From 881248d2c4f0b4556a23d671d355bb7258adf8bb Mon Sep 17 00:00:00 2001
From: Nadrieril
Date: Tue, 17 Dec 2019 14:33:06 +0000
Subject: Rename syntax::core to syntax::ast

---
 dhall/src/syntax/ast/expr.rs | 377 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 377 insertions(+)
 create mode 100644 dhall/src/syntax/ast/expr.rs

(limited to 'dhall/src/syntax/ast/expr.rs')

diff --git a/dhall/src/syntax/ast/expr.rs b/dhall/src/syntax/ast/expr.rs
new file mode 100644
index 0000000..5b9f401
--- /dev/null
+++ b/dhall/src/syntax/ast/expr.rs
@@ -0,0 +1,377 @@
+use crate::syntax::map::{DupTreeMap, DupTreeSet};
+use crate::syntax::visitor::{self, ExprFMutVisitor, ExprFVisitor};
+use crate::syntax::*;
+
+pub type Integer = isize;
+pub type Natural = usize;
+pub type Double = NaiveDouble;
+
+pub fn trivial_result<T>(x: Result<T, !>) -> T {
+    match x {
+        Ok(x) => x,
+        Err(e) => e,
+    }
+}
+
+/// Double with bitwise equality
+#[derive(Debug, Copy, Clone)]
+pub struct NaiveDouble(f64);
+
+impl PartialEq for NaiveDouble {
+    fn eq(&self, other: &Self) -> bool {
+        self.0.to_bits() == other.0.to_bits()
+    }
+}
+
+impl Eq for NaiveDouble {}
+
+impl std::hash::Hash for NaiveDouble {
+    fn hash<H>(&self, state: &mut H)
+    where
+        H: std::hash::Hasher,
+    {
+        self.0.to_bits().hash(state)
+    }
+}
+
+impl From<f64> for NaiveDouble {
+    fn from(x: f64) -> Self {
+        NaiveDouble(x)
+    }
+}
+
+impl From<NaiveDouble> for f64 {
+    fn from(x: NaiveDouble) -> f64 {
+        x.0
+    }
+}
+
+/// Constants for a pure type system
+#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub enum Const {
+    Type,
+    Kind,
+    Sort,
+}
+
+/// Bound variable
+///
+/// The `Label` field is the variable's name (i.e. \"`x`\").
+/// The `Int` field is a DeBruijn index.
+/// See dhall-lang/standard/semantics.md for details
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+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, Hash)]
+pub enum BinOp {
+    /// `x ? y`
+    ImportAlt,
+    /// `x || y`
+    BoolOr,
+    /// `x + y`
+    NaturalPlus,
+    /// `x ++ y`
+    TextAppend,
+    /// `x # y`
+    ListAppend,
+    /// `x && y`
+    BoolAnd,
+    /// `x ∧ y`
+    RecursiveRecordMerge,
+    /// `x ⫽ y`
+    RightBiasedRecordMerge,
+    /// `x ⩓ y`
+    RecursiveRecordTypeMerge,
+    /// `x * y`
+    NaturalTimes,
+    /// `x == y`
+    BoolEQ,
+    /// `x != y`
+    BoolNE,
+    /// x === y
+    Equivalence,
+}
+
+/// Built-ins
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
+pub enum Builtin {
+    Bool,
+    Natural,
+    Integer,
+    Double,
+    Text,
+    List,
+    Optional,
+    OptionalNone,
+    NaturalBuild,
+    NaturalFold,
+    NaturalIsZero,
+    NaturalEven,
+    NaturalOdd,
+    NaturalToInteger,
+    NaturalShow,
+    NaturalSubtract,
+    IntegerToDouble,
+    IntegerShow,
+    DoubleShow,
+    ListBuild,
+    ListFold,
+    ListLength,
+    ListHead,
+    ListLast,
+    ListIndexed,
+    ListReverse,
+    OptionalFold,
+    OptionalBuild,
+    TextShow,
+}
+
+// Each node carries an annotation.
