From 55b5be3407a8528bc47482a591b168a7cb0ce91e Mon Sep 17 00:00:00 2001
From: Nadrieril
Date: Mon, 6 May 2019 23:52:15 +0200
Subject: Move main datatypes into their own modules

---
 dhall/src/core/value.rs | 616 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 616 insertions(+)
 create mode 100644 dhall/src/core/value.rs

(limited to 'dhall/src/core/value.rs')

diff --git a/dhall/src/core/value.rs b/dhall/src/core/value.rs
new file mode 100644
index 0000000..31193d2
--- /dev/null
+++ b/dhall/src/core/value.rs
@@ -0,0 +1,616 @@
+use std::collections::BTreeMap;
+
+use dhall_proc_macros as dhall;
+use dhall_syntax::{
+    rc, Builtin, Const, ExprF, Integer, InterpolatedTextContents, Label,
+    Natural, V, X,
+};
+
+use crate::core::thunk::{Thunk, TypeThunk};
+use crate::phase::normalize::{
+    apply_builtin, normalize_one_layer, squash_textlit, OutputSubExpr,
+};
+use crate::phase::Typed;
+
+/// Stores a pair of variables: a normal one and if relevant one
+/// that corresponds to the alpha-normalized version of the first one.
+/// Equality is up to alpha-equivalence.
+#[derive(Debug, Clone, Eq)]
+pub(crate) struct AlphaVar {
+    normal: V<Label>,
+    alpha: Option<V<()>>,
+}
+
+// Exactly like a Label, but equality returns always true.
+// This is so that Value equality is exactly alpha-equivalence.
+#[derive(Debug, Clone, Eq)]
+pub(crate) struct AlphaLabel(Label);
+
+/// A semantic value.
+/// Equality is up to alpha-equivalence (renaming of bound variables)
+/// and beta-equivalence (normalization).
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub(crate) enum Value {
+    /// Closures
+    Lam(AlphaLabel, Thunk, Thunk),
+    AppliedBuiltin(Builtin, Vec<Thunk>),
+    /// `λ(x: a) -> Some x`
+    OptionalSomeClosure(TypeThunk),
+    /// `λ(x : a) -> λ(xs : List a) -> [ x ] # xs`
+    /// `λ(xs : List a) -> [ x ] # xs`
+    ListConsClosure(TypeThunk, Option<Thunk>),
+    /// `λ(x : Natural) -> x + 1`
+    NaturalSuccClosure,
+    Pi(AlphaLabel, TypeThunk, TypeThunk),
+
+    Var(AlphaVar),
+    Const(Const),
+    BoolLit(bool),
+    NaturalLit(Natural),
+    IntegerLit(Integer),
+    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(ExprF<Thunk, Label, X>),
+}
+
+impl AlphaVar {
+    pub(crate) fn to_var(&self, alpha: bool) -> V<Label> {
+        match (alpha, &self.alpha) {
+            (true, Some(x)) => V("_".into(), x.1),
+            _ => self.normal.clone(),
+        }
+    }
+    pub(crate) fn from_var(normal: V<Label>) -> Self {
+        AlphaVar {
+            normal,
+            alpha: None,
+        }
+    }
+    pub(crate) fn shift(&self, delta: isize, var: &AlphaVar) -> Self {
+        AlphaVar {
+            normal: self.normal.shift(delta, &var.normal),
+            alpha: match (&self.alpha, &var.alpha) {
+                (Some(x), Some(v)) => Some(x.shift(delta, v)),
+                _ => None,
+            },
+        }
+    }
+}
+
+impl AlphaLabel {
+    fn to_label_maybe_alpha(&self, alpha: bool) -> Label {
+        if alpha {
+            "_".into()
+        } else {
+            self.to_label()
+        }
+    }
+    fn to_label(&self) -> Label {
+        self.clone().into()
+    }
+}
+
+impl Value {
+    pub(crate) fn into_thunk(self) -> Thunk {
+        Thunk::from_value(self)
+    }
+
+    /// Convert the value to a fully normalized syntactic expression
+    pub(crate) fn normalize_to_expr(&self) -> OutputSubExpr {
+        self.normalize_to_expr_maybe_alpha(false)
+    }
+    /// Convert the value to a fully normalized syntactic expression. Also alpha-normalize
+    /// if alpha is `true`
+    pub(crate) fn normalize_to_expr_maybe_alpha(
+        &self,
+        alpha: bool,
+    ) -> OutputSubExpr {
+        match self {
+            Value::Lam(x, t, e) => rc(ExprF::Lam(
+                x.to_label_maybe_alpha(alpha),
+                t.normalize_to_expr_maybe_alpha(alpha),
+                e.normalize_to_expr_maybe_alpha(alpha),
+            )),
+            Value::AppliedBuiltin(b, args) => {
+                let mut e = rc(ExprF::Builtin(*b));
+                for v in args {
+                    e = rc(ExprF::App(
+                        e,
+                        v.normalize_to_expr_maybe_alpha(alpha),
+                    ));
+                }
+                e
+            }
+            Value::OptionalSomeClosure(n) => {
+                let a = n.normalize_to_expr_maybe_alpha(alpha);
+                dhall::subexpr!(λ(x: a) -> Some x)
+            }
+            Value::ListConsClosure(a, None) => {
+                // Avoid accidental capture of the new `x` variable
+                let a1 = a.shift(1, &Label::from("x").into());
+                let a1 = a1.normalize_to_expr_maybe_alpha(alpha);
+                let a = a.normalize_to_expr_maybe_alpha(alpha);
+                dhall::subexpr!(λ(x : a) -> λ(xs : List a1) -> [ x ] # xs)
+            }
