1 files changed, 254 insertions, 0 deletions
diff --git a/dhall/src/semantics/phase/mod.rs b/dhall/src/semantics/phase/mod.rs
new file mode 100644
index 0000000..918c4d0
--- /dev/null
+++ b/dhall/src/semantics/phase/mod.rs
@@ -0,0 +1,254 @@
+use std::fmt::Display;
+use std::path::Path;
+
+use crate::syntax::{Builtin, Const, Expr};
+
+use crate::core::value::{ToExprOptions, Value};
+use crate::core::valuef::ValueF;
+use crate::core::var::{AlphaVar, Shift, Subst};
+use crate::error::{EncodeError, Error, ImportError, TypeError};
+
+use resolve::ImportRoot;
+
+pub(crate) mod binary;
+pub(crate) mod normalize;
+pub(crate) mod parse;
+pub(crate) mod resolve;
+pub(crate) mod typecheck;
+
+pub type ParsedExpr = Expr<Normalized>;
+pub type DecodedExpr = Expr<Normalized>;
+pub type ResolvedExpr = Expr<Normalized>;
+pub type NormalizedExpr = Expr<Normalized>;
+
+#[derive(Debug, Clone)]
+pub struct Parsed(ParsedExpr, ImportRoot);
+
+/// An expression where all imports have been resolved
+///
+/// Invariant: there must be no `Import` nodes or `ImportAlt` operations left.
+#[derive(Debug, Clone)]
+pub struct Resolved(ResolvedExpr);
+
+/// A typed expression
+#[derive(Debug, Clone)]
+pub struct Typed(Value);
+
+/// A normalized expression.
+///
+/// Invariant: the contained Typed expression must be in normal form,
+#[derive(Debug, Clone)]
+pub struct Normalized(Typed);
+
+impl Parsed {
+    pub fn parse_file(f: &Path) -> Result<Parsed, Error> {
+        parse::parse_file(f)
+    }
+    pub fn parse_str(s: &str) -> Result<Parsed, Error> {
+        parse::parse_str(s)
+    }
+    pub fn parse_binary_file(f: &Path) -> Result<Parsed, Error> {
+        parse::parse_binary_file(f)
+    }
+    pub fn parse_binary(data: &[u8]) -> Result<Parsed, Error> {
+        parse::parse_binary(data)
+    }
+
+    pub fn resolve(self) -> Result<Resolved, ImportError> {
+        resolve::resolve(self)
+    }
+    pub fn skip_resolve(self) -> Result<Resolved, ImportError> {
+        resolve::skip_resolve_expr(self)
+    }
+
+    pub fn encode(&self) -> Result<Vec<u8>, EncodeError> {
+        crate::phase::binary::encode(&self.0)
+    }
+}
+
+impl Resolved {
+    pub fn typecheck(self) -> Result<Typed, TypeError> {
+        Ok(typecheck::typecheck(self.0)?.into_typed())
+    }
+    pub fn typecheck_with(self, ty: &Typed) -> Result<Typed, TypeError> {
+        Ok(typecheck::typecheck_with(self.0, ty.normalize_to_expr())?
