fix(dyn-abi): coerce JSON int values above i64::MAX for signed types (#1158)

eip712 coerce_json read signed integers only through serde_json's as_i64,
while the sibling uint path uses as_u64. serde_json stores any integer in
(i64::MAX, u64::MAX] as a u64, so a valid positive value for int72..int256
(e.g. 2^63 into int128) returned None and coerce_json failed, even though
the same value is accepted as a JSON string and accepted by uint as a number.
Add a u64 fallback mirroring uint, plus a regression test.

Author: nikolauspschuetz

crates/dyn-abi/src/eip712/coerce.rs

@@ -61,6 +61,9 @@ fn int(n: usize, value: &serde_json::Value) -> Option<I256> {
         if let Some(num) = value.as_i64() {
             return Some(I256::try_from(num).unwrap());
         }
+        if let Some(num) = value.as_u64() {
+            return Some(I256::try_from(num).unwrap());
+        }
         value.as_str().and_then(|s| s.parse().ok())
     })()
     .and_then(|x| (x.bits() <= n as u32).then_some(x))
@@ -202,6 +205,17 @@ mod tests {
         assert!(ty.coerce_json(&j).is_err());
     }
 
+    #[test]
+    fn int_coerces_json_number_above_i64_max() {
+        // serde_json stores this as a u64 (it exceeds i64::MAX), but it is a valid
+        // positive int128. The number form must coerce the same as the string form.
+        let n: u64 = 9223372036854775808; // 2^63
+        let ty = DynSolType::Int(128);
+        let want = DynSolValue::Int("9223372036854775808".parse().unwrap(), 128);
+        assert_eq!(ty.coerce_json(&json!(n.to_string())).unwrap(), want);
+        assert_eq!(ty.coerce_json(&json!(n)).unwrap(), want);
+    }
+
     #[test]
     fn it_coerces() {
         let j = json!({