From c857e18c4a83f2df36733e955301f89ee321f428 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Andr=C3=A9s=20N=2E=20Robalino?= <andres@androbtech.com>
Date: Tue, 24 Nov 2020 05:50:38 -0500
Subject: [PATCH] Avoid subtract overflow when no ending index given. (#2764)

---
 crates/nu-cli/src/commands/str_/substring.rs | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/crates/nu-cli/src/commands/str_/substring.rs b/crates/nu-cli/src/commands/str_/substring.rs
index cbfa4a4b3..dea5e13e0 100644
--- a/crates/nu-cli/src/commands/str_/substring.rs
+++ b/crates/nu-cli/src/commands/str_/substring.rs
@@ -159,12 +159,14 @@ fn action(input: &Value, options: &Substring, tag: impl Into<Tag>) -> Result<Val
                         "End must be greater than or equal to Start",
                         tag.span,
                     )),
-                    Ordering::Less => Ok(UntaggedValue::string(
+                    Ordering::Less => Ok(UntaggedValue::string(if end == isize::max_value() {
+                        s.chars().skip(start as usize).collect::<String>()
+                    } else {
                         s.chars()
                             .skip(start as usize)
                             .take((end - start) as usize)
-                            .collect::<String>(),
-                    )
+                            .collect::<String>()
+                    })
                     .into_value(tag)),
                 }
             } else {
@@ -330,6 +332,9 @@ mod tests {
             expectation("and", (0, -3)),
             expectation("andr", (0, -2)),
             expectation("andre", (0, -1)),
+            // str substring [ -4 , _ ]
+            // str substring   -4 ,
+            expectation("dres", (-4, isize::max_value())),
             expectation("", (0, -110)),
             expectation("", (6, 0)),
             expectation("", (6, -1)),