fix(ecmascript): Fix BigInt and Number equality comparison precision (#907)

Author: baseballyama

nova_vm/src/ecmascript/abstract_operations/testing_and_comparison.rs

@@ -707,9 +707,13 @@ pub(crate) fn is_loosely_equal<'a>(
         }
 
         // b. If ℝ(x) = ℝ(y), return true; otherwise return false.
-        let a = a.to_real(agent);
         let b = b.to_real(agent);
-        return Ok(a == b);
+
+        // Compare BigInt with f64 using precise comparison.
+        return Ok(match a {
+            BigInt::BigInt(heap_big_int) => agent[heap_big_int] == b,
+            BigInt::SmallBigInt(small_big_int) => small_big_int.into_i64() as f64 == b,
+        });
     }
 
     // 14. Return false.

nova_vm/src/ecmascript/types/language/bigint.rs

@@ -734,23 +734,6 @@ impl<'a> BigInt<'a> {
             gc,
         )
     }
-
-    pub(crate) fn to_real(self, agent: &mut Agent) -> f64 {
-        match self {
-            BigInt::BigInt(heap_big_int) => {
-                let mut value = 0f64;
-                for (i, digits) in agent[heap_big_int].data.iter_u64_digits().enumerate() {
-                    if i == 0 {
-                        value += digits as f64;
-                    } else {
-                        value += ((digits as u128) << (i * 64)) as f64;
-                    }
-                }
-                value
-            }
-            BigInt::SmallBigInt(small_big_int) => small_big_int.into_i64() as f64,
-        }
-    }
 }
 
 bindable_handle!(BigInt);

nova_vm/src/ecmascript/types/language/bigint/data.rs

@@ -12,6 +12,35 @@ pub struct BigIntHeapData {
     pub(crate) data: BigInt,
 }
 
+/// Convert f64 to exact BigInt for precise comparison.
+/// f64 (IEEE 754 double): 1 sign bit, 11 exponent bits, 52 mantissa bits.
+fn f64_to_exact_bigint(value: f64) -> BigInt {
+    if value == 0.0 {
+        return BigInt::from(0);
+    }
+
+    let bits = value.to_bits();
+    let sign_bit = bits >> 63;
+    let exponent_bits = ((bits >> 52) & 0x7ff) as i32;
+    let mantissa_bits = bits & 0xfffffffffffff;
+
+    // Actual exponent (subtract bias of 1023)
+    let exponent = exponent_bits - 1023;
+    // Mantissa with implicit leading 1 bit
+    let mantissa = mantissa_bits | 0x10000000000000u64;
+
+    // The value is mantissa * 2^(exponent - 52)
+    let shift = exponent - 52;
+
+    let result = if shift >= 0 {
+        BigInt::from(mantissa) << (shift as usize)
+    } else {
+        BigInt::from(mantissa) >> ((-shift) as usize)
+    };
+
+    if sign_bit == 1 { -result } else { result }
+}
+
 impl HeapMarkAndSweep for BigIntHeapData {
     #[inline(always)]
     fn mark_values(&self, _queues: &mut WorkQueues) {
@@ -30,37 +59,37 @@ impl PartialEq<f64> for BigIntHeapData {
             // Cannot be equal to non-integer.
             return false;
         }
-        let mut base: f64 = match self.data.sign() {
-            Sign::Minus => -1.0,
-            // We should never have 0 value BigIntHeapData.
-            Sign::NoSign => unreachable!(),
-            Sign::Plus => 1.0,
-        };
-        self.data
-            .iter_u64_digits()
-            .enumerate()
-            .for_each(|(index, digit)| {
-                base += (digit as f64) * 2f64.powi(index as i32);
-            });
-        base == *other
+        self.data == f64_to_exact_bigint(*other)
     }
 }
 
