What the heck am i doing wrong? I'm just trying to create a 8 bit unsigned variable.

[WhatMeWorry via Digitalmars-d-learn]

/+ SDL3 has a function
bool SDL_SetTextureAlphaMod(SDL_Texture *texture, Uint8 alpha);
which has a Uint8 for one of its parameters.  So I try to use a 
ubyte
+/

void main()
{
    ubyte a;
    a = a + 5; // onlineapp.d(11): Error: cannot implicitly 
convert expression `cast(int)a +
                  5` of type `int` to `ubyte`

    import core.stdc.stdint;
    uint8_t b;
    b = b + 5; // onlineapp.d(17): Error: cannot implicitly 
convert expression `cast(int)b +
                  5` of type `int` to `ubyte`

    cast(uint8_t) b = cast(uint8_t) b + cast(uint8_t) 5;  // 
onlineapp.d(19): Error: cannot
                                                             
implicitly convert expression
                                                             
`cast(int)b + 5` of type `int`
                                                             to 
`ubyte`

}