From b0c8c757668d41e97727ee1399f83bd6fece3487 Mon Sep 17 00:00:00 2001
From: David Tolnay <dtolnay@gmail.com>
Date: Sun, 6 Oct 2019 17:02:43 -0400
Subject: [PATCH] Omit '0:' if only one cause

---
 README.md      | 2 +-
 src/context.rs | 2 +-
 src/error.rs   | 9 ++++++---
 src/lib.rs     | 2 +-
 4 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/README.md b/README.md
index 310f915..4591322 100644
--- a/README.md
+++ b/README.md
@@ -57,7 +57,7 @@ anyhow = "=1.0.0-alpha.1"
   Error: failed to read instrs from ./path/to/instrs.jsox
 
   Caused by:
-      0: No such file or directory (os error 2)
+      No such file or directory (os error 2)
   ```
 
 - Downcasting is supported and can be by value, by shared reference, or by
diff --git a/src/context.rs b/src/context.rs
index 0b4a317..31539aa 100644
--- a/src/context.rs
+++ b/src/context.rs
@@ -45,7 +45,7 @@ use std::backtrace::Backtrace;
 /// Error: failed to read instrs from ./path/to/instrs.jsox
 ///
 /// caused by:
-///     0: No such file or directory (os error 2)
+///     No such file or directory (os error 2)
 /// ```
 pub trait Context<T, E> {
     /// Wrap the error value with additional context.
diff --git a/src/error.rs b/src/error.rs
index 267a03c..34158d7 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -316,10 +316,13 @@ impl Debug for Error {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         writeln!(f, "{}", self.inner.error())?;
 
-        let mut chain = self.chain().skip(1).enumerate();
+        let mut chain = self.chain().skip(1).enumerate().peekable();
         if let Some((n, error)) = chain.next() {
-            writeln!(f, "\nCaused by:")?;
-            writeln!(f, "    {}: {}", n, error)?;
+            write!(f, "\nCaused by:\n    ")?;
+            if chain.peek().is_some() {
+                write!(f, "{}: ", n)?;
+            }
+            writeln!(f, "{}", error)?;
             for (n, error) in chain {
                 writeln!(f, "    {}: {}", n, error)?;
             }
diff --git a/src/lib.rs b/src/lib.rs
index ff818d2..ec66f5c 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -81,7 +81,7 @@
 //!   Error: failed to read instrs from ./path/to/instrs.jsox
 //!
 //!   Caused by:
-//!       0: No such file or directory (os error 2)
+//!       No such file or directory (os error 2)
 //!   ```
 //!
 //! - Downcasting is supported and can be by value, by shared reference, or by