PatKind in rustc_hir::hir - Rust
Description: API documentation for the Rust `PatKind` enum in crate `rustc_hir`.

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## PatKind

# Enum PatKind

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    pub enum PatKind<'hir> {
    Show 16 variants    Missing,
        Wild,
        Binding(BindingMode, HirId, Ident, Option<&'hir Pat<'hir>>),
        Struct(QPath<'hir>, &'hir [PatField<'hir>], Option<Span>),
        TupleStruct(QPath<'hir>, &'hir [Pat<'hir>], DotDotPos),
        Or(&'hir [Pat<'hir>]),
        Never,
        Tuple(&'hir [Pat<'hir>], DotDotPos),
        Box(&'hir Pat<'hir>),
        Deref(&'hir Pat<'hir>),
        Ref(&'hir Pat<'hir>, Pinnedness, Mutability),
        Expr(&'hir PatExpr<'hir>),
        Guard(&'hir Pat<'hir>, &'hir Expr<'hir>),
        Range(Option<&'hir PatExpr<'hir>>, Option<&'hir PatExpr<'hir>>, RangeEnd),
        Slice(&'hir [Pat<'hir>], Option<&'hir Pat<'hir>>, &'hir [Pat<'hir>]),
        Err(ErrorGuaranteed),
    }

## Variants§

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### Missing

A missing pattern, e.g. for an anonymous param in a bare fn like `fn f(u32)`.

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### Wild

Represents a wildcard pattern (i.e., `_`).

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### Binding(BindingMode, HirId, Ident, Option<&'hir Pat<'hir>>)

A fresh binding `ref mut binding @ OPT_SUBPATTERN`. The `HirId` is the canonical ID for the variable being bound, (e.g., in `Ok(x) | Err(x)`, both `x` use the same canonical ID), which is the pattern ID of the first `x`.

The `BindingMode` is what’s provided by the user, before match ergonomics are applied. For the binding mode actually in use, see `TypeckResults::extract_binding_mode`.

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### Struct(QPath<'hir>, &'hir [PatField<'hir>], Option<Span>)

A struct or struct variant pattern (e.g., `Variant {x, y, ..}`). The `Option` contains the span of a possible `..`.

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### TupleStruct(QPath<'hir>, &'hir [Pat<'hir>], DotDotPos)

A tuple struct/variant pattern `Variant(x, y, .., z)`. If the `..` pattern fragment is present, then `DotDotPos` denotes its position. `0 <= position <= subpats.len()`

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### Or(&'hir [Pat<'hir>])

An or-pattern `A | B | C`. Invariant: `pats.len() >= 2`.

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### Never

A never pattern `!`.

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### Tuple(&'hir [Pat<'hir>], DotDotPos)

A tuple pattern (e.g., `(a, b)`). If the `..` pattern fragment is present, then `DotDotPos` denotes its position. `0 <= position <= subpats.len()`

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### Box(&'hir Pat<'hir>)

A `box` pattern.

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### Deref(&'hir Pat<'hir>)

A `deref` pattern (currently `deref!()` macro-based syntax).

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### Ref(&'hir Pat<'hir>, Pinnedness, Mutability)

A reference pattern (e.g., `&mut (a, b)`).

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### Expr(&'hir PatExpr<'hir>)

A literal, const block or path.

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### Guard(&'hir Pat<'hir>, &'hir Expr<'hir>)

A guard pattern (e.g., `x if guard(x)`).

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### Range(Option<&'hir PatExpr<'hir>>, Option<&'hir PatExpr<'hir>>, RangeEnd)

A range pattern (e.g., `1..=2` or `1..2`).

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### Slice(&'hir [Pat<'hir>], Option<&'hir Pat<'hir>>, &'hir [Pat<'hir>])

A slice pattern, `[before_0, ..., before_n, (slice, after_0, ..., after_n)?]`.

Here, `slice` is lowered from the syntax `($binding_mode $ident @)? ..`. If `slice` exists, then `after` can be non-empty.

The representation for e.g., `[a, b, .., c, d]` is:

ⓘ

    PatKind::Slice([Binding(a), Binding(b)], Some(Wild), [Binding(c), Binding(d)])

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### Err(ErrorGuaranteed)

A placeholder for a pattern that wasn’t well formed in some way.

