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-rw-r--r--dhall/src/normalize.rs236
-rw-r--r--dhall/src/typecheck.rs5
2 files changed, 160 insertions, 81 deletions
diff --git a/dhall/src/normalize.rs b/dhall/src/normalize.rs
index 3b21b86..461ce99 100644
--- a/dhall/src/normalize.rs
+++ b/dhall/src/normalize.rs
@@ -181,7 +181,7 @@ fn apply_builtin(b: Builtin, args: Vec<Value>) -> Value {
[_, NEListLit(xs), _, cons, nil] => {
let mut v = nil;
for x in xs.into_iter().rev() {
- v = cons.clone().app(x.normalize_whnf()).app(v);
+ v = cons.clone().app(x.as_whnf()).app(v);
}
v
}
@@ -215,7 +215,7 @@ fn apply_builtin(b: Builtin, args: Vec<Value>) -> Value {
nothing
},
[_, NEOptionalLit(x), _, just, _] => {
- just.app(x.normalize_whnf())
+ just.app(x.as_whnf())
}
),
NaturalBuild => improved_slice_patterns::match_vec!(args;
@@ -395,8 +395,8 @@ impl Value {
match self {
Value::Lam(x, t, e) => rc(ExprF::Lam(
x.clone(),
- t.to_nf().normalize_to_expr(),
- e.to_nf().normalize_to_expr(),
+ t.as_nf().normalize_to_expr(),
+ e.as_nf().normalize_to_expr(),
)),
Value::AppliedBuiltin(b, args) => {
let mut e = rc(ExprF::Builtin(b));
@@ -406,18 +406,18 @@ impl Value {
e
}
Value::OptionalSomeClosure(n) => {
- let a = n.to_nf().normalize_to_expr();
+ let a = n.as_nf().normalize_to_expr();
dhall::subexpr!(λ(x: a) -> Some x)
}
Value::ListConsClosure(n, None) => {
- let a = n.to_nf().normalize_to_expr();
+ let a = n.as_nf().normalize_to_expr();
// Avoid accidental capture of the new `x` variable
let a1 = a.shift0(1, &"x".into());
dhall::subexpr!(λ(x : a) -> λ(xs : List a1) -> [ x ] # xs)
}
Value::ListConsClosure(n, Some(v)) => {
- let v = v.to_nf().normalize_to_expr();
- let a = n.to_nf().normalize_to_expr();
+ let v = v.as_nf().normalize_to_expr();
+ let a = n.as_nf().normalize_to_expr();
// Avoid accidental capture of the new `xs` variable
let v = v.shift0(1, &"xs".into());
dhall::subexpr!(λ(xs : List a) -> [ v ] # xs)
@@ -427,8 +427,8 @@ impl Value {
}
Value::Pi(x, t, e) => rc(ExprF::Pi(
x,
- t.to_nf().normalize_to_expr(),
- e.to_nf().normalize_to_expr(),
+ t.as_nf().normalize_to_expr(),
+ e.as_nf().normalize_to_expr(),
)),
Value::Var(v) => rc(ExprF::Var(v)),
Value::Const(c) => rc(ExprF::Const(c)),
@@ -437,46 +437,46 @@ impl Value {
Value::IntegerLit(n) => rc(ExprF::IntegerLit(n)),
Value::EmptyOptionalLit(n) => rc(ExprF::App(
rc(ExprF::Builtin(Builtin::OptionalNone)),
- n.to_nf().normalize_to_expr(),
+ n.as_nf().normalize_to_expr(),
)),
Value::NEOptionalLit(n) => {
- rc(ExprF::SomeLit(n.to_nf().normalize_to_expr()))
+ rc(ExprF::SomeLit(n.as_nf().normalize_to_expr()))
}
Value::EmptyListLit(n) => {
- rc(ExprF::EmptyListLit(n.to_nf().normalize_to_expr()))
+ rc(ExprF::EmptyListLit(n.as_nf().normalize_to_expr()))
}
Value::NEListLit(elts) => rc(ExprF::NEListLit(
elts.into_iter()
- .map(|n| n.to_nf().normalize_to_expr())
+ .map(|n| n.as_nf().normalize_to_expr())
.collect(),
