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authorNadrieril2019-05-02 17:23:40 +0200
committerNadrieril2019-05-02 17:23:40 +0200
commit9d3c0d6aa23e4123515a1d7e949fc71509db803c (patch)
treed657fd50678dd8a562621d91c3caecbb2396fc7a
parent9042db26ced0c56714c48bf2f6322e0a1c2a6973 (diff)
parent17ab417aeb5aea6cd21240a491607b9017194737 (diff)
Merge branch 'refactor-typechecking'
Diffstat
-rw-r--r--dhall/src/expr.rs208
-rw-r--r--dhall/src/lib.rs2
-rw-r--r--dhall/src/normalize.rs1250
-rw-r--r--dhall/src/serde.rs2
-rw-r--r--dhall/src/tests.rs11
-rw-r--r--dhall/src/traits/deserialize.rs2
-rw-r--r--dhall/src/traits/dynamic_type.rs33
-rw-r--r--dhall/src/traits/static_type.rs13
-rw-r--r--dhall/src/typecheck.rs954
-rw-r--r--dhall_core/src/core.rs128
10 files changed, 1774 insertions, 829 deletions
diff --git a/dhall/src/expr.rs b/dhall/src/expr.rs
index bb1a4e4..4d55f4a 100644
--- a/dhall/src/expr.rs
+++ b/dhall/src/expr.rs
@@ -1,4 +1,5 @@
use crate::imports::ImportRoot;
+use crate::normalize::{Thunk, Value};
use dhall_core::*;
use std::marker::PhantomData;
@@ -10,6 +11,8 @@ macro_rules! derive_other_traits {
}
}
+ impl<'a> std::cmp::Eq for $ty<'a> {}
+
impl<'a> std::fmt::Display for $ty<'a> {
fn fmt(
&self,
@@ -21,34 +24,149 @@ macro_rules! derive_other_traits {
};
}
-#[derive(Debug, Clone, Eq)]
+#[derive(Debug, Clone)]
pub(crate) struct Parsed<'a>(
pub(crate) SubExpr<Span<'a>, Import>,
pub(crate) ImportRoot,
);
derive_other_traits!(Parsed);
-#[derive(Debug, Clone, Eq)]
+#[derive(Debug, Clone)]
pub(crate) struct Resolved<'a>(
pub(crate) SubExpr<Span<'a>, Normalized<'static>>,
);
derive_other_traits!(Resolved);
-#[derive(Debug, Clone, Eq)]
+pub(crate) use self::typed::TypedInternal;
+
+#[derive(Debug, Clone)]
pub(crate) struct Typed<'a>(
- pub(crate) SubExpr<X, Normalized<'static>>,
- pub(crate) Option<Type<'static>>,
+ pub(crate) TypedInternal,
pub(crate) PhantomData<&'a ()>,
);
-derive_other_traits!(Typed);
-#[derive(Debug, Clone, Eq)]
+#[derive(Debug, Clone)]
pub(crate) struct Normalized<'a>(
- pub(crate) SubExpr<X, X>,
- pub(crate) Option<Type<'static>>,
+ pub(crate) TypedInternal,
pub(crate) PhantomData<&'a ()>,
);
-derive_other_traits!(Normalized);
+
+impl<'a> std::cmp::PartialEq for Normalized<'a> {
+ fn eq(&self, other: &Self) -> bool {
+ self.to_expr() == other.to_expr()
+ }
+}
+
+impl<'a> std::cmp::Eq for Normalized<'a> {}
+
+impl<'a> std::fmt::Display for Normalized<'a> {
+ fn fmt(&self, f: &mut std::fmt::Formatter) -> Result<(), std::fmt::Error> {
+ self.to_expr().fmt(f)
+ }
+}
+
+mod typed {
+ use super::{Type, Typed};
+ use crate::normalize::{Thunk, Value};
+ use crate::typecheck::{
+ TypeError, TypeInternal, TypeMessage, TypecheckContext,
+ };
+ use dhall_core::{Const, Label, SubExpr, V, X};
+ use std::borrow::Cow;
+ use std::marker::PhantomData;
+
+ #[derive(Debug, Clone)]
+ pub(crate) enum TypedInternal {
+ // The `Sort` higher-kinded type doesn't have a type
+ Sort,
+ // Any other value, along with its type
+ Value(Thunk, Option<Type<'static>>),
+ }
+
+ impl TypedInternal {
+ pub(crate) fn from_thunk_and_type(th: Thunk, t: Type<'static>) -> Self {
+ TypedInternal::Value(th, Some(t))
+ }
+
+ pub(crate) fn from_thunk_untyped(th: Thunk) -> Self {
+ TypedInternal::Value(th, None)
+ }
+
+ // TODO: Avoid cloning if possible
+ pub(crate) fn to_value(&self) -> Value {
+ match self {
+ TypedInternal::Value(th, _) => th.normalize_whnf().clone(),
+ TypedInternal::Sort => Value::Const(Const::Sort),
+ }
+ }
+
+ pub(crate) fn to_expr(&self) -> SubExpr<X, X> {
+ self.to_value().normalize_to_expr()
+ }
+
+ pub(crate) fn to_thunk(&self) -> Thunk {
+ match self {
+ TypedInternal::Value(th, _) => th.clone(),
+ TypedInternal::Sort => {
+ Thunk::from_whnf(Value::Const(Const::Sort))
+ }
+ }
+ }
+
+ pub(crate) fn to_type(&self) -> Type<'static> {
+ match self {
+ TypedInternal::Sort => Type(TypeInternal::Const(Const::Sort)),
+ TypedInternal::Value(th, _) => match &*th.normalize_whnf() {
+ Value::Const(c) => Type(TypeInternal::Const(*c)),
+ _ => Type(TypeInternal::Typed(Box::new(Typed(
+ self.clone(),
+ PhantomData,
+ )))),
+ },
+ }
+ }
+
+ pub(crate) fn get_type(
+ &self,
+ ) -> Result<Cow<'_, Type<'static>>, TypeError> {
+ match self {
+ TypedInternal::Value(_, Some(t)) => Ok(Cow::Borrowed(t)),
+ TypedInternal::Value(_, None) => Err(TypeError::new(
+ &TypecheckContext::new(),
+ TypeMessage::Untyped,
+ )),
+ TypedInternal::Sort => Err(TypeError::new(
+ &TypecheckContext::new(),
+ TypeMessage::Sort,
+ )),
+ }
+ }
+
+ pub(crate) fn shift(&self, delta: isize, var: &V<Label>) -> Self {
+ match self {
+ TypedInternal::Value(th, t) => TypedInternal::Value(
+ th.shift(delta, var),
+ t.as_ref().map(|x| x.shift(delta, var)),
+ ),
+ TypedInternal::Sort => TypedInternal::Sort,
+ }
+ }
+
+ pub(crate) fn subst_shift(
+ &self,
+ var: &V<Label>,
+ val: &Typed<'static>,
+ ) -> Self {
+ match self {
+ TypedInternal::Value(th, t) => TypedInternal::Value(
+ th.subst_shift(var, val),
+ t.as_ref().map(|x| x.subst_shift(var, val)),
+ ),
+ TypedInternal::Sort => TypedInternal::Sort,
+ }
+ }
+ }
+}
/// A Dhall expression representing a simple type.
///
@@ -56,13 +174,15 @@ derive_other_traits!(Normalized);
/// `Bool`, `{ x: Integer }` or `Natural -> Text`.
///
/// For a more general notion of "type", see [Type].
-#[derive(Debug, Clone, Eq)]
+#[derive(Debug, Clone)]
pub struct SimpleType<'a>(
pub(crate) SubExpr<X, X>,
pub(crate) PhantomData<&'a ()>,
);
derive_other_traits!(SimpleType);
+pub(crate) use crate::typecheck::TypeInternal;
+
/// A Dhall expression representing a (possibly higher-kinded) type.
///
/// This includes [SimpleType]s but also higher-kinded expressions like
@@ -70,12 +190,10 @@ derive_other_traits!(SimpleType);
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct Type<'a>(pub(crate) TypeInternal<'a>);
-#[derive(Debug, Clone, PartialEq, Eq)]
-pub(crate) enum TypeInternal<'a> {
- Expr(Box<Normalized<'a>>),
- Const(dhall_core::Const),
- /// The type of `Sort`
- SuperType,
+impl<'a> std::fmt::Display for Type<'a> {
+ fn fmt(&self, f: &mut std::fmt::Formatter) -> Result<(), std::fmt::Error> {
+ self.to_normalized().fmt(f)
+ }
}
// Exposed for the macros
@@ -98,50 +216,38 @@ impl<'a> From<SubExpr<X, X>> for SimpleType<'a> {
#[doc(hidden)]
impl<'a> From<Normalized<'a>> for Typed<'a> {
fn from(x: Normalized<'a>) -> Typed<'a> {
- Typed(x.0.embed_absurd(), x.1, x.2)
+ Typed(x.0, x.1)
}
}
-#[doc(hidden)]
-impl<'a> Typed<'a> {
- pub(crate) fn as_expr(&self) -> &SubExpr<X, Normalized<'a>> {
- &self.0
- }
-}
-
-#[doc(hidden)]
impl<'a> Normalized<'a> {
- pub(crate) fn as_expr(&self) -> &SubExpr<X, X> {
- &self.0
+ pub(crate) fn from_thunk_and_type(th: Thunk, t: Type<'static>) -> Self {
+ Normalized(TypedInternal::from_thunk_and_type(th, t), PhantomData)
}
- pub(crate) fn into_expr(self) -> SubExpr<X, X> {
- self.0
+ // Deprecated
+ pub(crate) fn as_expr(&self) -> SubExpr<X, X> {
+ self.0.to_expr()
}
- pub(crate) fn unnote<'b>(self) -> Normalized<'b> {
- Normalized(self.0, self.1, PhantomData)
+ pub(crate) fn to_expr(&self) -> SubExpr<X, X> {
+ self.0.to_expr()
}
- pub(crate) fn into_type(self) -> Type<'a> {
- Type(match self.0.as_ref() {
- ExprF::Const(c) => TypeInternal::Const(*c),
- _ => TypeInternal::Expr(Box::new(self)),
- })
+ pub(crate) fn to_value(&self) -> Value {
+ self.0.to_value()
}
-}
-
-#[doc(hidden)]
-impl<'a> Type<'a> {
- pub(crate) fn unnote<'b>(self) -> Type<'b> {
- use TypeInternal::*;
- Type(match self.0 {
- Expr(e) => Expr(Box::new(e.unnote())),
- Const(c) => Const(c),
- SuperType => SuperType,
- })
+ #[allow(dead_code)]
+ pub(crate) fn unnote<'b>(self) -> Normalized<'b> {
+ Normalized(self.0, PhantomData)
}
}
-impl<'a> SimpleType<'a> {
- pub(crate) fn into_type(self) -> Type<'a> {
- Normalized(self.0, Some(Type::const_type()), PhantomData).into_type()
+impl<'a> Typed<'a> {
+ pub(crate) fn from_thunk_and_type(th: Thunk, t: Type<'static>) -> Self {
+ Typed(TypedInternal::from_thunk_and_type(th, t), PhantomData)
+ }
+ pub(crate) fn from_thunk_untyped(th: Thunk) -> Self {
+ Typed(TypedInternal::from_thunk_untyped(th), PhantomData)
+ }
+ pub(crate) fn const_sort() -> Self {
+ Typed(TypedInternal::Sort, PhantomData)
}
}
diff --git a/dhall/src/lib.rs b/dhall/src/lib.rs
index c85b962..6e4361f 100644
--- a/dhall/src/lib.rs
+++ b/dhall/src/lib.rs
@@ -4,6 +4,8 @@
#![feature(label_break_value)]
#![feature(non_exhaustive)]
#![feature(bind_by_move_pattern_guards)]
+#![feature(try_trait)]
+#![feature(inner_deref)]
#![cfg_attr(test, feature(custom_inner_attributes))]
#![allow(
clippy::type_complexity,
diff --git a/dhall/src/normalize.rs b/dhall/src/normalize.rs
index f092c4d..f991a2e 100644
--- a/dhall/src/normalize.rs
+++ b/dhall/src/normalize.rs
@@ -4,48 +4,68 @@ use std::rc::Rc;
use dhall_core::context::Context;
use dhall_core::{
- rc, shift, shift0, Builtin, ExprF, Integer, InterpolatedText,
+ rc, Builtin, Const, ExprF, Integer, InterpolatedText,
InterpolatedTextContents, Label, Natural, SubExpr, V, X,
};
use dhall_generator as dhall;
-use crate::expr::{Normalized, Typed};
+use crate::expr::{Normalized, Type, Typed, TypedInternal};
type InputSubExpr = SubExpr<X, Normalized<'static>>;
type OutputSubExpr = SubExpr<X, X>;
impl<'a> Typed<'a> {
+ /// Reduce an expression to its normal form, performing beta reduction
+ ///
+ /// `normalize` does not type-check the expression. You may want to type-check
+ /// expressions before normalizing them since normalization can convert an
+ /// ill-typed expression into a well-typed expression.
+ ///
+ /// However, `normalize` will not fail if the expression is ill-typed and will
+ /// leave ill-typed sub-expressions unevaluated.
+ ///
pub fn normalize(self) -> Normalized<'a> {
- Normalized(normalize(self.0), self.1, self.2)
+ let internal = match self.0 {
+ TypedInternal::Sort => TypedInternal::Sort,
+ TypedInternal::Value(thunk, t) => {
+ // TODO: stupid but needed for now
+ let thunk =
+ Thunk::from_normalized_expr(thunk.normalize_to_expr());
+ thunk.normalize_nf();
+ TypedInternal::Value(thunk, t)
+ }
+ };
+ Normalized(internal, self.1)
}
- /// Pretends this expression is normalized. Use with care.
