fn value_up(&self, values: &BTreeMap<Name, Literal>) -> Result<Literal, ApplicationError> {
let declaration = symtab.lookup(&name).expect("declarations of the representation variables should exist in the symbol table before expression_down is called");
.map(|(name, decl)| (name, Expression::Atomic(Metadata::new(), Atom::Reference(conjure_cp::ast::Reference::new(decl)))))