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use crate::algebraic_type::AlgebraicType;
use crate::meta_type::MetaType;
use crate::raw_identifier::RawIdentifier;
use crate::SpacetimeType;
/// A variant of a sum type.
///
/// NOTE: Each element has an implicit element tag based on its order.
/// Uniquely identifies an element similarly to protobuf tags.
#[derive(Debug, Clone, Eq, PartialEq, Ord, PartialOrd, Hash, SpacetimeType)]
#[sats(crate = crate)]
pub struct SumTypeVariant {
/// The name of the variant, if any.
pub name: Option<RawIdentifier>,
/// The type of the variant.
///
/// Unlike a language like Rust,
/// where we can have `enum _ { V1 { foo: A, bar: B, .. }, .. }`,
/// the product within the variant `V1`, i.e., `{ foo: A, bar: B, .. }`
/// is separated out in SATS into a separate product type.
/// So we would express this as `{ V1({ foo: A, bar: B, .. }), .. }`.
pub algebraic_type: AlgebraicType,
}
impl SumTypeVariant {
/// Returns a sum type variant with an optional `name` and `algebraic_type`.
pub const fn new(algebraic_type: AlgebraicType, name: Option<RawIdentifier>) -> Self {
Self { algebraic_type, name }
}
/// Returns a sum type variant with `name` and `algebraic_type`.
pub fn new_named(algebraic_type: AlgebraicType, name: impl Into<RawIdentifier>) -> Self {
Self {
algebraic_type,
name: Some(name.into()),
}
}
/// Returns a unit variant with `name`.
pub fn unit(name: impl Into<RawIdentifier>) -> Self {
Self::new_named(AlgebraicType::unit(), name)
}
/// Returns the name of the variant.
pub fn name(&self) -> Option<&RawIdentifier> {
self.name.as_ref()
}
/// Returns whether the variant has the given name.
pub fn has_name(&self, name: &str) -> bool {
self.name().is_some_and(|n| &**n == name)
}
/// Returns whether this is a unit variant.
pub fn is_unit(&self) -> bool {
self.algebraic_type == AlgebraicType::unit()
}
}
impl MetaType for SumTypeVariant {
fn meta_type() -> AlgebraicType {
AlgebraicType::product([
("name", AlgebraicType::option(AlgebraicType::String)),
("algebraic_type", AlgebraicType::ZERO_REF),
])
}
}
impl From<AlgebraicType> for SumTypeVariant {
fn from(algebraic_type: AlgebraicType) -> Self {
Self::new(algebraic_type, None)
}
}