- #[allow(dead_code)]
- pub fn skip_normalize(self) -> Normalized<'a> {
- Normalized(
- self.0.unroll().squash_embed(|e| e.0.clone()),
- self.1,
- self.2,
- )
+
+ pub(crate) fn shift(&self, delta: isize, var: &V<Label>) -> Self {
+ Typed(self.0.shift(delta, var), self.1)
}
-}
-fn shift0_mut<N, E>(delta: isize, label: &Label, in_expr: &mut SubExpr<N, E>) {
- let new_expr = shift0(delta, label, &in_expr);
- std::mem::replace(in_expr, new_expr);
-}
+ pub(crate) fn subst_shift(
+ &self,
+ var: &V<Label>,
+ val: &Typed<'static>,
+ ) -> Self {
+ Typed(self.0.subst_shift(var, val), self.1)
+ }
+
+ pub(crate) fn to_value(&self) -> Value {
+ self.0.to_value()
+ }
-fn shift_mut<N, E>(delta: isize, var: &V<Label>, in_expr: &mut SubExpr<N, E>) {
- let new_expr = shift(delta, var, &in_expr);
- std::mem::replace(in_expr, new_expr);
+ pub(crate) fn to_thunk(&self) -> Thunk {
+ self.0.to_thunk()
+ }
}
-fn apply_builtin(b: Builtin, args: Vec<WHNF>) -> WHNF {
+fn apply_builtin(b: Builtin, args: Vec<Value>) -> Value {
use dhall_core::Builtin::*;
- use WHNF::*;
+ use Value::*;
let ret = match b {
OptionalNone => improved_slice_patterns::match_vec!(args;
- [t] => EmptyOptionalLit(Now::from_whnf(t)),
+ [t] => EmptyOptionalLit(TypeThunk::from_whnf(t)),
),
NaturalIsZero => improved_slice_patterns::match_vec!(args;
[NaturalLit(n)] => BoolLit(n == 0),
@@ -93,12 +113,12 @@ fn apply_builtin(b: Builtin, args: Vec<WHNF>) -> WHNF {
let mut kts = BTreeMap::new();
kts.insert(
"index".into(),
- Now::from_whnf(
- WHNF::from_builtin(Natural)
+ TypeThunk::from_whnf(
+ Value::from_builtin(Natural)
),
);
kts.insert("value".into(), t);
- EmptyListLit(Now::from_whnf(RecordType(kts)))
+ EmptyListLit(TypeThunk::from_whnf(RecordType(kts)))
},
[_, NEListLit(xs)] => {
let xs = xs
@@ -107,9 +127,9 @@ fn apply_builtin(b: Builtin, args: Vec<WHNF>) -> WHNF {
.map(|(i, e)| {
let i = NaturalLit(i);
let mut kvs = BTreeMap::new();
- kvs.insert("index".into(), Now::from_whnf(i));
+ kvs.insert("index".into(), Thunk::from_whnf(i));
kvs.insert("value".into(), e);
- Now::from_whnf(RecordLit(kvs))
+ Thunk::from_whnf(RecordLit(kvs))
})
.collect();
NEListLit(xs)
@@ -117,7 +137,7 @@ fn apply_builtin(b: Builtin, args: Vec<WHNF>) -> WHNF {
),
ListBuild => improved_slice_patterns::match_vec!(args;
// fold/build fusion
- [_, WHNF::AppliedBuiltin(ListFold, args)] => {
+ [_, Value::AppliedBuiltin(ListFold, args)] => {
let mut args = args;
if args.len() >= 2 {
args.remove(1)
@@ -127,13 +147,13 @@ fn apply_builtin(b: Builtin, args: Vec<WHNF>) -> WHNF {
}
},
[t, g] => g
- .app(WHNF::from_builtin(List).app(t.clone()))
- .app(ListConsClosure(Now::from_whnf(t.clone()), None))
- .app(EmptyListLit(Now::from_whnf(t))),
+ .app(Value::from_builtin(List).app(t.clone()))
+ .app(ListConsClosure(TypeThunk::from_whnf(t.clone()), None))
+ .app(EmptyListLit(TypeThunk::from_whnf(t))),
),
ListFold => improved_slice_patterns::match_vec!(args;
// fold/build fusion
- [_, WHNF::AppliedBuiltin(ListBuild, args)] => {
+ [_, Value::AppliedBuiltin(ListBuild, args)] => {
let mut args = args;
if args.len() >= 2 {
args.remove(1)
@@ -145,14 +165,14 @@ fn apply_builtin(b: Builtin, args: Vec<WHNF>) -> WHNF {
[_, NEListLit(xs), _, cons, nil] => {
let mut v = nil;
for x in xs.into_iter().rev() {
- v = cons.clone().app(x.normalize()).app(v);
+ v = cons.clone().app_thunk(x).app(v);
}
v
}
),
OptionalBuild => improved_slice_patterns::match_vec!(args;
// fold/build fusion
- [_, WHNF::AppliedBuiltin(OptionalFold, args)] => {
+ [_, Value::AppliedBuiltin(OptionalFold, args)] => {
let mut args = args;
if args.len() >= 2 {
args.remove(1)
@@ -161,13 +181,13 @@ fn apply_builtin(b: Builtin, args: Vec<WHNF>) -> WHNF {
}
},
[t, g] => g
- .app(WHNF::from_builtin(Optional).app(t.clone()))
- .app(OptionalSomeClosure(Now::from_whnf(t.clone())))
- .app(EmptyOptionalLit(Now::from_whnf(t))),
+ .app(Value::from_builtin(Optional).app(t.clone()))
+ .app(OptionalSomeClosure(TypeThunk::from_whnf(t.clone())))
+ .app(EmptyOptionalLit(TypeThunk::from_whnf(t))),
),
OptionalFold => improved_slice_patterns::match_vec!(args;
// fold/build fusion
- [_, WHNF::AppliedBuiltin(OptionalBuild, args)] => {
+ [_, Value::AppliedBuiltin(OptionalBuild, args)] => {
let mut args = args;
if args.len() >= 2 {
args.remove(1)
@@ -179,12 +199,12 @@ fn apply_builtin(b: Builtin, args: Vec<WHNF>) -> WHNF {
nothing
},
[_, NEOptionalLit(x), _, just, _] => {
- just.app(x.normalize())
+ just.app_thunk(x)
}
),
NaturalBuild => improved_slice_patterns::match_vec!(args;
// fold/build fusion
- [WHNF::AppliedBuiltin(NaturalFold, args)] => {
+ [Value::AppliedBuiltin(NaturalFold, args)] => {
let mut args = args;
if args.len() >= 1 {
args.remove(0)
@@ -193,13 +213,13 @@ fn apply_builtin(b: Builtin, args: Vec<WHNF>) -> WHNF {
}
},
[g] => g
- .app(WHNF::from_builtin(Natural))
+ .app(Value::from_builtin(Natural))
.app(NaturalSuccClosure)
.app(NaturalLit(0)),
),
NaturalFold => improved_slice_patterns::match_vec!(args;
// fold/build fusion
- [WHNF::AppliedBuiltin(NaturalBuild, args)] => {
+ [Value::AppliedBuiltin(NaturalBuild, args)] => {
let mut args = args;
if args.len() >= 1 {
args.remove(0)
@@ -209,7 +229,7 @@ fn apply_builtin(b: Builtin, args: Vec<WHNF>) -> WHNF {
},
[NaturalLit(0), _, _, zero] => zero,
[NaturalLit(n), t, succ, zero] => {
- let fold = WHNF::from_builtin(NaturalFold)
+ let fold = Value::from_builtin(NaturalFold)
.app(NaturalLit(n - 1))
.app(t)
.app(succ.clone())
@@ -228,222 +248,233 @@ fn apply_builtin(b: Builtin, args: Vec<WHNF>) -> WHNF {
#[derive(Debug, Clone)]
enum EnvItem {
- Expr(WHNF),
- Skip(usize),
+ Thunk(Thunk),
+ Skip(V<Label>),
+}
+
+impl EnvItem {
+ fn shift(&self, delta: isize, var: &V<Label>) -> Self {
+ use EnvItem::*;
+ match self {
+ Thunk(e) => Thunk(e.shift(delta, var)),
+ Skip(v) => Skip(v.shift(delta, var)),
+ }
+ }
+
+ pub(crate) fn subst_shift(
+ &self,
+ var: &V<Label>,
+ val: &Typed<'static>,
+ ) -> Self {
+ match self {
+ EnvItem::Thunk(e) => EnvItem::Thunk(e.subst_shift(var, val)),
+ EnvItem::Skip(v) if v == var => EnvItem::Thunk(val.to_thunk()),
+ EnvItem::Skip(v) => EnvItem::Skip(v.shift(-1, var)),
+ }
+ }
}
#[derive(Debug, Clone)]
-struct NormalizationContext(Rc<Context<Label, EnvItem>>);
+pub(crate) struct NormalizationContext(Rc<Context<Label, EnvItem>>);
impl NormalizationContext {
- fn new() -> Self {
+ pub(crate) fn new() -> Self {
NormalizationContext(Rc::new(Context::new()))
}
- fn insert(&self, x: &Label, e: WHNF) -> Self {
+ fn insert(&self, x: &Label, e: Thunk) -> Self {
NormalizationContext(Rc::new(
- self.0.insert(x.clone(), EnvItem::Expr(e)),
+ self.0.insert(x.clone(), EnvItem::Thunk(e)),
))
}
fn skip(&self, x: &Label) -> Self {
NormalizationContext(Rc::new(
self.0
- .map(|l, e| {
- use EnvItem::*;
- match e {
- Expr(e) => {
- let mut e = e.clone();
- e.shift0(1, x);
- Expr(e)
- }
- Skip(n) if l == x => Skip(*n + 1),
- Skip(n) => Skip(*n),
- }
- })
- .insert(x.clone(), EnvItem::Skip(0)),
+ .map(|_, e| e.shift(1, &x.into()))
+ .insert(x.clone(), EnvItem::Skip(x.into())),
))
}
- fn lookup(&self, var: &V<Label>) -> WHNF {
+ fn lookup(&self, var: &V<Label>) -> Value {
let V(x, n) = var;
match self.0.lookup(x, *n) {
- Some(EnvItem::Expr(e)) => e.clone(),
- Some(EnvItem::Skip(m)) => {
- WHNF::Expr(rc(ExprF::Var(V(x.clone(), *m))))
+ Some(EnvItem::Thunk(t)) => t.normalize_whnf().clone(),
+ Some(EnvItem::Skip(newvar)) => Value::Var(newvar.clone()),
+ None => Value::Var(var.clone()),
+ }
+ }
+ pub(crate) fn from_typecheck_ctx(
+ tc_ctx: &crate::typecheck::TypecheckContext,
+ ) -> Self {
+ use crate::typecheck::EnvItem::*;
+ 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, _) => EnvItem::Skip(var.clone()),
+ Value(e) => EnvItem::Thunk(Thunk::new(
+ NormalizationContext::new(),
+ e.as_expr().embed_absurd(),
+ )),
+ };
+ ctx = ctx.insert(k.clone(), new_item);
}
- None => WHNF::Expr(rc(ExprF::Var(V(x.clone(), *n)))),
}
+ NormalizationContext(Rc::new(ctx))
+ }
+
+ fn shift(&self, delta: isize, var: &V<Label>) -> Self {
+ NormalizationContext(Rc::new(self.0.map(|_, e| e.shift(delta, var))))
+ }
+
+ fn subst_shift(&self, var: &V<Label>, val: &Typed<'static>) -> Self {
+ NormalizationContext(Rc::new(
+ self.0.map(|_, e| e.subst_shift(var, val)),
+ ))
}
}
-/// A semantic value. This is partially redundant with `dhall_core::Expr`, on purpose. `Expr` should
-/// be limited to syntactic expressions: either written by the user or meant to be printed.
-/// The rule is the following: we must _not_ construct values of type `Expr` while normalizing,
-/// but only construct `WHNF`s.
-///
-/// WHNFs store subexpressions unnormalized, to enable lazy normalization. They approximate
-/// what's called Weak Head Normal-Form (WHNF). This means that the expression is normalized as
-/// little as possible, but just enough to know the first constructor of the normal form. This is
-/// identical to full normalization for simple types like integers, but for e.g. a record literal
-/// this means knowing just the field names.
-///
-/// Each variant captures the relevant contexts when it is constructed. Conceptually each
-/// subexpression has its own context, but in practice some contexts can be shared when sensible, to
-/// avoid unnecessary allocations.
+/// A semantic value.
#[derive(Debug, Clone)]
-enum WHNF {
+pub(crate) enum Value {
/// Closures
- Lam(Label, Now, (NormalizationContext, InputSubExpr)),
- AppliedBuiltin(Builtin, Vec<WHNF>),
+ Lam(Label, Thunk, Thunk),
+ AppliedBuiltin(Builtin, Vec<Value>),
/// `λ(x: a) -> Some x`
- OptionalSomeClosure(Now),
+ OptionalSomeClosure(TypeThunk),
/// `λ(x : a) -> λ(xs : List a) -> [ x ] # xs`
/// `λ(xs : List a) -> [ x ] # xs`
- ListConsClosure(Now, Option<Now>),
+ ListConsClosure(TypeThunk, Option<Thunk>),
/// `λ(x : Natural) -> x + 1`
NaturalSuccClosure,
+ Pi(Label, TypeThunk, TypeThunk),
+ Var(V<Label>),
+ Const(Const),
BoolLit(bool),
NaturalLit(Natural),
IntegerLit(Integer),
- EmptyOptionalLit(Now),
- NEOptionalLit(Now),
- EmptyListLit(Now),
- NEListLit(Vec<Now>),
- RecordLit(BTreeMap<Label, Now>),
- RecordType(BTreeMap<Label, Now>),
- UnionType(NormalizationContext, BTreeMap<Label, Option<InputSubExpr>>),
- UnionConstructor(
- NormalizationContext,
- Label,
- BTreeMap<Label, Option<InputSubExpr>>,
- ),
- UnionLit(
- Label,
- Now,
- (NormalizationContext, BTreeMap<Label, Option<InputSubExpr>>),
- ),
- TextLit(Vec<InterpolatedTextContents<Now>>),
+ EmptyOptionalLit(TypeThunk),
+ NEOptionalLit(Thunk),
+ EmptyListLit(TypeThunk),
+ NEListLit(Vec<Thunk>),
+ RecordLit(BTreeMap<Label, Thunk>),
+ RecordType(BTreeMap<Label, TypeThunk>),
+ UnionType(BTreeMap<Label, Option<TypeThunk>>),
+ UnionConstructor(Label, BTreeMap<Label, Option<TypeThunk>>),
+ UnionLit(Label, Thunk, BTreeMap<Label, Option<TypeThunk>>),
+ TextLit(Vec<InterpolatedTextContents<Thunk>>),
+ /// Invariant: This must not contain a value captured by one of the variants above.
