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-rw-r--r--dhall/src/semantics/builtins.rs2
-rw-r--r--dhall/src/semantics/core/value.rs71
-rw-r--r--dhall/src/semantics/core/visitor.rs1
-rw-r--r--dhall/src/semantics/phase/mod.rs2
-rw-r--r--dhall/src/semantics/phase/normalize.rs11
-rw-r--r--dhall/src/semantics/tck/tyexpr.rs22
-rw-r--r--dhall/src/semantics/tck/typecheck.rs31
7 files changed, 95 insertions, 45 deletions
diff --git a/dhall/src/semantics/builtins.rs b/dhall/src/semantics/builtins.rs
index a536261..9d10d89 100644
--- a/dhall/src/semantics/builtins.rs
+++ b/dhall/src/semantics/builtins.rs
@@ -286,7 +286,7 @@ fn apply_builtin(
Value(Value),
DoneAsIs,
}
- let make_closure = |e| typecheck(&e).unwrap().normalize_whnf(&env);
+ let make_closure = |e| typecheck(&e).unwrap().eval(&env);
let ret = match (b, args.as_slice()) {
(OptionalNone, [t]) => Ret::ValueKind(EmptyOptionalLit(t.clone())),
diff --git a/dhall/src/semantics/core/value.rs b/dhall/src/semantics/core/value.rs
index 4c844ee..c881a9a 100644
--- a/dhall/src/semantics/core/value.rs
+++ b/dhall/src/semantics/core/value.rs
@@ -4,9 +4,11 @@ use std::rc::Rc;
use crate::error::{TypeError, TypeMessage};
use crate::semantics::core::var::Binder;
-use crate::semantics::phase::normalize::{apply_any, normalize_whnf};
+use crate::semantics::phase::normalize::{
+ apply_any, normalize_tyexpr_whnf, normalize_whnf,
+};
use crate::semantics::phase::{Normalized, NormalizedExpr, ToExprOptions};
-use crate::semantics::{type_of_builtin, TyExpr, TyExprKind};
+use crate::semantics::{type_of_builtin, typecheck, TyExpr, TyExprKind};
use crate::semantics::{BuiltinClosure, NzEnv, NzVar, VarEnv};
use crate::syntax::{
BinOp, Builtin, Const, ExprKind, Integer, InterpolatedTextContents, Label,
@@ -47,6 +49,14 @@ pub(crate) enum Form {
WHNF,
}
+/// An unevaluated subexpression
+#[derive(Debug, Clone)]
+pub(crate) struct Thunk {
+ env: NzEnv,
+ body: TyExpr,
+}
+
+/// An unevaluated subexpression that takes an argument.
#[derive(Debug, Clone)]
pub(crate) enum Closure {
/// Normal closure
@@ -99,6 +109,8 @@ pub(crate) enum ValueKind<Value> {
Equivalence(Value, Value),
// Invariant: in whnf, this must not contain a value captured by one of the variants above.
PartialExpr(ExprKind<Value, Normalized>),
+ // Invariant: absent in whnf
+ Thunk(Thunk),
}
impl Value {
@@ -120,6 +132,15 @@ impl Value {
}
.into_value()
}
+ pub(crate) fn new_thunk(env: &NzEnv, tye: TyExpr) -> Value {
+ ValueInternal {
+ form: Unevaled,
+ kind: ValueKind::Thunk(Thunk::new(env, tye.clone())),
+ ty: tye.get_type().ok(),
+ span: tye.span().clone(),
+ }
+ .into_value()
+ }
pub(crate) fn from_kind_and_type(v: ValueKind<Value>, t: Value) -> Value {
Value::new(v, Unevaled, t, Span::Artificial)
}
@@ -147,9 +168,7 @@ impl Value {
pub(crate) fn from_builtin_env(b: Builtin, env: &NzEnv) -> Self {
Value::from_kind_and_type(
ValueKind::from_builtin_env(b, env.clone()),
- crate::semantics::tck::typecheck::typecheck(&type_of_builtin(b))
- .unwrap()
- .normalize_whnf_noenv(),
+ typecheck(&type_of_builtin(b)).unwrap().eval_closed_expr(),
)
}
@@ -325,6 +344,7 @@ impl Value {
v.to_tyexpr(venv),
))
}
+ ValueKind::Thunk(th) => return th.to_tyexpr(venv),
self_kind => {
let self_kind = self_kind.map_ref(|v| v.to_tyexpr(venv));
let expr = match self_kind {
@@ -333,7 +353,8 @@ impl Value {
| ValueKind::PiClosure { .. }
| ValueKind::AppliedBuiltin(..)
| ValueKind::UnionConstructor(..)
