fix std::error::Error impl

Author: arcnmx

enumflags/src/fallible.rs

@@ -1,4 +1,5 @@
 use core::convert::TryFrom;
+use core::fmt;
 use super::BitFlags;
 use super::_internal::RawBitFlags;
 
@@ -47,9 +48,15 @@ impl<T: RawBitFlags> FromBitsError<T> {
     }
 }
 
+impl<T: RawBitFlags + fmt::Debug> fmt::Display for FromBitsError<T> {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        write!(fmt, "Invalid bits for {:?}: {:#b}", self.flags, self.invalid)
+    }
+}
+
 #[cfg(feature = "std")]
-impl<T: RawBitFlags> std::error::Error for FromBitsError<T> {
+impl<T: RawBitFlags + fmt::Debug> std::error::Error for FromBitsError<T> {
     fn description(&self) -> &str {
-        "invalid bit representation"
+        "invalid bitflags representation"
     }
 }

enumflags/src/formatting.rs

@@ -1,5 +1,5 @@
 use core::fmt::{self, Debug, Binary};
-use crate::{BitFlags, FromBitsError, _internal::RawBitFlags};
+use crate::{BitFlags, _internal::RawBitFlags};
 
 impl<T> fmt::Debug for BitFlags<T>
 where

enumflags/src/lib.rs

@@ -48,7 +48,7 @@
 #![warn(missing_docs)]
 #![cfg_attr(all(not(test), not(feature = "std")), no_std)]
 
-#[cfg(all(test, not(feature = "std")))]
+#[cfg(any(test, feature = "std"))]
 extern crate core;
 use core::{cmp, ops};
 use core::iter::FromIterator;