`Error` trait for type `Error<Data>` where `Data` is not `Display`

[pomoke]

Error trait is crucial in usage like converting error to something like Anyhow::Error，which can be used to propagate errors simply. Some functions use Error<()>, but unit type is not Display, so it will not have Error trait.

A workaround looks like this, which requires manual conversion of error.

let serial = bs.open_protocol_exclusive::<Serial>(serial_handle).map_err(|x| anyhow!("Failed to open serial protocol, status {}",x.status()))?;

Due to implementation of a trait cannot overlap, simply do impl<Data: Debug> Display for Error<Data> will not work.

[phip1611]

I think, Data should get a : Display bound, as all errors in the Rust ecosystem are supposed to implement core::error::Error, hence, need a Display implementation.

At the moment, our implementation looks like this:

#[cfg(feature = "unstable")]
impl<Data: Debug + Display> core::error::Error for Error<Data> {}

I'm not sure if supporting both, Data with Display and without Display, is the right thing to do?

I think the following solution is neat. I don't see why the error's inner payload needs to be Display as it just complicates the interface.

diff --git a/uefi/src/result/error.rs b/uefi/src/result/error.rs
index 26634c1..094d5be 100644
--- a/uefi/src/result/error.rs
+++ b/uefi/src/result/error.rs
@@ -1,7 +1,7 @@
 use super::Status;
 use core::fmt::{Debug, Display};
  
-impl<Data: Debug + Display> Display for Error<Data> {
+impl<Data: Debug> Display for Error<Data> {
     fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
-        write!(f, "UEFI Error {}: {}", self.status(), self.data())
+        write!(f, "UEFI Error {}: {:?}", self.status(), self.data())
     }
 }
 
 #[cfg(feature = "unstable")]
-impl<Data: Debug + Display> core::error::Error for Error<Data> {}
+impl<Data: Debug> core::error::Error for Error<Data> {}

What do you say, @nicholasbishop ?