+            .into_typed())
+    }
+}
+
+impl Typed {
+    /// 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(mut self) -> Normalized {
+        self.normalize_mut();
+        Normalized(self)
+    }
+
+    pub(crate) fn from_const(c: Const) -> Self {
+        Typed(Value::from_const(c))
+    }
+    pub(crate) fn from_valuef_and_type(v: ValueF, t: Typed) -> Self {
+        Typed(Value::from_valuef_and_type(v, t.into_value()))
+    }
+    pub(crate) fn from_value(th: Value) -> Self {
+        Typed(th)
+    }
+    pub(crate) fn const_type() -> Self {
+        Typed::from_const(Const::Type)
+    }
+
+    pub(crate) fn to_expr(&self) -> NormalizedExpr {
+        self.0.to_expr(ToExprOptions {
+            alpha: false,
+            normalize: false,
+        })
+    }
+    pub fn normalize_to_expr(&self) -> NormalizedExpr {
+        self.0.to_expr(ToExprOptions {
+            alpha: false,
+            normalize: true,
+        })
+    }
+    pub(crate) fn normalize_to_expr_alpha(&self) -> NormalizedExpr {
+        self.0.to_expr(ToExprOptions {
+            alpha: true,
+            normalize: true,
+        })
+    }
+    pub(crate) fn to_value(&self) -> Value {
+        self.0.clone()
+    }
+    pub(crate) fn into_value(self) -> Value {
+        self.0
+    }
+
+    pub(crate) fn normalize_mut(&mut self) {
+        self.0.normalize_mut()
+    }
+
+    pub(crate) fn get_type(&self) -> Result<Typed, TypeError> {
+        Ok(self.0.get_type()?.into_typed())
+    }
+
+    pub fn make_builtin_type(b: Builtin) -> Self {
+        Typed::from_value(Value::from_builtin(b))
+    }
+    pub fn make_optional_type(t: Typed) -> Self {
+        Typed::from_value(
+            Value::from_builtin(Builtin::Optional).app(t.to_value()),
+        )
+    }
+    pub fn make_list_type(t: Typed) -> Self {
+        Typed::from_value(Value::from_builtin(Builtin::List).app(t.to_value()))
+    }
+    pub fn make_record_type(
+        kts: impl Iterator<Item = (String, Typed)>,
+    ) -> Self {
+        Typed::from_valuef_and_type(
+            ValueF::RecordType(
+                kts.map(|(k, t)| (k.into(), t.into_value())).collect(),
+            ),
+            Typed::const_type(),
+        )
+    }
+    pub fn make_union_type(
+        kts: impl Iterator<Item = (String, Option<Typed>)>,
+    ) -> Self {
+        Typed::from_valuef_and_type(
+            ValueF::UnionType(
+                kts.map(|(k, t)| (k.into(), t.map(|t| t.into_value())))
+                    .collect(),
+            ),
+            Typed::const_type(),
+        )
+    }
+}
+
+impl Normalized {
+    pub fn encode(&self) -> Result<Vec<u8>, EncodeError> {
+        crate::phase::binary::encode(&self.to_expr())
+    }
+
+    pub(crate) fn to_expr(&self) -> NormalizedExpr {
+        self.0.normalize_to_expr()
+    }
+    pub(crate) fn to_expr_alpha(&self) -> NormalizedExpr {
+        self.0.normalize_to_expr_alpha()
+    }
+    pub(crate) fn into_typed(self) -> Typed {
+        self.0
+    }
+}
+
+impl Shift for Typed {
+    fn shift(&self, delta: isize, var: &AlphaVar) -> Option<Self> {
+        Some(Typed(self.0.shift(delta, var)?))
+    }
+}
+
+impl Shift for Normalized {
+    fn shift(&self, delta: isize, var: &AlphaVar) -> Option<Self> {
+        Some(Normalized(self.0.shift(delta, var)?))
+    }
+}
+
+impl Subst<Value> for Typed {
+    fn subst_shift(&self, var: &AlphaVar, val: &Value) -> Self {
+        Typed(self.0.subst_shift(var, val))
+    }
+}
+
+macro_rules! derive_traits_for_wrapper_struct {
+    ($ty:ident) => {
+        impl std::cmp::PartialEq for $ty {
+            fn eq(&self, other: &Self) -> bool {
+                self.0 == other.0
+            }
+        }
+
+        impl std::cmp::Eq for $ty {}
+
+        impl std::fmt::Display for $ty {
+            fn fmt(
+                &self,
+                f: &mut std::fmt::Formatter,
+            ) -> Result<(), std::fmt::Error> {
+                self.0.fmt(f)
+            }
+        }
+    };
+}
+
+derive_traits_for_wrapper_struct!(Parsed);
+derive_traits_for_wrapper_struct!(Resolved);
+derive_traits_for_wrapper_struct!(Normalized);
+
+impl std::hash::Hash for Normalized {
+    fn hash<H>(&self, state: &mut H)
+    where
+        H: std::hash::Hasher,
+    {
+        if let Ok(vec) = self.encode() {
+            vec.hash(state)
+        }
+    }
+}
+
+impl Eq for Typed {}
+impl PartialEq for Typed {
+    fn eq(&self, other: &Self) -> bool {
+        self.0 == other.0
+    }
+}
+
+impl Display for Typed {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> Result<(), std::fmt::Error> {
+        self.to_expr().fmt(f)
+    }
+}