Add a simple Debug impl for Error (#248)

* Add a simple Debug impl for Error
* Drop unneeded ok() calls

rustler/src/error.rs

@@ -1,9 +1,10 @@
 use crate::codegen_runtime::{NifReturnable, NifReturned};
 use crate::{types, Encoder, Env};
+use std::fmt;
 
 /// Represents usual errors that can happen in a nif. This enables you
 /// to return an error from anywhere, even places where you don't have
-/// an Env availible.
+/// an Env available.
 pub enum Error {
     /// Returned when the NIF has been called with the wrong number or type of
     /// arguments.
@@ -20,14 +21,12 @@ unsafe impl NifReturnable for crate::error::Error {
             Error::BadArg => NifReturned::BadArg,
             Error::Atom(atom_str) => {
                 let atom = types::atom::Atom::from_str(env, atom_str)
-                    .ok()
                     .expect("Error::Atom: bad atom")
                     .to_term(env);
                 NifReturned::Term(atom.as_c_arg())
             }
             Error::RaiseAtom(atom_str) => {
                 let atom = types::atom::Atom::from_str(env, atom_str)
-                    .ok()
                     .expect("Error::RaiseAtom: bad argument");
                 NifReturned::Raise(atom.as_c_arg())
             }
@@ -38,3 +37,14 @@ unsafe impl NifReturnable for crate::error::Error {
         }
     }
 }
+
+impl fmt::Debug for Error {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
+        match self {
+            Error::BadArg => write!(fmt, "{{error, badarg}}"),
+            Error::Atom(ref s) => write!(fmt, "{{error, {}}}", s),
+            Error::RaiseAtom(ref s) => write!(fmt, "throw({})", s),
+            Error::RaiseTerm(_) => write!(fmt, "throw(<term>)"),
+        }
+    }
+}

rustler/src/types/atom.rs

@@ -264,7 +264,7 @@ macro_rules! rustler_atoms {
     };
     { @internal_make_atom($env:ident, $name:ident = $str:expr) } => {
         $crate::types::atom::Atom::from_str($env, $str)
-            .ok().expect("rustler::atoms!: bad atom string")
+            .expect("rustler::atoms!: bad atom string")
     };
 }