+            Value::ListConsClosure(n, Some(v)) => {
+                // Avoid accidental capture of the new `xs` variable
+                let v = v.shift(1, &Label::from("xs").into());
+                let v = v.normalize_to_expr_maybe_alpha(alpha);
+                let a = n.normalize_to_expr_maybe_alpha(alpha);
+                dhall::subexpr!(λ(xs : List a) -> [ v ] # xs)
+            }
+            Value::NaturalSuccClosure => {
+                dhall::subexpr!(λ(x : Natural) -> x + 1)
+            }
+            Value::Pi(x, t, e) => rc(ExprF::Pi(
+                x.to_label_maybe_alpha(alpha),
+                t.normalize_to_expr_maybe_alpha(alpha),
+                e.normalize_to_expr_maybe_alpha(alpha),
+            )),
+            Value::Var(v) => rc(ExprF::Var(v.to_var(alpha))),
+            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_maybe_alpha(alpha),
+            )),
+            Value::NEOptionalLit(n) => {
+                rc(ExprF::SomeLit(n.normalize_to_expr_maybe_alpha(alpha)))
+            }
+            Value::EmptyListLit(n) => {
+                rc(ExprF::EmptyListLit(n.normalize_to_expr_maybe_alpha(alpha)))
+            }
+            Value::NEListLit(elts) => rc(ExprF::NEListLit(
+                elts.into_iter()
+                    .map(|n| n.normalize_to_expr_maybe_alpha(alpha))
+                    .collect(),
+            )),
+            Value::RecordLit(kvs) => rc(ExprF::RecordLit(
+                kvs.iter()
+                    .map(|(k, v)| {
+                        (k.clone(), v.normalize_to_expr_maybe_alpha(alpha))
+                    })
+                    .collect(),
+            )),
+            Value::RecordType(kts) => rc(ExprF::RecordType(
+                kts.iter()
+                    .map(|(k, v)| {
+                        (k.clone(), v.normalize_to_expr_maybe_alpha(alpha))
+                    })
+                    .collect(),
+            )),
+            Value::UnionType(kts) => rc(ExprF::UnionType(
+                kts.iter()
+                    .map(|(k, v)| {
+                        (
+                            k.clone(),
+                            v.as_ref().map(|v| {
+                                v.normalize_to_expr_maybe_alpha(alpha)
+                            }),
+                        )
+                    })
+                    .collect(),
+            )),
+            Value::UnionConstructor(l, kts) => {
+                let kts = kts
+                    .iter()
+                    .map(|(k, v)| {
+                        (
+                            k.clone(),
+                            v.as_ref().map(|v| {
+                                v.normalize_to_expr_maybe_alpha(alpha)
+                            }),
+                        )
+                    })
+                    .collect();
+                rc(ExprF::Field(rc(ExprF::UnionType(kts)), l.clone()))
+            }
+            Value::UnionLit(l, v, kts) => rc(ExprF::UnionLit(
+                l.clone(),
+                v.normalize_to_expr_maybe_alpha(alpha),
+                kts.iter()
+                    .map(|(k, v)| {
+                        (
+                            k.clone(),
+                            v.as_ref().map(|v| {
+                                v.normalize_to_expr_maybe_alpha(alpha)
+                            }),
+                        )
+                    })
+                    .collect(),
+            )),
+            Value::TextLit(elts) => {
+                use InterpolatedTextContents::{Expr, Text};
+                rc(ExprF::TextLit(
+                    elts.iter()
+                        .map(|contents| match contents {
+                            Expr(e) => {
+                                Expr(e.normalize_to_expr_maybe_alpha(alpha))
+                            }
+                            Text(s) => Text(s.clone()),
+                        })
+                        .collect(),
+                ))
+            }
+            Value::PartialExpr(e) => {
+                rc(e.map_ref_simple(|v| v.normalize_to_expr_maybe_alpha(alpha)))
+            }
+        }
+    }
+
+    // Deprecated
+    pub(crate) fn normalize(&self) -> Value {
+        let mut v = self.clone();
+        v.normalize_mut();
+        v
+    }
+
+    pub(crate) fn normalize_mut(&mut self) {
+        match self {
+            Value::NaturalSuccClosure
+            | Value::Var(_)
+            | Value::Const(_)
+            | Value::BoolLit(_)
+            | Value::NaturalLit(_)
+            | Value::IntegerLit(_) => {}
+
+            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();
+            }
+            Value::Pi(_, t, e) => {
+                t.normalize_mut();
+                e.normalize_mut();
+            }
+            Value::AppliedBuiltin(_, args) => {
+                for x in args.iter_mut() {
+                    x.normalize_mut();