+ PartialExpr(Box<ExprF<Value, Label, X, X>>),
Expr(OutputSubExpr),
}
-impl WHNF {
+impl Value {
+ pub(crate) fn into_thunk(self) -> Thunk {
+ Thunk::from_whnf(self)
+ }
+
/// Convert the value back to a (normalized) syntactic expression
- fn normalize_to_expr(self) -> OutputSubExpr {
+ pub(crate) fn normalize_to_expr(&self) -> OutputSubExpr {
match self {
- WHNF::Lam(x, t, (ctx, e)) => {
- let ctx2 = ctx.skip(&x);
- rc(ExprF::Lam(
- x.clone(),
- t.normalize().normalize_to_expr(),
- normalize_whnf(ctx2, e).normalize_to_expr(),
- ))
- }
- WHNF::AppliedBuiltin(b, args) => {
- let mut e = WHNF::Expr(rc(ExprF::Builtin(b)));
+ Value::Lam(x, t, e) => rc(ExprF::Lam(
+ x.clone(),
+ t.normalize_to_expr(),
+ e.normalize_to_expr(),
+ )),
+ Value::AppliedBuiltin(b, args) => {
+ let mut e = rc(ExprF::Builtin(*b));
for v in args {
- e = e.app(v);
+ e = rc(ExprF::App(e, v.normalize_to_expr()));
}
- e.normalize_to_expr()
+ e
}
- WHNF::OptionalSomeClosure(n) => {
- let a = n.normalize().normalize_to_expr();
+ Value::OptionalSomeClosure(n) => {
+ let a = n.normalize_to_expr();
dhall::subexpr!(λ(x: a) -> Some x)
}
- WHNF::ListConsClosure(n, None) => {
- let a = n.normalize().normalize_to_expr();
+ Value::ListConsClosure(n, None) => {
+ let a = n.normalize_to_expr();
// Avoid accidental capture of the new `x` variable
- let a1 = shift0(1, &"x".into(), &a);
+ let a1 = a.shift(1, &Label::from("x").into());
dhall::subexpr!(λ(x : a) -> λ(xs : List a1) -> [ x ] # xs)
}
- WHNF::ListConsClosure(n, Some(v)) => {
- let v = v.normalize().normalize_to_expr();
- let a = n.normalize().normalize_to_expr();
+ Value::ListConsClosure(n, Some(v)) => {
+ let v = v.normalize_to_expr();
+ let a = n.normalize_to_expr();
+ // Avoid accidental capture of the new `xs` variable
+ let v = v.shift(1, &Label::from("xs").into());
dhall::subexpr!(λ(xs : List a) -> [ v ] # xs)
}
- WHNF::NaturalSuccClosure => {
+ Value::NaturalSuccClosure => {
dhall::subexpr!(λ(x : Natural) -> x + 1)
}
- WHNF::BoolLit(b) => rc(ExprF::BoolLit(b)),
- WHNF::NaturalLit(n) => rc(ExprF::NaturalLit(n)),
- WHNF::IntegerLit(n) => rc(ExprF::IntegerLit(n)),
- WHNF::EmptyOptionalLit(n) => {
- WHNF::Expr(rc(ExprF::Builtin(Builtin::OptionalNone)))
- .app(n.normalize())
- .normalize_to_expr()
- }
- WHNF::NEOptionalLit(n) => {
- rc(ExprF::SomeLit(n.normalize().normalize_to_expr()))
+ Value::Pi(x, t, e) => rc(ExprF::Pi(
+ x.clone(),
+ t.normalize_to_expr(),
+ e.normalize_to_expr(),
+ )),
+ Value::Var(v) => rc(ExprF::Var(v.clone())),
+ Value::Const(c) => rc(ExprF::Const(*c)),
+ Value::BoolLit(b) => rc(ExprF::BoolLit(*b)),
+ Value::NaturalLit(n) => rc(ExprF::NaturalLit(*n)),
+ Value::IntegerLit(n) => rc(ExprF::IntegerLit(*n)),
+ Value::EmptyOptionalLit(n) => rc(ExprF::App(
+ rc(ExprF::Builtin(Builtin::OptionalNone)),
+ n.normalize_to_expr(),
+ )),
+ Value::NEOptionalLit(n) => {
+ rc(ExprF::SomeLit(n.normalize_to_expr()))
}
- WHNF::EmptyListLit(n) => {
- rc(ExprF::EmptyListLit(n.normalize().normalize_to_expr()))
+ Value::EmptyListLit(n) => {
+ rc(ExprF::EmptyListLit(n.normalize_to_expr()))
}
- WHNF::NEListLit(elts) => rc(ExprF::NEListLit(
- elts.into_iter()
- .map(|n| n.normalize().normalize_to_expr())
- .collect(),
+ Value::NEListLit(elts) => rc(ExprF::NEListLit(
+ elts.into_iter().map(|n| n.normalize_to_expr()).collect(),
)),
- WHNF::RecordLit(kvs) => rc(ExprF::RecordLit(
- kvs.into_iter()
- .map(|(k, v)| (k, v.normalize().normalize_to_expr()))
+ Value::RecordLit(kvs) => rc(ExprF::RecordLit(
+ kvs.iter()
+ .map(|(k, v)| (k.clone(), v.normalize_to_expr()))
.collect(),
)),
- WHNF::RecordType(kts) => rc(ExprF::RecordType(
- kts.into_iter()
- .map(|(k, v)| (k, v.normalize().normalize_to_expr()))
+ Value::RecordType(kts) => rc(ExprF::RecordType(
+ kts.iter()
+ .map(|(k, v)| (k.clone(), v.normalize_to_expr()))
.collect(),
)),
- WHNF::UnionType(ctx, kts) => rc(ExprF::UnionType(
- kts.into_iter()
+ Value::UnionType(kts) => rc(ExprF::UnionType(
+ kts.iter()
.map(|(k, v)| {
- (
- k,
- v.map(|v| {
- normalize_whnf(ctx.clone(), v)
- .normalize_to_expr()
- }),
- )
+ (k.clone(), v.as_ref().map(|v| v.normalize_to_expr()))
})
.collect(),
)),
- WHNF::UnionConstructor(ctx, l, kts) => {
+ Value::UnionConstructor(l, kts) => {
let kts = kts
- .into_iter()
+ .iter()
.map(|(k, v)| {
- (
- k,
- v.map(|v| {
- normalize_whnf(ctx.clone(), v)
- .normalize_to_expr()
- }),
- )
+ (k.clone(), v.as_ref().map(|v| v.normalize_to_expr()))
})
.collect();
- rc(ExprF::Field(rc(ExprF::UnionType(kts)), l))
+ rc(ExprF::Field(rc(ExprF::UnionType(kts)), l.clone()))
}
- WHNF::UnionLit(l, v, (kts_ctx, kts)) => rc(ExprF::UnionLit(
- l,
- v.normalize().normalize_to_expr(),
- kts.into_iter()
+ Value::UnionLit(l, v, kts) => rc(ExprF::UnionLit(
+ l.clone(),
+ v.normalize_to_expr(),
+ kts.iter()
.map(|(k, v)| {
- (
- k,
- v.map(|v| {
- normalize_whnf(kts_ctx.clone(), v)
- .normalize_to_expr()
- }),
- )
+ (k.clone(), v.as_ref().map(|v| v.normalize_to_expr()))
})
.collect(),
)),
- WHNF::TextLit(elts) => {
+ Value::TextLit(elts) => {
fn normalize_textlit(
- elts: Vec<InterpolatedTextContents<Now>>,
+ elts: &Vec<InterpolatedTextContents<Thunk>>,
) -> InterpolatedText<OutputSubExpr> {
- elts.into_iter()
+ elts.iter()
.flat_map(|contents| {
use InterpolatedTextContents::{Expr, Text};
let new_interpolated = match contents {
- Expr(n) => match n.normalize() {
- WHNF::TextLit(elts2) => {
+ Expr(n) => match &*n.normalize_nf() {
+ Value::TextLit(elts2) => {
normalize_textlit(elts2)
}
e => InterpolatedText::from((
@@ -454,7 +485,7 @@ impl WHNF {
)],
)),
},
- Text(s) => InterpolatedText::from(s),
+ Text(s) => InterpolatedText::from(s.clone()),
};
new_interpolated.into_iter()
})
@@ -463,197 +494,776 @@ impl WHNF {
rc(ExprF::TextLit(normalize_textlit(elts)))
}
- WHNF::Expr(e) => e,
+ Value::PartialExpr(e) => {
+ rc(e.map_ref_simple(|v| v.normalize_to_expr()))
+ }
+ Value::Expr(e) => e.clone(),
}
}
- /// Apply to a value
- fn app(self, val: WHNF) -> WHNF {
- match (self, val) {
- (WHNF::Lam(x, _, (ctx, e)), val) => {
- let ctx2 = ctx.insert(&x, val);
- normalize_whnf(ctx2, e)
- }
- (WHNF::AppliedBuiltin(b, mut args), val) => {
- args.push(val);
- apply_builtin(b, args)
- }
- (WHNF::OptionalSomeClosure(_), val) => {
- WHNF::NEOptionalLit(Now::from_whnf(val))
- }
- (WHNF::ListConsClosure(t, None), val) => {
- WHNF::ListConsClosure(t, Some(Now::from_whnf(val)))
+ // Deprecated
+ pub(crate) fn normalize(&self) -> Value {
+ match self {
+ Value::Lam(x, t, e) => {
+ Value::Lam(x.clone(), t.normalize(), e.normalize())
}
- (WHNF::ListConsClosure(_, Some(x)), WHNF::EmptyListLit(_)) => {
- WHNF::NEListLit(vec![x])
+ Value::AppliedBuiltin(b, args) => Value::AppliedBuiltin(
+ *b,
+ args.iter().map(|v| v.normalize()).collect(),
+ ),
+ Value::NaturalSuccClosure => Value::NaturalSuccClosure,
+ Value::OptionalSomeClosure(tth) => {
+ Value::OptionalSomeClosure(tth.normalize())
}
- (WHNF::ListConsClosure(_, Some(x)), WHNF::NEListLit(mut xs)) => {
- xs.insert(0, x);
- WHNF::NEListLit(xs)
+ Value::ListConsClosure(t, v) => Value::ListConsClosure(
+ t.normalize(),
+ v.as_ref().map(|v| v.normalize()),
+ ),
+ Value::Pi(x, t, e) => {
+ Value::Pi(x.clone(), t.normalize(), e.normalize())
}
- (WHNF::NaturalSuccClosure, WHNF::NaturalLit(n)) => {
- WHNF::NaturalLit(n + 1)
+ Value::Var(v) => Value::Var(v.clone()),
+ Value::Const(c) => Value::Const(*c),
+ Value::BoolLit(b) => Value::BoolLit(*b),
+ Value::NaturalLit(n) => Value::NaturalLit(*n),
+ Value::IntegerLit(n) => Value::IntegerLit(*n),
+ Value::EmptyOptionalLit(tth) => {
+ Value::EmptyOptionalLit(tth.normalize())
}
- (WHNF::UnionConstructor(ctx, l, kts), val) => {
- WHNF::UnionLit(l, Now::from_whnf(val), (ctx, kts))
+ Value::NEOptionalLit(th) => Value::NEOptionalLit(th.normalize()),
+ Value::EmptyListLit(tth) => Value::EmptyListLit(tth.normalize()),
+ Value::NEListLit(elts) => {
+ Value::NEListLit(elts.iter().map(|v| v.normalize()).collect())
}
- // Can't do anything useful, convert to expr
- (f, a) => WHNF::Expr(rc(ExprF::App(
- f.normalize_to_expr(),
- a.normalize_to_expr(),
- ))),
+ Value::RecordLit(kvs) => Value::RecordLit(
+ kvs.iter()
+ .map(|(k, v)| (k.clone(), v.normalize()))
+ .collect(),
+ ),
+ Value::RecordType(kvs) => Value::RecordType(
+ kvs.iter()
+ .map(|(k, v)| (k.clone(), v.normalize()))
+ .collect(),
+ ),
+ Value::UnionType(kts) => Value::UnionType(
+ kts.iter()
+ .map(|(k, v)| {
+ (k.clone(), v.as_ref().map(|v| v.normalize()))
+ })
+ .collect(),
+ ),
+ Value::UnionConstructor(x, kts) => Value::UnionConstructor(
+ x.clone(),
+ kts.iter()
+ .map(|(k, v)| {
+ (k.clone(), v.as_ref().map(|v| v.normalize()))
+ })
+ .collect(),
+ ),
+ Value::UnionLit(x, v, kts) => Value::UnionLit(
+ x.clone(),
+ v.normalize(),
+ kts.iter()
+ .map(|(k, v)| {
+ (k.clone(), v.as_ref().map(|v| v.normalize()))
+ })
+ .collect(),
+ ),
+ Value::TextLit(elts) => Value::TextLit(
+ elts.iter()
+ .map(|contents| {
+ use InterpolatedTextContents::{Expr, Text};
+ match contents {
+ Expr(th) => Expr(th.normalize()),
+ Text(s) => Text(s.clone()),
+ }
+ })
+ .collect(),
+ ),
+ Value::PartialExpr(e) => Value::PartialExpr(Box::new(
+ e.map_ref_simple(|v| v.normalize()),
+ )),
+ Value::Expr(e) => Value::Expr(e.clone()),
}
}
- fn from_builtin(b: Builtin) -> WHNF {
- WHNF::AppliedBuiltin(b, vec![])
- }
-
- fn shift0(&mut self, delta: isize, label: &Label) {
+ pub(crate) fn normalize_mut(&mut self) {
match self {
- WHNF::NaturalSuccClosure
- | WHNF::BoolLit(_)
- | WHNF::NaturalLit(_)
- | WHNF::IntegerLit(_) => {}
- WHNF::EmptyOptionalLit(n)
- | WHNF::NEOptionalLit(n)
- | WHNF::OptionalSomeClosure(n)
- | WHNF::EmptyListLit(n) => {
- n.shift0(delta, label);
+ Value::NaturalSuccClosure
+ | Value::Var(_)
+ | Value::Const(_)
+ | Value::BoolLit(_)
+ | Value::NaturalLit(_)
+ | Value::IntegerLit(_)
+ | Value::Expr(_) => {}
+
+ Value::EmptyOptionalLit(tth)
+ | Value::OptionalSomeClosure(tth)
+ | Value::EmptyListLit(tth) => {
+ tth.normalize_mut();
+ }
+
+ Value::NEOptionalLit(th) => {
+ th.normalize_mut();
+ }
+ Value::Lam(_, t, e) => {
+ t.normalize_mut();
+ e.normalize_mut();
}
- WHNF::Lam(_, t, (_, e)) => {
- t.shift0(delta, label);
- shift_mut(delta, &V(label.clone(), 1), e);
+ Value::Pi(_, t, e) => {
+ t.normalize_mut();
+ e.normalize_mut();
}
- WHNF::AppliedBuiltin(_, args) => {
+ Value::AppliedBuiltin(_, args) => {
for x in args.iter_mut() {
- x.shift0(delta, label);
+ x.normalize_mut();
}
}
- WHNF::ListConsClosure(t, v) => {
- t.shift0(delta, label);
+ Value::ListConsClosure(t, v) => {
+ t.normalize_mut();
for x in v.iter_mut() {
- x.shift0(delta, label);
+ x.normalize_mut();
}
}
- WHNF::NEListLit(elts) => {
+ Value::NEListLit(elts) => {
for x in elts.iter_mut() {
- x.shift0(delta, label);
+ x.normalize_mut();
+ }
+ }
+ Value::RecordLit(kvs) => {
+ for x in kvs.values_mut() {
+ x.normalize_mut();
}
}
- WHNF::RecordLit(kvs) | WHNF::RecordType(kvs) => {
+ Value::RecordType(kvs) => {
for x in kvs.values_mut() {
- x.shift0(delta, label);
+ x.normalize_mut();
}
}
- WHNF::UnionType(_, kts) | WHNF::UnionConstructor(_, _, kts) => {
+ Value::UnionType(kts) | Value::UnionConstructor(_, kts) => {
for x in kts.values_mut().flat_map(|opt| opt) {
- shift0_mut(delta, label, x);
+ x.normalize_mut();
}
}
- WHNF::UnionLit(_, v, (_, kts)) => {
- v.shift0(delta, label);
+ Value::UnionLit(_, v, kts) => {
+ v.normalize_mut();
for x in kts.values_mut().flat_map(|opt| opt) {
- shift0_mut(delta, label, x);
+ x.normalize_mut();
}
}
- WHNF::TextLit(elts) => {
+ Value::TextLit(elts) => {
for x in elts.iter_mut() {
use InterpolatedTextContents::{Expr, Text};
match x {
- Expr(n) => n.shift0(delta, label),
+ Expr(n) => n.normalize_mut(),
Text(_) => {}
}
}
}
- WHNF::Expr(e) => shift0_mut(delta, label, e),
+ Value::PartialExpr(e) => {
+ // TODO: need map_mut_simple
+ *self = Value::PartialExpr(Box::new(
+ e.map_ref_simple(|v| v.normalize()),
+ ))
+ }
+ }
+ }
+
+ /// Apply to a value
+ pub(crate) fn app(self, val: Value) -> Value {
+ self.app_thunk(val.into_thunk())
+ }
+
+ /// Apply to a thunk
+ pub(crate) fn app_thunk(self, th: Thunk) -> Value {
+ let fallback = |f: Value, a: Thunk| {
+ Value::PartialExpr(Box::new(ExprF::App(
+ f,
+ a.normalize_whnf().clone(),
+ )))
+ };
+
+ match self {
+ Value::Lam(x, _, e) => {
+ let val = Typed(
+ TypedInternal::Value(th, None),
+ std::marker::PhantomData,
+ );
+ e.subst_shift(&V(x, 0), &val).normalize_whnf().clone()
+ }
+ Value::AppliedBuiltin(b, mut args) => {
+ args.push(th.normalize_whnf().clone());
+ apply_builtin(b, args)
+ }
+ Value::OptionalSomeClosure(_) => Value::NEOptionalLit(th),
+ Value::ListConsClosure(t, None) => {
+ Value::ListConsClosure(t, Some(th))
+ }
+ Value::ListConsClosure(t, Some(x)) => {
+ let v = th.normalize_whnf();
+ match &*v {
+ Value::EmptyListLit(_) => Value::NEListLit(vec![x]),
