diff options
Diffstat (limited to 'dhall/src/semantics/nze')
| -rw-r--r-- | dhall/src/semantics/nze/mod.rs | 5 | ||||
| -rw-r--r-- | dhall/src/semantics/nze/value.rs | 698 | ||||
| -rw-r--r-- | dhall/src/semantics/nze/var.rs | 36 | ||||
| -rw-r--r-- | dhall/src/semantics/nze/visitor.rs | 167 |
4 files changed, 906 insertions, 0 deletions
diff --git a/dhall/src/semantics/nze/mod.rs b/dhall/src/semantics/nze/mod.rs index 1cd2363..f367f8f 100644 --- a/dhall/src/semantics/nze/mod.rs +++ b/dhall/src/semantics/nze/mod.rs @@ -1,2 +1,7 @@ pub mod env; +pub mod value; +pub mod var; +pub mod visitor; pub(crate) use env::*; +pub(crate) use value::*; +pub(crate) use var::*; diff --git a/dhall/src/semantics/nze/value.rs b/dhall/src/semantics/nze/value.rs new file mode 100644 index 0000000..4960076 --- /dev/null +++ b/dhall/src/semantics/nze/value.rs @@ -0,0 +1,698 @@ +use std::cell::{Ref, RefCell, RefMut}; +use std::collections::HashMap; +use std::rc::Rc; + +use crate::error::{TypeError, TypeMessage}; +use crate::semantics::nze::visitor; +use crate::semantics::phase::normalize::{ + apply_any, normalize_tyexpr_whnf, normalize_whnf, +}; +use crate::semantics::phase::{Normalized, NormalizedExpr, ToExprOptions}; +use crate::semantics::Binder; +use crate::semantics::{type_of_builtin, typecheck, TyExpr, TyExprKind}; +use crate::semantics::{BuiltinClosure, NzEnv, NzVar, VarEnv}; +use crate::syntax::{ + BinOp, Builtin, Const, ExprKind, Integer, InterpolatedTextContents, Label, + NaiveDouble, Natural, Span, +}; + +use self::Form::{Unevaled, WHNF}; + +/// Stores a possibly unevaluated value. Gets (partially) normalized on-demand, sharing computation +/// automatically. Uses a RefCell to share computation. +/// Can optionally store a type from typechecking to preserve type information. +/// If you compare for equality two `Value`s in WHNF, then equality will be up to alpha-equivalence +/// (renaming of bound variables) and beta-equivalence (normalization). It will recursively +/// normalize as needed. +#[derive(Clone)] +pub(crate) struct Value(Rc<RefCell<ValueInternal>>); + +/// Invariant: if `form` is `WHNF`, `value` must be in Weak Head Normal Form +#[derive(Debug)] +struct ValueInternal { + form: Form, + kind: ValueKind<Value>, + /// This is None if and only if `value` is `Sort` (which doesn't have a type) + ty: Option<Value>, + span: Span, +} + +#[derive(Debug, Clone, Copy)] +pub(crate) enum Form { + /// No constraints; expression may not be normalized at all. + Unevaled, + /// Weak Head Normal Form, i.e. normalized up to the first constructor, but subexpressions may + /// not be normalized. This means that the first constructor of the contained ValueKind is the first + /// constructor of the final Normal Form (NF). + /// When all the Values in a ValueKind are in WHNF, and recursively so, then the + /// ValueKind is in NF. This is because WHNF ensures that we have the first constructor of the NF; so + /// if we have the first constructor of the NF at all levels, we actually have the NF. + WHNF, +} + +/// An unevaluated subexpression +#[derive(Debug, Clone)] +pub(crate) struct Thunk { + env: NzEnv, + body: TyExpr, +} + +/// An unevaluated subexpression that takes an argument. +#[derive(Debug, Clone)] +pub(crate) enum Closure { + /// Normal closure + Closure { + arg_ty: Value, + env: NzEnv, + body: TyExpr, + }, + /// Closure that ignores the argument passed + ConstantClosure { env: NzEnv, body: TyExpr }, +} + +#[derive(Debug, Clone, PartialEq, Eq)] +pub(crate) enum ValueKind<Value> { + /// Closures + LamClosure { + binder: Binder, + annot: Value, + closure: Closure, + }, + PiClosure { + binder: Binder, + annot: Value, + closure: Closure, + }, + // Invariant: in whnf, the evaluation must not be able to progress further. + AppliedBuiltin(BuiltinClosure<Value>), + + Var(NzVar), + Const(Const), + BoolLit(bool), + NaturalLit(Natural), + IntegerLit(Integer), + DoubleLit(NaiveDouble), + EmptyOptionalLit(Value), + NEOptionalLit(Value), + // EmptyListLit(t) means `[] : List t`, not `[] : t` + EmptyListLit(Value), + NEListLit(Vec<Value>), + RecordType(HashMap<Label, Value>), + RecordLit(HashMap<Label, Value>), + UnionType(HashMap<Label, Option<Value>>), + // Also keep the type of the uniontype around + UnionConstructor(Label, HashMap<Label, Option<Value>>, Value), + // Also keep the type of the uniontype and the constructor around + UnionLit(Label, Value, HashMap<Label, Option<Value>>, Value, Value), + // Invariant: in whnf, this must not contain interpolations that are themselves TextLits, and + // contiguous text values must be merged. + TextLit(Vec<InterpolatedTextContents<Value>>), + Equivalence(Value, Value), + // Invariant: in whnf, this must not contain a value captured by one of the variants above. + PartialExpr(ExprKind<Value, Normalized>), + // Invariant: absent in whnf + Thunk(Thunk), +} + +impl Value { + fn new(kind: ValueKind<Value>, form: Form, ty: Value, span: Span) -> Value { + ValueInternal { + form, + kind, + ty: Some(ty), + span, + } + .into_value() + } + pub(crate) fn const_sort() -> Value { + ValueInternal { + form: WHNF, + kind: ValueKind::Const(Const::Sort), + ty: None, + span: Span::Artificial, + } + .into_value() + } + pub(crate) fn new_thunk(env: &NzEnv, tye: TyExpr) -> Value { + ValueInternal { + form: Unevaled, + kind: ValueKind::Thunk(Thunk::new(env, tye.clone())), + ty: tye.get_type().ok(), + span: tye.span().clone(), + } + .into_value() + } + pub(crate) fn from_kind_and_type(v: ValueKind<Value>, t: Value) -> Value { + Value::new(v, Unevaled, t, Span::Artificial) + } + pub(crate) fn from_kind_and_type_whnf( + v: ValueKind<Value>, + t: Value, + ) -> Value { + Value::new(v, WHNF, t, Span::Artificial) + } + pub(crate) fn from_const(c: Const) -> Self { + let v = ValueKind::Const(c); + match c { + Const::Type => { + Value::from_kind_and_type(v, Value::from_const(Const::Kind)) + } + Const::Kind => { + Value::from_kind_and_type(v, Value::from_const(Const::Sort)) + } + Const::Sort => Value::const_sort(), + } + } + pub(crate) fn from_builtin(b: Builtin) -> Self { + Self::from_builtin_env(b, &NzEnv::new()) + } + pub(crate) fn from_builtin_env(b: Builtin, env: &NzEnv) -> Self { + Value::from_kind_and_type( + ValueKind::from_builtin_env(b, env.clone()), + typecheck(&type_of_builtin(b)).unwrap().eval_closed_expr(), + ) + } + + pub(crate) fn as_const(&self) -> Option<Const> { + match &*self.kind() { + ValueKind::Const(c) => Some(*c), + _ => None, + } + } + pub(crate) fn span(&self) -> Span { + self.as_internal().span.clone() + } + + fn as_internal(&self) -> Ref<ValueInternal> { + self.0.borrow() + } + fn as_internal_mut(&self) -> RefMut<ValueInternal> { + self.0.borrow_mut() + } + /// This is what you want if you want to pattern-match on the value. + /// WARNING: drop this ref before normalizing the same value or you will run into BorrowMut + /// panics. + pub(crate) fn kind(&self) -> Ref<ValueKind<Value>> { + self.normalize_whnf(); + Ref::map(self.as_internal(), ValueInternal::as_kind) + } + + /// Converts a value back to the corresponding