+#[derive(Debug, Clone)]
+pub struct Expr<Embed>(Box<(RawExpr<Embed>, Span)>);
+
+pub type RawExpr<Embed> = ExprF<Expr<Embed>, Embed>;
+
+impl<Embed: PartialEq> std::cmp::PartialEq for Expr<Embed> {
+    fn eq(&self, other: &Self) -> bool {
+        self.0.as_ref().0 == other.0.as_ref().0
+    }
+}
+
+impl<Embed: Eq> std::cmp::Eq for Expr<Embed> {}
+
+impl<Embed: std::hash::Hash> std::hash::Hash for Expr<Embed> {
+    fn hash<H>(&self, state: &mut H)
+    where
+        H: std::hash::Hasher,
+    {
+        (self.0).0.hash(state)
+    }
+}
+
+/// Syntax tree for expressions
+// Having the recursion out of the enum definition enables writing
+// much more generic code and improves pattern-matching behind
+// smart pointers.
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub enum ExprF<SubExpr, Embed> {
+    Const(Const),
+    ///  `x`
+    ///  `x@n`
+    Var(V<Label>),
+    ///  `λ(x : A) -> b`
+    Lam(Label, SubExpr, SubExpr),
+    ///  `A -> B`
+    ///  `∀(x : A) -> B`
+    Pi(Label, SubExpr, SubExpr),
+    ///  `f a`
+    App(SubExpr, SubExpr),
+    ///  `let x     = r in e`
+    ///  `let x : t = r in e`
+    Let(Label, Option<SubExpr>, SubExpr, SubExpr),
+    ///  `x : t`
+    Annot(SubExpr, SubExpr),
+    ///  `assert : t`
+    Assert(SubExpr),
+    /// Built-in values
+    Builtin(Builtin),
+    // Binary operations
+    BinOp(BinOp, SubExpr, SubExpr),
+    ///  `True`
+    BoolLit(bool),
+    ///  `if x then y else z`
+    BoolIf(SubExpr, SubExpr, SubExpr),
+    ///  `1`
+    NaturalLit(Natural),
+    ///  `+2`
+    IntegerLit(Integer),
+    ///  `3.24`
+    DoubleLit(Double),
+    ///  `"Some ${interpolated} text"`
+    TextLit(InterpolatedText<SubExpr>),
+    ///  `[] : t`
+    EmptyListLit(SubExpr),
+    ///  `[x, y, z]`
+    NEListLit(Vec<SubExpr>),
+    ///  `Some e`
+    SomeLit(SubExpr),
+    ///  `{ k1 : t1, k2 : t1 }`
+    RecordType(DupTreeMap<Label, SubExpr>),
+    ///  `{ k1 = v1, k2 = v2 }`
+    RecordLit(DupTreeMap<Label, SubExpr>),
+    ///  `< k1 : t1, k2 >`
+    UnionType(DupTreeMap<Label, Option<SubExpr>>),
+    ///  `merge x y : t`
+    Merge(SubExpr, SubExpr, Option<SubExpr>),
+    ///  `toMap x : t`
+    ToMap(SubExpr, Option<SubExpr>),
+    ///  `e.x`
+    Field(SubExpr, Label),
+    ///  `e.{ x, y, z }`
+    Projection(SubExpr, DupTreeSet<Label>),
+    ///  `e.(t)`
+    ProjectionByExpr(SubExpr, SubExpr),
+    /// `./some/path`
+    Import(Import<SubExpr>),
+    /// Embeds the result of resolving an import
+    Embed(Embed),
+}
+
+impl<SE, E> ExprF<SE, E> {
+    pub fn traverse_ref_with_special_handling_of_binders<'a, SE2, Err>(
+        &'a self,
+        visit_subexpr: impl FnMut(&'a SE) -> Result<SE2, Err>,
+        visit_under_binder: impl FnOnce(&'a Label, &'a SE) -> Result<SE2, Err>,
+    ) -> Result<ExprF<SE2, E>, Err>
+    where
+        E: Clone,
+    {
+        visitor::TraverseRefWithBindersVisitor {
+            visit_subexpr,
+            visit_under_binder,
+        }
+        .visit(self)
+    }
+
+    fn traverse_ref<'a, SE2, Err>(
+        &'a self,
+        visit_subexpr: impl FnMut(&'a SE) -> Result<SE2, Err>,
+    ) -> Result<ExprF<SE2, E>, Err>
+    where
+        E: Clone,
+    {
+        visitor::TraverseRefVisitor { visit_subexpr }.visit(self)
+    }
+
+    fn traverse_mut<'a, Err>(
+        &'a mut self,
+        visit_subexpr: impl FnMut(&'a mut SE) -> Result<(), Err>,
+    ) -> Result<(), Err> {
