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use crate::ast::serde::{AsId, HasId};
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use crate::{ast::DeclarationPtr, bug};
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use derivative::Derivative;
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use parking_lot::MappedRwLockReadGuard;
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use serde::{Deserialize, Serialize};
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use serde_with::serde_as;
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use std::fmt::{Display, Formatter};
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use uniplate::Uniplate;
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use super::{
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    Atom, DeclarationKind, DomainPtr, Expression, GroundDomain, Literal, Metadata, Moo, Name,
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    categories::{Category, CategoryOf},
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    domains::HasDomain,
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};
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/// A reference to a declaration (variable, parameter, etc.)
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///
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/// This is a thin wrapper around [`DeclarationPtr`] with two main purposes:
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/// 1. Encapsulate the serde pragmas (e.g., serializing as IDs rather than full objects)
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/// 2. Enable type-directed traversals of references via uniplate
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#[serde_as]
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#[derive(
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    Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Serialize, Deserialize, Uniplate, Derivative,
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)]
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#[derivative(Hash)]
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#[uniplate()]
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#[biplate(to=DeclarationPtr)]
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#[biplate(to=Name)]
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pub struct Reference {
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    #[serde_as(as = "AsId")]
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    pub ptr: DeclarationPtr,
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}
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impl Reference {
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    pub fn new(ptr: DeclarationPtr) -> Self {
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        Reference { ptr }
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    }
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    pub fn ptr(&self) -> &DeclarationPtr {
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        &self.ptr
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    }
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    pub fn into_ptr(self) -> DeclarationPtr {
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        self.ptr
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    }
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    pub fn name(&self) -> MappedRwLockReadGuard<'_, Name> {
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        self.ptr.name()
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    }
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    pub fn id(&self) -> crate::ast::serde::ObjId {
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        self.ptr.id()
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    }
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    pub fn domain(&self) -> Option<DomainPtr> {
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        self.ptr.domain()
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    }
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    pub fn resolved_domain(&self) -> Option<Moo<GroundDomain>> {
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        self.domain()?.resolve()
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    }
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    /// Returns the expression behind a value-letting reference, if this is one.
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    pub fn resolve_expression(&self) -> Option<Expression> {
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        if let Some(expr) = self.ptr().as_value_letting() {
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            return Some(expr.clone());
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        }
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        let generator = {
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            let kind = self.ptr.kind();
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            if let DeclarationKind::Quantified(inner) = &*kind {
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                inner.generator().cloned()
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            } else {
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                None
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            }
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        };
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        if let Some(generator) = generator
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            && let Some(expr) = generator.as_value_letting()
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        {
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            return Some(expr.clone());
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        }
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        None
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    }
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    /// Evaluates this reference to a literal if it resolves to a constant.
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    pub fn resolve_constant(&self) -> Option<Literal> {
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        self.resolve_expression()
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            .and_then(|expr| super::eval::eval_constant(&expr))
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    }
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    /// Resolves this reference to an atomic expression, if possible.
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    pub fn resolve_atomic(&self) -> Option<Atom> {
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        self.resolve_expression().and_then(|expr| match expr {
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            Expression::Atomic(_, atom) => Some(atom),
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            _ => None,
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        })
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    }
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}
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impl From<Reference> for Expression {
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    fn from(value: Reference) -> Self {
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        Expression::Atomic(Metadata::new(), value.into())
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    }
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}
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impl From<DeclarationPtr> for Reference {
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    fn from(ptr: DeclarationPtr) -> Self {
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        Reference::new(ptr)
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    }
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}
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impl CategoryOf for Reference {
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    fn category_of(&self) -> Category {
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        self.ptr.category_of()
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    }
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}
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impl HasDomain for Reference {
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    fn domain_of(&self) -> DomainPtr {
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        self.ptr.domain().unwrap_or_else(|| {
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            bug!(
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                "reference ({name}) should have a domain",
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                name = self.ptr.name()
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            )
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        })
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    }
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}
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impl Display for Reference {
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    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
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        self.ptr.name().fmt(f)
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    }
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}