1 files changed, 68 insertions, 0 deletions
diff --git a/core/any_error.rs b/core/any_error.rs
new file mode 100644
index 000000000..001ca54eb
--- /dev/null
+++ b/core/any_error.rs
@@ -0,0 +1,68 @@
+use std::any::{Any, TypeId};
+use std::convert::From;
+use std::error::Error;
+use std::fmt;
+use std::ops::Deref;
+
+// The Send and Sync traits are required because deno is multithreaded and we
+// need to beable to handle errors across threads.
+pub trait AnyError: Any + Error + Send + Sync + 'static {}
+impl<T> AnyError for T where T: Any + Error + Send + Sync + Sized + 'static {}
+
+#[derive(Debug)]
+pub struct ErrBox(Box<dyn AnyError>);
+
+impl dyn AnyError {
+  pub fn downcast_ref<T: AnyError>(&self) -> Option<&T> {
+    if Any::type_id(self) == TypeId::of::<T>() {
+      let target = self as *const Self as *const T;
+      let target = unsafe { &*target };
+      Some(target)
+    } else {
+      None
+    }
+  }
+}
+
+impl ErrBox {
+  pub fn downcast<T: AnyError>(self) -> Result<T, Self> {
+    if Any::type_id(&*self.0) == TypeId::of::<T>() {
+      let target = Box::into_raw(self.0) as *mut T;
+      let target = unsafe { Box::from_raw(target) };
+      Ok(*target)
+    } else {
+      Err(self)
+    }
+  }
+}
+
+impl AsRef<dyn AnyError> for ErrBox {
+  fn as_ref(&self) -> &dyn AnyError {
+    self.0.as_ref()
+  }
+}
+
+impl Deref for ErrBox {
+  type Target = Box<AnyError>;
+  fn deref(&self) -> &Self::Target {
+    &self.0
+  }
+}
+
+impl<T: AnyError> From<T> for ErrBox {
+  fn from(error: T) -> Self {
+    Self(Box::new(error))
+  }
+}
+
+impl From<Box<dyn AnyError>> for ErrBox {
+  fn from(boxed: Box<dyn AnyError>) -> Self {
+    Self(boxed)
+  }
+}
+
+impl fmt::Display for ErrBox {
+  fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    self.0.fmt(f)
+  }
+}