)),
Value::RecordLit(kvs) => rc(ExprF::RecordLit(
kvs.into_iter()
- .map(|(k, v)| (k, v.to_nf().normalize_to_expr()))
+ .map(|(k, v)| (k, v.as_nf().normalize_to_expr()))
.collect(),
)),
Value::RecordType(kts) => rc(ExprF::RecordType(
kts.into_iter()
- .map(|(k, v)| (k, v.to_nf().normalize_to_expr()))
+ .map(|(k, v)| (k, v.as_nf().normalize_to_expr()))
.collect(),
)),
Value::UnionType(kts) => rc(ExprF::UnionType(
kts.into_iter()
- .map(|(k, v)| (k, v.map(|v| v.to_nf().normalize_to_expr())))
+ .map(|(k, v)| (k, v.map(|v| v.as_nf().normalize_to_expr())))
.collect(),
)),
Value::UnionConstructor(l, kts) => {
let kts = kts
.into_iter()
- .map(|(k, v)| (k, v.map(|v| v.to_nf().normalize_to_expr())))
+ .map(|(k, v)| (k, v.map(|v| v.as_nf().normalize_to_expr())))
.collect();
rc(ExprF::Field(rc(ExprF::UnionType(kts)), l))
}
Value::UnionLit(l, v, kts) => rc(ExprF::UnionLit(
l,
- v.to_nf().normalize_to_expr(),
+ v.as_nf().normalize_to_expr(),
kts.into_iter()
- .map(|(k, v)| (k, v.map(|v| v.to_nf().normalize_to_expr())))
+ .map(|(k, v)| (k, v.map(|v| v.as_nf().normalize_to_expr())))
.collect(),
)),
Value::TextLit(elts) => {
@@ -487,7 +487,7 @@ impl Value {
.flat_map(|contents| {
use InterpolatedTextContents::{Expr, Text};
let new_interpolated = match contents {
- Expr(n) => match n.to_nf() {
+ Expr(n) => match n.as_nf() {
Value::TextLit(elts2) => {
normalize_textlit(elts2)
}
@@ -600,7 +600,7 @@ impl Value {
(Value::Lam(x, _, e), val) => {
let val =
PartiallyNormalized(val, None, std::marker::PhantomData);
- e.subst_shift(&V(x, 0), &val).normalize_whnf()
+ e.subst_shift(&V(x, 0), &val).as_whnf()
}
(Value::AppliedBuiltin(b, mut args), val) => {
args.push(val);
@@ -825,74 +825,156 @@ impl Value {
}
}
-/// Contains either a (partially) normalized value or a
-/// non-normalized value alongside a normalization context.
-#[derive(Debug, Clone)]
-pub(crate) enum Thunk {
- // Normal form, i.e. completely normalized
- NF(Box<Value>),
- // Weak Head Normal Form, i.e. subexpressions may not be normalized
- WHNF(Box<Value>),
- Unnormalized(NormalizationContext, InputSubExpr),
-}
+mod thunk {
+ use super::{normalize_whnf, InputSubExpr, NormalizationContext, Value};
+ use crate::expr::PartiallyNormalized;
+ use dhall_core::{Label, V};
+ use std::cell::RefCell;
+ use std::rc::Rc;
-impl Thunk {
- fn new(ctx: NormalizationContext, e: InputSubExpr) -> Thunk {
- Thunk::Unnormalized(ctx, e)
+ #[derive(Debug)]
+ enum ThunkInternal {
+ /// Non-normalized value alongside a normalization context
+ Unnormalized(NormalizationContext, InputSubExpr),
+ /// Weak Head Normal Form, i.e. subexpressions may not be normalized
+ WHNF(Box<Value>),
+ /// Normal form, i.e. completely normalized
+ NF(Box<Value>),
}
- fn from_whnf(v: Value) -> Thunk {
- Thunk::WHNF(Box::new(v))
- }
+ /// Stores a possibl unevaluated value. Uses RefCell to ensure that
+ /// the value gets normalized at most once.