AST expression. + pub(crate) fn to_expr(&self, opts: ToExprOptions) -> NormalizedExpr { + if opts.normalize { + self.normalize_nf(); + } + + self.to_tyexpr_noenv().to_expr(opts) + } + pub(crate) fn to_whnf_ignore_type(&self) -> ValueKind<Value> { + self.kind().clone() + } + /// Before discarding type information, check that it matches the expected return type. + pub(crate) fn to_whnf_check_type(&self, ty: &Value) -> ValueKind<Value> { + self.check_type(ty); + self.to_whnf_ignore_type() + } + + /// Mutates the contents. If no one else shares this, this avoids a RefCell lock. + fn mutate_internal(&mut self, f: impl FnOnce(&mut ValueInternal)) { + match Rc::get_mut(&mut self.0) { + // Mutate directly if sole owner + Some(refcell) => f(RefCell::get_mut(refcell)), + // Otherwise mutate through the refcell + None => f(&mut self.as_internal_mut()), + } + } + /// Normalizes contents to normal form; faster than `normalize_nf` if + /// no one else shares this. + pub(crate) fn normalize_mut(&mut self) { + self.mutate_internal(|vint| vint.normalize_nf()) + } + + pub(crate) fn normalize_whnf(&self) { + let borrow = self.as_internal(); + match borrow.form { + Unevaled => { + drop(borrow); + self.as_internal_mut().normalize_whnf(); + } + // Already in WHNF + WHNF => {} + } + } + pub(crate) fn normalize_nf(&self) { + self.as_internal_mut().normalize_nf(); + } + + pub(crate) fn app(&self, v: Value) -> Value { + let body_t = match &*self.get_type_not_sort().kind() { + ValueKind::PiClosure { annot, closure, .. } => { + v.check_type(annot); + closure.apply(v.clone()) + } + _ => unreachable!("Internal type error"), + }; + Value::from_kind_and_type_whnf( + apply_any(self.clone(), v, &body_t), + body_t, + ) + } + + /// In debug mode, panic if the provided type doesn't match the value's type. + /// Otherwise does nothing. + pub(crate) fn check_type(&self, _ty: &Value) { + // TODO: reenable + // debug_assert_eq!( + // Some(ty), + // self.get_type().ok().as_ref(), + // "Internal type error" + // ); + } + pub(crate) fn get_type(&self) -> Result<Value, TypeError> { + Ok(self.as_internal().get_type()?.clone()) + } + /// When we know the value isn't `Sort`, this gets the type directly + pub(crate) fn get_type_not_sort(&self) -> Value { + self.get_type() + .expect("Internal type error: value is `Sort` but shouldn't be") + } + + pub fn to_tyexpr(&self, venv: VarEnv) -> TyExpr { + let tye = match &*self.kind() { + ValueKind::Var(v) => TyExprKind::Var(venv.lookup(v)), + ValueKind::LamClosure { + binder, + annot, + closure, + } => TyExprKind::Expr(ExprKind::Lam( + binder.to_label(), + annot.to_tyexpr(venv), + closure.to_tyexpr(venv), + )), + ValueKind::PiClosure { + binder, + annot, + closure, + } => TyExprKind::Expr(ExprKind::Pi( + binder.to_label(), + annot.to_tyexpr(venv), + closure.to_tyexpr(venv), + )), + ValueKind::AppliedBuiltin(closure) => closure.to_tyexprkind(venv), + ValueKind::UnionConstructor(l, kts, t) => { + TyExprKind::Expr(ExprKind::Field( + TyExpr::new( + TyExprKind::Expr(ExprKind::UnionType( + kts.into_iter() + .map(|(k, v)| { + ( + k.clone(), + v.as_ref().map(|v| v.to_tyexpr(venv)), + ) + }) + .collect(), + )), + Some(t.clone()), + Span::Artificial, + ), + l.clone(), + )) + } + ValueKind::UnionLit(l, v, kts, uniont, ctort) => { + TyExprKind::Expr(ExprKind::App( + TyExpr::new( + TyExprKind::Expr(ExprKind::Field( + TyExpr::new( + TyExprKind::Expr(ExprKind::UnionType( + kts.into_iter() + .map(|(k, v)| { + ( + k.clone(), + v.as_ref() + .map(|v| v.to_tyexpr(venv)), + ) + }) + .collect(), + )), + Some(uniont.clone()), + Span::Artificial, + ), + l.clone(), + )), + Some(ctort.clone()), + Span::Artificial, + ), + v.to_tyexpr(venv), + )) + } + ValueKind::Thunk(th) => return