1.34.0[−][src]Enum nom::lib::std::convert::Infallible
The error type for errors that can never happen.
Since this enum has no variant, a value of this type can never actually exist.
This can be useful for generic APIs that use Result
and parameterize the error type,
to indicate that the result is always Ok
.
For example, the TryFrom
trait (conversion that returns a Result
)
has a blanket implementation for all types where a reverse Into
implementation exists.
impl<T, U> TryFrom<U> for T where U: Into<T> { type Error = Infallible; fn try_from(value: U) -> Result<Self, Infallible> { Ok(U::into(value)) // Never returns `Err` } }
Future compatibility
This enum has the same role as the !
“never” type,
which is unstable in this version of Rust.
When !
is stabilized, we plan to make Infallible
a type alias to it:
pub type Infallible = !;
… and eventually deprecate Infallible
.
However there is one case where !
syntax can be used
before !
is stabilized as a full-fleged type: in the position of a function’s return type.
Specifically, it is possible implementations for two different function pointer types:
trait MyTrait {} impl MyTrait for fn() -> ! {} impl MyTrait for fn() -> std::convert::Infallible {}
With Infallible
being an enum, this code is valid.
However when Infallible
becomes an alias for the never type,
the two impl
s will start to overlap
and therefore will be disallowed by the language’s trait coherence rules.
Trait Implementations
impl Error for Infallible
1.8.0[src]
fn description(&self) -> &str
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default fn cause(&self) -> Option<&dyn Error>
1.0.0[src]
replaced by Error::source, which can support downcasting
The lower-level cause of this error, if any. Read more
default fn source(&self) -> Option<&(dyn Error + 'static)>
1.30.0[src]
The lower-level source of this error, if any. Read more
default fn type_id(&self) -> TypeId where
Self: 'static,
[src]
Self: 'static,
Gets the TypeId
of self
impl Debug for Infallible
[src]
impl From<Infallible> for TryFromIntError
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fn from(x: Infallible) -> TryFromIntError
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impl From<!> for Infallible
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fn from(x: !) -> Infallible
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impl Ord for Infallible
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fn cmp(&self, _other: &Infallible) -> Ordering
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default fn max(self, other: Self) -> Self
1.21.0[src]
Compares and returns the maximum of two values. Read more
default fn min(self, other: Self) -> Self
1.21.0[src]
Compares and returns the minimum of two values. Read more
default fn clamp(self, min: Self, max: Self) -> Self
[src]
clamp
)Restrict a value to a certain interval. Read more
impl Eq for Infallible
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impl PartialEq<Infallible> for Infallible
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fn eq(&self, &Infallible) -> bool
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#[must_use]
default fn ne(&self, other: &Rhs) -> bool
1.0.0[src]
This method tests for !=
.
impl Copy for Infallible
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impl Clone for Infallible
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fn clone(&self) -> Infallible
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default fn clone_from(&mut self, source: &Self)
1.0.0[src]
Performs copy-assignment from source
. Read more
impl PartialOrd<Infallible> for Infallible
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fn partial_cmp(&self, _other: &Infallible) -> Option<Ordering>
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#[must_use]
default fn lt(&self, other: &Rhs) -> bool
1.0.0[src]
This method tests less than (for self
and other
) and is used by the <
operator. Read more
#[must_use]
default fn le(&self, other: &Rhs) -> bool
1.0.0[src]
This method tests less than or equal to (for self
and other
) and is used by the <=
operator. Read more
#[must_use]
default fn gt(&self, other: &Rhs) -> bool
1.0.0[src]
This method tests greater than (for self
and other
) and is used by the >
operator. Read more
#[must_use]
default fn ge(&self, other: &Rhs) -> bool
1.0.0[src]
This method tests greater than or equal to (for self
and other
) and is used by the >=
operator. Read more
impl Display for Infallible
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Auto Trait Implementations
impl Send for Infallible
impl Sync for Infallible
Blanket Implementations
impl<T, U> Into for T where
U: From<T>,
[src]
U: From<T>,
impl<T> ToOwned for T where
T: Clone,
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T: Clone,
impl<T> ToString for T where
T: Display + ?Sized,
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T: Display + ?Sized,
impl<T> From for T
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impl<T, U> TryFrom for T where
U: Into<T>,
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U: Into<T>,
type Error = Infallible
The type returned in the event of a conversion error.
fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>
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impl<T> Borrow for T where
T: ?Sized,
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T: ?Sized,
impl<T> BorrowMut for T where
T: ?Sized,
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T: ?Sized,
ⓘImportant traits for &'_ mut Ifn borrow_mut(&mut self) -> &mut T
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impl<T, U> TryInto for T where
U: TryFrom<T>,
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U: TryFrom<T>,
type Error = <U as TryFrom<T>>::Error
The type returned in the event of a conversion error.
fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>
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impl<T> Any for T where
T: 'static + ?Sized,
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T: 'static + ?Sized,