Commits on Jun 26, 2015

1. Make Debug fancy again and handle #[cfg] properly. …

   `Debug` was implemented using the nice readable flag names in bitflags#7, but
   the flag names were removed in bitflags#9 because it used `$Flags` which broke
   trivial `#[cfg]`-based removal of flags. Changing `.contains($Flag)` to
   `.contains($BitFlags { bits: $value })` instead (akin to what `.all()`
   did) would have fixed that issue, allowing a friendly `Debug` again, but
   then I found a further improvement to make, because the `#[cfg]`
   behaviour was still off, as a flag’s value was still written out
   regardless of the `#[cfg]` attribute, so if *it* contained stuff that
   didn’t exist `bitflags!` would still blow up. This is inconsistent with
   how such things work in Rust proper, so I’ve fixed it.
   
   The fix is rather convoluted, involving a dummy module, a bunch of dummy
   constants, a nested function and glob imports, but it works, avoiding
   referring to `$value` successfully. This change causes this to work:
   
   ```rust
   bitflags! {
       flags Foo: u32 {
           #[cfg(a)]
           const A = 0b1,
           #[cfg(a)]
           const B = A.bits,  // or anything else that is `#[cfg(a)]`
       }
   }
   ```
   
   (Formerly `all()` was still trying to use `A.bits` when `cfg(not(a))`
   and thus `A` wasn’t defined.)
   
   This change allows `#[cfg]` on a flag to work like it should, allowing
   it to depend on things that don’t exist unless the conditions are met.
   Sure, that seems a pretty rare case for flags, but it’s real. Beyond
   the style of example above, my imagined scenario is a -sys crate
   having declared certain flag values, but only when certain features are
   enabled, and so when defining the bitflags in another crate (for the
   -sys crate doesn’t use bitflags) you can only use those values with the
   appropriate features.

   

   chris-morgan committed Jun 26, 2015
   Configuration menu

   • View commit details
   • Copy full SHA for 4f12093
   • Browse repository at this point

   Copy the full SHA

   4f12093 View commit details

   Browse the repository at this point in the history