- | ValueKind::UnionLit(..) => unreachable!(),
+ | ValueKind::UnionLit(..)
+ | ValueKind::Thunk(..) => unreachable!(),
ValueKind::Const(c) => ExprKind::Const(c),
ValueKind::BoolLit(b) => ExprKind::BoolLit(b),
ValueKind::NaturalLit(n) => ExprKind::NaturalLit(n),
@@ -501,6 +522,9 @@ impl ValueKind<Value> {
ValueKind::PartialExpr(e) => {
e.map_mut(Value::normalize_mut);
}
+ ValueKind::Thunk(..) => {
+ unreachable!("Should only normalize_mut values in WHNF")
+ }
}
}
@@ -553,6 +577,22 @@ impl<V> ValueKind<V> {
}
}
+impl Thunk {
+ pub fn new(env: &NzEnv, body: TyExpr) -> Self {
+ Thunk {
+ env: env.clone(),
+ body,
+ }
+ }
+
+ pub fn eval(&self) -> Value {
+ normalize_tyexpr_whnf(&self.body, &self.env)
+ }
+ pub fn to_tyexpr(&self, venv: VarEnv) -> TyExpr {
+ self.eval().to_tyexpr(venv)
+ }
+}
+
impl Closure {
pub fn new(arg_ty: Value, env: &NzEnv, body: TyExpr) -> Self {
Closure::Closure {
@@ -572,11 +612,9 @@ impl Closure {
pub fn apply(&self, val: Value) -> Value {
match self {
Closure::Closure { env, body, .. } => {
- body.normalize_whnf(&env.insert_value(val))
- }
- Closure::ConstantClosure { env, body, .. } => {
- body.normalize_whnf(env)
+ body.eval(&env.insert_value(val))
}
+ Closure::ConstantClosure { env, body, .. } => body.eval(env),
}
}
fn apply_var(&self, var: NzVar) -> Value {
@@ -588,9 +626,7 @@ impl Closure {
);
self.apply(val)
}
- Closure::ConstantClosure { env, body, .. } => {
- body.normalize_whnf(env)
- }
+ Closure::ConstantClosure { env, body, .. } => body.eval(env),
}
}
@@ -626,6 +662,15 @@ impl std::cmp::PartialEq for Value {
}
impl std::cmp::Eq for Value {}
+impl std::cmp::PartialEq for Thunk {
+ fn eq(&self, _other: &Self) -> bool {
+ unreachable!(
+ "Trying to compare thunks but we should only compare WHNFs"
+ )
+ }
+}
+impl std::cmp::Eq for Thunk {}
+
impl std::cmp::PartialEq for Closure {
fn eq(&self, other: &Self) -> bool {
let v = NzVar::fresh();
diff --git a/dhall/src/semantics/core/visitor.rs b/dhall/src/semantics/core/visitor.rs
index a78c219..d1a85d8 100644
--- a/dhall/src/semantics/core/visitor.rs
+++ b/dhall/src/semantics/core/visitor.rs
@@ -133,6 +133,7 @@ where
),
Equivalence(x, y) => Equivalence(v.visit_val(x)?, v.visit_val(y)?),
PartialExpr(e) => PartialExpr(e.traverse_ref(|e| v.visit_val(e))?),
+ Thunk(th) => Thunk(th.clone()),
})
}
diff --git a/dhall/src/semantics/phase/mod.rs b/dhall/src/semantics/phase/mod.rs
index f24a668..a25f096 100644
--- a/dhall/src/semantics/phase/mod.rs
+++ b/dhall/src/semantics/phase/mod.rs
@@ -91,7 +91,7 @@ impl Resolved {
impl Typed {
/// Reduce an expression to its normal form, performing beta reduction
pub fn normalize(&self) -> Normalized {
- Normalized(self.0.normalize_nf_noenv())
+ Normalized(self.0.rec_eval_closed_expr())
}
/// Converts a value back to the corresponding AST expression.
