From dea6c93a0b64be8bd423ff5b4e567d6910835503 Mon Sep 17 00:00:00 2001
From: dot <dot@youknowone.org>
Date: Tue, 3 Nov 2026 20:49:17 +0900
Subject: [PATCH 1/2] Fix integer-to-float overflow rounding boundary

Preserve the nearest finite result until the actual halfway overflow threshold for integer division and integer-to-float conversion.

Assisted-by: OpenAI Codex:model version not exposed
---
 crates/common/src/int.rs | 20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/crates/common/src/int.rs b/crates/common/src/int.rs
index f0e84d9b730..d787b18678c 100644
--- a/crates/common/src/int.rs
+++ b/crates/common/src/int.rs
@@ -6,13 +6,10 @@ use num_traits::{One, ToPrimitive, Zero};
 #[must_use]
 pub fn true_div(numerator: &BigInt, denominator: &BigInt) -> f64 {
     let rational = Rational::from_integers_ref(numerator.into(), denominator.into());
-    match rational.rounding_into(RoundingMode::Nearest) {
-        // returned value is $t::MAX but still less than the original
-        (val, core::cmp::Ordering::Less) if val == f64::MAX => f64::INFINITY,
-        // returned value is $t::MIN but still greater than the original
-        (val, core::cmp::Ordering::Greater) if val == f64::MIN => f64::NEG_INFINITY,
-        (val, _) => val,
-    }
+    // Nearest rounding can return the largest finite value for a quotient
+    // slightly beyond it; overflow starts at the halfway rounding boundary.
+    let (rounded, _) = rational.rounding_into(RoundingMode::Nearest);
+    rounded
 }
 
 #[must_use]
@@ -202,11 +199,16 @@ fn word_all_ascii_digits(word: u64) -> bool {
     (below | above) & 0x8080_8080_8080_8080 == 0
 }
 
-// num-bigint now returns Some(inf) for to_f64() in some cases, so just keep that the same for now
+/// Convert an integer to a finite float, or return None when it overflows.
 #[inline(always)]
 #[must_use]
 pub fn bigint_to_finite_float(int: &BigInt) -> Option<f64> {
-    int.to_f64().filter(|f| f.is_finite())
+    // malachite-bigint's ToPrimitive returns None when the input exceeds
+    // the largest finite magnitude, even when nearest rounding is finite.
+    let value = int
+        .to_f64()
+        .unwrap_or_else(|| true_div(int, &BigInt::one()));
+    value.is_finite().then_some(value)
 }
 
 #[cfg(test)]

From 4fd589aa40b5e3160284e3a9902d9a5f97418809 Mon Sep 17 00:00:00 2001
From: dot <dot@youknowone.org>
Date: Wed, 4 Nov 2026 01:10:06 +0900
Subject: [PATCH 2/2] Retire passing float conversion expected failure

Assisted-by: OpenAI Codex:model version not exposed
---
 Lib/test/test_long.py | 1 -
 1 file changed, 1 deletion(-)

diff --git a/Lib/test/test_long.py b/Lib/test/test_long.py
index 0241616e292..73739323bd5 100644
--- a/Lib/test/test_long.py
+++ b/Lib/test/test_long.py
@@ -403,7 +403,6 @@ def check_float_conversion(self, n):
                "Got {}, expected {}.".format(n, actual, expected))
         self.assertEqual(actual, expected, msg)
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
     @support.requires_IEEE_754
     def test_float_conversion(self):