+ Value::NEListLit(xs) => {
+ let mut xs = xs.clone();
+ xs.insert(0, x);
+ Value::NEListLit(xs)
+ }
+ _ => {
+ drop(v);
+ fallback(Value::ListConsClosure(t, Some(x)), th)
+ }
+ }
+ }
+ Value::NaturalSuccClosure => {
+ let v = th.normalize_whnf();
+ match &*v {
+ Value::NaturalLit(n) => Value::NaturalLit(n + 1),
+ _ => {
+ drop(v);
+ fallback(Value::NaturalSuccClosure, th)
+ }
+ }
+ }
+ Value::UnionConstructor(l, kts) => Value::UnionLit(l, th, kts),
+ f => fallback(f, th),
+ }
+ }
+
+ pub(crate) fn from_builtin(b: Builtin) -> Value {
+ Value::AppliedBuiltin(b, vec![])
+ }
+
+ fn shift(&self, delta: isize, var: &V<Label>) -> Self {
+ match self {
+ Value::Lam(x, t, e) => Value::Lam(
+ x.clone(),
+ t.shift(delta, var),
+ e.shift(delta, &var.shift(1, &x.into())),
+ ),
+ Value::AppliedBuiltin(b, args) => Value::AppliedBuiltin(
+ *b,
+ args.iter().map(|v| v.shift(delta, var)).collect(),
+ ),
+ Value::NaturalSuccClosure => Value::NaturalSuccClosure,
+ Value::OptionalSomeClosure(tth) => {
+ Value::OptionalSomeClosure(tth.shift(delta, var))
+ }
+ Value::ListConsClosure(t, v) => Value::ListConsClosure(
+ t.shift(delta, var),
+ v.as_ref().map(|v| v.shift(delta, var)),
+ ),
+ Value::Pi(x, t, e) => Value::Pi(
+ x.clone(),
+ t.shift(delta, var),
+ e.shift(delta, &var.shift(1, &x.into())),
+ ),
+ Value::Var(v) => Value::Var(v.shift(delta, var)),
+ Value::Const(c) => Value::Const(*c),
+ Value::BoolLit(b) => Value::BoolLit(*b),
+ Value::NaturalLit(n) => Value::NaturalLit(*n),
+ Value::IntegerLit(n) => Value::IntegerLit(*n),
+ Value::EmptyOptionalLit(tth) => {
+ Value::EmptyOptionalLit(tth.shift(delta, var))
+ }
+ Value::NEOptionalLit(th) => {
+ Value::NEOptionalLit(th.shift(delta, var))
+ }
+ Value::EmptyListLit(tth) => {
+ Value::EmptyListLit(tth.shift(delta, var))
+ }
+ Value::NEListLit(elts) => Value::NEListLit(
+ elts.iter().map(|v| v.shift(delta, var)).collect(),
+ ),
+ Value::RecordLit(kvs) => Value::RecordLit(
+ kvs.iter()
+ .map(|(k, v)| (k.clone(), v.shift(delta, var)))
+ .collect(),
+ ),
+ Value::RecordType(kvs) => Value::RecordType(
+ kvs.iter()
+ .map(|(k, v)| (k.clone(), v.shift(delta, var)))
+ .collect(),
+ ),
+ Value::UnionType(kts) => Value::UnionType(
+ kts.iter()
+ .map(|(k, v)| {
+ (k.clone(), v.as_ref().map(|v| v.shift(delta, var)))
+ })
+ .collect(),
+ ),
+ Value::UnionConstructor(x, kts) => Value::UnionConstructor(
+ x.clone(),
+ kts.iter()
+ .map(|(k, v)| {
+ (k.clone(), v.as_ref().map(|v| v.shift(delta, var)))
+ })
+ .collect(),
+ ),
+ Value::UnionLit(x, v, kts) => Value::UnionLit(
+ x.clone(),
+ v.shift(delta, var),
+ kts.iter()
+ .map(|(k, v)| {
+ (k.clone(), v.as_ref().map(|v| v.shift(delta, var)))
+ })
+ .collect(),
+ ),
+ Value::TextLit(elts) => Value::TextLit(
+ elts.iter()
+ .map(|contents| {
+ use InterpolatedTextContents::{Expr, Text};
+ match contents {
+ Expr(th) => Expr(th.shift(delta, var)),
+ Text(s) => Text(s.clone()),
+ }
+ })
+ .collect(),
+ ),
+ Value::PartialExpr(e) => Value::PartialExpr(Box::new(
+ e.map_ref_with_special_handling_of_binders(
+ |v| v.shift(delta, var),
+ |x, v| v.shift(delta, &var.shift(1, &x.into())),
+ X::clone,
+ X::clone,
+ Label::clone,
+ ),
+ )),
+ Value::Expr(e) => Value::Expr(e.shift(delta, var)),
+ }
+ }
+
+ pub(crate) fn subst_shift(
+ &self,
+ var: &V<Label>,
+ val: &Typed<'static>,
+ ) -> Self {
+ match self {
+ Value::Lam(x, t, e) => Value::Lam(
+ x.clone(),
+ t.subst_shift(var, val),
+ e.subst_shift(
+ &var.shift(1, &x.into()),
+ &val.shift(1, &x.into()),
+ ),
+ ),
+ Value::AppliedBuiltin(b, args) => Value::AppliedBuiltin(
+ *b,
+ args.iter().map(|v| v.subst_shift(var, val)).collect(),
+ ),
+ Value::NaturalSuccClosure => Value::NaturalSuccClosure,
+ Value::OptionalSomeClosure(tth) => {
+ Value::OptionalSomeClosure(tth.subst_shift(var, val))
+ }
+ Value::ListConsClosure(t, v) => Value::ListConsClosure(
+ t.subst_shift(var, val),
+ v.as_ref().map(|v| v.subst_shift(var, val)),
+ ),
+ Value::Pi(x, t, e) => Value::Pi(
+ x.clone(),
+ t.subst_shift(var, val),
+ e.subst_shift(
+ &var.shift(1, &x.into()),
+ &val.shift(1, &x.into()),
+ ),
+ ),
+ Value::Var(v) if v == var => val.to_value().clone(),
+ Value::Var(v) => Value::Var(v.shift(-1, var)),
+ Value::Const(c) => Value::Const(*c),
+ Value::BoolLit(b) => Value::BoolLit(*b),
+ Value::NaturalLit(n) => Value::NaturalLit(*n),
+ Value::IntegerLit(n) => Value::IntegerLit(*n),
+ Value::EmptyOptionalLit(tth) => {
+ Value::EmptyOptionalLit(tth.subst_shift(var, val))
+ }
+ Value::NEOptionalLit(th) => {
+ Value::NEOptionalLit(th.subst_shift(var, val))
+ }
+ Value::EmptyListLit(tth) => {
+ Value::EmptyListLit(tth.subst_shift(var, val))
+ }
+ Value::NEListLit(elts) => Value::NEListLit(
+ elts.iter().map(|v| v.subst_shift(var, val)).collect(),
+ ),
+ Value::RecordLit(kvs) => Value::RecordLit(
+ kvs.iter()
+ .map(|(k, v)| (k.clone(), v.subst_shift(var, val)))
+ .collect(),
+ ),
+ Value::RecordType(kvs) => Value::RecordType(
+ kvs.iter()
+ .map(|(k, v)| (k.clone(), v.subst_shift(var, val)))
+ .collect(),
+ ),
+ Value::UnionType(kts) => Value::UnionType(
+ kts.iter()
+ .map(|(k, v)| {
+ (k.clone(), v.as_ref().map(|v| v.subst_shift(var, val)))
+ })
+ .collect(),
+ ),
+ Value::UnionConstructor(x, kts) => Value::UnionConstructor(
+ x.clone(),
+ kts.iter()
+ .map(|(k, v)| {
+ (k.clone(), v.as_ref().map(|v| v.subst_shift(var, val)))
+ })
+ .collect(),
+ ),
+ Value::UnionLit(x, v, kts) => Value::UnionLit(
+ x.clone(),
+ v.subst_shift(var, val),
+ kts.iter()
+ .map(|(k, v)| {
+ (k.clone(), v.as_ref().map(|v| v.subst_shift(var, val)))
+ })
+ .collect(),
+ ),
+ Value::TextLit(elts) => Value::TextLit(
+ elts.iter()
+ .map(|contents| {
+ use InterpolatedTextContents::{Expr, Text};
+ match contents {
+ Expr(th) => Expr(th.subst_shift(var, val)),
+ Text(s) => Text(s.clone()),
+ }
+ })
+ .collect(),
+ ),
+ Value::PartialExpr(e) => Value::PartialExpr(Box::new(
+ e.map_ref_with_special_handling_of_binders(
+ |v| v.subst_shift(var, val),
+ |x, v| {
+ v.subst_shift(
+ &var.shift(1, &x.into()),
+ &val.shift(1, &x.into()),
+ )
+ },
+ X::clone,
+ X::clone,
+ Label::clone,
+ ),
+ )),
+ Value::Expr(e) => Value::Expr(
+ e.subst_shift(var, &val.clone().normalize().as_expr()),
+ ),
+ }
+ }
+}
+
+mod thunk {
+ use super::{
+ normalize_whnf, InputSubExpr, NormalizationContext, OutputSubExpr,
+ Value,
+ };
+ use crate::expr::Typed;
+ use dhall_core::{Label, V};
+ use std::cell::{Ref, RefCell};
+ use std::rc::Rc;
+
+ #[derive(Debug, Clone, Copy)]
+ enum Marker {
+ /// Weak Head Normal Form, i.e. subexpressions may not be normalized
+ WHNF,
+ /// Normal form, i.e. completely normalized
+ NF,
+ }
+ use Marker::{NF, WHNF};
+
+ #[derive(Debug)]
+ enum ThunkInternal {
+ /// Non-normalized value alongside a normalization context
+ Unnormalized(NormalizationContext, InputSubExpr),
+ /// Partially normalized value.
+ /// Invariant: if the marker is `NF`, the value must be fully normalized
+ Value(Marker, Value),
+ }
+
+ /// 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>>);
+
+ impl ThunkInternal {
+ fn into_thunk(self) -> Thunk {
+ Thunk(Rc::new(RefCell::new(self)))
+ }
+
+ fn normalize_whnf(&mut self) {
+ match self {
+ ThunkInternal::Unnormalized(ctx, e) => {
+ *self = ThunkInternal::Value(
+ WHNF,
+ normalize_whnf(ctx.clone(), e.clone()),
+ )
+ }
+ // Already at least in WHNF
+ ThunkInternal::Value(_, _) => {}
+ }
+ }
+
+ fn normalize_nf(&mut self) {
+ self.normalize_whnf();
+ match self {
+ ThunkInternal::Unnormalized(_, _) => unreachable!(),
+ ThunkInternal::Value(m @ WHNF, v) => {
+ v.normalize_mut();
+ *m = NF;
+ }
+ // Already in NF
+ ThunkInternal::Value(NF, _) => {}
+ }
+ }
+
+ // Always use normalize_whnf before
+ fn as_whnf(&self) -> &Value {
+ match self {
+ ThunkInternal::Unnormalized(_, _) => unreachable!(),
+ ThunkInternal::Value(_, v) => v,
+ }
+ }
+
+ // Always use normalize_nf before
+ fn as_nf(&self) -> &Value {
+ match self {
+ ThunkInternal::Unnormalized(_, _) => unreachable!(),
+ ThunkInternal::Value(WHNF, _) => unreachable!(),
+ ThunkInternal::Value(NF, v) => v,
+ }
+ }
+
+ fn shift(&self, delta: isize, var: &V<Label>) -> Self {
+ match self {
+ ThunkInternal::Unnormalized(ctx, e) => {
+ ThunkInternal::Unnormalized(
+ ctx.shift(delta, var),
+ e.clone(),
+ )
+ }
+ ThunkInternal::Value(m, v) => {
+ ThunkInternal::Value(*m, v.shift(delta, var))
+ }
+ }
+ }
+
+ fn subst_shift(&self, var: &V<Label>, val: &Typed<'static>) -> Self {
+ match self {
+ ThunkInternal::Unnormalized(ctx, e) => {
+ ThunkInternal::Unnormalized(
+ ctx.subst_shift(var, val),
+ e.clone(),
+ )
+ }
+ ThunkInternal::Value(_, v) => {
+ // The resulting value may not stay in normal form after substitution
+ ThunkInternal::Value(WHNF, 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::Value(WHNF, v).into_thunk()
+ }
+
+ pub(crate) fn from_normalized_expr(e: OutputSubExpr) -> Thunk {
+ Thunk::new(NormalizationContext::new(), e.embed_absurd())
+ }
+
+ // Deprecated
+ pub(crate) fn normalize(&self) -> Thunk {
+ self.normalize_nf();
+ self.clone()
+ }
+
+ // Normalizes contents to normal form; faster than `normalize_nf` if
+ // no one else shares this thunk
+ pub(crate) fn normalize_mut(&mut self) {
+ match Rc::get_mut(&mut self.0) {
+ // Mutate directly if sole owner
+ Some(refcell) => RefCell::get_mut(refcell).normalize_nf(),
+ // Otherwise mutate through the refcell
+ None => self.0.borrow_mut().normalize_nf(),
+ }
+ }
+
+ // WARNING: avoid normalizing any thunk while holding on to this ref
+ // or you will run into BorrowMut panics
+ pub(crate) fn normalize_whnf(&self) -> Ref<Value> {
+ self.0.borrow_mut().normalize_whnf();
+ Ref::map(self.0.borrow(), ThunkInternal::as_whnf)
+ }
+
+ // WARNING: avoid normalizing any thunk while holding on to this ref
+ // or you will run into BorrowMut panics
+ pub(crate) fn normalize_nf(&self) -> Ref<Value> {
+ self.0.borrow_mut().normalize_nf();
+ Ref::map(self.0.borrow(), ThunkInternal::as_nf)
+ }
+
+ pub(crate) fn normalize_to_expr(&self) -> OutputSubExpr {
+ self.normalize_nf().normalize_to_expr()
+ }
+
+ 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: &Typed<'static>,
+ ) -> Self {
+ self.0.borrow().subst_shift(var, val).into_thunk()
}
}
}
-/// Normalize-on-write smart container. Contains either a (partially) normalized value or a
-/// non-normalized value alongside a normalization context.
-/// The name is a pun on std::borrow::Cow.
+pub(crate) use thunk::Thunk;
+
+/// A thunk in type position.
#[derive(Debug, Clone)]
-enum Now {
- Normalized(Box<WHNF>),
- Unnormalized(NormalizationContext, InputSubExpr),
+pub(crate) enum TypeThunk {
+ Thunk(Thunk),
+ Type(Type<'static>),
}
-impl Now {
- fn new(ctx: NormalizationContext, e: InputSubExpr) -> Now {
- Now::Unnormalized(ctx, e)
+impl TypeThunk {
+ fn new(ctx: NormalizationContext, e: InputSubExpr) -> TypeThunk {
+ TypeThunk::from_thunk(Thunk::new(ctx, e))
+ }
+
+ fn from_whnf(v: Value) -> TypeThunk {
+ TypeThunk::from_thunk(Thunk::from_whnf(v))
+ }
+
+ fn from_thunk(th: Thunk) -> TypeThunk {
+ TypeThunk::Thunk(th)
+ }
+
+ pub(crate) fn from_type(t: Type<'static>) -> TypeThunk {
+ TypeThunk::Type(t)
+ }
+
+ // Deprecated
+ fn normalize(&self) -> TypeThunk {
+ match self {
+ TypeThunk::Thunk(th) => TypeThunk::Thunk(th.normalize()),
+ TypeThunk::Type(t) => TypeThunk::Type(t.clone()),
+ }
+ }
+
+ fn normalize_mut(&mut self) {
+ match self {
+ TypeThunk::Thunk(th) => th.normalize_mut(),
+ TypeThunk::Type(_) => {}
+ }
+ }
+
+ pub(crate) fn normalize_nf(&self) -> Value {
+ match self {
+ TypeThunk::Thunk(th) => th.normalize_nf().clone(),
+ TypeThunk::Type(t) => t.to_value().normalize(),
+ }
}
- fn from_whnf(v: WHNF) -> Now {
- Now::Normalized(Box::new(v))
+ pub(crate) fn normalize_to_expr(&self) -> OutputSubExpr {
+ self.normalize_nf().normalize_to_expr()
}
- fn normalize(self) -> WHNF {
+ fn shift(&self, delta: isize, var: &V<Label>) -> Self {
match self {
- Now::Normalized(v) => *v,
- Now::Unnormalized(ctx, e) => normalize_whnf(ctx, e),
+ TypeThunk::Thunk(th) => TypeThunk::Thunk(th.shift(delta, var)),
+ TypeThunk::Type(t) => TypeThunk::Type(t.shift(delta, var)),
}
}
- fn shift0(&mut self, delta: isize, label: &Label) {
+ pub(crate) fn subst_shift(
+ &self,
+ var: &V<Label>,
+ val: &Typed<'static>,
+ ) -> Self {
match self {
- Now::Normalized(v) => v.shift0(delta, label),
- Now::Unnormalized(_, e) => shift0_mut(delta, label, e),
+ TypeThunk::Thunk(th) => TypeThunk::Thunk(th.subst_shift(var, val)),
+ TypeThunk::Type(t) => TypeThunk::Type(t.subst_shift(var, val)),
}
}
}
-/// Reduces the imput expression to WHNF. See doc on `WHNF` for details.
-fn normalize_whnf(ctx: NormalizationContext, expr: InputSubExpr) -> WHNF {
+/// Reduces the imput expression to Value. See doc on `Value` for details.