diff --git a/dhall/src/semantics/phase/normalize.rs b/dhall/src/semantics/phase/normalize.rs
index f36ec4a..ea1a25b 100644
--- a/dhall/src/semantics/phase/normalize.rs
+++ b/dhall/src/semantics/phase/normalize.rs
@@ -457,6 +457,7 @@ pub(crate) fn normalize_whnf(
match v {
ValueKind::AppliedBuiltin(closure) => closure.ensure_whnf(ty),
ValueKind::PartialExpr(e) => normalize_one_layer(e, ty, &NzEnv::new()),
+ ValueKind::Thunk(th) => th.eval().kind().clone(),
ValueKind::TextLit(elts) => {
ValueKind::TextLit(squash_textlit(elts.into_iter()))
}
@@ -475,7 +476,7 @@ pub(crate) fn normalize_tyexpr_whnf(tye: &TyExpr, env: &NzEnv) -> Value {
let kind = match tye.kind() {
TyExprKind::Var(var) => return env.lookup_val(var),
TyExprKind::Expr(ExprKind::Lam(binder, annot, body)) => {
- let annot = annot.normalize_whnf(env);
+ let annot = annot.eval(env);
ValueKind::LamClosure {
binder: Binder::new(binder.clone()),
annot: annot.clone(),
@@ -483,7 +484,7 @@ pub(crate) fn normalize_tyexpr_whnf(tye: &TyExpr, env: &NzEnv) -> Value {
}
}
TyExprKind::Expr(ExprKind::Pi(binder, annot, body)) => {
- let annot = annot.normalize_whnf(env);
+ let annot = annot.eval(env);
let closure = Closure::new(annot.clone(), env, body.clone());
ValueKind::PiClosure {
binder: Binder::new(binder.clone()),
@@ -492,11 +493,11 @@ pub(crate) fn normalize_tyexpr_whnf(tye: &TyExpr, env: &NzEnv) -> Value {
}
}
TyExprKind::Expr(ExprKind::Let(_, None, val, body)) => {
- let val = val.normalize_whnf(env);
- return body.normalize_whnf(&env.insert_value(val));
+ let val = val.eval(env);
+ return body.eval(&env.insert_value(val));
}
TyExprKind::Expr(e) => {
- let e = e.map_ref(|tye| tye.normalize_whnf(env));
+ let e = e.map_ref(|tye| tye.eval(env));
normalize_one_layer(e, &ty, env)
}
};
diff --git a/dhall/src/semantics/tck/tyexpr.rs b/dhall/src/semantics/tck/tyexpr.rs
index 5492b8b..0a27f32 100644
--- a/dhall/src/semantics/tck/tyexpr.rs
+++ b/dhall/src/semantics/tck/tyexpr.rs
@@ -49,6 +49,9 @@ impl TyExpr {
pub fn kind(&self) -> &TyExprKind {
&*self.kind
}
+ pub fn span(&self) -> &Span {
+ &self.span
+ }
pub fn get_type(&self) -> Result<Type, TypeError> {
match &self.ty {
Some(t) => Ok(t.clone()),
@@ -69,17 +72,18 @@ impl TyExpr {
tyexpr_to_expr(self, opts, &mut env)
}
- pub fn normalize_whnf(&self, env: &NzEnv) -> Value {
- normalize_tyexpr_whnf(self, env)
- }
- pub fn normalize_whnf_noenv(&self) -> Value {
- self.normalize_whnf(&NzEnv::new())
+ /// Eval the TyExpr. It will actually get evaluated only as needed on demand.
+ pub fn eval(&self, env: &NzEnv) -> Value {
+ Value::new_thunk(env, self.clone())
}
- pub fn normalize_nf(&self, env: &NzEnv) -> Value {
- self.normalize_whnf(env)
+ /// Eval a closed TyExpr (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())
}
- pub fn normalize_nf_noenv(&self) -> Value {
- self.normalize_nf(&NzEnv::new())
+ /// Eval a closed TyExpr fully and recursively;
+ pub fn rec_eval_closed_expr(&self) -> Value {
+ normalize_tyexpr_whnf(self, &NzEnv::new())
}
}
diff --git a/dhall/src/semantics/tck/typecheck.rs b/dhall/src/semantics/tck/typecheck.rs
index bc1c87f..d741b40 100644
--- a/dhall/src/semantics/tck/typecheck.rs
+++ b/dhall/src/semantics/tck/typecheck.rs
@@ -74,7 +74,7 @@ fn type_one_layer(
ExprKind::Builtin(b) => {
let t_expr = type_of_builtin(*b);
let t_tyexpr = type_with(env, &t_expr)?;
- t_tyexpr.normalize_whnf(env.as_nzenv())
+ t_tyexpr.eval(env.as_nzenv())
}