+        visitor::TraverseMutVisitor { visit_subexpr }.visit(self)
+    }
+
+    pub fn map_ref_with_special_handling_of_binders<'a, SE2>(
+        &'a self,
+        mut map_subexpr: impl FnMut(&'a SE) -> SE2,
+        mut map_under_binder: impl FnMut(&'a Label, &'a SE) -> SE2,
+    ) -> ExprF<SE2, E>
+    where
+        E: Clone,
+    {
+        trivial_result(self.traverse_ref_with_special_handling_of_binders(
+            |x| Ok(map_subexpr(x)),
+            |l, x| Ok(map_under_binder(l, x)),
+        ))
+    }
+
+    pub fn map_ref<'a, SE2>(
+        &'a self,
+        mut map_subexpr: impl FnMut(&'a SE) -> SE2,
+    ) -> ExprF<SE2, E>
+    where
+        E: Clone,
+    {
+        trivial_result(self.traverse_ref(|x| Ok(map_subexpr(x))))
+    }
+
+    pub fn map_mut<'a>(&'a mut self, mut map_subexpr: impl FnMut(&'a mut SE)) {
+        trivial_result(self.traverse_mut(|x| Ok(map_subexpr(x))))
+    }
+}
+
+impl<E> Expr<E> {
+    pub fn as_ref(&self) -> &RawExpr<E> {
+        &self.0.as_ref().0
+    }
+    pub fn as_mut(&mut self) -> &mut RawExpr<E> {
+        &mut self.0.as_mut().0
+    }
+    pub fn span(&self) -> Span {
+        self.0.as_ref().1.clone()
+    }
+
+    pub fn new(x: RawExpr<E>, n: Span) -> Self {
+        Expr(Box::new((x, n)))
+    }
+
+    pub fn rewrap<E2>(&self, x: RawExpr<E2>) -> Expr<E2> {
+        Expr(Box::new((x, (self.0).1.clone())))
+    }
+
+    pub fn traverse_resolve_mut<Err, F1>(
+        &mut self,
+        f: &mut F1,
+    ) -> Result<(), Err>
+    where
+        E: Clone,
+        F1: FnMut(Import<Expr<E>>) -> Result<E, Err>,
+    {
+        match self.as_mut() {
+            ExprF::BinOp(BinOp::ImportAlt, l, r) => {
+                let garbage_expr = ExprF::BoolLit(false);
+                let new_self = if l.traverse_resolve_mut(f).is_ok() {
+                    l
+                } else {
+                    r.traverse_resolve_mut(f)?;
+                    r
+                };
+                *self.as_mut() =
+                    std::mem::replace(new_self.as_mut(), garbage_expr);
+            }
+            _ => {
+                self.as_mut().traverse_mut(|e| e.traverse_resolve_mut(f))?;
+                if let ExprF::Import(import) = self.as_mut() {
+                    let garbage_import = Import {
+                        mode: ImportMode::Code,
+                        location: ImportLocation::Missing,
+                        hash: None,
+                    };
+                    // Move out of &mut import
+                    let import = std::mem::replace(import, garbage_import);
+                    *self.as_mut() = ExprF::Embed(f(import)?);
+                }
+            }
+        }
+        Ok(())
+    }
+}
+
+/// Add an isize to an usize
+/// Returns `None` on over/underflow
+fn add_ui(u: usize, i: isize) -> Option<usize> {
+    Some(if i < 0 {
+        u.checked_sub(i.checked_neg()? as usize)?
+    } else {
+        u.checked_add(i as usize)?
+    })
+}
+
+impl<Label: PartialEq + Clone> V<Label> {
+    pub fn shift(&self, delta: isize, var: &V<Label>) -> Option<Self> {
+        let V(x, n) = var;
+        let V(y, m) = self;
+        Some(if x == y && n <= m {
+            V(y.clone(), add_ui(*m, delta)?)
+        } else {
+            V(y.clone(), *m)
+        })
+    }
+
+    pub fn over_binder(&self, x: &Label) -> Option<Self> {
+        self.shift(-1, &V(x.clone(), 0))
+    }
+}
-- 
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