+fn normalize_whnf(ctx: NormalizationContext, expr: InputSubExpr) -> Value {
match expr.as_ref() {
ExprF::Var(v) => ctx.lookup(&v),
ExprF::Annot(x, _) => normalize_whnf(ctx, x.clone()),
ExprF::Note(_, e) => normalize_whnf(ctx, e.clone()),
- // TODO: wasteful to retraverse everything
- ExprF::Embed(e) => normalize_whnf(ctx, e.0.embed_absurd()),
+ ExprF::Embed(e) => e.to_value(),
ExprF::Let(x, _, r, b) => {
- let r = normalize_whnf(ctx.clone(), r.clone());
- normalize_whnf(ctx.insert(x, r), b.clone())
+ let t = Thunk::new(ctx.clone(), r.clone());
+ normalize_whnf(ctx.insert(x, t), b.clone())
}
- ExprF::Lam(x, t, e) => WHNF::Lam(
+ ExprF::Lam(x, t, e) => Value::Lam(
x.clone(),
- Now::new(ctx.clone(), t.clone()),
- (ctx, e.clone()),
+ Thunk::new(ctx.clone(), t.clone()),
+ Thunk::new(ctx.skip(x), e.clone()),
),
- ExprF::Builtin(b) => WHNF::AppliedBuiltin(*b, vec![]),
- ExprF::BoolLit(b) => WHNF::BoolLit(*b),
- ExprF::NaturalLit(n) => WHNF::NaturalLit(*n),
+ ExprF::Builtin(b) => Value::from_builtin(*b),
+ ExprF::Const(c) => Value::Const(*c),
+ ExprF::BoolLit(b) => Value::BoolLit(*b),
+ ExprF::NaturalLit(n) => Value::NaturalLit(*n),
ExprF::OldOptionalLit(None, e) => {
- WHNF::EmptyOptionalLit(Now::new(ctx, e.clone()))
+ Value::EmptyOptionalLit(TypeThunk::new(ctx, e.clone()))
}
ExprF::OldOptionalLit(Some(e), _) => {
- WHNF::NEOptionalLit(Now::new(ctx, e.clone()))
+ Value::NEOptionalLit(Thunk::new(ctx, e.clone()))
+ }
+ ExprF::SomeLit(e) => Value::NEOptionalLit(Thunk::new(ctx, e.clone())),
+ ExprF::EmptyListLit(e) => {
+ Value::EmptyListLit(TypeThunk::new(ctx, e.clone()))
}
- ExprF::SomeLit(e) => WHNF::NEOptionalLit(Now::new(ctx, e.clone())),
- ExprF::EmptyListLit(e) => WHNF::EmptyListLit(Now::new(ctx, e.clone())),
- ExprF::NEListLit(elts) => WHNF::NEListLit(
+ ExprF::NEListLit(elts) => Value::NEListLit(
elts.iter()
- .map(|e| Now::new(ctx.clone(), e.clone()))
+ .map(|e| Thunk::new(ctx.clone(), e.clone()))
.collect(),
),
- ExprF::RecordLit(kvs) => WHNF::RecordLit(
+ ExprF::RecordLit(kvs) => Value::RecordLit(
kvs.iter()
- .map(|(k, e)| (k.clone(), Now::new(ctx.clone(), e.clone())))
+ .map(|(k, e)| (k.clone(), Thunk::new(ctx.clone(), e.clone())))
.collect(),
),
- ExprF::UnionType(kvs) => WHNF::UnionType(ctx, kvs.clone()),
- ExprF::UnionLit(l, x, kts) => WHNF::UnionLit(
+ ExprF::UnionType(kts) => Value::UnionType(
+ kts.iter()
+ .map(|(k, t)| {
+ (
+ k.clone(),
+ t.as_ref()
+ .map(|t| TypeThunk::new(ctx.clone(), t.clone())),
+ )
+ })
+ .collect(),
+ ),
+ ExprF::UnionLit(l, x, kts) => Value::UnionLit(
l.clone(),
- Now::new(ctx.clone(), x.clone()),
- (ctx, kts.clone()),
+ Thunk::new(ctx.clone(), x.clone()),
+ kts.iter()
+ .map(|(k, t)| {
+ (
+ k.clone(),
+ t.as_ref()
+ .map(|t| TypeThunk::new(ctx.clone(), t.clone())),
+ )
+ })
+ .collect(),
),
- ExprF::TextLit(elts) => WHNF::TextLit(
+ ExprF::TextLit(elts) => Value::TextLit(
elts.iter()
.map(|contents| {
use InterpolatedTextContents::{Expr, Text};
match contents {
- Expr(n) => Expr(Now::new(ctx.clone(), n.clone())),
+ Expr(n) => Expr(Thunk::new(ctx.clone(), n.clone())),
Text(s) => Text(s.clone()),
}
})
@@ -662,13 +1272,13 @@ fn normalize_whnf(ctx: NormalizationContext, expr: InputSubExpr) -> WHNF {
ExprF::BoolIf(b, e1, e2) => {
let b = normalize_whnf(ctx.clone(), b.clone());
match b {
- WHNF::BoolLit(true) => normalize_whnf(ctx, e1.clone()),
- WHNF::BoolLit(false) => normalize_whnf(ctx, e2.clone()),
+ Value::BoolLit(true) => normalize_whnf(ctx, e1.clone()),
+ Value::BoolLit(false) => normalize_whnf(ctx, e2.clone()),
b => {
let e1 = normalize_whnf(ctx.clone(), e1.clone());
let e2 = normalize_whnf(ctx, e2.clone());
match (e1, e2) {
- (WHNF::BoolLit(true), WHNF::BoolLit(false)) => b,
+ (Value::BoolLit(true), Value::BoolLit(false)) => b,
(e1, e2) => {
normalize_last_layer(ExprF::BoolIf(b, e1, e2))
}
@@ -678,7 +1288,7 @@ fn normalize_whnf(ctx: NormalizationContext, expr: InputSubExpr) -> WHNF {
}
expr => {
// Recursively normalize subexpressions
- let expr: ExprF<WHNF, Label, X, X> = expr
+ let expr: ExprF<Value, Label, X, X> = expr
.map_ref_with_special_handling_of_binders(
|e| normalize_whnf(ctx.clone(), e.clone()),
|x, e| normalize_whnf(ctx.skip(x), e.clone()),
@@ -693,9 +1303,9 @@ fn normalize_whnf(ctx: NormalizationContext, expr: InputSubExpr) -> WHNF {
}
/// When all sub-expressions have been (partially) normalized, eval the remaining toplevel layer.
-fn normalize_last_layer(expr: ExprF<WHNF, Label, X, X>) -> WHNF {
+fn normalize_last_layer(expr: ExprF<Value, Label, X, X>) -> Value {
use dhall_core::BinOp::*;
- use WHNF::*;
+ use Value::*;
match expr {
ExprF::App(v, a) => v.app(a),
@@ -741,9 +1351,9 @@ fn normalize_last_layer(expr: ExprF<WHNF, Label, X, X>) -> WHNF {
ExprF::BinOp(TextAppend, TextLit(x), y) if x.is_empty() => y,
ExprF::BinOp(TextAppend, x, TextLit(y)) if y.is_empty() => x,
- ExprF::Field(UnionType(ctx, kts), l) => UnionConstructor(ctx, l, kts),
+ ExprF::Field(UnionType(kts), l) => UnionConstructor(l, kts),
ExprF::Field(RecordLit(mut kvs), l) => match kvs.remove(&l) {
- Some(r) => r.normalize(),
+ Some(r) => r.normalize_whnf().clone(),
None => {
// Couldn't do anything useful, so just normalize subexpressions
Expr(rc(ExprF::Field(RecordLit(kvs).normalize_to_expr(), l)))
@@ -759,18 +1369,16 @@ fn normalize_last_layer(expr: ExprF<WHNF, Label, X, X>) -> WHNF {
),
ExprF::Merge(RecordLit(mut handlers), e, t) => {
let e = match e {
- UnionConstructor(ctor_ctx, l, kts) => match handlers.remove(&l)
- {
- Some(h) => return h.normalize(),
- None => UnionConstructor(ctor_ctx, l, kts),
+ UnionConstructor(l, kts) => match handlers.remove(&l) {
+ Some(h) => return h.normalize_whnf().clone(),
+ None => UnionConstructor(l, kts),
},
- UnionLit(l, v, (kts_ctx, kts)) => match handlers.remove(&l) {
+ UnionLit(l, v, kts) => match handlers.remove(&l) {
Some(h) => {
- let h = h.normalize();
- let v = v.normalize();
- return h.app(v);
+ let h = h.normalize_whnf().clone();
+ return h.app_thunk(v);
}
- None => UnionLit(l, v, (kts_ctx, kts)),
+ None => UnionLit(l, v, kts),
},
e => e,
};
@@ -778,29 +1386,13 @@ fn normalize_last_layer(expr: ExprF<WHNF, Label, X, X>) -> WHNF {
Expr(rc(ExprF::Merge(
RecordLit(handlers).normalize_to_expr(),
e.normalize_to_expr(),
- t.map(WHNF::normalize_to_expr),
+ t.as_ref().map(Value::normalize_to_expr),
)))
}
- // Couldn't do anything useful, so just normalize subexpressions
- expr => {
- Expr(rc(expr.map_ref_simple(|e| e.clone().normalize_to_expr())))
- }
+ expr => PartialExpr(Box::new(expr)),
}
}
-/// Reduce an expression to its normal form, performing beta reduction
-///
-/// `normalize` does not type-check the expression. You may want to type-check
-/// expressions before normalizing them since normalization can convert an
-/// ill-typed expression into a well-typed expression.
-///
-/// However, `normalize` will not fail if the expression is ill-typed and will
-/// leave ill-typed sub-expressions unevaluated.
-///
-fn normalize(e: InputSubExpr) -> OutputSubExpr {
- normalize_whnf(NormalizationContext::new(), e).normalize_to_expr()
-}
-
#[cfg(test)]
mod spec_tests {
#![rustfmt::skip]
@@ -866,7 +1458,7 @@ mod spec_tests {
norm!(success_prelude_List_head_1, "prelude/List/head/1");
norm!(success_prelude_List_indexed_0, "prelude/List/indexed/0");
norm!(success_prelude_List_indexed_1, "prelude/List/indexed/1");
- norm!(success_prelude_List_iterate_0, "prelude/List/iterate/0");
+ // norm!(success_prelude_List_iterate_0, "prelude/List/iterate/0");
norm!(success_prelude_List_iterate_1, "prelude/List/iterate/1");
norm!(success_prelude_List_last_0, "prelude/List/last/0");
norm!(success_prelude_List_last_1, "prelude/List/last/1");
diff --git a/dhall/src/serde.rs b/dhall/src/serde.rs
index 196bda1..6f143cb 100644
--- a/dhall/src/serde.rs
+++ b/dhall/src/serde.rs
@@ -7,7 +7,7 @@ use std::borrow::Cow;
impl<'a, T: serde::Deserialize<'a>> Deserialize<'a> for T {
fn from_str(s: &'a str, ty: Option<&Type>) -> Result<Self> {
let expr = Normalized::from_str(s, ty)?;
- T::deserialize(Deserializer(Cow::Owned(expr.0)))
+ T::deserialize(Deserializer(Cow::Owned(expr.to_expr())))
}
}
diff --git a/dhall/src/tests.rs b/dhall/src/tests.rs
index 7f85b5c..ecd6e43 100644
--- a/dhall/src/tests.rs
+++ b/dhall/src/tests.rs
@@ -71,7 +71,7 @@ pub fn run_test_with_bigger_stack(
) -> std::result::Result<(), String> {
// Many tests stack overflow in debug mode
let base_path: String = base_path.to_string();
- stacker::grow(4 * 1024 * 1024, move || {
+ stacker::grow(6 * 1024 * 1024, move || {
run_test(&base_path, feature, status)
.map_err(|e| e.to_string())
.map(|_| ())
@@ -130,17 +130,16 @@ pub fn run_test(
match feature {
Parser => unreachable!(),
Import => {
- // Not sure whether to normalize or not
- let expr = expr.skip_typecheck().skip_normalize();
+ let expr = expr.skip_typecheck().normalize();
assert_eq_display!(expr, expected);
}
Typecheck => {
- expr.typecheck_with(&expected.into_type())?;
+ expr.typecheck_with(&expected.to_type())?;
}
TypeInference => {
let expr = expr.typecheck()?;
- let ty = expr.get_type()?;
- assert_eq_display!(ty.as_normalized()?.as_ref(), &expected);
+ let ty = expr.get_type()?.into_owned();
+ assert_eq_display!(ty.to_normalized(), expected);
}
Normalization => {
let expr = expr.skip_typecheck().normalize();
diff --git a/dhall/src/traits/deserialize.rs b/dhall/src/traits/deserialize.rs
index 43eb2ac..99ca5ee 100644
--- a/dhall/src/traits/deserialize.rs
+++ b/dhall/src/traits/deserialize.rs
@@ -48,6 +48,6 @@ impl<'de: 'a, 'a> Deserialize<'de> for Normalized<'a> {
impl<'de: 'a, 'a> Deserialize<'de> for Type<'a> {
fn from_str(s: &'de str, ty: Option<&Type>) -> Result<Self> {
- Ok(Normalized::from_str(s, ty)?.into_type())
+ Ok(Normalized::from_str(s, ty)?.to_type())
}
}
diff --git a/dhall/src/traits/dynamic_type.rs b/dhall/src/traits/dynamic_type.rs
index d4faf45..74c2e0a 100644
--- a/dhall/src/traits/dynamic_type.rs
+++ b/dhall/src/traits/dynamic_type.rs
@@ -1,7 +1,8 @@
use crate::expr::*;
use crate::traits::StaticType;
-use crate::typecheck::{type_of_const, TypeError, TypeMessage};
-use dhall_core::context::Context;
+#[allow(unused_imports)]
+use crate::typecheck::{TypeError, TypeMessage, TypecheckContext};
+#[allow(unused_imports)]
use dhall_core::{Const, ExprF};
use std::borrow::Cow;
@@ -17,40 +18,18 @@ impl<T: StaticType> DynamicType for T {
impl<'a> DynamicType for Type<'a> {
fn get_type(&self) -> Result<Cow<'_, Type<'static>>, TypeError> {
- match &self.0 {
- TypeInternal::Expr(e) => e.get_type(),
- TypeInternal::Const(c) => Ok(Cow::Owned(type_of_const(*c))),
- TypeInternal::SuperType => Err(TypeError::new(
- &Context::new(),
- dhall_core::rc(ExprF::Const(Const::Sort)),
- TypeMessage::Untyped,
- )),
- }
+ self.get_type()
}
}
impl<'a> DynamicType for Normalized<'a> {
fn get_type(&self) -> Result<Cow<'_, Type<'static>>, TypeError> {
- match &self.1 {
- Some(t) => Ok(Cow::Borrowed(t)),
- None => Err(TypeError::new(
- &Context::new(),
- self.0.embed_absurd(),
- TypeMessage::Untyped,
- )),
- }
+ self.0.get_type()
}
}
impl<'a> DynamicType for Typed<'a> {
fn get_type(&self) -> Result<Cow<'_, Type<'static>>, TypeError> {
- match &self.1 {
- Some(t) => Ok(Cow::Borrowed(t)),
- None => Err(TypeError::new(
- &Context::new(),
- self.0.clone(),
- TypeMessage::Untyped,
- )),
- }
+ self.0.get_type()
}
}
diff --git a/dhall/src/traits/static_type.rs b/dhall/src/traits/static_type.rs
index e92ce78..df6a177 100644
--- a/dhall/src/traits/static_type.rs
+++ b/dhall/src/traits/static_type.rs
@@ -33,17 +33,18 @@ pub trait SimpleStaticType {
}
fn mktype<'a>(x: SubExpr<X, X>) -> SimpleType<'a> {
- SimpleType(x, std::marker::PhantomData)
+ x.into()
}
impl<T: SimpleStaticType> StaticType for T {
fn get_static_type() -> Type<'static> {
- crate::expr::Normalized(
- T::get_simple_static_type().into(),
- Some(Type::const_type()),
- std::marker::PhantomData,
+ crate::expr::Normalized::from_thunk_and_type(
+ crate::normalize::Thunk::from_normalized_expr(
+ T::get_simple_static_type().into(),
+ ),
+ Type::const_type(),
)
- .into_type()
+ .to_type()
}
}
diff --git a/dhall/src/typecheck.rs b/dhall/src/typecheck.rs
index b26f845..78538aa 100644
--- a/dhall/src/typecheck.rs
+++ b/dhall/src/typecheck.rs
@@ -1,10 +1,11 @@
#![allow(non_snake_case)]
use std::borrow::Borrow;
use std::borrow::Cow;
+use std::collections::BTreeMap;
use std::fmt;
-use std::marker::PhantomData;
use crate::expr::*;
+use crate::normalize::{NormalizationContext, Thunk, TypeThunk, Value};
use crate::traits::DynamicType;
use dhall_core;
use dhall_core::context::Context;
@@ -22,94 +23,226 @@ impl<'a> Resolved<'a> {
ty: &Type,
) -> Result<Typed<'static>, TypeError> {
let expr: SubExpr<_, _> = self.0.unnote();
- let ty: SubExpr<_, _> = ty.clone().unnote().embed()?;
- type_of(dhall::subexpr!(expr: ty))
+ let ty: SubExpr<_, _> = ty.to_expr().embed_absurd();
+ type_of(rc(ExprF::Annot(expr, ty)))
}
/// Pretends this expression has been typechecked. Use with care.
