2 files changed, 58 insertions, 0 deletions
diff --git a/dhall/src/traits/dynamic_type.rs b/dhall/src/traits/dynamic_type.rs
new file mode 100644
index 0000000..25fe52d
--- /dev/null
+++ b/dhall/src/traits/dynamic_type.rs
@@ -0,0 +1,56 @@
+use crate::expr::*;
+use crate::traits::StaticType;
+use crate::typecheck::{TypeError, TypeMessage};
+use dhall_core::context::Context;
+use dhall_core::{Const, ExprF, X};
+use std::borrow::Cow;
+
+pub trait DynamicType {
+    fn get_type<'a>(&'a self) -> Result<Cow<'a, Type>, TypeError<X>>;
+}
+
+impl<T: StaticType> DynamicType for T {
+    fn get_type<'a>(&'a self) -> Result<Cow<'a, Type>, TypeError<X>> {
+        Ok(Cow::Owned(T::get_static_type()))
+    }
+}
+
+impl DynamicType for Type {
+    fn get_type(&self) -> Result<Cow<'_, Type>, TypeError<X>> {
+        use TypeInternal::*;
+        match &self.0 {
+            Expr(e) => e.get_type(),
+            SuperType => Err(TypeError::new(
+                &Context::new(),
+                dhall_core::rc(ExprF::Const(Const::Sort)),
+                TypeMessage::Untyped,
+            )),
+        }
+    }
+}
+
+impl DynamicType for Normalized {
+    fn get_type(&self) -> Result<Cow<'_, Type>, TypeError<X>> {
+        match &self.1 {
+            Some(t) => Ok(Cow::Borrowed(t)),
+            None => Err(TypeError::new(
+                &Context::new(),
+                self.0.clone(),
+                TypeMessage::Untyped,
+            )),
+        }
+    }
+}
+
+impl DynamicType for Typed {
+    fn get_type(&self) -> Result<Cow<'_, Type>, TypeError<X>> {
+        match &self.1 {
+            Some(t) => Ok(Cow::Borrowed(t)),
+            None => Err(TypeError::new(
+                &Context::new(),
+                self.0.clone(),
+                TypeMessage::Untyped,
+            )),
+        }
+    }
+}
diff --git a/dhall/src/traits/mod.rs b/dhall/src/traits/mod.rs
index 4ce8f97..315e17a 100644
--- a/dhall/src/traits/mod.rs
+++ b/dhall/src/traits/mod.rs
@@ -1,4 +1,6 @@
 mod deserialize;
+mod dynamic_type;
 mod static_type;
 pub use deserialize::Deserialize;
+pub use dynamic_type::DynamicType;
 pub use static_type::{SimpleStaticType, StaticType};