derive_more/
convert.rs

1//! Definitions used in derived implementations of [`core::convert`] traits.
2
3#[cfg(feature = "try_from")]
4pub use self::try_from::TryFromReprError;
5#[cfg(feature = "try_into")]
6pub use self::try_into::TryIntoError;
7
8#[cfg(feature = "try_from")]
9mod try_from {
10    use core::{error::Error, fmt};
11
12    /// Error returned by the derived [`TryFrom`] implementation on enums to
13    /// convert from their repr.
14    ///
15    /// [`TryFrom`]: macro@crate::TryFrom
16    #[derive(Clone, Copy, Debug)]
17    pub struct TryFromReprError<T> {
18        /// Original input value which failed to convert via the derived
19        /// [`TryFrom`] implementation.
20        ///
21        /// [`TryFrom`]: macro@crate::TryFrom
22        pub input: T,
23    }
24
25    impl<T> TryFromReprError<T> {
26        #[doc(hidden)]
27        #[must_use]
28        #[inline]
29        pub const fn new(input: T) -> Self {
30            Self { input }
31        }
32    }
33
34    // `T`, as a discriminant, should only be an integer type, and therefore be `Debug`.
35    impl<T: fmt::Debug> fmt::Display for TryFromReprError<T> {
36        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
37            write!(
38                f,
39                "`{:?}` does not correspond to a unit variant",
40                self.input
41            )
42        }
43    }
44
45    // `T` should only be an integer type and therefore be `Debug`.
46    impl<T: fmt::Debug> Error for TryFromReprError<T> {}
47}
48
49#[cfg(feature = "try_into")]
50mod try_into {
51    use core::{error::Error, fmt};
52
53    /// Error returned by the derived [`TryInto`] implementation.
54    ///
55    /// [`TryInto`]: macro@crate::TryInto
56    #[derive(Clone, Copy, Debug)]
57    pub struct TryIntoError<T> {
58        /// Original input value which failed to convert via the derived
59        /// [`TryInto`] implementation.
60        ///
61        /// [`TryInto`]: macro@crate::TryInto
62        pub input: T,
63        variant_names: &'static str,
64        output_type: &'static str,
65    }
66
67    impl<T> TryIntoError<T> {
68        #[doc(hidden)]
69        #[must_use]
70        #[inline]
71        pub const fn new(
72            input: T,
73            variant_names: &'static str,
74            output_type: &'static str,
75        ) -> Self {
76            Self {
77                input,
78                variant_names,
79                output_type,
80            }
81        }
82    }
83
84    impl<T> fmt::Display for TryIntoError<T> {
85        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
86            write!(
87                f,
88                "Only {} can be converted to {}",
89                self.variant_names, self.output_type,
90            )
91        }
92    }
93
94    impl<T: fmt::Debug> Error for TryIntoError<T> {}
95}
derive_more/convert.rs

derive_more/
convert.rs
