tests: add BigInt vs Number comparison edge-case tests (large & non-integer cases)

Author: ssrlive

tests/bigint_comparison_edgecases.rs

@@ -0,0 +1,62 @@
+use javascript::{Value, evaluate_script};
+
+#[test]
+fn bigint_vs_number_comparison_edgecases() {
+    // 1n == 1
+    let r1 = evaluate_script("1n == 1");
+    match r1 {
+        Ok(Value::Boolean(b)) => assert!(b),
+        Ok(Value::Number(n)) => assert_eq!(n, 1.0),
+        other => panic!("unexpected result for 1n == 1: {:?}", other),
+    }
+
+    // 1n == 1.5 -> false
+    let r2 = evaluate_script("1n == 1.5");
+    match r2 {
+        Ok(Value::Boolean(b)) => assert!(!b),
+        Ok(Value::Number(n)) => assert_eq!(n, 0.0),
+        other => panic!("unexpected result for 1n == 1.5: {:?}", other),
+    }
+
+    // Integer conversion path: for integers that are exactly representable in Number
+    // (e.g. 2^53-1) comparison with BigInt should succeed
+    let r3 = evaluate_script("9007199254740991n == 9007199254740991");
+    match r3 {
+        Ok(Value::Boolean(b)) => assert!(b),
+        Ok(Value::Number(n)) => assert_eq!(n, 1.0),
+        other => panic!("unexpected result for equality of representable integer and BigInt: {:?}", other),
+    }
+
+    // But if a Number literal cannot represent the integer exactly, equality should be false
+    let r3b = evaluate_script("123456789123456789n == 123456789123456789");
+    match r3b {
+        Ok(Value::Boolean(b)) => assert!(!b),
+        Ok(Value::Number(n)) => assert_eq!(n, 0.0),
+        other => panic!("unexpected result for equality of imprecise integer and BigInt: {:?}", other),
+    }
+
+    // Non-integer number with BigInt: should compare numerically -> 1n < 1.5 true
+    let r4 = evaluate_script("1n < 1.5");
+    match r4 {
+        Ok(Value::Boolean(b)) => assert!(b),
+        Ok(Value::Number(n)) => assert_eq!(n, 1.0),
+        other => panic!("unexpected result for 1n < 1.5: {:?}", other),
+    }
+
+    // Very large BigInt vs a large Number (1e20): expect BigInt which is larger to compare greater
+    let r5 = evaluate_script("123456789123456789123456789n > 1e20");
+    match r5 {
+        Ok(Value::Boolean(b)) => assert!(b),
+        Ok(Value::Number(n)) => assert_eq!(n, 1.0),
+        other => panic!("unexpected result for huge BigInt vs 1e20: {:?}", other),
+    }
+
+    // Conversely, a huge negative BigInt < a negative floating number
+    // Note: parser currently doesn't treat unary - on BigInt as a bigint literal, use 0n - Xn
+    let r6 = evaluate_script("(0n - 123456789123456789123456789n) < -1e20");
+    match r6 {
+        Ok(Value::Boolean(b)) => assert!(b),
+        Ok(Value::Number(n)) => assert_eq!(n, 1.0),
+        other => panic!("unexpected result for negative huge BigInt vs -1e20: {:?}", other),
+    }
+}