+ #[derive(Debug, Clone)]
+ pub struct Thunk(Rc<RefCell<ThunkInternal>>);
- pub(crate) fn normalize_whnf(&self) -> Value {
- match self {
- Thunk::WHNF(v) => (**v).clone(),
- Thunk::NF(v) => (**v).clone(),
- Thunk::Unnormalized(ctx, e) => {
- normalize_whnf(ctx.clone(), e.clone())
+ impl ThunkInternal {
+ fn into_thunk(self) -> Thunk {
+ Thunk(Rc::new(RefCell::new(self)))
+ }
+
+ fn normalize_whnf(&mut self) {
+ match self {
+ ThunkInternal::Unnormalized(ctx, e) => {
+ let new = ThunkInternal::WHNF(Box::new(normalize_whnf(
+ ctx.clone(),
+ e.clone(),
+ )));
+ std::mem::replace(self, new);
+ }
+ ThunkInternal::WHNF(_) => {}
+ ThunkInternal::NF(_) => {}
}
}
- }
- fn normalize(&self) -> Thunk {
- Thunk::NF(Box::new(self.normalize_whnf().normalize()))
- }
+ fn normalize_nf(&mut self) {
+ self.normalize_whnf();
+ match self {
+ ThunkInternal::Unnormalized(_, _) => unreachable!(),
+ ThunkInternal::WHNF(v) => {
+ let new = ThunkInternal::NF(Box::new(v.normalize()));
+ std::mem::replace(self, new);
+ }
+ ThunkInternal::NF(_) => {}
+ }
+ }
- fn shift(&self, delta: isize, var: &V<Label>) -> Self {
- match self {
- Thunk::WHNF(v) => Thunk::WHNF(Box::new(v.shift(delta, var))),
- Thunk::NF(v) => Thunk::NF(Box::new(v.shift(delta, var))),
- Thunk::Unnormalized(ctx, e) => {
- Thunk::Unnormalized(ctx.shift(delta, var), e.clone())
+ // Always use normalize_whnf before
+ fn as_whnf(&self) -> Value {
+ match self {
+ ThunkInternal::Unnormalized(_, _) => unreachable!(),
+ ThunkInternal::WHNF(v) => v.as_ref().clone(),
+ ThunkInternal::NF(v) => v.as_ref().clone(),
}
}
- }
- pub(crate) fn subst_shift(
- &self,
- var: &V<Label>,
- val: &PartiallyNormalized<'static>,
- ) -> Self {
- match self {
- Thunk::WHNF(v) => Thunk::WHNF(Box::new(v.subst_shift(var, val))),
- Thunk::NF(v) => Thunk::NF(Box::new(v.subst_shift(var, val))),
- Thunk::Unnormalized(ctx, e) => {
- Thunk::Unnormalized(ctx.subst_shift(var, val), e.clone())
+ // Always use normalize_nf before
+ fn as_nf(&self) -> Value {
+ match self {
+ ThunkInternal::Unnormalized(_, _) => unreachable!(),
+ ThunkInternal::WHNF(_) => unreachable!(),
+ ThunkInternal::NF(v) => v.as_ref().clone(),
}
}
- }
- pub(crate) fn to_nf(&self) -> Value {
- match self {
- Thunk::NF(v) => (**v).clone(),
- Thunk::WHNF(_) | Thunk::Unnormalized(_, _) => {
- self.normalize_whnf().normalize()
+ fn shift(&self, delta: isize, var: &V<Label>) -> Self {
+ match self {
+ ThunkInternal::Unnormalized(ctx, e) => {
+ ThunkInternal::Unnormalized(
+ ctx.shift(delta, var),
+ e.clone(),
+ )
+ }
+ ThunkInternal::WHNF(v) => {
+ ThunkInternal::WHNF(Box::new(v.shift(delta, var)))
+ }
+ ThunkInternal::NF(v) => {
+ ThunkInternal::NF(Box::new(v.shift(delta, var)))
+ }
+ }
+ }
+
+ fn subst_shift(
+ &self,
+ var: &V<Label>,
+ val: &PartiallyNormalized<'static>,
+ ) -> Self {
+ match self {
+ ThunkInternal::Unnormalized(ctx, e) => {
+ ThunkInternal::Unnormalized(
+ ctx.subst_shift(var, val),
