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#![allow(dead_code)]
use crate::semantics::{rc, NameEnv, NzEnv, TyEnv, Value};
use crate::syntax::{ExprKind, Span, V};
use crate::{Normalized, NormalizedExpr, ToExprOptions};
/// Stores an alpha-normalized variable.
#[derive(Debug, Clone, Copy)]
pub struct AlphaVar {
idx: usize,
}
#[derive(Debug, Clone)]
pub(crate) enum HirKind {
Var(AlphaVar),
// Forbidden ExprKind variants: Var, Import, Embed
Expr(ExprKind<Hir, Normalized>),
}
// An expression with resolved variables and imports.
#[derive(Debug, Clone)]
pub(crate) struct Hir {
kind: Box<HirKind>,
span: Span,
}
impl AlphaVar {
pub(crate) fn new(idx: usize) -> Self {
AlphaVar { idx }
}
pub(crate) fn idx(&self) -> usize {
self.idx
}
}
impl Hir {
pub fn new(kind: HirKind, span: Span) -> Self {
Hir {
kind: Box::new(kind),
span,
}
}
pub fn kind(&self) -> &HirKind {
&*self.kind
}
pub fn span(&self) -> Span {
self.span.clone()
}
/// Converts a HIR expr back to the corresponding AST expression.
pub fn to_expr(&self, opts: ToExprOptions) -> NormalizedExpr {
hir_to_expr(self, opts, &mut NameEnv::new())
}
pub fn to_expr_tyenv(&self, env: &TyEnv) -> NormalizedExpr {
let opts = ToExprOptions {
normalize: true,
alpha: false,
};
let mut env = env.as_nameenv().clone();
hir_to_expr(self, opts, &mut env)
}
/// Eval the Hir. It will actually get evaluated only as needed on demand.
pub fn eval(&self, env: &NzEnv) -> Value {
Value::new_thunk(env, self.clone())
}
/// Eval a closed Hir (i.e. without free variables). It will actually get evaluated only as
/// needed on demand.
pub fn eval_closed_expr(&self) -> Value {
self.eval(&NzEnv::new())
}
/// Eval a closed Hir fully and recursively (TODO: ish, need to fix under lambdas)
pub fn rec_eval_closed_expr(&self) -> Value {
let mut val = self.eval_closed_expr();
val.normalize_mut();
val
}
}
fn hir_to_expr(
hir: &Hir,
opts: ToExprOptions,
env: &mut NameEnv,
) -> NormalizedExpr {
rc(match hir.kind() {
HirKind::Var(v) if opts.alpha => ExprKind::Var(V("_".into(), v.idx())),
HirKind::Var(v) => ExprKind::Var(env.label_var(v)),
HirKind::Expr(e) => {
let e = e.map_ref_maybe_binder(|l, hir| {
if let Some(l) = l {
env.insert_mut(l);
}
let e = hir_to_expr(hir, opts, env);
if let Some(_) = l {
env.remove_mut();
}
e
});
match e {
ExprKind::Lam(_, t, e) if opts.alpha => {
ExprKind::Lam("_".into(), t, e)
}
ExprKind::Pi(_, t, e) if opts.alpha => {
ExprKind::Pi("_".into(), t, e)
}
e => e,
}
}
})
}
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