Struct bevy_internal::utils::smallvec::alloc::fmt::Arguments

1.0.0 · source ·
pub struct Arguments<'a> { /* private fields */ }
Expand description

This structure represents a safely precompiled version of a format string and its arguments. This cannot be generated at runtime because it cannot safely be done, so no constructors are given and the fields are private to prevent modification.

The format_args! macro will safely create an instance of this structure. The macro validates the format string at compile-time so usage of the write() and format() functions can be safely performed.

You can use the Arguments<'a> that format_args! returns in Debug and Display contexts as seen below. The example also shows that Debug and Display format to the same thing: the interpolated format string in format_args!.

let debug = format!("{:?}", format_args!("{} foo {:?}", 1, 2));
let display = format!("{}", format_args!("{} foo {:?}", 1, 2));
assert_eq!("1 foo 2", display);
assert_eq!(display, debug);

Implementations§

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impl<'a> Arguments<'a>

1.52.0 (const: unstable) · source

pub fn as_str(&self) -> Option<&'static str>

Get the formatted string, if it has no arguments to be formatted at runtime.

This can be used to avoid allocations in some cases.

Guarantees

For format_args!("just a literal"), this function is guaranteed to return Some("just a literal").

For most cases with placeholders, this function will return None.

However, the compiler may perform optimizations that can cause this function to return Some(_) even if the format string contains placeholders. For example, format_args!("Hello, {}!", "world") may be optimized to format_args!("Hello, world!"), such that as_str() returns Some("Hello, world!").

The behavior for anything but the trivial case (without placeholders) is not guaranteed, and should not be relied upon for anything other than optimization.

Examples
use std::fmt::Arguments;

fn write_str(_: &str) { /* ... */ }

fn write_fmt(args: &Arguments<'_>) {
    if let Some(s) = args.as_str() {
        write_str(s)
    } else {
        write_str(&args.to_string());
    }
}
assert_eq!(format_args!("hello").as_str(), Some("hello"));
assert_eq!(format_args!("").as_str(), Some(""));
assert_eq!(format_args!("{:?}", std::env::current_dir()).as_str(), None);

Trait Implementations§

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impl<'a> Clone for Arguments<'a>

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fn clone(&self) -> Arguments<'a>

Returns a copy of the value. Read more
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fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more
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impl Debug for Arguments<'_>

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fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter. Read more
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impl Display for Arguments<'_>

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fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter. Read more
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impl<'a> Serialize for Arguments<'a>

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fn serialize<S>( &self, serializer: S ) -> Result<<S as Serializer>::Ok, <S as Serializer>::Error>
where S: Serializer,

Serialize this value into the given Serde serializer. Read more
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impl<'a, const CAP: usize> TryFrom<Arguments<'a>> for ArrayString<CAP>

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type Error = CapacityError<Error>

The type returned in the event of a conversion error.
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fn try_from( f: Arguments<'a> ) -> Result<ArrayString<CAP>, <ArrayString<CAP> as TryFrom<Arguments<'a>>>::Error>

Performs the conversion.
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impl<'a> Value for Arguments<'a>

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fn record(&self, key: &Field, visitor: &mut dyn Visit)

Visits this value with the given Visitor.
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impl<'a> Copy for Arguments<'a>

Auto Trait Implementations§

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impl<'a> !RefUnwindSafe for Arguments<'a>

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impl<'a> !Send for Arguments<'a>

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impl<'a> !Sync for Arguments<'a>

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impl<'a> Unpin for Arguments<'a>

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impl<'a> !UnwindSafe for Arguments<'a>

Blanket Implementations§

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impl<T> Any for T
where T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T, U> AsBindGroupShaderType<U> for T
where U: ShaderType, &'a T: for<'a> Into<U>,

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fn as_bind_group_shader_type(&self, _images: &RenderAssets<Image>) -> U

Return the T ShaderType for self. When used in AsBindGroup derives, it is safe to assume that all images in self exist.
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impl<T> Borrow<T> for T
where T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for T
where T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T> Downcast<T> for T

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fn downcast(&self) -> &T

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impl<T> Downcast for T
where T: Any,

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fn into_any(self: Box<T>) -> Box<dyn Any>

Convert Box<dyn Trait> (where Trait: Downcast) to Box<dyn Any>. Box<dyn Any> can then be further downcast into Box<ConcreteType> where ConcreteType implements Trait.
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fn into_any_rc(self: Rc<T>) -> Rc<dyn Any>

Convert Rc<Trait> (where Trait: Downcast) to Rc<Any>. Rc<Any> can then be further downcast into Rc<ConcreteType> where ConcreteType implements Trait.
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fn as_any(&self) -> &(dyn Any + 'static)

Convert &Trait (where Trait: Downcast) to &Any. This is needed since Rust cannot generate &Any’s vtable from &Trait’s.
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fn as_any_mut(&mut self) -> &mut (dyn Any + 'static)

Convert &mut Trait (where Trait: Downcast) to &Any. This is needed since Rust cannot generate &mut Any’s vtable from &mut Trait’s.
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<S> FromSample<S> for S

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fn from_sample_(s: S) -> S

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impl<T> Instrument for T

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fn instrument(self, span: Span) -> Instrumented<Self>

Instruments this type with the provided Span, returning an Instrumented wrapper. Read more
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fn in_current_span(self) -> Instrumented<Self>

Instruments this type with the current Span, returning an Instrumented wrapper. Read more
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impl<T, U> Into<U> for T
where U: From<T>,

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fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<T> Serialize for T
where T: Serialize + ?Sized,

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fn erased_serialize(&self, serializer: &mut dyn Serializer) -> Result<(), Error>

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fn do_erased_serialize( &self, serializer: &mut dyn Serializer ) -> Result<(), ErrorImpl>

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impl<T> ToOwned for T
where T: Clone,

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type Owned = T

The resulting type after obtaining ownership.
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fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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impl<T, U> ToSample<U> for T
where U: FromSample<T>,

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fn to_sample_(self) -> U

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impl<T> ToSmolStr for T
where T: Display + ?Sized,

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impl<T> ToString for T
where T: Display + ?Sized,

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default fn to_string(&self) -> String

Converts the given value to a String. Read more
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impl<T, U> TryFrom<U> for T
where U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.
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impl<T> Upcast<T> for T

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fn upcast(&self) -> Option<&T>

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impl<T> WithSubscriber for T

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fn with_subscriber<S>(self, subscriber: S) -> WithDispatch<Self>
where S: Into<Dispatch>,

Attaches the provided Subscriber to this type, returning a WithDispatch wrapper. Read more
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Attaches the current default Subscriber to this type, returning a WithDispatch wrapper. Read more
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impl<S, T> Duplex<S> for T
where T: FromSample<S> + ToSample<S>,