+ e.clone(),
+ )
+ }
+ ThunkInternal::WHNF(v) => {
+ ThunkInternal::WHNF(Box::new(v.subst_shift(var, val)))
+ }
+ ThunkInternal::NF(v) => {
+ ThunkInternal::NF(Box::new(v.subst_shift(var, val)))
+ }
}
}
}
+
+ impl Thunk {
+ pub(crate) fn new(ctx: NormalizationContext, e: InputSubExpr) -> Thunk {
+ ThunkInternal::Unnormalized(ctx, e).into_thunk()
+ }
+
+ pub(crate) fn from_whnf(v: Value) -> Thunk {
+ ThunkInternal::WHNF(Box::new(v)).into_thunk()
+ }
+
+ pub(crate) fn normalize(&self) -> Thunk {
+ self.0.borrow_mut().normalize_nf();
+ self.clone()
+ }
+
+ pub(crate) fn as_whnf(&self) -> Value {
+ self.0.borrow_mut().normalize_whnf();
+ self.0.borrow().as_whnf()
+ }
+
+ pub(crate) fn as_nf(&self) -> Value {
+ self.0.borrow_mut().normalize_nf();
+ self.0.borrow().as_nf()
+ }
+
+ pub(crate) fn shift(&self, delta: isize, var: &V<Label>) -> Self {
+ self.0.borrow().shift(delta, var).into_thunk()
+ }
+
+ pub(crate) fn subst_shift(
+ &self,
+ var: &V<Label>,
+ val: &PartiallyNormalized<'static>,
+ ) -> Self {
+ self.0.borrow().subst_shift(var, val).into_thunk()
+ }
+ }
}
+pub(crate) use thunk::Thunk;
+
/// A thunk in type position.
#[derive(Debug, Clone)]
pub(crate) enum TypeThunk {
@@ -942,9 +1024,9 @@ impl TypeThunk {
}
}
- pub(crate) fn to_nf(&self) -> Value {
+ pub(crate) fn as_nf(&self) -> Value {
match self {
- TypeThunk::Thunk(th) => th.to_nf(),
+ TypeThunk::Thunk(th) => th.as_nf(),
// TODO: let's hope for the best with the unwrap
TypeThunk::Type(t) => t
.clone()
@@ -1118,7 +1200,7 @@ fn normalize_last_layer(expr: ExprF<Value, Label, X, X>) -> Value {
ExprF::Field(UnionType(kts), l) => UnionConstructor(l, kts),
ExprF::Field(RecordLit(mut kvs), l) => match kvs.remove(&l) {
- Some(r) => r.normalize_whnf(),
+ Some(r) => r.as_whnf(),
None => {
// Couldn't do anything useful, so just normalize subexpressions
Expr(rc(ExprF::Field(RecordLit(kvs).normalize_to_expr(), l)))
@@ -1135,13 +1217,13 @@ fn normalize_last_layer(expr: ExprF<Value, Label, X, X>) -> Value {
ExprF::Merge(RecordLit(mut handlers), e, t) => {
let e = match e {
UnionConstructor(l, kts) => match handlers.remove(&l) {
- Some(h) => return h.normalize_whnf(),
+ Some(h) => return h.as_whnf(),
None => UnionConstructor(l, kts),
},
UnionLit(l, v, kts) => match handlers.remove(&l) {
Some(h) => {
- let h = h.normalize_whnf();
- let v = v.normalize_whnf();
+ let h = h.as_whnf();
+ let v = v.as_whnf();
return h.app(v);
}
None => UnionLit(l, v, kts),
diff --git a/dhall/src/typecheck.rs b/dhall/src/typecheck.rs
index 38da955..d924f41 100644
--- a/dhall/src/typecheck.rs
+++ b/dhall/src/typecheck.rs
@@ -152,10 +152,7 @@ impl TypeThunk {
TypeThunk::Type(t) => Ok(t),
TypeThunk::Thunk(th) => {
// TODO: rule out statically
- mktype(
- ctx,
- th.normalize_whnf().normalize_to_expr().embed_absurd(),
- )
+ mktype(ctx, th.as_whnf().normalize_to_expr().embed_absurd())
}
}
}
generated by cgit v1.2.3 (git 2.25.1) at 2024-12-28 16:12:11 +0000