1 files changed, 87 insertions, 0 deletions
diff --git a/src/private/cast/boxed.rs b/src/private/cast/boxed.rs
new file mode 100644
index 0000000..074346c
--- /dev/null
+++ b/src/private/cast/boxed.rs
@@ -0,0 +1,87 @@
+//! Originally from Intertrait by CodeChain
+//!
+//! <https://github.com/CodeChain-io/intertrait>
+//! <https://crates.io/crates/intertrait/0.2.2>
+//!
+//! Licensed under either of
+//!
+//! Apache License, Version 2.0 (LICENSE-APACHE or <http://www.apache.org/licenses/LICENSE-2.0>)
+//! MIT license (LICENSE-MIT or <http://opensource.org/licenses/MIT>)
+//!
+//! at your option.
+
+use std::any::type_name;
+
+use crate::private::cast::error::CastError;
+use crate::private::cast::{get_caster, CastFrom};
+
+pub trait CastBox
+{
+    /// Casts a `Box` with `Self` into a `Box` with `Dest`.
+    fn cast<Dest: ?Sized + 'static>(self: Box<Self>) -> Result<Box<Dest>, CastError>;
+}
+
+/// A blanket implementation of `CastBox` for traits extending `CastFrom`.
+impl<CastFromSelf: ?Sized + CastFrom> CastBox for CastFromSelf
+{
+    fn cast<Dest: ?Sized + 'static>(self: Box<Self>) -> Result<Box<Dest>, CastError>
+    {
+        let caster =
+            get_caster::<Dest>((*self).type_id()).map_err(CastError::GetCasterFailed)?;
+
+        (caster.cast_box)(self.box_any()).map_err(|err| CastError::CastFailed {
+            source: err,
+            from: type_name::<Self>(),
+            to: type_name::<Dest>(),
+        })
+    }
+}
+
+#[cfg(test)]
+mod tests
+{
+    use std::any::Any;
+    use std::fmt::{Debug, Display};
+
+    use super::*;
+    use crate::test_utils::subjects;
+
+    #[test]
+    fn can_cast_box()
+    {
+        let concrete_ninja = Box::new(subjects::Ninja);
+
+        let abstract_ninja: Box<dyn subjects::INinja> = concrete_ninja;
+
+        let debug_ninja_result = abstract_ninja.cast::<dyn Debug>();
+
+        assert!(debug_ninja_result.is_ok());
+    }
+
+    #[test]
+    fn cannot_cast_box_wrong()
+    {
+        let concrete_ninja = Box::new(subjects::Ninja);
+
+        let abstract_ninja: Box<dyn subjects::INinja> = concrete_ninja;
+
+        let display_ninja_result = abstract_ninja.cast::<dyn Display>();
+
+        assert!(matches!(
+            display_ninja_result,
+            Err(CastError::GetCasterFailed(_))
+        ));
+    }
+
+    #[test]
+    fn can_cast_box_from_any()
+    {
+        let concrete_ninja = Box::new(subjects::Ninja);
+
+        let any_ninja: Box<dyn Any> = concrete_ninja;
+
+        let debug_ninja_result = any_ninja.cast::<dyn Debug>();
+
+        assert!(debug_ninja_result.is_ok());
+    }
+}