Struct FieldKey 

pub struct FieldKey<'de> {
    pub name: Option<Cow<'de, str>>,
    pub location: FieldLocationHint,
    pub doc: Option<Vec<Cow<'de, str>>>,
    pub tag: Option<Cow<'de, str>>,
}

Field key for a serialized field.

For self-describing formats, this represents either:

• A named key (struct field or map key with string name)
• A tagged key (e.g., @string in Styx for type pattern keys)
• A unit key (map key with no name, e.g., @ in Styx representing None in Option<String> keys)

Fields

name: Option<Cow<'de, str>>

Field name.

None represents a unit key (e.g., @ in Styx) which can be deserialized as None for Option<String> map keys. For struct field deserialization, None is an error since struct fields always have names.

location: FieldLocationHint

Location hint.

doc: Option<Vec<Cow<'de, str>>>

Documentation comments attached to this field (for formats that support them).

Used by formats like Styx where /// comment before a field is preserved. When deserializing into a metadata_container type like Documented<T>, these doc lines are used to populate the metadata.

tag: Option<Cow<'de, str>>

Tag name for tagged keys (for formats that support them).

Used by formats like Styx where @string in key position represents a type pattern. When deserializing into a metadata_container type with #[facet(metadata = "tag")], this tag name is used to populate the metadata.

• None: not a tagged key (bare identifier like name)
• Some(""): unit tag (@ alone)
• Some("string"): named tag (@string)

Implementations

impl<'de> FieldKey<'de>

pub fn new(name: impl Into<Cow<'de, str>>, location: FieldLocationHint) -> Self

Create a new field key with a name.

pub fn with_doc( name: impl Into<Cow<'de, str>>, location: FieldLocationHint, doc: Vec<Cow<'de, str>>, ) -> Self

Create a new field key with a name and documentation.

pub fn tagged( tag: impl Into<Cow<'de, str>>, location: FieldLocationHint, ) -> Self

Create a tagged field key (e.g., @string in Styx).

Used for type pattern keys where the key is a tag rather than a bare identifier.

pub fn tagged_with_doc( tag: impl Into<Cow<'de, str>>, location: FieldLocationHint, doc: Vec<Cow<'de, str>>, ) -> Self

Create a tagged field key with documentation.

pub fn unit(location: FieldLocationHint) -> Self

Create a unit field key (no name).

Used for formats like Styx where @ represents a unit key in maps. This is equivalent to tagged("") - a tag with an empty name.

pub fn unit_with_doc( location: FieldLocationHint, doc: Vec<Cow<'de, str>>, ) -> Self

Create a unit field key with documentation.

Trait Implementations

impl<'de> Clone for FieldKey<'de>

fn clone(&self) -> FieldKey<'de>

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<'de> Debug for FieldKey<'de>

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

Formats the value using the given formatter.

impl<'de> PartialEq for FieldKey<'de>

fn eq(&self, other: &FieldKey<'de>) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

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

impl<'de> Eq for FieldKey<'de>

impl<'de> StructuralPartialEq for FieldKey<'de>