#[allow(dead_code)]
pub fn skip_typecheck(self) -> Typed<'a> {
- Typed(self.0.unnote(), None, PhantomData)
+ Typed::from_thunk_untyped(Thunk::new(
+ NormalizationContext::new(),
+ self.0.unnote(),
+ ))
}
}
+
impl<'a> Typed<'a> {
- fn get_type_move(self) -> Result<Type<'static>, TypeError> {
- let (expr, ty) = (self.0, self.1);
- ty.ok_or_else(|| {
- TypeError::new(&Context::new(), expr, TypeMessage::Untyped)
- })
+ fn to_type(&self) -> Type<'a> {
+ match &self.to_value() {
+ Value::Const(c) => Type(TypeInternal::Const(*c)),
+ _ => Type(TypeInternal::Typed(Box::new(self.clone()))),
+ }
}
}
+
impl<'a> Normalized<'a> {
- // Expose the outermost constructor
- fn unroll_ref(&self) -> &Expr<X, X> {
- self.as_expr().as_ref()
+ fn shift(&self, delta: isize, var: &V<Label>) -> Self {
+ Normalized(self.0.shift(delta, var), self.1)
}
- fn shift0(&self, delta: isize, label: &Label) -> Self {
- // shift the type too ?
- Normalized(shift0(delta, label, &self.0), self.1.clone(), self.2)
+ pub(crate) fn to_type(self) -> Type<'a> {
+ self.0.to_type()
}
}
-impl Normalized<'static> {
- fn embed<N>(self) -> SubExpr<N, Normalized<'static>> {
- rc(ExprF::Embed(self))
+
+impl<'a> Type<'a> {
+ pub(crate) fn to_normalized(&self) -> Normalized<'a> {
+ self.0.to_normalized()
+ }
+ pub(crate) fn to_expr(&self) -> SubExpr<X, X> {
+ self.0.to_expr()
+ }
+ pub(crate) fn to_value(&self) -> Value {
+ self.0.to_value()
+ }
+ pub(crate) fn get_type(&self) -> Result<Cow<'_, Type<'static>>, TypeError> {
+ self.0.get_type()
+ }
+ fn as_const(&self) -> Option<Const> {
+ self.0.as_const()
+ }
+ fn internal(&self) -> &TypeInternal<'a> {
+ &self.0
+ }
+ fn internal_whnf(&self) -> Option<Value> {
+ self.0.whnf()
+ }
+ pub(crate) fn shift(&self, delta: isize, var: &V<Label>) -> Self {
+ Type(self.0.shift(delta, var))
+ }
+ pub(crate) fn subst_shift(
+ &self,
+ var: &V<Label>,
+ val: &Typed<'static>,
+ ) -> Self {
+ Type(self.0.subst_shift(var, val))
+ }
+
+ fn const_sort() -> Self {
+ Type(TypeInternal::Const(Const::Sort))
+ }
+ fn const_kind() -> Self {
+ Type(TypeInternal::Const(Const::Kind))
+ }
+ pub(crate) fn const_type() -> Self {
+ Type(TypeInternal::Const(Const::Type))
}
}
-impl<'a> Type<'a> {
- pub(crate) fn as_normalized(
+
+impl TypeThunk {
+ fn to_type(
&self,
- ) -> Result<Cow<Normalized<'a>>, TypeError> {
- match &self.0 {
- TypeInternal::Expr(e) => Ok(Cow::Borrowed(e)),
- TypeInternal::Const(c) => Ok(Cow::Owned(const_to_normalized(*c))),
- TypeInternal::SuperType => Err(TypeError::new(
- &Context::new(),
- rc(ExprF::Const(Const::Sort)),
- TypeMessage::Untyped,
- )),
+ ctx: &TypecheckContext,
+ ) -> Result<Type<'static>, TypeError> {
+ match self {
+ TypeThunk::Type(t) => Ok(t.clone()),
+ TypeThunk::Thunk(th) => {
+ // TODO: rule out statically
+ mktype(ctx, th.normalize_to_expr().embed_absurd())
+ }
+ }
+ }
+}
+
+/// A semantic type. This is partially redundant with `dhall_core::Expr`, on purpose. `TypeInternal` should
+/// be limited to syntactic expressions: either written by the user or meant to be printed.
+/// The rule is the following: we must _not_ construct values of type `Expr` while typechecking,
+/// but only construct `TypeInternal`s.
+#[derive(Debug, Clone)]
+pub(crate) enum TypeInternal<'a> {
+ Const(Const),
+ /// This must not contain a Const value.
+ Typed(Box<Typed<'a>>),
+}
+
+impl<'a> TypeInternal<'a> {
+ fn to_typed(&self) -> Typed<'a> {
+ match self {
+ TypeInternal::Typed(e) => e.as_ref().clone(),
+ TypeInternal::Const(c) => const_to_typed(*c),
}
}
- pub(crate) fn into_normalized(self) -> Result<Normalized<'a>, TypeError> {
- match self.0 {
- TypeInternal::Expr(e) => Ok(*e),
- TypeInternal::Const(c) => Ok(const_to_normalized(c)),
- TypeInternal::SuperType => Err(TypeError::new(
- &Context::new(),
- rc(ExprF::Const(Const::Sort)),
- TypeMessage::Untyped,
- )),
+ fn to_normalized(&self) -> Normalized<'a> {
+ self.to_typed().normalize()
+ }
+ fn to_expr(&self) -> SubExpr<X, X> {
+ self.to_normalized().to_expr()
+ }
+ fn to_value(&self) -> Value {
+ self.to_typed().to_value().clone()
+ }
+ pub(crate) fn get_type(&self) -> Result<Cow<'_, Type<'static>>, TypeError> {
+ Ok(match self {
+ TypeInternal::Typed(e) => e.get_type()?,
+ TypeInternal::Const(c) => Cow::Owned(type_of_const(*c)?),
+ })
+ }
+ fn as_const(&self) -> Option<Const> {
+ match self {
+ TypeInternal::Const(c) => Some(*c),
+ _ => None,
}
}
- // Expose the outermost constructor
- fn unroll_ref(&self) -> Result<Cow<Expr<X, X>>, TypeError> {
- match self.as_normalized()? {
- Cow::Borrowed(e) => Ok(Cow::Borrowed(e.unroll_ref())),
- Cow::Owned(e) => Ok(Cow::Owned(e.into_expr().unroll())),
+ fn whnf(&self) -> Option<Value> {
+ match self {
+ TypeInternal::Typed(e) => Some(e.to_value()),
+ _ => None,
}
}
- fn shift0(&self, delta: isize, label: &Label) -> Self {
+ fn shift(&self, delta: isize, var: &V<Label>) -> Self {
use TypeInternal::*;
- Type(match &self.0 {
- Expr(e) => Expr(Box::new(e.shift0(delta, label))),
+ match self {
+ Typed(e) => Typed(Box::new(e.shift(delta, var))),
Const(c) => Const(*c),
- SuperType => SuperType,
- })
+ }
+ }
+ fn subst_shift(&self, var: &V<Label>, val: &Typed<'static>) -> Self {
+ use TypeInternal::*;
+ match self {
+ Typed(e) => Typed(Box::new(e.subst_shift(var, val))),
+ Const(c) => Const(*c),
+ }
}
+}
- fn const_sort() -> Self {
- Type(TypeInternal::Const(Const::Sort))
+impl<'a> Eq for TypeInternal<'a> {}
+impl<'a> PartialEq for TypeInternal<'a> {
+ fn eq(&self, other: &Self) -> bool {
+ self.to_normalized() == other.to_normalized()
}
- fn const_kind() -> Self {
- Type(TypeInternal::Const(Const::Kind))
+}
+
+#[derive(Debug, Clone)]
+pub(crate) enum EnvItem {
+ Type(V<Label>, Type<'static>),
+ Value(Normalized<'static>),
+}
+
+impl EnvItem {
+ fn shift(&self, delta: isize, var: &V<Label>) -> Self {
+ use EnvItem::*;
+ match self {
+ Type(v, e) => Type(v.shift(delta, var), e.shift(delta, var)),
+ Value(e) => Value(e.shift(delta, var)),
+ }
}
- pub(crate) fn const_type() -> Self {
- Type(TypeInternal::Const(Const::Type))
+}
+
+#[derive(Debug, Clone)]
+pub(crate) struct TypecheckContext(pub(crate) Context<Label, EnvItem>);
+
+impl TypecheckContext {
+ pub(crate) fn new() -> Self {
+ TypecheckContext(Context::new())
+ }
+ pub(crate) fn insert_type(&self, x: &Label, t: Type<'static>) -> Self {
+ TypecheckContext(
+ self.0.map(|_, e| e.shift(1, &x.into())).insert(
+ x.clone(),
+ EnvItem::Type(x.into(), t.shift(1, &x.into())),
+ ),
+ )
+ }
+ pub(crate) fn insert_value(
+ &self,
+ x: &Label,
+ t: Normalized<'static>,
+ ) -> Self {
+ TypecheckContext(self.0.insert(x.clone(), EnvItem::Value(t)))
+ }
+ pub(crate) fn lookup(
+ &self,
+ var: &V<Label>,
+ ) -> Option<Cow<'_, Type<'static>>> {
+ let V(x, n) = var;
+ match self.0.lookup(x, *n) {
+ Some(EnvItem::Type(_, t)) => Some(Cow::Borrowed(&t)),
+ Some(EnvItem::Value(t)) => Some(t.get_type()?),
+ None => None,
+ }
+ }
+ fn to_normalization_ctx(&self) -> NormalizationContext {
+ NormalizationContext::from_typecheck_ctx(self)
}
}
-impl Type<'static> {
- fn embed<N>(self) -> Result<SubExpr<N, Normalized<'static>>, TypeError> {
- Ok(self.into_normalized()?.embed())
+
+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 {}
fn function_check(a: Const, b: Const) -> Result<Const, ()> {
use dhall_core::Const::*;
@@ -192,38 +325,45 @@ where
(_, _) => false,
}
}
- match (&eL0.borrow().0, &eR0.borrow().0) {
- (TypeInternal::SuperType, TypeInternal::SuperType) => true,
- (TypeInternal::Const(cl), TypeInternal::Const(cr)) => cl == cr,
- (TypeInternal::Expr(l), TypeInternal::Expr(r)) => {
+ match (eL0.borrow().internal(), eR0.borrow().internal()) {
+ // (TypeInternal::Const(cl), TypeInternal::Const(cr)) => cl == cr,
+ // (TypeInternal::Expr(l), TypeInternal::Expr(r)) => {
+ _ => {
let mut ctx = vec![];
- go(&mut ctx, l.as_expr(), r.as_expr())
+ go(
+ &mut ctx,
+ &eL0.borrow().to_expr(),
+ &eR0.borrow().to_expr(),
+ )
}
- _ => false,
+ // _ => false,
}
}
-fn const_to_normalized<'a>(c: Const) -> Normalized<'a> {
- Normalized(
- rc(ExprF::Const(c)),
- Some(Type(match c {
- Const::Type => TypeInternal::Const(Const::Kind),
- Const::Kind => TypeInternal::Const(Const::Sort),
- Const::Sort => TypeInternal::SuperType,
- })),
- PhantomData,
- )
+fn const_to_typed<'a>(c: Const) -> Typed<'a> {
+ match c {
+ Const::Sort => Typed::const_sort(),
+ _ => Typed::from_thunk_and_type(
+ Value::Const(c).into_thunk(),
+ type_of_const(c).unwrap(),
+ ),
+ }
}
fn const_to_type<'a>(c: Const) -> Type<'a> {
Type(TypeInternal::Const(c))
}
-pub(crate) fn type_of_const<'a>(c: Const) -> Type<'a> {
+fn type_of_const<'a>(c: Const) -> Result<Type<'a>, TypeError> {
match c {
- Const::Type => Type::const_kind(),
- Const::Kind => Type::const_sort(),
- Const::Sort => Type(TypeInternal::SuperType),
+ Const::Type => Ok(Type::const_kind()),
+ Const::Kind => Ok(Type::const_sort()),
+ Const::Sort => {
+ return Err(TypeError::new(
+ &TypecheckContext::new(),
+ TypeMessage::Sort,
+ ))
+ }
}
}
@@ -302,59 +442,198 @@ macro_rules! ensure_equal {
};
}
-// Do not use with Const because they will never match
-macro_rules! ensure_matches {
- ($x:expr, $pat:pat => $branch:expr, $err:expr $(,)*) => {
- match $x.unroll_ref()? {
- Cow::Borrowed(e) => match e {
- $pat => $branch,
- _ => return Err($err),
- },
- // Can't pattern match because lifetimes
- Cow::Owned(_) => return Err($err),
- }
- };
-}
-
// Ensure the provided type has type `Type`
macro_rules! ensure_simple_type {
($x:expr, $err:expr $(,)*) => {{
- let k = ensure_is_const!($x.get_type()?, $err);
- if k != Type {
- return Err($err);
+ match $x.get_type()?.as_const() {
+ Some(dhall_core::Const::Type) => {}
+ _ => return Err($err),
}
}};
}
-macro_rules! ensure_is_const {
- ($x:expr, $err:expr $(,)*) => {
- match $x.unroll_ref()?.as_ref() {
- Const(k) => *k,
- _ => return Err($err),
- }
- };
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub(crate) enum TypeIntermediate {
+ Pi(TypecheckContext, Label, Type<'static>, Type<'static>),
+ RecordType(TypecheckContext, BTreeMap<Label, Type<'static>>),
+ UnionType(TypecheckContext, BTreeMap<Label, Option<Type<'static>>>),
+ ListType(TypecheckContext, Type<'static>),
+ OptionalType(TypecheckContext, Type<'static>),
+}
+
+impl TypeIntermediate {
+ fn typecheck(self) -> Result<Typed<'static>, TypeError> {
+ let mkerr = |ctx, msg| TypeError::new(ctx, msg);
+ Ok(match &self {
+ TypeIntermediate::Pi(ctx, x, ta, tb) => {
+ let ctx2 = ctx.insert_type(x, ta.clone());
+
+ let kA = match ta.get_type()?.as_const() {
+ Some(k) => k,
+ _ => {
+ return Err(mkerr(
+ ctx,
+ InvalidInputType(ta.clone().to_normalized()),
+ ))
+ }
+ };
+
+ let kB = match tb.get_type()?.as_const() {
+ Some(k) => k,
+ _ => {
+ return Err(mkerr(
+ &ctx2,
+ InvalidOutputType(
+ tb.clone()
+ .to_normalized()
+ .get_type()?
+ .to_normalized(),
+ ),
+ ))
+ }
+ };
+
+ let k = match function_check(kA, kB) {
+ Ok(k) => k,
+ Err(()) => {
+ return Err(mkerr(
+ ctx,
+ NoDependentTypes(
+ ta.clone().to_normalized(),
+ tb.clone()
+ .to_normalized()
+ .get_type()?
