Struct proc_macro_kwargs::parse::ExplicitOption

pub struct ExplicitOption<T>(pub Option<T>);

A version of Option that is parsed with explicit Some(<inner>) or None syntax

This is as opposed to a regular Option, which requires no extra syntax and always parses to Some (it’s intended for use with optional args)

Tuple Fields

0: Option<T>

Methods from Deref<Target = Option<T>>

pub const fn is_some(&self) -> bool

Returns true if the option is a Some value.

Examples

let x: Option<u32> = Some(2);
assert_eq!(x.is_some(), true);

let x: Option<u32> = None;
assert_eq!(x.is_some(), false);

pub const fn is_none(&self) -> bool

Returns true if the option is a None value.

Examples

let x: Option<u32> = Some(2);
assert_eq!(x.is_none(), false);

let x: Option<u32> = None;
assert_eq!(x.is_none(), true);

pub fn contains<U>(&self, x: &U) -> bool where
    U: PartialEq<T>, 

🔬 This is a nightly-only experimental API. (option_result_contains)

Returns true if the option is a Some value containing the given value.

Examples

#![feature(option_result_contains)]

let x: Option<u32> = Some(2);
assert_eq!(x.contains(&2), true);

let x: Option<u32> = Some(3);
assert_eq!(x.contains(&2), false);

let x: Option<u32> = None;
assert_eq!(x.contains(&2), false);

pub const fn as_ref(&self) -> Option<&T>

Converts from &Option<T> to Option<&T>.

Examples

Converts an Option<String> into an Option<usize>, preserving the original. The map method takes the self argument by value, consuming the original, so this technique uses as_ref to first take an Option to a reference to the value inside the original.

let text: Option<String> = Some("Hello, world!".to_string());
// First, cast `Option<String>` to `Option<&String>` with `as_ref`,
// then consume *that* with `map`, leaving `text` on the stack.
let text_length: Option<usize> = text.as_ref().map(|s| s.len());
println!("still can print text: {:?}", text);

pub fn as_pin_ref(self: Pin<&Option<T>>) -> Option<Pin<&T>>

Converts from Pin<&Option<T>> to Option<Pin<&T>>.

pub fn as_pin_mut(self: Pin<&mut Option<T>>) -> Option<Pin<&mut T>>

Converts from Pin<&mut Option<T>> to Option<Pin<&mut T>>.

pub fn iter(&self) -> Iter<'_, T>

Returns an iterator over the possibly contained value.

Examples

let x = Some(4);
assert_eq!(x.iter().next(), Some(&4));

let x: Option<u32> = None;
assert_eq!(x.iter().next(), None);

pub fn as_deref(&self) -> Option<&<T as Deref>::Target>

Converts from Option<T> (or &Option<T>) to Option<&T::Target>.

Leaves the original Option in-place, creating a new one with a reference to the original one, additionally coercing the contents via Deref.

Examples

let x: Option<String> = Some("hey".to_owned());
assert_eq!(x.as_deref(), Some("hey"));

let x: Option<String> = None;
assert_eq!(x.as_deref(), None);

Trait Implementations

impl<T: Clone> Clone for ExplicitOption<T>

fn clone(&self) -> ExplicitOption<T>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T: Debug> Debug for ExplicitOption<T>

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

Formats the value using the given formatter.

impl<T> Deref for ExplicitOption<T>

type Target = Option<T>

The resulting type after dereferencing.

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

Dereferences the value.

impl<T> From<ExplicitOption<T>> for Option<T>

fn from(explicit: ExplicitOption<T>) -> Option<T>

Performs the conversion.

impl<T> From<Option<T>> for ExplicitOption<T>

fn from(opt: Option<T>) -> Self

Performs the conversion.

impl<T: Hash> Hash for ExplicitOption<T>

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H) where
    H: Hasher, 

Feeds a slice of this type into the given Hasher.

impl<T: MacroArg> MacroArg for ExplicitOption<T>

fn parse_macro_arg(stream: ParseStream<'_>) -> Result<Self>

Parse the argument to the macro

impl<T: PartialEq> PartialEq<ExplicitOption<T>> for ExplicitOption<T>

fn eq(&self, other: &ExplicitOption<T>) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &ExplicitOption<T>) -> bool

This method tests for !=.

impl<T: Copy> Copy for ExplicitOption<T>

impl<T: Eq> Eq for ExplicitOption<T>

impl<T> StructuralEq for ExplicitOption<T>

impl<T> StructuralPartialEq for ExplicitOption<T>