bp3d_util/
simple_error.rs

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28
29//! Error umbrella type generation macro.
30
31//Because Rust macros are a peace of shit.
32/// This macro is internal and called by another macro.
33#[macro_export]
34macro_rules! typed_ident {
35    ($t: ty, $name: ident) => {
36        $name
37    };
38}
39
40//Because Rust macros are a peace of shit.
41/// This macro is internal and called by another macro.
42#[macro_export]
43macro_rules! hack_rust_buggy_macros {
44    ($name: ident, $ty: ident, $e: ident, $data: ty) => {
45        impl $e<$data> for $name {
46            fn from(value: $data) -> Self {
47                Self::$ty(value)
48            }
49        }
50    };
51    ($name: ident, $ty: ty, $($e: ident)?, $($data: ty)?) => {};
52}
53
54/// Generates a simple enum which maps multiple error types and implements [Error](std::error::Error) and
55/// [Display](std::fmt::Display) automatically. This optionally can generate [From](From) implementations
56/// on demand.
57///
58/// # Example
59///
60/// ```
61/// use bp3d_util::simple_error;
62/// simple_error!(
63///     /// Doc.
64///     TestError {
65///         /// This is a doc comment which is recorded by the macro.
66///         Untyped => "untyped variant",
67///         /// Another doc comment.
68///         (impl From) Io(std::io::Error) => "io error {}",
69///         Other(u8) => "other u8 error {}"
70///     }
71/// );
72/// println!("{}", TestError::Untyped);
73/// ```
74#[macro_export]
75macro_rules! simple_error {
76    (
77        $(#[$meta: meta])*
78        $vis: vis $name: ident {
79            $(
80                $(#[$field_meta: meta])*
81                $((impl $e: ident))? $ty: ident $(($data: ty))? => $desc: literal
82            ),*
83        }
84    ) => {
85        $(#[$meta])*
86        #[derive(Debug)]
87        $vis enum $name {
88            $(
89                $(#[$field_meta])*
90                $ty $(($data))?
91            ),*
92        }
93
94        $(
95            $crate::hack_rust_buggy_macros!($name, $ty, $($e)?, $($data)?);
96        )*
97
98        impl std::fmt::Display for $name {
99            fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
100                match self {
101                    $($name::$ty $(($crate::typed_ident!($data, e)))? => write!(f, $desc $(, $crate::typed_ident!($data, e))?) ),*
102                }
103            }
104        }
105
106        impl std::error::Error for $name {}
107    };
108}
bp3d_util/simple_error.rs

bp3d_util/
simple_error.rs
