Method new

crates/csskit_derives/src/parse.rs:327–360

(variant: &Variant, post_parse_steps: &TokenStream)

impl VariantPlan {
	fn new(variant: &Variant, post_parse_steps: &TokenStream) -> Result<Self> {
		let ident = variant.ident.clone();
		let parse_mode = ParseArg::from_attributes(&variant.attrs)?.parse_mode();
		let variant_atom = extract_atom(&variant.attrs)?;
		let fields = Field::from_fields(&variant.fields)?;
		let first_type = fields
			.first()
			.map(|f| f.ty.clone())
			.ok_or_else(|| Error::new(ident.span(), "enum variant must have at least one field"))?;
		let members = members_tokens(&variant.fields);

		// Prefer variant-level atom; fall back to first field's atom except for
		// must-occur variants with all-optional fields.
		let all_optional = fields.iter().all(|f| f.ty.is_option());
		let effective_atom = if variant_atom.is_some() {
			variant_atom
		} else if (parse_mode == FieldParseMode::OneMustOccur || parse_mode == FieldParseMode::AllMustOccur)
			&& all_optional
		{
			None
		} else {
			fields.first().and_then(|f| f.atom.clone())
		};

		Ok(Self {
			ident,
			first_type,
			effective_atom,
			parse_mode,
			fields,
			members,
			post_parse_steps: post_parse_steps.clone(),
		})
	}

	/// Render the body for this variant, consuming where-bounds into `wc`.
	/// Picks `SequentialPlan` or `MustOccurPlan` based on `parse_mode`.