ExprKind::BoolLit(_) => Value::from_builtin(Builtin::Bool),
ExprKind::NaturalLit(_) => Value::from_builtin(Builtin::Natural),
@@ -93,7 +93,7 @@ fn type_one_layer(
text_type
}
ExprKind::EmptyListLit(t) => {
- let t = t.normalize_nf(env.as_nzenv());
+ let t = t.eval(env.as_nzenv());
match &*t.kind() {
ValueKind::AppliedBuiltin(BuiltinClosure {
b: Builtin::List,
@@ -196,7 +196,7 @@ fn type_one_layer(
},
// TODO: branch here only when scrut.get_type() is a Const
_ => {
- let scrut_nf = scrut.normalize_nf(env.as_nzenv());
+ let scrut_nf = scrut.eval(env.as_nzenv());
let scrut_nf_borrow = scrut_nf.kind();
match &*scrut_nf_borrow {
ValueKind::UnionType(kts) => match kts.get(x) {
@@ -224,7 +224,7 @@ fn type_one_layer(
}
}
ExprKind::Annot(x, t) => {
- let t = t.normalize_whnf(env.as_nzenv());
+ let t = t.eval(env.as_nzenv());
let x_ty = x.get_type()?;
if x_ty != t {
return mkerr(format!(
@@ -243,7 +243,7 @@ fn type_one_layer(
x_ty
}
ExprKind::Assert(t) => {
- let t = t.normalize_whnf(env.as_nzenv());
+ let t = t.eval(env.as_nzenv());
match &*t.kind() {
ValueKind::Equivalence(x, y) if x == y => {}
ValueKind::Equivalence(..) => return mkerr("AssertMismatch"),
@@ -268,7 +268,7 @@ fn type_one_layer(
));
}
- let arg_nf = arg.normalize_nf(env.as_nzenv());
+ let arg_nf = arg.eval(env.as_nzenv());
closure.apply(arg_nf)
}
_ => return mkerr(format!("apply to not Pi")),
@@ -329,11 +329,11 @@ fn type_one_layer(
);
let ty = type_one_layer(env, &ekind)?;
TyExpr::new(TyExprKind::Expr(ekind), Some(ty), Span::Artificial)
- .normalize_nf(env.as_nzenv())
+ .eval(env.as_nzenv())
}
ExprKind::BinOp(BinOp::RecursiveRecordTypeMerge, x, y) => {
- let x_val = x.normalize_whnf(env.as_nzenv());
- let y_val = y.normalize_whnf(env.as_nzenv());
+ let x_val = x.eval(env.as_nzenv());
+ let y_val = y.eval(env.as_nzenv());
let x_val_borrow = x_val.kind();
let y_val_borrow = y_val.kind();
let kts_x = match &*x_val_borrow {
@@ -478,9 +478,8 @@ fn type_one_layer(
}
}
- let type_annot = type_annot
- .as_ref()
- .map(|t| t.normalize_whnf(env.as_nzenv()));
+ let type_annot =
+ type_annot.as_ref().map(|t| t.eval(env.as_nzenv()));
match (inferred_type, type_annot) {
(Some(t1), Some(t2)) => {
if t1 != t2 {
@@ -542,7 +541,7 @@ pub(crate) fn type_with(
},
ExprKind::Lam(binder, annot, body) => {
let annot = type_with(env, annot)?;
- let annot_nf = annot.normalize_nf(env.as_nzenv());
+ let annot_nf = annot.eval(env.as_nzenv());
let body_env = env.insert_type(&binder, annot_nf.clone());
let body = type_with(&body_env, body)?;
let body_ty = body.get_type()?;
@@ -555,7 +554,7 @@ pub(crate) fn type_with(
Some(type_of_function(annot.get_type()?, body_ty.get_type()?)?),
Span::Artificial,
);
- let ty = ty.normalize_whnf(env.as_nzenv());
+ let ty = ty.eval(env.as_nzenv());
(
TyExprKind::Expr(ExprKind::Lam(binder.clone(), annot, body)),
Some(ty),
@@ -563,7 +562,7 @@ pub(crate) fn type_with(
}
ExprKind::Pi(binder, annot, body) => {
let annot = type_with(env, annot)?;
- let annot_nf = annot.normalize_whnf(env.as_nzenv());
+ let annot_nf = annot.eval(env.as_nzenv());
let body =
type_with(&env.insert_type(binder, annot_nf.clone()), body)?;
let ty = type_of_function(annot.get_type()?, body.get_type()?)?;
@@ -580,7 +579,7 @@ pub(crate) fn type_with(
};
let val = type_with(env, &val)?;
- let val_nf = val.normalize_nf(&env.as_nzenv());
+ let val_nf = val.eval(&env.as_nzenv());
let body = type_with(&env.insert_value(&binder, val_nf), body)?;
let body_ty = body.get_type().ok();
(