Should unreachable code be considered an error?

[Stewart Gordon]

On 25/08/2011 02:41, Michel Fortin wrote:
<snip>
> bool frontEquals(R, V)(R range, V value)
> {
>     if (range.empty)
>         return false;
>     else
>         return range.front == value;
> }
>
> This will work fine with most ranges, but if you encounter an infinite range (with empty
> defined as "enum empty = false") then the "return false" statement becomes unreachable and
> you'll get an error/warning? It doesn't make sense.
<snip>

The structure of a flowchart is not affected by the values of variables, or even 
constants, in it.
                                   _____________
                                  ( frontEquals )
                                   ¯¯¯¯¯¯|¯¯¯¯¯¯
      ______________               ______v______
     ( return false )<--- true ---< range.empty >
      ¯¯¯¯¯¯¯¯¯¯¯¯¯¯               ¯¯¯¯¯¯|¯¯¯¯¯¯
                                       false
                                         |
                           ______________v______________
                          ( return range.front == value )
                           ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
Replacing "range.empty" with "false" doesn't magically cause the true arrow to vanish.

Stewart.