1 files changed, 73 insertions, 0 deletions
diff --git a/serde_dhall/src/value.rs b/serde_dhall/src/value.rs
new file mode 100644
index 0000000..a24f211
--- /dev/null
+++ b/serde_dhall/src/value.rs
@@ -0,0 +1,73 @@
+use dhall::semantics::Hir;
+use dhall::syntax::Expr;
+use dhall::{Normalized, Parsed};
+
+use crate::simple::{SimpleType, SimpleValue};
+use crate::Error;
+
+/// A Dhall value.
+#[derive(Debug, Clone)]
+pub struct Value {
+    /// Invariant: in normal form
+    pub(crate) hir: Hir,
+    /// Cached conversions because they are annoying to construct from Hir.
+    /// At most one of them will be `Some`.
+    pub(crate) as_simple_val: Option<SimpleValue>,
+    pub(crate) as_simple_ty: Option<SimpleType>,
+}
+
+impl Value {
+    /// Parse a string into a Value, and optionally ensure that the value matches the provided type
+    /// annotation.
+    pub fn from_str_with_annot(
+        s: &str,
+        ty: Option<&Self>,
+    ) -> Result<Self, Error> {
+        Self::from_str_with_annot_dhall_error(s, ty).map_err(Error::Dhall)
+    }
+    fn from_normalized(x: &Normalized) -> Self {
+        Value {
+            hir: x.to_hir(),
+            as_simple_val: SimpleValue::from_nir(x.as_nir()),
+            as_simple_ty: SimpleType::from_nir(x.as_nir()),
+        }
+    }
+
+    fn from_str_with_annot_dhall_error(
+        s: &str,
+        ty: Option<&Self>,
+    ) -> Result<Self, dhall::error::Error> {
+        let resolved = Parsed::parse_str(s)?.resolve()?;
+        let typed = match ty {
+            None => resolved.typecheck()?,
+            Some(ty) => resolved.typecheck_with(&ty.hir)?,
+        };
+        Ok(Self::from_normalized(&typed.normalize()))
+    }
+
+    /// Converts a Value into a SimpleValue.
+    pub fn to_simple_value(&self) -> Option<SimpleValue> {
+        self.as_simple_val.clone()
+    }
+    /// Converts a Value into a SimpleType.
+    pub fn to_simple_type(&self) -> Option<SimpleType> {
+        self.as_simple_ty.clone()
+    }
+
+    /// Converts a value back to the corresponding AST expression.
+    pub fn to_expr(&self) -> Expr {
+        self.hir.to_expr(Default::default())
+    }
+}
+
+impl Eq for Value {}
+impl PartialEq for Value {
+    fn eq(&self, other: &Self) -> bool {
+        self.hir == other.hir
+    }
+}
+impl std::fmt::Display for Value {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> Result<(), std::fmt::Error> {
+        self.to_expr().fmt(f)
+    }
+}