From e3996ffcb6bcb72d1c364ff19131fe60a9c77b9b Mon Sep 17 00:00:00 2001
From: Fabian Wolff <fabian.wolff@alumni.ethz.ch>
Date: Sun, 3 Oct 2021 23:05:03 +0200
Subject: [PATCH 1/2] Fix Lower/UpperExp formatting for integers and precision
 zero

---
 library/core/src/fmt/num.rs   | 3 +--
 library/core/tests/fmt/num.rs | 1 +
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/library/core/src/fmt/num.rs b/library/core/src/fmt/num.rs
index db45640df48d6..05ca50a97a644 100644
--- a/library/core/src/fmt/num.rs
+++ b/library/core/src/fmt/num.rs
@@ -305,7 +305,6 @@ macro_rules! impl_Exp {
                     n /= 10;
                     exponent += 1;
                 }
-                let trailing_zeros = exponent;
 
                 let (added_precision, subtracted_precision) = match f.precision() {
                     Some(fmt_prec) => {
@@ -333,7 +332,7 @@ macro_rules! impl_Exp {
                         n += 1;
                     }
                 }
-                (n, exponent, trailing_zeros, added_precision)
+                (n, exponent, exponent, added_precision)
             };
 
             // 39 digits (worst case u128) + . = 40
diff --git a/library/core/tests/fmt/num.rs b/library/core/tests/fmt/num.rs
index 275a1d062cafb..41eaf5a487880 100644
--- a/library/core/tests/fmt/num.rs
+++ b/library/core/tests/fmt/num.rs
@@ -146,6 +146,7 @@ fn test_format_int_exp_precision() {
     assert_eq!(format!("{:.1000e}", 1), format!("1.{}e0", "0".repeat(1000)));
     //test zero precision
     assert_eq!(format!("{:.0e}", 1), format!("1e0",));
+    assert_eq!(format!("{:.0e}", 25), format!("3e1",));
 
     //test padding with precision (and sign)
     assert_eq!(format!("{:+10.3e}", 1), "  +1.000e0");

From 199b33f0d77c3fae1c2c982029df7168899f8aba Mon Sep 17 00:00:00 2001
From: Josh Triplett <josh@joshtriplett.org>
Date: Sun, 3 Oct 2021 20:15:12 -0700
Subject: [PATCH 2/2] Use a test value that doesn't depend on the handling of
 even/odd rounding

---
 library/core/tests/fmt/num.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/library/core/tests/fmt/num.rs b/library/core/tests/fmt/num.rs
index 41eaf5a487880..b958422d14f84 100644
--- a/library/core/tests/fmt/num.rs
+++ b/library/core/tests/fmt/num.rs
@@ -146,7 +146,7 @@ fn test_format_int_exp_precision() {
     assert_eq!(format!("{:.1000e}", 1), format!("1.{}e0", "0".repeat(1000)));
     //test zero precision
     assert_eq!(format!("{:.0e}", 1), format!("1e0",));
-    assert_eq!(format!("{:.0e}", 25), format!("3e1",));
+    assert_eq!(format!("{:.0e}", 35), format!("4e1",));
 
     //test padding with precision (and sign)
     assert_eq!(format!("{:+10.3e}", 1), "  +1.000e0");