Struct VariantData 

pub struct VariantData {
    pub tag: u32,
    pub fields: Box<[Value]>,
}

VariantData: Composite values (sum types)

Fields are stored in a heap-allocated array, NOT linked via next pointers. This is the key difference from cem2, which used StackCell.next for field linking.

Arc and Reference Cycles

Variants use Arc<VariantData> for O(1) cloning, which could theoretically create reference cycles. However, cycles are prevented by design:

• VariantData.fields is immutable (no mutation after creation)
• All variant operations create new variants rather than modifying existing ones
• The Seq language has no mutation primitives for variant fields

This functional/immutable design ensures Arc reference counts always reach zero.

Fields

tag: u32

Tag identifies which variant constructor was used

fields: Box<[Value]>

Fields stored as an owned array of values This is independent of any stack structure

Implementations

impl VariantData

pub fn new(tag: u32, fields: Vec<Value>) -> Self

Create a new variant with the given tag and fields

Trait Implementations

impl Clone for VariantData

fn clone(&self) -> VariantData

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for VariantData

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

Formats the value using the given formatter.

impl PartialEq for VariantData

fn eq(&self, other: &VariantData) -> 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 StructuralPartialEq for VariantData