From c3f0c9419e39a52758f99c156c41969341ff59da Mon Sep 17 00:00:00 2001
From: Ethan Brierley <ethanboxx@gmail.com>
Date: Tue, 6 Nov 2018 08:34:30 +0000
Subject: [PATCH] Add very useful documentation

---
 src/libcore/num/mod.rs | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/libcore/num/mod.rs b/src/libcore/num/mod.rs
index 7657b45f0246..b8f291f6d050 100644
--- a/src/libcore/num/mod.rs
+++ b/src/libcore/num/mod.rs
@@ -4771,6 +4771,7 @@ pub struct ParseIntError {
     pub kind: IntErrorKind,
 }
 
+/// Enum to store the various types of errors that can cause parsing an integer to fail.
 #[unstable(feature = "int_error_matching",
            reason = "it can be useful to match errors when making error messages \
                      for integer parsing",
@@ -4778,9 +4779,16 @@ pub struct ParseIntError {
 #[derive(Debug, Clone, PartialEq, Eq)]
 #[non_exhaustive]
 pub enum IntErrorKind {
+    /// Value being parsed is empty.
+    /// Among other causes, this variant will be constructed when parsing an empty string.
     Empty,
+    /// Contains an invalid digit.
+    /// Among other causes, this variant will be constructed when parsing a string that
+    /// contains a letter.
     InvalidDigit,
+    /// Integer is too small to store in target integer type.
     Overflow,
+    /// Integer is too large to store in target integer type.
     Underflow,
 }