Render alt display on one line with colons

src/fmt.rs

@@ -2,39 +2,36 @@ use crate::error::ErrorImpl;
 use std::fmt::{self, Debug};
 
 impl ErrorImpl<()> {
-    fn print_chain(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    pub(crate) fn display(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(f, "{}", self.error())?;
 
-        let mut chain = self.chain().skip(1).enumerate().peekable();
-        if let Some((n, error)) = chain.next() {
-            write!(f, "\n\nCaused by:\n    ")?;
-            if chain.peek().is_some() {
-                write!(f, "{}: ", n)?;
-            }
-            write!(f, "{}", error)?;
-            for (n, error) in chain {
-                write!(f, "\n    {}: {}", n, error)?;
+        if f.alternate() {
+            for cause in self.chain().skip(1) {
+                write!(f, ": {}", cause)?;
             }
         }
 
         Ok(())
     }
 
-    pub(crate) fn display(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        if f.alternate() {
-            self.print_chain(f)
-        } else {
-            write!(f, "{}", self.error())
-        }
-    }
-
     pub(crate) fn debug(&self, f: &mut fmt::Formatter) -> fmt::Result {
         if f.alternate() {
             return Debug::fmt(self.error(), f);
         }
 
-        self.print_chain(f)?;
-        writeln!(f)?;
+        writeln!(f, "{}", self.error())?;
+
+        let mut chain = self.chain().skip(1).enumerate().peekable();
+        if let Some((n, error)) = chain.next() {
+            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)?;
+            }
+        }
 
         #[cfg(backtrace)]
         {

src/lib.rs

@@ -213,10 +213,7 @@ pub use anyhow as format_err;
 /// alternate selector "{:#}".
 ///
 /// ```console
-/// failed to read instrs from ./path/to/instrs.jsox
-///
-/// Caused by:
-///     No such file or directory (os error 2)
+/// failed to read instrs from ./path/to/instrs.jsox: No such file or directory (os error 2)
 /// ```
 ///
 /// The Debug format "{:?}" includes your backtrace if one was captured. Note

tests/test_fmt.rs

@@ -18,18 +18,11 @@ oh no!\
 ";
 
 const EXPECTED_ALTDISPLAY_G: &str = "\
-f failed
-
-Caused by:
-    oh no!\
+f failed: oh no!\
 ";
 
 const EXPECTED_ALTDISPLAY_H: &str = "\
-g failed
-
-Caused by:
-    0: f failed
-    1: oh no!\
+g failed: f failed: oh no!\
 ";
 
 const EXPECTED_DEBUG_F: &str = "\