main(): Print "error: " in front of each error line

Prefix each error line with the text "error: " to make it clear that's
what it is, and that it's separate from errors printed on other lines.

Worked out how to set up an `Iterator` for `MultiError` based on a
comment by 'chris-morgan' (https://old.reddit.com/user/chris-morgan) on
Reddit /r/rust:

> 1. Implement your own iterator type which wraps existing iterator
>    types (std::slice::Iter, and std::vec::IntoIter if you want a
>    consuming iterator).
>    Advantages: most flexible, ensures API stability if you
>    need to change internal details.
>    Disadvantages: a lot more effort, if you want to do it properly
>    (which involves implementing about ten traits on your iterator
>    wrapper type); and if slices or their iterators add something new,
>    you don’t get it unless you implement a wrapper yourself.
>
> 2. Have your iter() functions and IntoIterator implementations use the
>    standard iterator types directly.
>    Advantages: easier, gets you all the other trait implementations on
>    std::slice::Iter for free—AsRef, Clone, FusedIterator,
>    ExactSizeIterator, Debug, Send, DoubleEndedIterator, TrustedLen,
>    Sync).
>    Disadvantages: if you need to restructure things so that this is no
>    longer an option (e.g. store things in a different type of vector
>    and thus need to map it before presenting it to the user) it’s a
>    breaking change.
>
> 3. Implement Deref<Target = [(K, V)]> and just treat your Bucket<K, V>
>    as a &[(K, V)]. (Read-only; implement DerefMut if you want to allow
>    mutations of values.)
>    Advantages: easy, and lets you simply treat the whole thing as a
>    slice (this is what Vec<T> does).
>    Disadvantages: there really aren’t any, if it matches your purpose.
>    (If not, it’s useless.)

(https://old.reddit.com/r/rust/comments/7a0slp/questionimplementing_iterator_for_a_struct_with_a/)

2 files changed, 37 insertions, 1 deletions

diff --git a/src/main.rs b/src/main.rs
index 792b45a..9117674 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -41,7 +41,17 @@ fn main() {
     match run() {
         Ok(_) => (),
         Err(e) => {
-            eprintln!("error: {}", e);
+            // format!("{}", e)
+            //     .lines()
+            //     .for_each(|l| eprintln!("error: {}", e));
+            // eprintln!();
+
+            // let errors = *e;
+            // errors.for_each(|e| eprintln!("error: {}", e));
+
+            e
+                .into_iter()
+                .for_each(|e| eprintln!("error: {:#}", e));
 
             process::exit(exitcode::SOFTWARE);
         },
diff --git a/src/multi_error.rs b/src/multi_error.rs
index 6163f40..d3fdba5 100644
--- a/src/multi_error.rs
+++ b/src/multi_error.rs
@@ -17,6 +17,7 @@
 
 
 use std::fmt;
+// use std::ops::Deref;
 
 
 /// Wraps a list of errors.
@@ -50,3 +51,28 @@ impl From<Vec<anyhow::Error>> for MultiError {
         MultiError { errors: errors }
     }
 }
+
+// impl Iterator for MultiError {
+//     type Item = anyhow::Error;
+//
+//     fn next(&mut self) -> Option<Self::Item> {
+//         self.errors.next()
+//     }
+// }
+
+impl IntoIterator for MultiError {
+    type Item = anyhow::Error;
+    type IntoIter = std::vec::IntoIter<Self::Item>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.errors.into_iter()
+    }
+}
+
+// impl Deref for MultiError {
+//     type Target = [anyhow::Error];
+//
+//     fn deref(&self) -> &Self::Target {
+//         &self.errors
+//     }
+// }