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use std::borrow::Cow;
use std::rc::Rc;
use dhall_syntax::context::Context;
use dhall_syntax::{Label, V};
use crate::core::thunk::Thunk;
use crate::core::value::Value;
use crate::core::var::{AlphaVar, Shift, Subst};
use crate::phase::{Normalized, Type, Typed};
#[derive(Debug, Clone)]
enum NzEnvItem {
Thunk(Thunk),
Skip(AlphaVar),
}
#[derive(Debug, Clone)]
pub(crate) struct NormalizationContext(Rc<Context<Label, NzEnvItem>>);
#[derive(Debug, Clone)]
pub(crate) enum TyEnvItem {
Type(AlphaVar, Type),
Value(Normalized),
}
#[derive(Debug, Clone)]
pub(crate) struct TypecheckContext(pub(crate) Context<Label, TyEnvItem>);
impl NormalizationContext {
pub(crate) fn new() -> Self {
NormalizationContext(Rc::new(Context::new()))
}
pub(crate) fn skip(&self, x: &Label) -> Self {
NormalizationContext(Rc::new(
self.0
.map(|_, e| e.shift(1, &x.into()))
.insert(x.clone(), NzEnvItem::Skip(x.into())),
))
}
pub(crate) fn lookup(&self, var: &V<Label>) -> Value {
let V(x, n) = var;
match self.0.lookup(x, *n) {
Some(NzEnvItem::Thunk(t)) => t.to_value(),
Some(NzEnvItem::Skip(newvar)) => Value::Var(newvar.clone()),
// Free variable
None => Value::Var(AlphaVar::from_var(var.clone())),
}
}
pub(crate) fn from_typecheck_ctx(tc_ctx: &TypecheckContext) -> Self {
use TyEnvItem::*;
let mut ctx = Context::new();
for (k, vs) in tc_ctx.0.iter_keys() {
for v in vs.iter() {
let new_item = match v {
Type(var, _) => NzEnvItem::Skip(var.clone()),
Value(e) => NzEnvItem::Thunk(e.to_thunk()),
};
ctx = ctx.insert(k.clone(), new_item);
}
}
NormalizationContext(Rc::new(ctx))
}
}
impl TypecheckContext {
pub(crate) fn new() -> Self {
TypecheckContext(Context::new())
}
pub(crate) fn insert_type(&self, x: &Label, t: Type) -> Self {
TypecheckContext(self.0.map(|_, e| e.shift(1, &x.into())).insert(
x.clone(),
TyEnvItem::Type(x.into(), t.shift(1, &x.into())),
))
}
pub(crate) fn insert_value(&self, x: &Label, t: Normalized) -> Self {
TypecheckContext(self.0.insert(x.clone(), TyEnvItem::Value(t)))
}
pub(crate) fn lookup(&self, var: &V<Label>) -> Option<Cow<'_, Type>> {
let V(x, n) = var;
match self.0.lookup(x, *n) {
Some(TyEnvItem::Type(_, t)) => Some(Cow::Borrowed(&t)),
Some(TyEnvItem::Value(t)) => Some(t.get_type()?),
None => None,
}
}
pub(crate) fn to_normalization_ctx(&self) -> NormalizationContext {
NormalizationContext::from_typecheck_ctx(self)
}
}
impl Shift for NzEnvItem {
fn shift(&self, delta: isize, var: &AlphaVar) -> Self {
use NzEnvItem::*;
match self {
Thunk(e) => Thunk(e.shift(delta, var)),
Skip(v) => Skip(v.shift(delta, var)),
}
}
}
impl Shift for NormalizationContext {
fn shift(&self, delta: isize, var: &AlphaVar) -> Self {
NormalizationContext(Rc::new(self.0.map(|_, e| e.shift(delta, var))))
}
}
impl Shift for TyEnvItem {
fn shift(&self, delta: isize, var: &AlphaVar) -> Self {
use TyEnvItem::*;
match self {
Type(v, e) => Type(v.shift(delta, var), e.shift(delta, var)),
Value(e) => Value(e.shift(delta, var)),
}
}
}
impl Subst<Typed> for NzEnvItem {
fn subst_shift(&self, var: &AlphaVar, val: &Typed) -> Self {
match self {
NzEnvItem::Thunk(e) => NzEnvItem::Thunk(e.subst_shift(var, val)),
NzEnvItem::Skip(v) if v == var => NzEnvItem::Thunk(val.to_thunk()),
NzEnvItem::Skip(v) => NzEnvItem::Skip(v.shift(-1, var)),
}
}
}
impl Subst<Typed> for NormalizationContext {
fn subst_shift(&self, var: &AlphaVar, val: &Typed) -> Self {
NormalizationContext(Rc::new(
self.0.map(|_, e| e.subst_shift(var, val)),
))
}
}
impl PartialEq for TypecheckContext {
fn eq(&self, _: &Self) -> bool {
// don't count contexts when comparing stuff
// this is dirty but needed for now
true
}
}
impl Eq for TypecheckContext {}
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