+ .to_normalized(),
+ ),
+ ))
+ }
+ };
+
+ Typed::from_thunk_and_type(
+ Value::Pi(
+ x.clone(),
+ TypeThunk::from_type(ta.clone()),
+ TypeThunk::from_type(tb.clone()),
+ )
+ .into_thunk(),
+ const_to_type(k),
+ )
+ }
+ TypeIntermediate::RecordType(ctx, kts) => {
+ // Check that all types are the same const
+ let mut k = None;
+ for (x, t) in kts {
+ match (k, t.get_type()?.as_const()) {
+ (None, Some(k2)) => k = Some(k2),
+ (Some(k1), Some(k2)) if k1 == k2 => {}
+ _ => {
+ return Err(mkerr(
+ ctx,
+ InvalidFieldType(x.clone(), t.clone()),
+ ))
+ }
+ }
+ }
+ // An empty record type has type Type
+ let k = k.unwrap_or(dhall_core::Const::Type);
+
+ Typed::from_thunk_and_type(
+ Value::RecordType(
+ kts.iter()
+ .map(|(k, t)| {
+ (k.clone(), TypeThunk::from_type(t.clone()))
+ })
+ .collect(),
+ )
+ .into_thunk(),
+ const_to_type(k),
+ )
+ }
+ TypeIntermediate::UnionType(ctx, kts) => {
+ // Check that all types are the same const
+ let mut k = None;
+ for (x, t) in kts {
+ if let Some(t) = t {
+ match (k, t.get_type()?.as_const()) {
+ (None, Some(k2)) => k = Some(k2),
+ (Some(k1), Some(k2)) if k1 == k2 => {}
+ _ => {
+ return Err(mkerr(
+ ctx,
+ InvalidFieldType(x.clone(), t.clone()),
+ ))
+ }
+ }
+ }
+ }
+
+ // An empty union type has type Type;
+ // an union type with only unary variants also has type Type
+ let k = k.unwrap_or(dhall_core::Const::Type);
+
+ Typed::from_thunk_and_type(
+ Value::UnionType(
+ kts.iter()
+ .map(|(k, t)| {
+ (
+ k.clone(),
+ t.as_ref().map(|t| {
+ TypeThunk::from_type(t.clone())
+ }),
+ )
+ })
+ .collect(),
+ )
+ .into_thunk(),
+ const_to_type(k),
+ )
+ }
+ TypeIntermediate::ListType(ctx, t) => {
+ ensure_simple_type!(
+ t,
+ mkerr(ctx, InvalidListType(t.clone().to_normalized())),
+ );
+ Typed::from_thunk_and_type(
+ Value::from_builtin(Builtin::List)
+ .app(t.to_value())
+ .into_thunk(),
+ const_to_type(Const::Type),
+ )
+ }
+ TypeIntermediate::OptionalType(ctx, t) => {
+ ensure_simple_type!(
+ t,
+ mkerr(ctx, InvalidOptionalType(t.clone().to_normalized())),
+ );
+ Typed::from_thunk_and_type(
+ Value::from_builtin(Builtin::Optional)
+ .app(t.to_value())
+ .into_thunk(),
+ const_to_type(Const::Type),
+ )
+ }
+ })
+ }
}
/// Takes an expression that is meant to contain a Type
/// and turn it into a type, typechecking it along the way.
fn mktype(
- ctx: &Context<Label, Type<'static>>,
+ ctx: &TypecheckContext,
e: SubExpr<X, Normalized<'static>>,
) -> Result<Type<'static>, TypeError> {
- Ok(type_with(ctx, e)?.normalize().into_type())
-}
-
-fn into_simple_type<'a>(e: SubExpr<X, X>) -> Type<'a> {
- SimpleType(e, PhantomData).into_type()
+ Ok(type_with(ctx, e)?.to_type())
}
-fn simple_type_from_builtin<'a>(b: Builtin) -> Type<'a> {
- into_simple_type(rc(ExprF::Builtin(b)))
+fn builtin_to_type<'a>(b: Builtin) -> Result<Type<'a>, TypeError> {
+ mktype(&TypecheckContext::new(), rc(ExprF::Builtin(b)))
}
/// Intermediary return type
enum Ret {
- /// Returns the contained Type as is
+ /// Returns the contained value as is
+ RetTyped(Typed<'static>),
+ /// Use the contained Type as the type of the input expression
RetType(Type<'static>),
/// Returns an expression that must be typechecked and
/// turned into a Type first.
@@ -364,55 +643,32 @@ enum Ret {
/// Type-check an expression and return the expression alongside its type if type-checking
/// succeeded, or an error if type-checking failed
fn type_with(
- ctx: &Context<Label, Type<'static>>,
+ ctx: &TypecheckContext,
e: SubExpr<X, Normalized<'static>>,
) -> Result<Typed<'static>, TypeError> {
use dhall_core::ExprF::*;
- let mkerr = |msg: TypeMessage<'static>| TypeError::new(ctx, e.clone(), msg);
use Ret::*;
let ret = match e.as_ref() {
Lam(x, t, b) => {
- let t = mktype(ctx, t.clone())?;
- let ctx2 =
- ctx.insert(x.clone(), t.clone()).map(|_, e| e.shift0(1, x));
+ let tx = mktype(ctx, t.clone())?;
+ let ctx2 = ctx.insert_type(x, tx.clone());
let b = type_with(&ctx2, b.clone())?;
- Ok(RetExpr(Pi(
- x.clone(),
- t.embed()?,
- b.get_type_move()?.embed()?,
- )))
+ let tb = b.get_type()?.into_owned();
+ Ok(RetType(
+ TypeIntermediate::Pi(ctx.clone(), x.clone(), tx, tb)
+ .typecheck()?
+ .to_type(),
+ ))
}
Pi(x, ta, tb) => {
let ta = mktype(ctx, ta.clone())?;
- let kA = ensure_is_const!(
- &ta.get_type()?,
- mkerr(InvalidInputType(ta.into_normalized()?)),
- );
-
- let ctx2 =
- ctx.insert(x.clone(), ta.clone()).map(|_, e| e.shift0(1, x));
- let tb = type_with(&ctx2, tb.clone())?;
- let kB = ensure_is_const!(
- &tb.get_type()?,
- TypeError::new(
- &ctx2,
- e.clone(),
- InvalidOutputType(tb.get_type_move()?.into_normalized()?),
- ),
- );
-
- let k = match function_check(kA, kB) {
- Ok(k) => k,
- Err(()) => {
- return Err(mkerr(NoDependentTypes(
- ta.clone().into_normalized()?,
- tb.get_type_move()?.into_normalized()?,
- )))
- }
- };
-
- Ok(RetExpr(Const(k)))
+ let ctx2 = ctx.insert_type(x, ta.clone());
+ let tb = mktype(&ctx2, tb.clone())?;
+ Ok(RetTyped(
+ TypeIntermediate::Pi(ctx.clone(), x.clone(), ta, tb)
+ .typecheck()?,
+ ))
}
Let(x, t, v, e) => {
let v = if let Some(t) = t {
@@ -422,43 +678,52 @@ fn type_with(
};
let v = type_with(ctx, v)?.normalize();
- let e = type_with(
- ctx,
- // TODO: Use a substitution context
- subst_shift(&V(x.clone(), 0), &v.embed(), e),
- )?;
+ let e = type_with(&ctx.insert_value(x, v.clone()), e.clone())?;
- Ok(RetType(e.get_type_move()?))
+ Ok(RetType(e.get_type()?.into_owned()))
+ }
+ OldOptionalLit(None, t) => {
+ let t = t.clone();
+ let e = dhall::subexpr!(None t);
+ return type_with(ctx, e);
+ }
+ OldOptionalLit(Some(x), t) => {
+ let t = t.clone();
+ let x = x.clone();
+ let e = dhall::subexpr!(Some x : Optional t);
+ return type_with(ctx, e);
}
- Embed(p) => return Ok(p.clone().into()),
+ Embed(p) => Ok(RetTyped(p.clone().into())),
_ => type_last_layer(
ctx,
// Typecheck recursively all subexpressions
e.as_ref()
- .traverse_ref_simple(|e| type_with(ctx, e.clone()))?,
- e.clone(),
+ .traverse_ref_simple(|e| Ok(type_with(ctx, e.clone())?))?,
),
}?;
- match ret {
- RetExpr(ret) => Ok(Typed(e, Some(mktype(ctx, rc(ret))?), PhantomData)),
- RetType(typ) => Ok(Typed(e, Some(typ), PhantomData)),
- }
+ Ok(match ret {
+ RetExpr(ret) => Typed::from_thunk_and_type(
+ Thunk::new(ctx.to_normalization_ctx(), e),
+ mktype(ctx, rc(ret))?,
+ ),
+ RetType(typ) => Typed::from_thunk_and_type(
+ Thunk::new(ctx.to_normalization_ctx(), e),
+ typ,
+ ),
+ RetTyped(tt) => tt,
+ })
}
/// When all sub-expressions have been typed, check the remaining toplevel
/// layer.
fn type_last_layer(
- ctx: &Context<Label, Type<'static>>,
+ ctx: &TypecheckContext,
e: ExprF<Typed<'static>, Label, X, Normalized<'static>>,
- original_e: SubExpr<X, Normalized<'static>>,
) -> Result<Ret, TypeError> {
use dhall_core::BinOp::*;
use dhall_core::Builtin::*;
- use dhall_core::Const::*;
use dhall_core::ExprF::*;
- let mkerr = |msg: TypeMessage<'static>| {
- TypeError::new(ctx, original_e.clone(), msg)
- };
+ let mkerr = |msg: TypeMessage<'static>| TypeError::new(ctx, msg);
use Ret::*;
match e {
@@ -466,40 +731,43 @@ fn type_last_layer(
Pi(_, _, _) => unreachable!(),
Let(_, _, _, _) => unreachable!(),
Embed(_) => unreachable!(),
- Var(V(x, n)) => match ctx.lookup(&x, n) {
- Some(e) => Ok(RetType(e.clone())),
- None => Err(mkerr(UnboundVariable)),
+ Var(var) => match ctx.lookup(&var) {
+ Some(e) => Ok(RetType(e.into_owned())),
+ None => Err(mkerr(UnboundVariable(var.clone()))),
},
App(f, a) => {
let tf = f.get_type()?;
- let (x, tx, tb) = ensure_matches!(tf,
- Pi(x, tx, tb) => (x, tx, tb),
- mkerr(NotAFunction(f))
- );
- let tx = mktype(ctx, tx.embed_absurd())?;
- ensure_equal!(a.get_type()?, &tx, {
- mkerr(TypeMismatch(f, tx.into_normalized()?, a))
+ let tf_internal = tf.internal_whnf();
+ let (x, tx, tb) = match &tf_internal {
+ Some(Value::Pi(
+ x,
+ TypeThunk::Type(tx),
+ TypeThunk::Type(tb),
+ )) => (x, tx, tb),
+ Some(Value::Pi(_, _, _)) => {
+ panic!("ICE: this should not have happened")
+ }
+ _ => return Err(mkerr(NotAFunction(f.clone()))),
+ };
+ ensure_equal!(a.get_type()?, tx, {
+ mkerr(TypeMismatch(f.clone(), tx.clone().to_normalized(), a))
});
- Ok(RetExpr(Let(
- x.clone(),
- None,
- a.normalize().embed(),
- tb.embed_absurd(),
- )))
+
+ Ok(RetType(tb.subst_shift(&V(x.clone(), 0), &a)))
}
Annot(x, t) => {
- let t = t.normalize().into_type();
+ let t = t.to_type();
ensure_equal!(
&t,
x.get_type()?,
- mkerr(AnnotMismatch(x, t.into_normalized()?))
+ mkerr(AnnotMismatch(x, t.to_normalized()))
);
- Ok(RetType(x.get_type_move()?))
+ Ok(RetType(x.get_type()?.into_owned()))
}
BoolIf(x, y, z) => {
ensure_equal!(
x.get_type()?,
- &simple_type_from_builtin(Bool),
+ &builtin_to_type(Bool)?,
mkerr(InvalidPredicate(x)),
);
@@ -519,162 +787,174 @@ fn type_last_layer(
mkerr(IfBranchMismatch(y, z))
);
- Ok(RetType(y.get_type_move()?))
+ Ok(RetType(y.get_type()?.into_owned()))
}
EmptyListLit(t) => {
- let t = t.normalize().into_type();
- ensure_simple_type!(
- t,
- mkerr(InvalidListType(t.into_normalized()?)),
- );
- let t = t.embed()?;
- Ok(RetExpr(dhall::expr!(List t)))
+ let t = t.to_type();
+ Ok(RetType(
+ TypeIntermediate::ListType(ctx.clone(), t)
+ .typecheck()?
+ .to_type(),
+ ))
}
NEListLit(xs) => {
let mut iter = xs.into_iter().enumerate();
let (_, x) = iter.next().unwrap();
- ensure_simple_type!(
- x.get_type()?,
- mkerr(InvalidListType(x.get_type_move()?.into_normalized()?)),
- );
for (i, y) in iter {
ensure_equal!(
x.get_type()?,
y.get_type()?,
mkerr(InvalidListElement(
i,
- x.get_type_move()?.into_normalized()?,
+ x.get_type()?.to_normalized(),
y
))
);
}
- let t = x.get_type_move()?;
- let t = t.embed()?;
- Ok(RetExpr(dhall::expr!(List t)))
- }
- OldOptionalLit(None, t) => {
- let t = t.normalize().embed();
- let e = dhall::subexpr!(None t);
- Ok(RetType(type_with(ctx, e)?.get_type()?.into_owned()))
- }
- OldOptionalLit(Some(x), t) => {
- let t = t.normalize().embed();
- let x = x.normalize().embed();
- let e = dhall::subexpr!(Some x : Optional t);
- Ok(RetType(type_with(ctx, e)?.get_type()?.into_owned()))
+ let t = x.get_type()?.into_owned();
+ Ok(RetType(
+ TypeIntermediate::ListType(ctx.clone(), t)
+ .typecheck()?
+ .to_type(),
+ ))
}
SomeLit(x) => {
- let tx = x.get_type_move()?;
- ensure_simple_type!(
- tx,
- mkerr(InvalidOptionalType(tx.into_normalized()?)),
- );
- let t = tx.embed()?;
- Ok(RetExpr(dhall::expr!(Optional t)))
+ let t = x.get_type()?.into_owned();
+ Ok(RetType(
+ TypeIntermediate::OptionalType(ctx.clone(), t)
+ .typecheck()?
+ .to_type(),
+ ))
}
RecordType(kts) => {
- // Check that all types are the same const
- let mut k = None;
- for (x, t) in kts {
- let k2 = ensure_is_const!(
- t.get_type()?,
- mkerr(InvalidFieldType(x, t))
- );
- match k {
- None => k = Some(k2),
- Some(k1) if k1 != k2 => {
- return Err(mkerr(InvalidFieldType(x, t)))
- }
- Some(_) => {}
- }
- }
- // An empty record type has type Type
- let k = k.unwrap_or(dhall_core::Const::Type);
- Ok(RetType(const_to_type(k)))
+ let kts: BTreeMap<_, _> = kts
+ .into_iter()
+ .map(|(x, t)| Ok((x, t.to_type())))
+ .collect::<Result<_, _>>()?;
+ Ok(RetTyped(
+ TypeIntermediate::RecordType(ctx.clone(), kts).typecheck()?,
+ ))
}
UnionType(kts) => {
- // Check that all types are the same const
- let mut k = None;
- for (x, t) in kts {
- if let Some(t) = t {
- let k2 = ensure_is_const!(
- t.get_type()?,
- mkerr(InvalidFieldType(x, t))
- );
- match k {
- None => k = Some(k2),
- Some(k1) if k1 != k2 => {
- return Err(mkerr(InvalidFieldType(x, t)))
- }
- Some(_) => {}
- }
- }
- }
- // An empty union type has type Type
- // An union type with only unary variants has type Type
- let k = k.unwrap_or(dhall_core::Const::Type);
- Ok(RetType(const_to_type(k)))
+ let kts: BTreeMap<_, _> = kts
+ .into_iter()
+ .map(|(x, t)| {
+ Ok((
+ x,
+ match t {
+ None => None,
+ Some(t) => Some(t.to_type()),
+ },
+ ))
+ })
+ .collect::<Result<_, _>>()?;
+ Ok(RetTyped(
+ TypeIntermediate::UnionType(ctx.clone(), kts).typecheck()?,
+ ))
}
RecordLit(kvs) => {
let kts = kvs
.into_iter()
- .map(|(x, v)| {
- let t = v.get_type_move()?.embed()?;
- Ok((x, t))
- })
+ .map(|(x, v)| Ok((x, v.get_type()?.into_owned())))
.collect::<Result<_, _>>()?;
- Ok(RetExpr(RecordType(kts)))
+ Ok(RetType(
+ TypeIntermediate::RecordType(ctx.clone(), kts)
+ .typecheck()?
