From d49da0fe54251fbee190dc2adcdbffe787aecae7 Mon Sep 17 00:00:00 2001
From: Federico Stra <stra.federico@gmail.com>
Date: Tue, 26 Sep 2023 16:05:51 +0200
Subject: [PATCH] isqrt: add more tests

---
 library/core/tests/num/int_macros.rs  | 17 +++++++++++++++++
 library/core/tests/num/uint_macros.rs | 15 +++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/library/core/tests/num/int_macros.rs b/library/core/tests/num/int_macros.rs
index a9ce8433864..dd0ea5e9238 100644
--- a/library/core/tests/num/int_macros.rs
+++ b/library/core/tests/num/int_macros.rs
@@ -299,6 +299,23 @@ macro_rules! int_module {
                 assert_eq!((2 as $T).isqrt(), 1 as $T);
                 assert_eq!((99 as $T).isqrt(), 9 as $T);
                 assert_eq!((100 as $T).isqrt(), 10 as $T);
+
+                let n_max: $T = (1024 * 1024).min($T::MAX as u128) as $T;
+                for n in 0..=n_max {
+                    let isqrt: $T = n.isqrt();
+
+                    assert!(isqrt.pow(2) <= n);
+                    let (square, overflow) = (isqrt + 1).overflowing_pow(2);
+                    assert!(overflow || square > n);
+                }
+
+                for n in ($T::MAX - 127)..=$T::MAX {
+                    let isqrt: $T = n.isqrt();
+
+                    assert!(isqrt.pow(2) <= n);
+                    let (square, overflow) = (isqrt + 1).overflowing_pow(2);
+                    assert!(overflow || square > n);
+                }
             }
 
             #[test]
diff --git a/library/core/tests/num/uint_macros.rs b/library/core/tests/num/uint_macros.rs
index 9a8421c7b95..1ae7d048757 100644
--- a/library/core/tests/num/uint_macros.rs
+++ b/library/core/tests/num/uint_macros.rs
@@ -214,6 +214,21 @@ macro_rules! uint_module {
                 assert_eq!((99 as $T).isqrt(), 9 as $T);
                 assert_eq!((100 as $T).isqrt(), 10 as $T);
                 assert_eq!($T::MAX.isqrt(), (1 << ($T::BITS / 2)) - 1);
+
+                let n_max: $T = (1024 * 1024).min($T::MAX as u128) as $T;
+                for n in 0..=n_max {
+                    let isqrt: $T = n.isqrt();
+
+                    assert!(isqrt.pow(2) <= n);
+                    assert!(isqrt + 1 == (1 as $T) << ($T::BITS / 2) || (isqrt + 1).pow(2) > n);
+                }
+
+                for n in ($T::MAX - 255)..=$T::MAX {
+                    let isqrt: $T = n.isqrt();
+
+                    assert!(isqrt.pow(2) <= n);
+                    assert!(isqrt + 1 == (1 as $T) << ($T::BITS / 2) || (isqrt + 1).pow(2) > n);
+                }
             }
 
             #[test]