe { new_dCell(*d) } }
    }
}

      

        
        
        
      

    

What I love about Rust is the same as OCaml, if it compiles it works :)