Trait PanicFmt 

pub trait PanicFmt {
    type This: ?Sized;
    type Kind;

    const PV_COUNT: usize;
    const PROOF: IsPanicFmt<Self, Self::This, Self::Kind> = IsPanicFmt::NEW;
}

Trait for types that can be formatted by const panics.

Implementor

Implementors are expected to also define this inherent method to format the type:

const fn to_panicvals<'a>(&'a self, f: FmtArg) -> [PanicVal<'a>; <Self as PanicFmt>::PV_COUNT]

The returned PanicVal can also be PanicVal<'static>.

Implementation examples

This trait can be implemented in these ways (in increasing order of verbosity):

• Using the PanicFmt derive macro (requires the opt-in "derive" feature)
• Using the impl_panicfmt macro (requires the default-enabled "non_basic" feature)
• Using the flatten_panicvals macro (requires the default-enabled "non_basic" feature)
• Using no macros at all

Macro-less impl

Implementing this trait for a simple enum without using macros.

use const_panic::{ArrayString, FmtArg, PanicFmt, PanicVal};

// `ArrayString` requires the "non_basic" crate feature (enabled by default),
// everything else in this example works with no enabled crate features.
assert_eq!(
    ArrayString::<99>::concat_panicvals(&[
        &Foo::Bar.to_panicvals(FmtArg::DEBUG),
        &[PanicVal::write_str(",")],
        &Foo::Baz.to_panicvals(FmtArg::DEBUG),
        &[PanicVal::write_str(",")],
        &Foo::Qux.to_panicvals(FmtArg::DEBUG),
    ]).unwrap(),
    "Bar,Baz,Qux",
);


enum Foo {
    Bar,
    Baz,
    Qux,
}

impl PanicFmt for Foo {
    type This = Self;
    type Kind = const_panic::IsCustomType;
    const PV_COUNT: usize = 1;
}

impl Foo {
    pub const fn to_panicvals(self, _: FmtArg) -> [PanicVal<'static>; Foo::PV_COUNT] {
        match self {
            Self::Bar => [PanicVal::write_str("Bar")],
            Self::Baz => [PanicVal::write_str("Baz")],
            Self::Qux => [PanicVal::write_str("Qux")],
        }
    }
}

Required Associated Constants

const PV_COUNT: usize

The length of the array returned in Self::to_panicvals (an inherent method that formats the type for panic messages).

Provided Associated Constants

const PROOF: IsPanicFmt<Self, Self::This, Self::Kind> = IsPanicFmt::NEW

A marker type that proves that Self implements PanicFmt.

Used by const_panic macros to coerce both standard library and user-defined types into some type that has a to_panicvals method.

Required Associated Types

type This: ?Sized

The type after dereferencing all references.

User-defined types should generally set this to Self.

type Kind

Whether this is a user-defined type or standard library type.

User-defined types should generally set this to IsCustomType.

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementations on Foreign Types

impl PanicFmt for Ordering

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = Ordering

type Kind = IsStdType

impl PanicFmt for Infallible

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = Infallible

type Kind = IsStdType

impl PanicFmt for FromBytesWithNulError

Available on crate features non_basic and rust_1_88 only.

const PV_COUNT: usize

type This = FromBytesWithNulError

type Kind = IsStdType

impl PanicFmt for IntErrorKind

Available on crate feature rust_1_82 only.

const PV_COUNT: usize = 1

type This = IntErrorKind

type Kind = IsStdType

impl PanicFmt for Ordering

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = Ordering

type Kind = IsStdType

impl PanicFmt for bool

const PV_COUNT: usize = 1

type This = bool

type Kind = IsStdType

impl PanicFmt for char

const PV_COUNT: usize = 1

type This = char

type Kind = IsStdType

impl PanicFmt for i8

const PV_COUNT: usize = 1

type This = i8

type Kind = IsStdType

impl PanicFmt for i16

const PV_COUNT: usize = 1

type This = i16

type Kind = IsStdType

impl PanicFmt for i32

const PV_COUNT: usize = 1

type This = i32

type Kind = IsStdType

impl PanicFmt for i64

const PV_COUNT: usize = 1

type This = i64

type Kind = IsStdType

impl PanicFmt for i128

const PV_COUNT: usize = 1

type This = i128

type Kind = IsStdType

impl PanicFmt for isize

const PV_COUNT: usize = 1

type This = isize

type Kind = IsStdType

impl PanicFmt for str

const PV_COUNT: usize = 1

type This = str

type Kind = IsStdType

impl PanicFmt for u8

const PV_COUNT: usize = 1

type This = u8

type Kind = IsStdType

impl PanicFmt for u16

const PV_COUNT: usize = 1

type This = u16

type Kind = IsStdType

impl PanicFmt for u32

const PV_COUNT: usize = 1

type This = u32

type Kind = IsStdType

impl PanicFmt for u64

const PV_COUNT: usize = 1

type This = u64

type Kind = IsStdType

impl PanicFmt for u128

const PV_COUNT: usize = 1

type This = u128

type Kind = IsStdType

impl PanicFmt for ()