th.to_tyexpr(venv), + self_kind => { + let self_kind = self_kind.map_ref(|v| v.to_tyexpr(venv)); + let expr = match self_kind { + ValueKind::Var(..) + | ValueKind::LamClosure { .. } + | ValueKind::PiClosure { .. } + | ValueKind::AppliedBuiltin(..) + | ValueKind::UnionConstructor(..) + | ValueKind::UnionLit(..) + | ValueKind::Thunk(..) => unreachable!(), + ValueKind::Const(c) => ExprKind::Const(c), + ValueKind::BoolLit(b) => ExprKind::BoolLit(b), + ValueKind::NaturalLit(n) => ExprKind::NaturalLit(n), + ValueKind::IntegerLit(n) => ExprKind::IntegerLit(n), + ValueKind::DoubleLit(n) => ExprKind::DoubleLit(n), + ValueKind::EmptyOptionalLit(n) => ExprKind::App( + Value::from_builtin(Builtin::OptionalNone) + .to_tyexpr(venv), + n, + ), + ValueKind::NEOptionalLit(n) => ExprKind::SomeLit(n), + ValueKind::EmptyListLit(n) => { + ExprKind::EmptyListLit(TyExpr::new( + TyExprKind::Expr(ExprKind::App( + Value::from_builtin(Builtin::List) + .to_tyexpr(venv), + n, + )), + Some(Value::from_const(Const::Type)), + Span::Artificial, + )) + } + ValueKind::NEListLit(elts) => ExprKind::NEListLit(elts), + ValueKind::RecordLit(kvs) => { + ExprKind::RecordLit(kvs.into_iter().collect()) + } + ValueKind::RecordType(kts) => { + ExprKind::RecordType(kts.into_iter().collect()) + } + ValueKind::UnionType(kts) => { + ExprKind::UnionType(kts.into_iter().collect()) + } + ValueKind::TextLit(elts) => { + ExprKind::TextLit(elts.into_iter().collect()) + } + ValueKind::Equivalence(x, y) => { + ExprKind::BinOp(BinOp::Equivalence, x, y) + } + ValueKind::PartialExpr(e) => e, + }; + TyExprKind::Expr(expr) + } + }; + + let self_ty = self.as_internal().ty.clone(); + let self_span = self.as_internal().span.clone(); + TyExpr::new(tye, self_ty, self_span) + } + pub fn to_tyexpr_noenv(&self) -> TyExpr { + self.to_tyexpr(VarEnv::new()) + } +} + +impl ValueInternal { + fn into_value(self) -> Value { + Value(Rc::new(RefCell::new(self))) + } + fn as_kind(&self) -> &ValueKind<Value> { + &self.kind + } + + fn normalize_whnf(&mut self) { + let dummy = ValueInternal { + form: Unevaled, + kind: ValueKind::Const(Const::Type), + ty: None, + span: Span::Artificial, + }; + let vint = std::mem::replace(self, dummy); + *self = match (&vint.form, &vint.ty) { + (Unevaled, Some(ty)) => ValueInternal { + form: WHNF, + kind: normalize_whnf(vint.kind, &ty), + ty: vint.ty, + span: vint.span, + }, + // `value` is `Sort` + (Unevaled, None) => ValueInternal { + form: WHNF, + kind: ValueKind::Const(Const::Sort), + ty: None, + span: vint.span, + }, + // Already in WHNF + (WHNF, _) => vint, + } + } + fn normalize_nf(&mut self) { + if let Unevaled = self.form { + self.normalize_whnf(); + } + self.kind.normalize_mut(); + } + + fn get_type(&self) -> Result<&Value, TypeError> { + match &self.ty { + Some(t) => Ok(t), + None => Err(TypeError::new(TypeMessage::Sort)), + } + } +} + +impl ValueKind<Value> { + pub(crate) fn into_value_with_type(self, t: Value) -> Value { + Value::from_kind_and_type(self, t) + } + + pub(crate) fn normalize_mut(&mut self) { + match self { + ValueKind::Var(..) + | ValueKind::Const(_) + | ValueKind::BoolLit(_) + | ValueKind::NaturalLit(_) + | ValueKind::IntegerLit(_) + | ValueKind::DoubleLit(_) => {} + + ValueKind::EmptyOptionalLit(tth) | ValueKind::EmptyListLit(tth) => { + tth.normalize_mut(); + } + + ValueKind::NEOptionalLit(th) => { + th.normalize_mut(); + } + ValueKind::LamClosure { annot, .. } + | ValueKind::PiClosure { annot, .. } => { + annot.normalize_mut(); + } + ValueKind::AppliedBuiltin(closure) => closure.normalize_mut(), + ValueKind::NEListLit(elts) => { + for x in elts.iter_mut() { + x.normalize_mut(); + } + } + ValueKind::RecordLit(kvs) => { + for x in kvs.values_mut() { + x.normalize_mut(); + } + } + ValueKind::RecordType(kvs) => { + for x in kvs.values_mut() { + x.normalize_mut(); + } + } + ValueKind::UnionType(kts) + | ValueKind::UnionConstructor(_, kts, _) => { + for x in kts.values_mut().flat_map(|opt| opt) { + x.normalize_mut(); + } + } + ValueKind::UnionLit(_, v, kts, _, _) => { + v.normalize_mut(); + for x in kts.values_mut().flat_map(|opt| opt) { + x.normalize_mut(); + } + } + ValueKind::TextLit(elts) => { + for x in elts.iter_mut() { + x.map_mut(Value::normalize_mut); + } + } + ValueKind::Equivalence(x, y) => { + x.normalize_mut(); + y.normalize_mut(); + } + ValueKind::PartialExpr(e) => { + e.map_mut(Value::normalize_mut); + } + ValueKind::Thunk(..) => { + unreachable!("Should only normalize_mut values in WHNF") + } + } + } + + pub(crate) fn from_builtin(b: Builtin) -> ValueKind<Value> { + ValueKind::from_builtin_env(b, NzEnv::new()) + } + pub(crate) fn from_builtin_env(b: Builtin, env: NzEnv) -> ValueKind<Value> { + ValueKind::AppliedBuiltin(BuiltinClosure::new(b, env)) + } +} + +impl<V> ValueKind<V> { + fn traverse_ref_with_special_handling_of_binders<'a, V2, E>( + &'a self, + visit_val: impl FnMut(&'a V) -> Result<V2, E>, + visit_under_binder: impl for<'b> FnMut( + &'a Binder, + &'b V, + &'a V, + ) -> Result<V2, E>, + ) -> Result<ValueKind<V2>, E> { + use visitor::ValueKindVisitor; + visitor::TraverseRefWithBindersVisitor { + visit_val, + visit_under_binder, + } + .visit(self) + } + + fn map_ref_with_special_handling_of_binders<'a, V2>( + &'a self, + mut map_val: impl FnMut(&'a V) -> V2, + mut map_under_binder: impl for<'b> FnMut(&'a Binder, &'b V, &'a V) -> V2, + ) -> ValueKind<V2> { + use crate::syntax::trivial_result; + trivial_result(self.traverse_ref_with_special_handling_of_binders( + |x| Ok(map_val(x)), + |l, t, x| Ok(map_under_binder(l, t, x)), + )) + } + + fn map_ref<'a, V2>( + &'a self, + map_val: impl Fn(&'a V) -> V2, + ) -> ValueKind<V2> { + self.map_ref_with_special_handling_of_binders(&map_val, |_, _, x| { + map_val(x) + }) + } +} + +impl Thunk { + pub fn new(env: &NzEnv, body: TyExpr) -> Self { + Thunk { + env: env.clone(), + body, + } + } + + pub fn eval(&self) -> Value { + normalize_tyexpr_whnf(&self.body, &self.env) + } + pub fn to_tyexpr(&self, venv: VarEnv) -> TyExpr { + self.eval().to_tyexpr(venv) + } +} + +impl Closure { + pub fn new(arg_ty: Value, env: &NzEnv, body: TyExpr) -> Self { + Closure::Closure { + arg_ty, + env: env.clone(), + body, + } + } + /// New closure that ignores its argument + pub fn new_constant(env: &NzEnv, body: TyExpr) -> Self { + Closure::ConstantClosure { + env: env.clone(), + body, + } + } + + pub fn apply(&self, val: Value) -> Value { + match self { + Closure::Closure { env, body, .. } => { + body.eval(&env.insert_value(val)) + } + Closure::ConstantClosure { env, body, .. } => body.eval(env), + } + } + fn apply_var(&self, var: NzVar) -> Value { + match self { + Closure::Closure { arg_ty, .. } => { + let val = Value::from_kind_and_type( + ValueKind::Var(var), + arg_ty.clone(), + ); + self.apply(val) + } + Closure::ConstantClosure { env, body, .. } => body.eval(env), + } + } + + /// Convert this closure to a TyExpr + pub fn to_tyexpr(&self, venv: VarEnv) -> TyExpr { + self.apply_var(NzVar::new(venv.size())) + .to_tyexpr(venv.insert()) + } + /// If the closure variable is free in the closure, return Err. Otherwise, return the value + /// with that free variable remove. + pub fn remove_binder(&self) -> Result<Value, ()> { + let v = NzVar::fresh(); + match self { + Closure::Closure { .. } => { + // TODO: handle case where variable is used in closure + // TODO: return information about where the variable is used + Ok(self.apply_var(v)) + } + Closure::ConstantClosure { .. } => { + // Ok: the variable is indeed ignored + Ok(self.apply_var(v)) + } + } + } +} + +/// Compare two values for equality modulo alpha/beta-equivalence. +// TODO: use Rc comparison to shortcut on identical pointers +impl std::cmp::PartialEq for Value { + fn eq(&self, other: &Self) -> bool { + *self.kind() == *other.kind() + } +} +impl std::cmp::Eq for Value {} + +impl std::cmp::PartialEq for Thunk { + fn eq(&self, _other: &Self) -> bool { + unreachable!( + "Trying to compare thunks but we should only compare WHNFs" + ) + } +} +impl std::cmp::Eq for Thunk {} + +impl std::cmp::PartialEq for Closure { + fn eq(&self, other: &Self) -> bool { + let v = NzVar::fresh(); + self.apply_var(v) == other.apply_var(v) + } +} +impl std::cmp::Eq for Closure {} + +impl std::fmt::Debug for Value { + fn fmt(&self, fmt: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { + let vint: &ValueInternal = &self.as_internal(); + if let ValueKind::Const(c) = &vint.kind { + write!(fmt, "{:?}", c) + } else { + let mut x = fmt.debug_struct(&format!("Value@{:?}", &vint.form)); + x.field("value", &vint.kind); + if let Some(ty) = vint.ty.as_ref() { + x.field("type", &ty); + } else { + x.field("type", &None::<()>); + } + x.finish() + } + } +} diff --git a/dhall/src/semantics/nze/var.rs b/dhall/src/semantics/nze/var.rs new file mode 100644 index 0000000..264b81d --- /dev/null +++ b/dhall/src/semantics/nze/var.rs @@ -0,0 +1,36 @@ +use crate::syntax::Label; + +// Exactly like a Label, but equality returns always true. +// This is so that ValueKind equality is exactly alpha-equivalence. +#[derive(Clone, Eq)] +pub struct Binder { + name: Label, +} + +impl Binder { + pub(crate) fn new(name: Label) -> Self { + Binder { name } + } + pub(crate) fn to_label(&self) -> Label { + self.clone().into() + } +} + +/// Equality up to alpha-equivalence +impl std::cmp::PartialEq for Binder { + fn eq(&self, _other: &Self) -> bool { + true + } +} + +impl std::fmt::Debug for Binder { + fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { + write!(f, "Binder({})", &self.name) + } +} + +impl From<Binder> for Label { + fn from(x: Binder) -> Label { + x.name + } +} diff --git a/dhall/src/semantics/nze/visitor.rs b/dhall/src/semantics/nze/visitor.rs new file mode 100644 index 0000000..d1a85d8 --- /dev/null +++ b/dhall/src/semantics/nze/visitor.rs @@ -0,0 +1,167 @@ +use std::iter::FromIterator; + +use crate::semantics::{Binder, BuiltinClosure, ValueKind}; +use crate::syntax::Label; + +/// A visitor trait that can be used to traverse `ValueKind`s. We need this pattern so that Rust lets +/// us have as much mutability as we can. See the equivalent file in `crate::syntax` for more +/// details. +pub(crate) trait ValueKindVisitor<'a, V1, V2>: Sized { + type Error; + + fn visit_val(&mut self, val: &'a V1) -> Result<V2, Self::Error>; + fn visit_binder( + mut self, + _label: &'a Binder, + ty: &'a V1, + val: &'a V1, + ) -> Result<(V2, V2), Self::Error> { + Ok((self.visit_val(ty)?, self.visit_val(val)?)) + } + fn