diff options
author | Nadrieril Feneanar | 2020-02-19 17:25:57 +0000 |
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committer | GitHub | 2020-02-19 17:25:57 +0000 |
commit | ffbde252a850c7d96e1000e1be52792c41733a28 (patch) | |
tree | e668b7f764fb4981a802bc619e0b2ff62fa9ce16 /dhall/src/semantics/nze/nir.rs | |
parent | e4b3a879907b6dcc75d25847ae21a23d0201aae1 (diff) | |
parent | 7cbfc1a0d32766a383d1f48902502adaa2234d2f (diff) |
Merge pull request #131 from Nadrieril/hir
Decouple main expression types
Diffstat (limited to '')
-rw-r--r-- | dhall/src/semantics/nze/nir.rs | 510 |
1 files changed, 510 insertions, 0 deletions
diff --git a/dhall/src/semantics/nze/nir.rs b/dhall/src/semantics/nze/nir.rs new file mode 100644 index 0000000..4ed66b7 --- /dev/null +++ b/dhall/src/semantics/nze/nir.rs @@ -0,0 +1,510 @@ +use std::collections::HashMap; +use std::rc::Rc; + +use crate::semantics::nze::lazy; +use crate::semantics::{ + apply_any, normalize_hir_whnf, normalize_one_layer, squash_textlit, Binder, + BuiltinClosure, Hir, HirKind, NzEnv, NzVar, TyEnv, Type, Universe, VarEnv, +}; +use crate::syntax::{ + BinOp, Builtin, Const, ExprKind, InterpolatedTextContents, Label, LitKind, + Span, +}; +use crate::{NormalizedExpr, ToExprOptions}; + +/// Stores a possibly unevaluated value. Gets (partially) normalized on-demand, sharing computation +/// automatically. Uses a Rc<RefCell> to share computation. +/// If you compare for equality two `Nir`s, then equality will be up to alpha-equivalence +/// (renaming of bound variables) and beta-equivalence (normalization). It will recursively +/// normalize as needed. +/// Stands for "Normalized intermediate representation" +#[derive(Clone)] +pub(crate) struct Nir(Rc<NirInternal>); + +#[derive(Debug)] +struct NirInternal { + kind: lazy::Lazy<Thunk, NirKind>, +} + +/// An unevaluated subexpression +#[derive(Debug, Clone)] +pub(crate) enum Thunk { + /// A completely unnormalized expression. + Thunk { env: NzEnv, body: Hir }, + /// A partially normalized expression that may need to go through `normalize_one_layer`. + PartialExpr { env: NzEnv, expr: ExprKind<Nir> }, +} + +/// An unevaluated subexpression that takes an argument. +#[derive(Debug, Clone)] +pub(crate) enum Closure { + /// Normal closure + Closure { env: NzEnv, body: Hir }, + /// Closure that ignores the argument passed + ConstantClosure { body: Nir }, +} + +/// A text literal with interpolations. +// Invariant: this must not contain interpolations that are themselves TextLits, and contiguous +// text values must be merged. +#[derive(Debug, Clone, PartialEq, Eq)] +pub(crate) struct TextLit(Vec<InterpolatedTextContents<Nir>>); + +/// This represents a value in Weak Head Normal Form (WHNF). This means that the value is +/// normalized up to the first constructor, but subexpressions may not be fully normalized. +/// When all the Nirs in a NirKind are in WHNF, and recursively so, then the NirKind is in +/// Normal Form (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. +/// In particular, this means that once we get a `NirKind`, it can be considered immutable, and +/// we only need to recursively normalize its sub-`Nir`s to get to the NF. +#[derive(Debug, Clone, PartialEq, Eq)] +pub(crate) enum NirKind { + /// Closures + LamClosure { + binder: Binder, + annot: Nir, + closure: Closure, + }, + PiClosure { + binder: Binder, + annot: Nir, + closure: Closure, + }, + AppliedBuiltin(BuiltinClosure<Nir>), + + Var(NzVar), + Const(Const), + Lit(LitKind), + EmptyOptionalLit(Nir), + NEOptionalLit(Nir), + // EmptyListLit(t) means `[] : List t`, not `[] : t` + EmptyListLit(Nir), + NEListLit(Vec<Nir>), + RecordType(HashMap<Label, Nir>), + RecordLit(HashMap<Label, Nir>), + UnionType(HashMap<Label, Option<Nir>>), + UnionConstructor(Label, HashMap<Label, Option<Nir>>), + UnionLit(Label, Nir, HashMap<Label, Option<Nir>>), + TextLit(TextLit), + Equivalence(Nir, Nir), + /// Invariant: evaluation must not be able to progress with `normalize_one_layer`. + PartialExpr(ExprKind<Nir>), +} + +impl Nir { + /// Construct a Nir from a completely unnormalized expression. + pub(crate) fn new_thunk(env: NzEnv, hir: Hir) -> Nir { + NirInternal::from_thunk(Thunk::new(env, hir)).into_nir() + } + /// Construct a Nir from a partially normalized expression that's not in WHNF. + pub(crate) fn from_partial_expr(e: ExprKind<Nir>) -> Nir { + // TODO: env + let env = NzEnv::new(); + NirInternal::from_thunk(Thunk::from_partial_expr(env, e)).into_nir() + } + /// Make a Nir from a NirKind + pub(crate) fn from_kind(v: NirKind) -> Nir { + NirInternal::from_whnf(v).into_nir() + } + pub(crate) fn from_const(c: Const) -> Self { + let v = NirKind::Const(c); + NirInternal::from_whnf(v).into_nir() + } + 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 { + Nir::from_kind(NirKind::from_builtin_env(b, env.clone())) + } + pub(crate) fn from_text(txt: impl ToString) -> Self { + Nir::from_kind(NirKind::TextLit(TextLit::from_text(txt.to_string()))) + } + + pub(crate) fn as_const(&self) -> Option<Const> { + match &*self.kind() { + NirKind::Const(c) => Some(*c), + _ => None, + } + } + + /// This is what you want if you want to pattern-match on the value. + pub(crate) fn kind(&self) -> &NirKind { + self.0.kind() + } + + pub(crate) fn to_type(&self, u: impl Into<Universe>) -> Type { + Type::new(self.clone(), u.into()) + } + /// Converts a value back to the corresponding AST expression. + pub(crate) fn to_expr(&self, opts: ToExprOptions) -> NormalizedExpr { + self.to_hir_noenv().to_expr(opts) + } + pub(crate) fn to_expr_tyenv(&self, tyenv: &TyEnv) -> NormalizedExpr { + self.to_hir(tyenv.as_varenv()).to_expr_tyenv(tyenv) + } + + pub(crate) fn normalize(&self) { + self.0.normalize() + } + + pub(crate) fn app(&self, v: Nir) -> Nir { + Nir::from_kind(apply_any(self.clone(), v)) + } + + pub fn to_hir(&self, venv: VarEnv) -> Hir { + let map_uniontype = |kts: &HashMap<Label, Option<Nir>>| { + ExprKind::UnionType( + kts.iter() + .map(|(k, v)| { + (k.clone(), v.as_ref().map(|v| v.to_hir(venv))) + }) + .collect(), + ) + }; + + let hir = match &*self.kind() { + NirKind::Var(v) => HirKind::Var(venv.lookup(v)), + NirKind::AppliedBuiltin(closure) => closure.to_hirkind(venv), + self_kind => HirKind::Expr(match self_kind { + NirKind::Var(..) | NirKind::AppliedBuiltin(..) => { + unreachable!() + } + NirKind::LamClosure { + binder, + annot, + closure, + } => ExprKind::Lam( + binder.to_label(), + annot.to_hir(venv), + closure.to_hir(venv), + ), + NirKind::PiClosure { + binder, + annot, + closure, + } => ExprKind::Pi( + binder.to_label(), + annot.to_hir(venv), + closure.to_hir(venv), + ), + NirKind::Const(c) => ExprKind::Const(*c), + NirKind::Lit(l) => ExprKind::Lit(l.clone()), + NirKind::EmptyOptionalLit(n) => ExprKind::App( + Nir::from_builtin(Builtin::OptionalNone).to_hir(venv), + n.to_hir(venv), + ), + NirKind::NEOptionalLit(n) => ExprKind::SomeLit(n.to_hir(venv)), + NirKind::EmptyListLit(n) => ExprKind::EmptyListLit(Hir::new( + HirKind::Expr(ExprKind::App( + Nir::from_builtin(Builtin::List).to_hir(venv), + n.to_hir(venv), + )), + Span::Artificial, + )), + NirKind::NEListLit(elts) => ExprKind::NEListLit( + elts.iter().map(|v| v.to_hir(venv)).collect(), + ), + NirKind::TextLit(elts) => ExprKind::TextLit( + elts.iter() + .map(|t| t.map_ref(|v| v.to_hir(venv))) + .collect(), + ), + NirKind::RecordLit(kvs) => ExprKind::RecordLit( + kvs.iter() + .map(|(k, v)| (k.clone(), v.to_hir(venv))) + .collect(), + ), + NirKind::RecordType(kts) => ExprKind::RecordType( + kts.iter() + .map(|(k, v)| (k.clone(), v.to_hir(venv))) + .collect(), + ), + NirKind::UnionType(kts) => map_uniontype(kts), + NirKind::UnionConstructor(l, kts) => ExprKind::Field( + Hir::new( + HirKind::Expr(map_uniontype(kts)), + Span::Artificial, + ), + l.clone(), + ), + NirKind::UnionLit(l, v, kts) => ExprKind::App( + Hir::new( + HirKind::Expr(ExprKind::Field( + Hir::new( + HirKind::Expr(map_uniontype(kts)), + Span::Artificial, + ), + l.clone(), + )), + Span::Artificial, + ), + v.to_hir(venv), + ), + NirKind::Equivalence(x, y) => ExprKind::BinOp( + BinOp::Equivalence, + x.to_hir(venv), + y.to_hir(venv), + ), + NirKind::PartialExpr(e) => e.map_ref(|v| v.to_hir(venv)), + }), + }; + + Hir::new(hir, Span::Artificial) + } + pub fn to_hir_noenv(&self) -> Hir { + self.to_hir(VarEnv::new()) + } +} + +impl NirInternal { + fn from_whnf(k: NirKind) -> Self { + NirInternal { + kind: lazy::Lazy::new_completed(k), + } + } + fn from_thunk(th: Thunk) -> Self { + NirInternal { + kind: lazy::Lazy::new(th), + } + } + fn into_nir(self) -> Nir { + Nir(Rc::new(self)) + } + + fn kind(&self) -> &NirKind { + &self.kind + } + fn normalize(&self) { + self.kind().normalize(); + } +} + +impl NirKind { + pub(crate) fn into_nir(self) -> Nir { + Nir::from_kind(self) + } + + pub(crate) fn normalize(&self) { + match self { + NirKind::Var(..) | NirKind::Const(_) | NirKind::Lit(_) => {} + + NirKind::EmptyOptionalLit(tth) | NirKind::EmptyListLit(tth) => { + tth.normalize(); + } + + NirKind::NEOptionalLit(th) => { + th.normalize(); + } + NirKind::LamClosure { annot, closure, .. } + | NirKind::PiClosure { annot, closure, .. } => { + annot.normalize(); + closure.normalize(); + } + NirKind::AppliedBuiltin(closure) => closure.normalize(), + NirKind::NEListLit(elts) => { + for x in elts.iter() { + x.normalize(); + } + } + NirKind::RecordLit(kvs) => { + for x in kvs.values() { + x.normalize(); + } + } + NirKind::RecordType(kvs) => { + for x in kvs.values() { + x.normalize(); + } + } + NirKind::UnionType(kts) | NirKind::UnionConstructor(_, kts) => { + for x in kts.values().flat_map(|opt| opt) { + x.normalize(); + } + } + NirKind::UnionLit(_, v, kts) => { + v.normalize(); + for x in kts.values().flat_map(|opt| opt) { + x.normalize(); + } + } + NirKind::TextLit(tlit) => tlit.normalize(), + NirKind::Equivalence(x, y) => { + x.normalize(); + y.normalize(); + } + NirKind::PartialExpr(e) => { + e.map_ref(Nir::normalize); + } + } + } + + pub(crate) fn from_builtin(b: Builtin) -> NirKind { + NirKind::from_builtin_env(b, NzEnv::new()) + } + pub(crate) fn from_builtin_env(b: Builtin, env: NzEnv) -> NirKind { + NirKind::AppliedBuiltin(BuiltinClosure::new(b, env)) + } +} + +impl Thunk { + fn new(env: NzEnv, body: Hir) -> Self { + Thunk::Thunk { env, body } + } + fn from_partial_expr(env: NzEnv, expr: ExprKind<Nir>) -> Self { + Thunk::PartialExpr { env, expr } + } + fn eval(self) -> NirKind { + match self { + Thunk::Thunk { env, body } => normalize_hir_whnf(&env, &body), + Thunk::PartialExpr { env, expr } => normalize_one_layer(expr, &env), + } + } +} + +impl Closure { + pub fn new(env: &NzEnv, body: Hir) -> Self { + Closure::Closure { + env: env.clone(), + body, + } + } + /// New closure that ignores its argument + pub fn new_constant(body: Nir) -> Self { + Closure::ConstantClosure { body } + } + + pub fn apply(&self, val: Nir) -> Nir { + match self { + Closure::Closure { env, body, .. } => { + body.eval(env.insert_value(val, ())) + } + Closure::ConstantClosure { body, .. } => body.clone(), + } + } + fn apply_var(&self, var: NzVar) -> Nir { + match self { + Closure::Closure { .. } => { + self.apply(Nir::from_kind(NirKind::Var(var))) + } + Closure::ConstantClosure { body, .. } => body.clone(), + } + } + + // TODO: somehow normalize the body. Might require to pass an env. + pub fn normalize(&self) {} + + /// Convert this closure to a Hir expression + pub fn to_hir(&self, venv: VarEnv) -> Hir { + self.apply_var(NzVar::new(venv.size())) + .to_hir(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<Nir, ()> { + match self { + Closure::Closure { .. } => { + let v = NzVar::fresh(); + // 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 { body, .. } => Ok(body.clone()), + } + } +} + +impl TextLit { + pub fn new( + elts: impl Iterator<Item = InterpolatedTextContents<Nir>>, + ) -> Self { + TextLit(squash_textlit(elts)) + } + pub fn interpolate(v: Nir) -> TextLit { + TextLit(vec![InterpolatedTextContents::Expr(v)]) + } + pub fn from_text(s: String) -> TextLit { + TextLit(vec![InterpolatedTextContents::Text(s)]) + } + + pub fn concat(&self, other: &TextLit) -> TextLit { + TextLit::new(self.iter().chain(other.iter()).cloned()) + } + pub fn is_empty(&self) -> bool { + self.0.is_empty() + } + /// If the literal consists of only one interpolation and not text, return the interpolated + /// value. + pub fn as_single_expr(&self) -> Option<&Nir> { + use InterpolatedTextContents::Expr; + if let [Expr(v)] = self.0.as_slice() { + Some(v) + } else { + None + } + } + /// If there are no interpolations, return the corresponding text value. + pub fn as_text(&self) -> Option<String> { + use InterpolatedTextContents::Text; + if self.is_empty() { + Some(String::new()) + } else if let [Text(s)] = self.0.as_slice() { + Some(s.clone()) + } else { + None + } + } + pub fn iter(&self) -> impl Iterator<Item = &InterpolatedTextContents<Nir>> { + self.0.iter() + } + /// Normalize the contained values. This does not break the invariant because we have already + /// ensured that no contained values normalize to a TextLit. + pub fn normalize(&self) { + for x in self.0.iter() { + x.map_ref(Nir::normalize); + } + } +} + +impl lazy::Eval<NirKind> for Thunk { + fn eval(self) -> NirKind { + self.eval() + } +} + +/// Compare two values for equality modulo alpha/beta-equivalence. +impl std::cmp::PartialEq for Nir { + fn eq(&self, other: &Self) -> bool { + Rc::ptr_eq(&self.0, &other.0) || self.kind() == other.kind() + } +} +impl std::cmp::Eq for Nir {} + +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 Nir { + fn fmt(&self, fmt: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { + let vint: &NirInternal = &self.0; + let kind = vint.kind(); + if let NirKind::Const(c) = kind { + return write!(fmt, "{:?}", c); + } + let mut x = fmt.debug_struct(&format!("Nir@WHNF")); + x.field("kind", kind); + x.finish() + } +} |