Closes https://github.com/Lokathor/bytemuck/issues/22

Cargo.toml

@@ -15,7 +15,9 @@ exclude = ["/scripts/*", "/.travis.yml", "/appveyor.yml", "/bors.toml", "/pedant
 all-features = true
 
 [features]
+# Note: Yeah these names are non-standard, we'll fix it in v2 some day maybe
 extern_crate_alloc = []
+extern_crate_std = ["extern_crate_alloc"]
 
 [badges]
 appveyor = { repository = "Lokathor/bytemuck" }

changelog.md

@@ -8,6 +8,8 @@
 * The `offset_of!` macro now supports a 2-arg version. For types that impl
   Default, it'll just make an instance using `default` and then call over to the
   3-arg version.
+* The `PodCastError` type now supports `Hash` and `Display`. Also if you enable
+  the `extern_crate_std` feature then it will support `std::error::Error`.
 
 ## 1.2.0
 

src/lib.rs

@@ -56,6 +56,9 @@ macro_rules! impl_unsafe_marker_for_array {
   }
 }
 
+#[cfg(feature = "extern_crate_std")]
+extern crate std;
+
 #[cfg(feature = "extern_crate_alloc")]
 extern crate alloc;
 #[cfg(feature = "extern_crate_alloc")]
@@ -187,7 +190,7 @@ pub fn try_from_bytes_mut<T: Pod>(
 }
 
 /// The things that can go wrong when casting between [`Pod`] data forms.
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub enum PodCastError {
   /// You tried to cast a slice to an element type with a higher alignment
   /// requirement but the slice wasn't aligned.
@@ -204,6 +207,13 @@ pub enum PodCastError {
   /// were not so now you're sad.
   AlignmentMismatch,
 }
+impl core::fmt::Display for PodCastError {
+  fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
+    write!(f, "{:?}", self)
+  }
+}
+#[cfg(feature = "extern_crate_std")]
+impl std::error::Error for PodCastError {}
 
 /// Cast `T` into `U`
 ///