visit_vec(&mut self, x: &'a [V1]) -> Result<Vec<V2>, Self::Error> { + x.iter().map(|e| self.visit_val(e)).collect() + } + fn visit_opt( + &mut self, + x: &'a Option<V1>, + ) -> Result<Option<V2>, Self::Error> { + Ok(match x { + Some(x) => Some(self.visit_val(x)?), + None => None, + }) + } + fn visit_map<T>( + &mut self, + x: impl IntoIterator<Item = (&'a Label, &'a V1)>, + ) -> Result<T, Self::Error> + where + V1: 'a, + T: FromIterator<(Label, V2)>, + { + x.into_iter() + .map(|(k, x)| Ok((k.clone(), self.visit_val(x)?))) + .collect() + } + fn visit_optmap<T>( + &mut self, + x: impl IntoIterator<Item = (&'a Label, &'a Option<V1>)>, + ) -> Result<T, Self::Error> + where + V1: 'a, + T: FromIterator<(Label, Option<V2>)>, + { + x.into_iter() + .map(|(k, x)| Ok((k.clone(), self.visit_opt(x)?))) + .collect() + } + + fn visit( + self, + input: &'a ValueKind<V1>, + ) -> Result<ValueKind<V2>, Self::Error> { + visit_ref(self, input) + } +} + +fn visit_ref<'a, Visitor, V1, V2>( + mut v: Visitor, + input: &'a ValueKind<V1>, +) -> Result<ValueKind<V2>, Visitor::Error> +where + Visitor: ValueKindVisitor<'a, V1, V2>, +{ + use ValueKind::*; + Ok(match input { + LamClosure { + binder, + annot, + closure, + } => LamClosure { + binder: binder.clone(), + annot: v.visit_val(annot)?, + closure: closure.clone(), + }, + PiClosure { + binder, + annot, + closure, + } => PiClosure { + binder: binder.clone(), + annot: v.visit_val(annot)?, + closure: closure.clone(), + }, + AppliedBuiltin(BuiltinClosure { + b, + args, + types, + env, + }) => AppliedBuiltin(BuiltinClosure { + b: *b, + args: v.visit_vec(args)?, + types: v.visit_vec(types)?, + env: env.clone(), + }), + Var(v) => Var(*v), + Const(k) => Const(*k), + BoolLit(b) => BoolLit(*b), + NaturalLit(n) => NaturalLit(*n), + IntegerLit(n) => IntegerLit(*n), + DoubleLit(n) => DoubleLit(*n), + EmptyOptionalLit(t) => EmptyOptionalLit(v.visit_val(t)?), + NEOptionalLit(x) => NEOptionalLit(v.visit_val(x)?), + EmptyListLit(t) => EmptyListLit(v.visit_val(t)?), + NEListLit(xs) => NEListLit(v.visit_vec(xs)?), + RecordType(kts) => RecordType(v.visit_map(kts)?), + RecordLit(kvs) => RecordLit(v.visit_map(kvs)?), + UnionType(kts) => UnionType(v.visit_optmap(kts)?), + UnionConstructor(l, kts, uniont) => UnionConstructor( + l.clone(), + v.visit_optmap(kts)?, + v.visit_val(uniont)?, + ), + UnionLit(l, x, kts, uniont, ctort) => UnionLit( + l.clone(), + v.visit_val(x)?, + v.visit_optmap(kts)?, + v.visit_val(uniont)?, + v.visit_val(ctort)?, + ), + TextLit(ts) => TextLit( + ts.iter() + .map(|t| t.traverse_ref(|e| v.visit_val(e))) + .collect::<Result<_, _>>()?, + ), + Equivalence(x, y) => Equivalence(v.visit_val(x)?, v.visit_val(y)?), + PartialExpr(e) => PartialExpr(e.traverse_ref(|e| v.visit_val(e))?), + Thunk(th) => Thunk(th.clone()), + }) +} + +pub struct TraverseRefWithBindersVisitor<F1, F2> { + pub visit_val: F1, + pub visit_under_binder: F2, +} + +impl<'a, V1, V2, Err, F1, F2> ValueKindVisitor<'a, V1, V2> + for TraverseRefWithBindersVisitor<F1, F2> +where + V1: 'a, + F1: FnMut(&'a V1) -> Result<V2, Err>, + F2: for<'b> FnOnce(&'a Binder, &'b V1, &'a V1) -> Result<V2, Err>, +{ + type Error = Err; + + fn visit_val(&mut self, val: &'a V1) -> Result<V2, Self::Error> { + (self.visit_val)(val) + } + fn visit_binder<'b>( + mut self, + label: &'a Binder, + ty: &'a V1, + val: &'a V1, + ) -> Result<(V2, V2), Self::Error> { + let val = (self.visit_under_binder)(label, ty, val)?; + let ty = (self.visit_val)(ty)?; + Ok((ty, val)) + } +} |