Delimiter in proc_macro - Rust
Description: Describes how a sequence of token trees is delimited.

## Delimiter

# Enum Delimiter

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    pub enum Delimiter {
        Parenthesis,
        Brace,
        Bracket,
        None,
    }

Expand description

Describes how a sequence of token trees is delimited.

## Variants§

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### Parenthesis

`( ... )`

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### Brace

`{ ... }`

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### Bracket

`[ ... ]`

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### None

`∅ ... ∅` An invisible delimiter, that may, for example, appear around tokens coming from a “macro variable” `$var`. It is important to preserve operator priorities in cases like `$var * 3` where `$var` is `1 + 2`. Invisible delimiters might not survive roundtrip of a token stream through a string.

Note: rustc currently can ignore the grouping of tokens delimited by `None` in the output of a proc_macro. Only `None`-delimited groups created by a macro_rules macro in the input of a proc_macro macro are preserved, and only in very specific circumstances. Any `None`-delimited groups (re)created by a proc_macro will therefore not preserve operator priorities as indicated above. The other `Delimiter` variants should be used instead in this context. This is a rustc bug. For details, see rust-lang/rust#67062.

## Trait Implementations§

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### impl Clone for Delimiter

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#### fn clone(&self) -> Delimiter

Returns a duplicate 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 Delimiter

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

Formats the value using the given formatter. Read more
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### impl PartialEq for Delimiter

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#### fn eq(&self, other: &Delimiter) -> bool

Tests for `self` and `other` values to be equal, and is used by `==`.
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#### fn ne(&self, other: &Rhs) -> bool

Tests for `!=`. The default implementation is almost always sufficient, and should not be overridden without very good reason.
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### impl Copy for Delimiter

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### impl Eq for Delimiter

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### impl StructuralPartialEq for Delimiter

## Auto Trait Implementations§

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### impl Freeze for Delimiter

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### impl RefUnwindSafe for Delimiter

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### impl Send for Delimiter

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### impl Sync for Delimiter

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### impl Unpin for Delimiter

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### impl UnwindSafe for Delimiter

## 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> 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> CloneToUninit for T
where T: Clone,

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#### unsafe fn clone_to_uninit(&self, dest: *mut u8)

🔬This is a nightly-only experimental API. (`clone_to_uninit` #126799)
Performs copy-assignment from `self` to `dest`. Read more
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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<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> 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> 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.