 impl PartialOrd<f64> for BigIntHeapData {
     fn partial_cmp(&self, other: &f64) -> Option<Ordering> {
-        let mut base: f64 = match self.data.sign() {
-            Sign::Minus => -1.0,
-            // We should never have 0 value BigIntHeapData.
-            Sign::NoSign => unreachable!(),
-            Sign::Plus => 1.0,
-        };
-        self.data
-            .iter_u64_digits()
-            .enumerate()
-            .for_each(|(index, digit)| {
-                base += (digit as f64) * 2f64.powi(index as i32);
-            });
-        base.partial_cmp(other)
+        if other.is_nan() {
+            return None;
+        }
+        if *other == f64::INFINITY {
+            return Some(Ordering::Less);
+        }
+        if *other == f64::NEG_INFINITY {
+            return Some(Ordering::Greater);
+        }
+        // For non-integer f64, compare with truncated value and adjust
+        if other.trunc() != *other {
+            let truncated = f64_to_exact_bigint(other.trunc());
+            return match self.data.cmp(&truncated) {
+                Ordering::Equal => {
+                    // BigInt equals truncated value, so compare with fractional part
+                    if *other > 0.0 {
+                        Some(Ordering::Less) // e.g., 5n < 5.5
+                    } else {
+                        Some(Ordering::Greater) // e.g., -5n > -5.5
+                    }
+                }
+                ord => Some(ord),
+            };
+        }
+        Some(self.data.cmp(&f64_to_exact_bigint(*other)))
     }
 }
 

tests/expectations.json

@@ -6269,7 +6269,6 @@
   "language/expressions/delete/11.4.1-4.a-6.js": "FAIL",
   "language/expressions/delete/super-property-uninitialized-this.js": "FAIL",
   "language/expressions/division/S11.5.2_A4_T10.js": "FAIL",
-  "language/expressions/does-not-equals/bigint-and-number-extremes.js": "CRASH",
   "language/expressions/dynamic-import/assignment-expression/await-identifier.js": "FAIL",
   "language/expressions/dynamic-import/catch/nested-arrow-import-catch-eval-script-code-target.js": "FAIL",
   "language/expressions/dynamic-import/catch/nested-arrow-import-catch-import-source-source-text-module.js": "UNRESOLVED",
@@ -6414,7 +6413,6 @@
   "language/expressions/dynamic-import/usage/nested-while-import-then-eval-script-code-host-resolves-module-code.js": "FAIL",
   "language/expressions/dynamic-import/usage/syntax-nested-block-labeled-eval-script-code-host-resolves-module-code.js": "FAIL",
   "language/expressions/dynamic-import/usage/top-level-import-then-eval-script-code-host-resolves-module-code.js": "FAIL",
-  "language/expressions/equals/bigint-and-number-extremes.js": "CRASH",
   "language/expressions/exponentiation/applying-the-exp-operator_A6.js": "FAIL",
   "language/expressions/function/static-init-await-binding.js": "FAIL",
   "language/expressions/function/static-init-await-reference.js": "FAIL",
@@ -6424,20 +6422,16 @@
   "language/expressions/greater-than-or-equal/S11.8.4_A4.12_T1.js": "FAIL",
   "language/expressions/greater-than-or-equal/bigint-and-bigint.js": "FAIL",
   "language/expressions/greater-than-or-equal/bigint-and-incomparable-string.js": "FAIL",
-  "language/expressions/greater-than-or-equal/bigint-and-number-extremes.js": "FAIL",
   "language/expressions/greater-than/S11.8.2_A4.12_T1.js": "FAIL",
   "language/expressions/greater-than/bigint-and-bigint.js": "FAIL",
   "language/expressions/greater-than/bigint-and-incomparable-string.js": "FAIL",
-  "language/expressions/greater-than/bigint-and-number-extremes.js": "FAIL",
   "language/expressions/in/private-field-rhs-await-absent.js": "FAIL",
   "language/expressions/less-than-or-equal/S11.8.3_A4.12_T1.js": "FAIL",
   "language/expressions/less-than-or-equal/bigint-and-bigint.js": "FAIL",
   "language/expressions/less-than-or-equal/bigint-and-incomparable-string.js": "FAIL",
-  "language/expressions/less-than-or-equal/bigint-and-number-extremes.js": "FAIL",
   "language/expressions/less-than/S11.8.1_A4.12_T1.js": "FAIL",
   "language/expressions/less-than/bigint-and-bigint.js": "FAIL",
   "language/expressions/less-than/bigint-and-incomparable-string.js": "FAIL",
-  "language/expressions/less-than/bigint-and-number-extremes.js": "FAIL",
   "language/expressions/logical-and/tco-right.js": "FAIL",
   "language/expressions/logical-or/tco-right.js": "FAIL",
   "language/expressions/multiplication/S11.5.1_A4_T7.js": "FAIL",

tests/metrics.json

@@ -1,8 +1,8 @@
 {
   "results": {
-    "crash": 72,
-    "fail": 7455,
-    "pass": 39825,
+    "crash": 70,
+    "fail": 7451,
+    "pass": 39831,
     "skip": 3326,
     "timeout": 18,
     "unresolved": 37