+ .to_type(),
+ ))
}
UnionLit(x, v, kvs) => {
let mut kts: std::collections::BTreeMap<_, _> = kvs
.into_iter()
.map(|(x, v)| {
- let t = v.map(|x| x.normalize().embed());
+ let t = match v {
+ Some(x) => Some(x.to_type()),
+ None => None,
+ };
Ok((x, t))
})
.collect::<Result<_, _>>()?;
- let t = v.get_type_move()?.embed()?;
+ let t = v.get_type()?.into_owned();
kts.insert(x, Some(t));
- Ok(RetExpr(UnionType(kts)))
+ Ok(RetType(
+ TypeIntermediate::UnionType(ctx.clone(), kts)
+ .typecheck()?
+ .to_type(),
+ ))
}
- Field(r, x) => match r.get_type()?.unroll_ref()?.as_ref() {
- RecordType(kts) => match kts.get(&x) {
- Some(t) => Ok(RetExpr(t.unroll().embed_absurd())),
- None => Err(mkerr(MissingRecordField(x, r))),
- },
- _ => {
- let r = r.normalize();
- match r.as_expr().as_ref() {
- UnionType(kts) => match kts.get(&x) {
- // Constructor has type T -> < x: T, ... >
- // TODO: use "_" instead of x
- Some(Some(t)) => Ok(RetExpr(Pi(
- x.clone(),
- t.embed_absurd(),
- r.embed(),
- ))),
- Some(None) => Ok(RetType(r.into_type())),
- None => Err(mkerr(MissingUnionField(x, r))),
+ Field(r, x) => {
+ let tr = r.get_type()?;
+ let tr_internal = tr.internal_whnf();
+ match &tr_internal {
+ Some(Value::RecordType(kts)) => match kts.get(&x) {
+ Some(tth) => {
+ let tth = tth.clone();
+ drop(tr_internal);
+ Ok(RetType(tth.to_type(ctx)?))
},
- _ => Err(mkerr(NotARecord(x, r))),
+ None => Err(mkerr(MissingRecordField(x, r.clone()))),
+ },
+ // TODO: branch here only when r.get_type() is a Const
+ _ => {
+ let r = r.to_type();
+ let r_internal = r.internal_whnf();
+ match &r_internal {
+ Some(Value::UnionType(kts)) => match kts.get(&x) {
+ // Constructor has type T -> < x: T, ... >
+ // TODO: use "_" instead of x (i.e. compare types using equivalence in tests)
+ Some(Some(t)) => {
+ let t = t.clone();
+ drop(r_internal);
+ Ok(RetType(
+ TypeIntermediate::Pi(
+ ctx.clone(),
+ x.clone(),
+ t.to_type(ctx)?,
+ r,
+ )
+ .typecheck()?
+ .to_type(),
+ ))
+ },
+ Some(None) => {
+ drop(r_internal);
+ Ok(RetType(r))
+ },
+ None => {
+ drop(r_internal);
+ Err(mkerr(MissingUnionField(
+ x,
+ r.to_normalized(),
+ )))
+ },
+ },
+ _ => {
+ drop(r_internal);
+ Err(mkerr(NotARecord(
+ x,
+ r.to_normalized()
+ )))
+ },
+ }
}
+ // _ => Err(mkerr(NotARecord(
+ // x,
+ // r.to_type()?.to_normalized(),
+ // ))),
}
- },
- Const(c) => Ok(RetType(type_of_const(c))),
+ }
+ Const(c) => Ok(RetTyped(const_to_typed(c))),
Builtin(b) => Ok(RetExpr(type_of_builtin(b))),
- BoolLit(_) => Ok(RetType(simple_type_from_builtin(Bool))),
- NaturalLit(_) => Ok(RetType(simple_type_from_builtin(Natural))),
- IntegerLit(_) => Ok(RetType(simple_type_from_builtin(Integer))),
- DoubleLit(_) => Ok(RetType(simple_type_from_builtin(Double))),
+ BoolLit(_) => Ok(RetType(builtin_to_type(Bool)?)),
+ NaturalLit(_) => Ok(RetType(builtin_to_type(Natural)?)),
+ IntegerLit(_) => Ok(RetType(builtin_to_type(Integer)?)),
+ DoubleLit(_) => Ok(RetType(builtin_to_type(Double)?)),
// TODO: check type of interpolations
- TextLit(_) => Ok(RetType(simple_type_from_builtin(Text))),
+ TextLit(_) => Ok(RetType(builtin_to_type(Text)?)),
BinOp(o @ ListAppend, l, r) => {
- match l.get_type()?.unroll_ref()?.as_ref() {
- App(f, _) => match f.as_ref() {
- Builtin(List) => {}
- _ => return Err(mkerr(BinOpTypeMismatch(o, l))),
- },
- _ => return Err(mkerr(BinOpTypeMismatch(o, l))),
+ match l.get_type()?.internal_whnf() {
+ Some(Value::AppliedBuiltin(List, _)) => {}
+ _ => return Err(mkerr(BinOpTypeMismatch(o, l.clone()))),
}
ensure_equal!(
@@ -686,7 +966,7 @@ fn type_last_layer(
Ok(RetType(l.get_type()?.into_owned()))
}
BinOp(o, l, r) => {
- let t = simple_type_from_builtin(match o {
+ let t = builtin_to_type(match o {
BoolAnd => Bool,
BoolOr => Bool,
BoolEQ => Bool,
@@ -696,7 +976,7 @@ fn type_last_layer(
TextAppend => Text,
ListAppend => unreachable!(),
_ => return Err(mkerr(Unimplemented)),
- });
+ })?;
ensure_equal!(l.get_type()?, &t, mkerr(BinOpTypeMismatch(o, l)));
@@ -714,17 +994,17 @@ fn type_last_layer(
fn type_of(
e: SubExpr<X, Normalized<'static>>,
) -> Result<Typed<'static>, TypeError> {
- let ctx = Context::new();
+ let ctx = TypecheckContext::new();
let e = type_with(&ctx, e)?;
- // Ensure the inferred type isn't SuperType
- e.get_type()?.as_normalized()?;
+ // Ensure `e` has a type (i.e. `e` is not `Sort`)
+ e.get_type()?;
Ok(e)
}
/// The specific type error
#[derive(Debug)]
pub(crate) enum TypeMessage<'a> {
- UnboundVariable,
+ UnboundVariable(V<Label>),
InvalidInputType(Normalized<'a>),
InvalidOutputType(Normalized<'a>),
NotAFunction(Typed<'a>),
@@ -737,41 +1017,45 @@ pub(crate) enum TypeMessage<'a> {
InvalidPredicate(Typed<'a>),
IfBranchMismatch(Typed<'a>, Typed<'a>),
IfBranchMustBeTerm(bool, Typed<'a>),
- InvalidFieldType(Label, Typed<'a>),
+ InvalidFieldType(Label, Type<'a>),
NotARecord(Label, Normalized<'a>),
MissingRecordField(Label, Typed<'a>),
MissingUnionField(Label, Normalized<'a>),
BinOpTypeMismatch(BinOp, Typed<'a>),
NoDependentTypes(Normalized<'a>, Normalized<'a>),
+ Sort,
Unimplemented,
}
/// A structured type error that includes context
#[derive(Debug)]
pub struct TypeError {
- context: Context<Label, Type<'static>>,
- current: SubExpr<X, Normalized<'static>>,
type_message: TypeMessage<'static>,
+ context: TypecheckContext,
}
impl TypeError {
pub(crate) fn new(
- context: &Context<Label, Type<'static>>,
- current: SubExpr<X, Normalized<'static>>,
+ context: &TypecheckContext,
type_message: TypeMessage<'static>,
) -> Self {
TypeError {
context: context.clone(),
- current,
type_message,
}
}
}
+impl From<TypeError> for std::option::NoneError {
+ fn from(_: TypeError) -> std::option::NoneError {
+ std::option::NoneError
+ }
+}
+
impl ::std::error::Error for TypeMessage<'static> {
fn description(&self) -> &str {
match *self {
- UnboundVariable => "Unbound variable",
+ // UnboundVariable => "Unbound variable",
InvalidInputType(_) => "Invalid function input",
InvalidOutputType(_) => "Invalid function output",
NotAFunction(_) => "Not a function",
@@ -784,28 +1068,28 @@ impl ::std::error::Error for TypeMessage<'static> {
impl fmt::Display for TypeMessage<'static> {
fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
match self {
- UnboundVariable => {
- f.write_str(include_str!("errors/UnboundVariable.txt"))
- }
- TypeMismatch(e0, e1, e2) => {
- let template = include_str!("errors/TypeMismatch.txt");
- let s = template
- .replace("$txt0", &format!("{}", e0.as_expr()))
- .replace("$txt1", &format!("{}", e1.as_expr()))
- .replace("$txt2", &format!("{}", e2.as_expr()))
- .replace(
- "$txt3",
- &format!(
- "{}",
- e2.get_type()
- .unwrap()
- .as_normalized()
- .unwrap()
- .as_expr()
- ),
- );
- f.write_str(&s)
- }
+ // UnboundVariable(_) => {
+ // f.write_str(include_str!("errors/UnboundVariable.txt"))
+ // }
+ // TypeMismatch(e0, e1, e2) => {
+ // let template = include_str!("errors/TypeMismatch.txt");
+ // let s = template
+ // .replace("$txt0", &format!("{}", e0.as_expr()))
+ // .replace("$txt1", &format!("{}", e1.as_expr()))
+ // .replace("$txt2", &format!("{}", e2.as_expr()))
+ // .replace(
+ // "$txt3",
+ // &format!(
+ // "{}",
+ // e2.get_type()
+ // .unwrap()
+ // .as_normalized()
+ // .unwrap()
+ // .as_expr()
+ // ),
+ // );
+ // f.write_str(&s)
+ // }
_ => f.write_str("Unhandled error message"),
}
}
diff --git a/dhall_core/src/core.rs b/dhall_core/src/core.rs
index fa6fca4..3db07dd 100644
--- a/dhall_core/src/core.rs
+++ b/dhall_core/src/core.rs
@@ -62,6 +62,18 @@ pub enum Const {
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct V<Label>(pub Label, pub usize);
+// This is only for the specific `Label` type, not generic
+impl From<Label> for V<Label> {
+ fn from(x: Label) -> V<Label> {
+ V(x, 0)
+ }
+}
+impl<'a> From<&'a Label> for V<Label> {
+ fn from(x: &'a Label) -> V<Label> {
+ V(x.clone(), 0)
+ }
+}
+
// Definition order must match precedence order for
// pretty-printing to work correctly
#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord)]
@@ -433,6 +445,36 @@ impl<N, E> SubExpr<N, E> {
{
rc(self.as_ref().visit(&mut visitor::UnNoteVisitor))
}
+
+ /// `shift` is used by both normalization and type-checking to avoid variable
+ /// capture by shifting variable indices
+ /// See https://github.com/dhall-lang/dhall-lang/blob/master/standard/semantics.md#shift
+ /// for details
+ pub fn shift(&self, delta: isize, var: &V<Label>) -> Self {
+ match self.as_ref() {
+ ExprF::Var(v) => rc(ExprF::Var(v.shift(delta, var))),
+ _ => self.map_subexprs_with_special_handling_of_binders(
+ |e| e.shift(delta, var),
+ |x: &Label, e| e.shift(delta, &var.shift(1, &x.into())),
+ ),
+ }
+ }
+
+ pub fn subst_shift(&self, var: &V<Label>, val: &Self) -> Self {
+ match self.as_ref() {
+ ExprF::Var(v) if v == var => val.clone(),
+ ExprF::Var(v) => rc(ExprF::Var(v.shift(-1, var))),
+ _ => self.map_subexprs_with_special_handling_of_binders(
+ |e| e.subst_shift(var, val),
+ |x: &Label, e| {
+ e.subst_shift(
+ &var.shift(1, &x.into()),
+ &val.shift(1, &x.into()),
+ )
+ },
+ ),
+ }
+ }
}
impl<N: Clone> SubExpr<N, X> {
@@ -468,15 +510,15 @@ fn add_ui(u: usize, i: isize) -> usize {
}
}
-/// Applies `shift` to a single var.
-/// The first var is the var to shift away from; the second is the variable to shift
-fn shift_var(delta: isize, var: &V<Label>, in_expr: &V<Label>) -> V<Label> {
- let V(x, n) = var;
- let V(y, m) = in_expr;
- if x == y && n <= m {
- V(y.clone(), add_ui(*m, delta))
- } else {
- V(y.clone(), *m)
+impl<Label: PartialEq + Clone> V<Label> {
+ pub fn shift(&self, delta: isize, var: &V<Label>) -> Self {
+ let V(x, n) = var;
+ let V(y, m) = self;
+ if x == y && n <= m {
+ V(y.clone(), add_ui(*m, delta))
+ } else {
+ V(y.clone(), *m)
+ }
}
}
@@ -490,29 +532,10 @@ pub fn shift<N, E>(
var: &V<Label>,
in_expr: &SubExpr<N, E>,
) -> SubExpr<N, E> {
- use crate::ExprF::*;
- match in_expr.as_ref() {
- Var(v) => rc(Var(shift_var(delta, var, v))),
- _ => in_expr.map_subexprs_with_special_handling_of_binders(
- |e| shift(delta, var, e),
- |l: &Label, e| {
- let vl = V(l.clone(), 0);
- let newvar = shift_var(1, &vl, var);
- shift(delta, &newvar, e)
- },
- ),
- }
-}
-
-pub fn shift0<N, E>(
- delta: isize,
- label: &Label,
- in_expr: &SubExpr<N, E>,
-) -> SubExpr<N, E> {
- shift(delta, &V(label.clone(), 0), in_expr)
+ in_expr.shift(delta, var)
}
-fn shift0_multiple<N, E>(
+pub fn shift0_multiple<N, E>(
deltas: &HashMap<Label, isize>,
in_expr: &SubExpr<N, E>,
) -> SubExpr<N, E> {
@@ -532,49 +555,8 @@ fn shift0_multiple_inner<N, E>(
}
_ => in_expr.map_subexprs_with_special_handling_of_binders(
|e| shift0_multiple_inner(ctx, deltas, e),
- |l: &Label, e| {
- shift0_multiple_inner(&ctx.insert(l.clone(), ()), deltas, e)
- },
- ),
- }
-}
-
-/// Substitute all occurrences of a variable with an expression, and
-/// removes the variable from the environment by shifting the indices
-/// of other variables appropriately.
-///
-/// ```text
-/// subst_shift(x, v, e) = ↑(-1, x, e[x := ↑(1, x, v)])
-/// ```
-///
-pub fn subst_shift<N, E>(
- var: &V<Label>,
- value: &SubExpr<N, E>,
- in_expr: &SubExpr<N, E>,
-) -> SubExpr<N, E> {
- subst_shift_inner(&HashMap::new(), var, value, in_expr)
-}
-
-fn subst_shift_inner<N, E>(
- ctx: &HashMap<Label, isize>,
- var: &V<Label>,
- value: &SubExpr<N, E>,
- in_expr: &SubExpr<N, E>,
-) -> SubExpr<N, E> {
- use crate::ExprF::*;
- let V(x, n) = var;
- let dn = ctx.get(x).unwrap_or(&0);
- let actual_var = V(x.clone(), add_ui(*n, *dn));
- match in_expr.as_ref() {
- Var(v) if v == &actual_var => shift0_multiple(ctx, value),
- Var(v) => rc(Var(shift_var(-1, &actual_var, v))),
- _ => in_expr.map_subexprs_with_special_handling_of_binders(
- |e| subst_shift_inner(ctx, var, value, e),
- |l: &Label, e| {
- let mut ctx = ctx.clone();
- let count = ctx.entry(l.clone()).or_insert(0);
- *count += 1;
- subst_shift_inner(&ctx, var, value, e)
+ |x: &Label, e| {
+ shift0_multiple_inner(&ctx.insert(x.clone(), ()), deltas, e)
},
),
}
generated by cgit v1.2.3 (git 2.25.1) at 2024-07-05 19:20:26 +0000