## Trait Implementations§

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### impl<'hir> Clone for PatKind<'hir>

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#### fn clone(&self) -> PatKind<'hir>

Returns a duplicate of the value. Read more
1.0.0 (const: unstable) · Source§

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

Performs copy-assignment from `source`. Read more
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### impl<'hir> Debug for PatKind<'hir>

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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<'hir> StableHash for PatKind<'hir>

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#### fn stable_hash<__Hcx: StableHashCtxt>( &self, __hcx: &mut __Hcx, __hasher: &mut StableHasher, )

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### impl<'hir> Copy for PatKind<'hir>

## Auto Trait Implementations§

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### impl<'hir> DynSend for PatKind<'hir>

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### impl<'hir> DynSync for PatKind<'hir>

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### impl<'hir> Freeze for PatKind<'hir>

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### impl<'hir> RefUnwindSafe for PatKind<'hir>

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### impl<'hir> Send for PatKind<'hir>

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### impl<'hir> Sync for PatKind<'hir>

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### impl<'hir> Unpin for PatKind<'hir>

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### impl<'hir> UnsafeUnpin for PatKind<'hir>

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### impl<'hir> UnwindSafe for PatKind<'hir>

## Blanket Implementations§

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### impl<T> Aligned for T

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#### const ALIGN: Alignment

Alignment of `Self`.
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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<'tcx, T> ArenaAllocatable<'tcx, IsCopy> for T
where T: Copy,

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#### fn allocate_on(self, arena: &'tcx Arena<'tcx>) -> &'tcx mut T

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#### fn allocate_from_iter( arena: &'tcx Arena<'tcx>, iter: impl IntoIterator<Item = T>, ) -> &'tcx mut [T]

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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`)
Performs copy-assignment from `self` to `dest`. Read more
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### impl<T> DynClone for T
where T: Clone,

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#### fn __clone_box(&self, _: Private) -> *mut ()

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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> 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> IntoEither for T

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#### fn into_either(self, into_left: bool) -> Either<Self, Self>

Converts `self` into a `Left` variant of `Either<Self, Self>` if `into_left` is `true`. Converts `self` into a `Right` variant of `Either<Self, Self>` otherwise. Read more
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#### fn into_either_with<F>(self, into_left: F) -> Either<Self, Self>
where F: FnOnce(&Self) -> bool,

Converts `self` into a `Left` variant of `Either<Self, Self>` if `into_left(&self)` returns `true`. Converts `self` into a `Right` variant of `Either<Self, Self>` otherwise. Read more
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### impl<T> Pointable for T

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#### const ALIGN: usize

The alignment of pointer.
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#### type Init = T

The type for initializers.
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#### unsafe fn init(init: <T as Pointable>::Init) -> usize

Initializes a with the given initializer. Read more
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#### unsafe fn deref<'a>(ptr: usize) -> &'a T

Dereferences the given pointer. Read more
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#### unsafe fn deref_mut<'a>(ptr: usize) -> &'a mut T

Mutably dereferences the given pointer. Read more
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#### unsafe fn drop(ptr: usize)

Drops the object pointed to by the given pointer. Read more
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### impl<T> Same for T

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#### type Output = T

Should always be `Self`
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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.
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### impl<V, T> VZip<V> for T
where V: MultiLane<T>,

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#### fn vzip(self) -> V

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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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#### fn with_current_subscriber(self) -> WithDispatch<Self>

Attaches the current default `Subscriber` to this type, returning a `WithDispatch` wrapper. Read more
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### impl<T> ErasedDestructor for T
where T: 'static,

## Layout§

Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain `repr(...)` attributes. Please see the Rust Reference's “Type Layout” chapter for details on type layout guarantees.

Size: 56 bytes

Size for each variant:

- `Missing`: 0 bytes
- `Wild`: 0 bytes
- `Binding`: 40 bytes
- `Struct`: 56 bytes
- `TupleStruct`: 56 bytes
- `Or`: 24 bytes
- `Never`: 0 bytes
- `Tuple`: 32 bytes
- `Box`: 16 bytes
- `Deref`: 16 bytes
- `Ref`: 24 bytes
- `Expr`: 16 bytes
- `Guard`: 24 bytes
- `Range`: 32 bytes
- `Slice`: 48 bytes
- `Err`: 0 bytes