## ExpnData

# Struct ExpnData

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    pub struct ExpnData {Show 13 fields
        pub kind: ExpnKind,
        pub parent: ExpnId,
        pub call_site: Span,
        disambiguator: u32,
        pub def_site: Span,
        pub allow_internal_unstable: Option<Arc<[Symbol]>>,
        pub edition: Edition,
        pub macro_def_id: Option<DefId>,
        pub parent_module: Option<DefId>,
        pub(crate) allow_internal_unsafe: bool,
        pub local_inner_macros: bool,
        pub(crate) collapse_debuginfo: bool,
        pub hide_backtrace: bool,
    }

Expand description

A subset of properties from both macro definition and macro call available through global data. Avoid using this if you have access to the original definition or call structures.

## Fields§

§`kind: ExpnKind`§`parent: ExpnId`

The expansion that contains the definition of the macro for this expansion.

§`call_site: Span`

The span of the macro call which produced this expansion.

This span will typically have a different `ExpnData` and `call_site`. This recursively traces back through any macro calls which expanded into further macro calls, until the “source call-site” is reached at the root SyntaxContext. For example, if `food!()` expands to `fruit!()` which then expands to `grape`, then the call-site of `grape` is `fruit!()` and the call-site of `fruit!()` is `food!()`.

For a desugaring expansion, this is the span of the expression or node that was desugared.

§`disambiguator: u32`

Used to force two `ExpnData`s to have different `Fingerprint`s. Due to macro expansion, it’s possible to end up with two `ExpnId`s that have identical `ExpnData`s. This violates the contract of `HashStable`

- the two `ExpnId`s are not equal, but their `Fingerprint`s are equal (since the numerical `ExpnId` value is not considered by the `HashStable` implementation).

The `disambiguator` field is set by `update_disambiguator` when two distinct `ExpnId`s would end up with the same `Fingerprint`. Since `ExpnData` includes a `krate` field, this value only needs to be unique within a single crate.

§`def_site: Span`

The span of the macro definition (possibly dummy). This span serves only informational purpose and is not used for resolution.

§`allow_internal_unstable: Option<Arc<[Symbol]>>`

List of `#[unstable]`/feature-gated features that the macro is allowed to use internally without forcing the whole crate to opt-in to them.

§`edition: Edition`

Edition of the crate in which the macro is defined.

§`macro_def_id: Option<DefId>`

The `DefId` of the macro being invoked, if this `ExpnData` corresponds to a macro invocation

§`parent_module: Option<DefId>`

The normal module (`mod`) in which the expanded macro was defined.

§`allow_internal_unsafe: bool`

Suppresses the `unsafe_code` lint for code produced by this macro.

§`local_inner_macros: bool`

Enables the macro helper hack (`ident!(...)` -> `$crate::ident!(...)`) for this macro.

§`collapse_debuginfo: bool`

Should debuginfo for the macro be collapsed to the outermost expansion site (in other words, was the macro definition annotated with `#[collapse_debuginfo]`)?

§`hide_backtrace: bool`

When true, we do not display the note telling people to use the `-Zmacro-backtrace` flag.

## Implementations§

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### impl ExpnData

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#### pub fn new( kind: ExpnKind, parent: ExpnId, call_site: Span, def_site: Span, allow_internal_unstable: Option<Arc<[Symbol]>>, edition: Edition, macro_def_id: Option<DefId>, parent_module: Option<DefId>, allow_internal_unsafe: bool, local_inner_macros: bool, collapse_debuginfo: bool, hide_backtrace: bool, ) -> ExpnData

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#### pub fn default( kind: ExpnKind, call_site: Span, edition: Edition, macro_def_id: Option<DefId>, parent_module: Option<DefId>, ) -> ExpnData

Constructs expansion data with default properties.

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#### pub fn allow_unstable( kind: ExpnKind, call_site: Span, edition: Edition, allow_internal_unstable: Arc<[Symbol]>, macro_def_id: Option<DefId>, parent_module: Option<DefId>, ) -> ExpnData

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#### pub fn is_root(&self) -> bool

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#### fn hash_expn(&self, ctx: &mut impl HashStableContext) -> Hash64

## Trait Implementations§

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### impl Clone for ExpnData

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

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 ExpnData

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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<__D: SpanDecoder> Decodable<__D> for ExpnData

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#### fn decode(__decoder: &mut __D) -> Self

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### impl<__E: SpanEncoder> Encodable<__E> for ExpnData

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#### fn encode(&self, __encoder: &mut __E)

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### impl<__CTX> HashStable<__CTX> for ExpnData
where __CTX: HashStableContext,

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#### fn hash_stable(&self, __hcx: &mut __CTX, __hasher: &mut StableHasher)

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### impl !Hash for ExpnData

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### impl !PartialEq for ExpnData

## Auto Trait Implementations§

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### impl DynSend for ExpnData

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### impl DynSync for ExpnData

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### impl Freeze for ExpnData

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### impl RefUnwindSafe for ExpnData

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### impl Send for ExpnData

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### impl Sync for ExpnData

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### impl Unpin for ExpnData

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### impl UnwindSafe for ExpnData

## 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<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> 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<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

## 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: 80 bytes