1use super::BitFlag;
2use super::BitFlags;
3use core::convert::TryFrom;
4use core::fmt;
5
6// Coherence doesn't let us use a generic type here. Work around by implementing
7// for each integer type manually.
8for_each_uint! { $ty $hide_docs =>
9 impl<T> TryFrom<$ty> for BitFlags<T>
10 where
11 T: BitFlag<Numeric=$ty>,
12 {
13 type Error = FromBitsError<T>;
14
15 fn try_from(bits: T::Numeric) -> Result<Self, Self::Error> {
16 Self::from_bits(bits)
17 }
18 }
19}
20
21/// The error struct used by [`BitFlags::from_bits`]
22/// and the [`TryFrom`] implementation for invalid values.
23///
24/// Note that the implementation of [`std::error::Error`]
25/// for this type is gated on the `std` feature flag.
26///
27/// ```
28/// # use std::convert::TryInto;
29/// # use enumflags2::{bitflags, BitFlags};
30/// #[bitflags]
31/// #[derive(Clone, Copy, Debug)]
32/// #[repr(u8)]
33/// enum MyFlags {
34/// A = 0b0001,
35/// B = 0b0010,
36/// C = 0b0100,
37/// D = 0b1000,
38/// }
39///
40/// let result: Result<BitFlags<MyFlags>, _> = 0b10101u8.try_into();
41/// assert!(result.is_err());
42/// let error = result.unwrap_err();
43/// assert_eq!(error.truncate(), MyFlags::C | MyFlags::A);
44/// assert_eq!(error.invalid_bits(), 0b10000);
45/// ```
46#[derive(Debug, Copy, Clone)]
47pub struct FromBitsError<T: BitFlag> {
48 pub(crate) flags: BitFlags<T>,
49 pub(crate) invalid: T::Numeric,
50}
51
52impl<T: BitFlag> FromBitsError<T> {
53 /// Return the truncated result of the conversion.
54 pub fn truncate(self) -> BitFlags<T> {
55 self.flags
56 }
57
58 /// Return the bits that didn't correspond to any flags.
59 pub fn invalid_bits(self) -> T::Numeric {
60 self.invalid
61 }
62}
63
64impl<T: BitFlag + fmt::Debug> fmt::Display for FromBitsError<T> {
65 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
66 write!(
67 fmt,
68 "Invalid bits for {:?}: {:#b}",
69 self.flags, self.invalid
70 )
71 }
72}
73
74#[cfg(feature = "std")]
75impl<T: BitFlag + fmt::Debug> std::error::Error for FromBitsError<T> {
76 fn description(&self) -> &str {
77 "invalid bitflags representation"
78 }
79}
80