Struct FieldBuilder 

pub struct FieldBuilder { /* private fields */ }

Builder for constructing Field instances in const contexts.

This builder is primarily used by derive macros to generate more compact code. All methods are const fn to allow usage in static/const contexts.

Example

// For normal fields (default, most efficient):
const FIELD: Field = FieldBuilder::new(
    "field_name",
    <T as Facet>::SHAPE,
    offset_of!(MyStruct, field_name)
).build();

// For recursive type fields (use lazy to break cycles):
const FIELD: Field = FieldBuilder::new_lazy(
    "children",
    || <Vec<Self> as Facet>::SHAPE,
    offset_of!(MyStruct, children)
).build();

Implementations

impl FieldBuilder

pub const fn new( name: &'static str, shape: fn() -> &'static Shape, offset: usize, ) -> FieldBuilder

Creates a new FieldBuilder with a shape function.

The shape is provided as a function pointer to enable lazy evaluation, which improves compile times by deferring const evaluation to runtime.

Use the shape_of::<T> helper function for the common case:

FieldBuilder::new("field", shape_of::<i32>, offset)

pub const fn new_lazy( name: &'static str, shape: fn() -> &'static Shape, offset: usize, ) -> FieldBuilder

Alias for new - kept for backward compatibility.

Previously used for recursive types, but now all fields use lazy shape references.

pub const fn attributes(self, attributes: &'static [Attr]) -> FieldBuilder

Sets the attributes for this field.

pub const fn doc(self, doc: &'static [&'static str]) -> FieldBuilder

Sets the documentation for this field.

pub const fn flags(self, flags: FieldFlags) -> FieldBuilder

Sets the flags for this field.

pub const fn rename(self, rename: &'static str) -> FieldBuilder

Sets the rename for this field.

pub const fn alias(self, alias: &'static str) -> FieldBuilder

Sets the alias for this field.

pub const fn default_from_trait(self) -> FieldBuilder

Sets the default to use the type’s Default trait.

pub const fn default_custom( self, f: unsafe fn(PtrUninit) -> PtrMut, ) -> FieldBuilder

Sets a custom default function.

pub const fn skip_serializing_if( self, f: unsafe fn(PtrConst) -> bool, ) -> FieldBuilder

Sets the skip_serializing_if predicate.

pub const fn invariants(self, f: unsafe fn(PtrConst) -> bool) -> FieldBuilder

Sets the invariants validation function.

pub const fn proxy(self, proxy: &'static ProxyDef) -> FieldBuilder

Available on crate feature alloc only.

Sets the proxy definition for custom ser/de.

pub const fn metadata(self, kind: &'static str) -> FieldBuilder

Marks this field as storing metadata of the given kind.

Metadata fields are excluded from structural hashing and equality, and are populated by deserializers that support the metadata kind.

Common metadata kinds:

• "span": Source byte offset and length
• "line": Source line number
• "column": Source column number

pub const fn build(self) -> Field

Builds the final Field instance.