Fix Xcode 26.4 compiler issue

Author: farkasseb

Sources/BigNumber/Swift-Big-Number-Core.swift

@@ -2999,7 +2999,7 @@ public struct BDouble:
 			return true;
 		} else if diff <= epsilon {
 			return true // shortcut
-		} else if (lhs == 0 || rhs == 0 || diff < Double.leastNormalMagnitude) {
+		} else if (lhs.isZero() || rhs.isZero() || diff < Double.leastNormalMagnitude) {
 			// lhs or rhs is zero or both are extremely close to it
 			// relative error is less meaningful here
 			return diff < (epsilon * Double.leastNormalMagnitude);

Tests/BigNumberTests/BDoubleTests.swift

@@ -493,6 +493,20 @@ class BDoubleTests : XCTestCase {
 		XCTAssert(BDouble.nearlyEqual(BDouble(0.000000001), BDMin));
 		XCTAssert(BDouble.nearlyEqual(BDMin, BDouble(0.000000001)));
 		XCTAssert(BDouble.nearlyEqual(-BDMin, BDouble(0.000000001)));
+
+		// Non-canonical zero (negative sign with zero numerator via raw initializer)
+		let rawNegZero = BDouble(sign: true, numerator: [0], denominator: [2])
+		XCTAssert(rawNegZero.isZero())
+		XCTAssert(BDouble.nearlyEqual(rawNegZero, BDouble(0.0)))
+		XCTAssert(BDouble.nearlyEqual(BDouble(0.0), rawNegZero))
+		XCTAssert(BDouble.nearlyEqual(rawNegZero, rawNegZero))
+		XCTAssert(BDouble.nearlyEqual(rawNegZero, BDouble(0.00000001)))
+
+		// Integer-literal zero (the pattern that triggered the Xcode 26.4 ambiguity)
+		let intZero: BDouble = 0
+		XCTAssert(intZero.isZero())
+		XCTAssert(BDouble.nearlyEqual(intZero, BDouble(0.0)))
+		XCTAssert(BDouble.nearlyEqual(intZero, rawNegZero))
 	}
 
 	func testRadix() {