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = ()

type Kind = IsStdType

impl PanicFmt for usize

const PV_COUNT: usize = 1

type This = usize

type Kind = IsStdType

impl PanicFmt for FromBytesUntilNulError

Available on crate features non_basic and rust_1_88 only.

const PV_COUNT: usize

type This = FromBytesUntilNulError

type Kind = IsStdType

impl PanicFmt for PhantomPinned

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = PhantomPinned

type Kind = IsStdType

impl PanicFmt for ParseIntError

Available on crate feature rust_1_82 only.

const PV_COUNT: usize = 1

type This = ParseIntError

type Kind = IsStdType

impl PanicFmt for Range<usize>

Available on crate feature non_basic only.

const PV_COUNT: usize = 3

type This = Range<usize>

type Kind = IsStdType

impl PanicFmt for RangeFrom<usize>

Available on crate feature non_basic only.

const PV_COUNT: usize = 2

type This = RangeFrom<usize>

type Kind = IsStdType

impl PanicFmt for RangeFull

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = RangeFull

type Kind = IsStdType

impl PanicFmt for RangeInclusive<usize>

Available on crate feature non_basic only.

const PV_COUNT: usize = 3

type This = RangeInclusive<usize>

type Kind = IsStdType

impl PanicFmt for RangeTo<usize>

Available on crate feature non_basic only.

const PV_COUNT: usize = 2

type This = RangeTo<usize>

type Kind = IsStdType

impl PanicFmt for RangeToInclusive<usize>

Available on crate feature non_basic only.

const PV_COUNT: usize = 2

type This = RangeToInclusive<usize>

type Kind = IsStdType

impl PanicFmt for Utf8Error

Available on crate feature rust_1_64 only.

const PV_COUNT: usize = 5

type This = Utf8Error

type Kind = IsStdType

impl PanicFmt for NonZeroI8

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = NonZero<i8>

type Kind = IsStdType

impl PanicFmt for NonZeroI16

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = NonZero<i16>

type Kind = IsStdType

impl PanicFmt for NonZeroI32

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = NonZero<i32>

type Kind = IsStdType

impl PanicFmt for NonZeroI64

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = NonZero<i64>

type Kind = IsStdType

impl PanicFmt for NonZeroI128

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = NonZero<i128>

type Kind = IsStdType

impl PanicFmt for NonZeroIsize

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = NonZero<isize>

type Kind = IsStdType

impl PanicFmt for NonZeroU8

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = NonZero<u8>

type Kind = IsStdType

impl PanicFmt for NonZeroU16

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = NonZero<u16>

type Kind = IsStdType

impl PanicFmt for NonZeroU32

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = NonZero<u32>

type Kind = IsStdType

impl PanicFmt for NonZeroU64

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = NonZero<u64>

type Kind = IsStdType

impl PanicFmt for NonZeroU128

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = NonZero<u128>

type Kind = IsStdType

impl PanicFmt for NonZeroUsize

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = NonZero<usize>

type Kind = IsStdType

impl<'a> PanicFmt for [PanicVal<'a>]

const PV_COUNT: usize = usize::MAX

type This = [PanicVal<'a>]

type Kind = IsStdType

impl<'a, T: PanicFmt + ?Sized> PanicFmt for &'a T

const PV_COUNT: usize = T::PV_COUNT

type This = <T as PanicFmt>::This

type Kind = <T as PanicFmt>::Kind

impl<'a, const N: usize> PanicFmt for [PanicVal<'a>; N]

const PV_COUNT: usize = N

type This = [PanicVal<'a>; N]

type Kind = IsStdType

impl<'s> PanicFmt for [&'s str]

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = [&'s str]

type Kind = IsStdType

impl<'s> PanicFmt for [bool]

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = [bool]

type Kind = IsStdType

impl<'s> PanicFmt for [char]

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = [char]

type Kind = IsStdType

impl<'s> PanicFmt for [i8]