+                }
+            }
+            Value::ListConsClosure(t, v) => {
+                t.normalize_mut();
+                for x in v.iter_mut() {
+                    x.normalize_mut();
+                }
+            }
+            Value::NEListLit(elts) => {
+                for x in elts.iter_mut() {
+                    x.normalize_mut();
+                }
+            }
+            Value::RecordLit(kvs) => {
+                for x in kvs.values_mut() {
+                    x.normalize_mut();
+                }
+            }
+            Value::RecordType(kvs) => {
+                for x in kvs.values_mut() {
+                    x.normalize_mut();
+                }
+            }
+            Value::UnionType(kts) | Value::UnionConstructor(_, kts) => {
+                for x in kts.values_mut().flat_map(|opt| opt) {
+                    x.normalize_mut();
+                }
+            }
+            Value::UnionLit(_, v, kts) => {
+                v.normalize_mut();
+                for x in kts.values_mut().flat_map(|opt| opt) {
+                    x.normalize_mut();
+                }
+            }
+            Value::TextLit(elts) => {
+                for x in elts.iter_mut() {
+                    use InterpolatedTextContents::{Expr, Text};
+                    match x {
+                        Expr(n) => n.normalize_mut(),
+                        Text(_) => {}
+                    }
+                }
+            }
+            Value::PartialExpr(e) => {
+                // TODO: need map_mut_simple
+                e.map_ref_simple(|v| {
+                    v.normalize_nf();
+                });
+            }
+        }
+    }
+
+    /// Apply to a value
+    pub(crate) fn app(self, val: Value) -> Value {
+        self.app_val(val)
+    }
+
+    /// Apply to a value
+    pub(crate) fn app_val(self, val: Value) -> Value {
+        self.app_thunk(val.into_thunk())
+    }
+
+    /// Apply to a thunk
+    pub(crate) fn app_thunk(self, th: Thunk) -> Value {
+        Thunk::from_value(self).app_thunk(th)
+    }
+
+    pub(crate) fn from_builtin(b: Builtin) -> Value {
+        Value::AppliedBuiltin(b, vec![])
+    }
+
+    pub(crate) fn shift(&self, delta: isize, var: &AlphaVar) -> 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(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,
+                    Label::clone,
+                ))
+            }
+        }
+    }
+
+    pub(crate) fn subst_shift(&self, var: &AlphaVar, val: &Typed) -> Self {
+        match self {
+            // Retry normalizing since substituting may allow progress
+            Value::AppliedBuiltin(b, args) => apply_builtin(
+                *b,
+                args.iter().map(|v| v.subst_shift(var, val)).collect(),
+            ),
+            // Retry normalizing since substituting may allow progress
+            Value::PartialExpr(e) => {
+                normalize_one_layer(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,
+                    Label::clone,
+                ))
+            }
+            // Retry normalizing since substituting may allow progress
+            Value::TextLit(elts) => {
+                Value::TextLit(squash_textlit(elts.iter().map(|contents| {
+                    use InterpolatedTextContents::{Expr, Text};
+                    match contents {
+                        Expr(th) => Expr(th.subst_shift(var, val)),
+                        Text(s) => Text(s.clone()),
+                    }
+                })))
+            }
+            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::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(),
+            ),
+        }
+    }
+}
+
+impl std::cmp::PartialEq for AlphaVar {
+    fn eq(&self, other: &Self) -> bool {
+        match (&self.alpha, &other.alpha) {
+            (Some(x), Some(y)) => x == y,
+            (None, None) => self.normal == other.normal,
+            _ => false,
+        }
+    }
+}
+impl std::cmp::PartialEq for AlphaLabel {
+    fn eq(&self, _other: &Self) -> bool {
+        true
+    }
+}
+
+impl From<Label> for AlphaVar {
+    fn from(x: Label) -> AlphaVar {
+        AlphaVar {
+            normal: V(x, 0),
+            alpha: Some(V((), 0)),
+        }
+    }
+}
+impl<'a> From<&'a Label> for AlphaVar {
+    fn from(x: &'a Label) -> AlphaVar {
+        x.clone().into()
+    }
+}
+impl From<AlphaLabel> for AlphaVar {
+    fn from(x: AlphaLabel) -> AlphaVar {
+        let l: Label = x.into();
+        l.into()
+    }
+}
+impl<'a> From<&'a AlphaLabel> for AlphaVar {
+    fn from(x: &'a AlphaLabel) -> AlphaVar {
+        x.clone().into()
+    }
+}
+
+impl From<Label> for AlphaLabel {
+    fn from(x: Label) -> AlphaLabel {
+        AlphaLabel(x)
+    }
+}
+impl From<AlphaLabel> for Label {
+    fn from(x: AlphaLabel) -> Label {
+        x.0
+    }
+}
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