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = [i8]

type Kind = IsStdType

impl<'s> PanicFmt for [i16]

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = [i16]

type Kind = IsStdType

impl<'s> PanicFmt for [i32]

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = [i32]

type Kind = IsStdType

impl<'s> PanicFmt for [i64]

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = [i64]

type Kind = IsStdType

impl<'s> PanicFmt for [i128]

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = [i128]

type Kind = IsStdType

impl<'s> PanicFmt for [isize]

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = [isize]

type Kind = IsStdType

impl<'s> PanicFmt for [u8]

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = [u8]

type Kind = IsStdType

impl<'s> PanicFmt for [u16]

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = [u16]

type Kind = IsStdType

impl<'s> PanicFmt for [u32]

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = [u32]

type Kind = IsStdType

impl<'s> PanicFmt for [u64]

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = [u64]

type Kind = IsStdType

impl<'s> PanicFmt for [u128]

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = [u128]

type Kind = IsStdType

impl<'s> PanicFmt for [usize]

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = [usize]

type Kind = IsStdType

impl<'s, const LEN: usize> PanicFmt for [&'s str; LEN]

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = [&'s str; LEN]

type Kind = IsStdType

impl<'s, const LEN: usize> PanicFmt for [bool; LEN]

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = [bool; LEN]

type Kind = IsStdType

impl<'s, const LEN: usize> PanicFmt for [char; LEN]

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = [char; LEN]

type Kind = IsStdType

impl<'s, const LEN: usize> PanicFmt for [i8; LEN]

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = [i8; LEN]

type Kind = IsStdType

impl<'s, const LEN: usize> PanicFmt for [i16; LEN]

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = [i16; LEN]

type Kind = IsStdType

impl<'s, const LEN: usize> PanicFmt for [i32; LEN]

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = [i32; LEN]

type Kind = IsStdType

impl<'s, const LEN: usize> PanicFmt for [i64; LEN]

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = [i64; LEN]

type Kind = IsStdType

impl<'s, const LEN: usize> PanicFmt for [i128; LEN]

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = [i128; LEN]

type Kind = IsStdType

impl<'s, const LEN: usize> PanicFmt for [isize; LEN]

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = [isize; LEN]

type Kind = IsStdType

impl<'s, const LEN: usize> PanicFmt for [u8; LEN]

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = [u8; LEN]

type Kind = IsStdType

impl<'s, const LEN: usize> PanicFmt for [u16; LEN]

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = [u16; LEN]

type Kind = IsStdType

impl<'s, const LEN: usize> PanicFmt for [u32; LEN]

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = [u32; LEN]

type Kind = IsStdType

impl<'s, const LEN: usize> PanicFmt for [u64; LEN]

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = [u64; LEN]

type Kind = IsStdType

impl<'s, const LEN: usize> PanicFmt for [u128; LEN]

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = [u128; LEN]

type Kind = IsStdType

impl<'s, const LEN: usize> PanicFmt for [usize; LEN]

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = [usize; LEN]

type Kind = IsStdType

impl<T> PanicFmt for Option<T>

where T: PanicFmt,

Available on crate feature non_basic only.

Note: there is only to_panicvals methods for Options of standard library types for now.

const PV_COUNT: usize

type This = Option<T>

type Kind = IsStdType

impl<T: ?Sized> PanicFmt for *const T

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = *const T

type Kind = IsStdType

impl<T: ?Sized> PanicFmt for *mut T

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = *mut T

type Kind = IsStdType

impl<T: ?Sized> PanicFmt for PhantomData<T>

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = PhantomData<T>

type Kind = IsStdType

impl<T: ?Sized> PanicFmt for NonNull<T>

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = NonNull<T>

type Kind = IsStdType

Implementors

impl PanicFmt for Delimiter

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = Delimiter

type Kind = IsCustomType

impl PanicFmt for PanicVal<'_>

const PV_COUNT: usize = 1

type This = PanicVal<'_>

type Kind = IsCustomType

impl PanicFmt for Separator<'_>

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = Separator<'_>

type Kind = IsCustomType

impl<T> PanicFmt for StdWrapper<T>

where T: PanicFmt,

const PV_COUNT: usize = T::PV_COUNT

type This = StdWrapper<T>

type Kind = IsCustomType

impl<const CAP: usize> PanicFmt for ArrayString<CAP>

Available on crate feature non_basic only.

const PV_COUNT: usize = 1

type This = ArrayString<CAP>

type Kind = IsCustomType