overflow on PartialEq for BigDecimal

[austinabell]

The following lines:

bigdecimal-rs/src/lib.rs

Line 799 in 272123e

let scaled_int_val = &rhs.int_val * ten_to_the((self.scale - rhs.scale) as u64);

bigdecimal-rs/src/lib.rs

Line 802 in 272123e

let scaled_int_val = &self.int_val * ten_to_the((rhs.scale - self.scale) as u64);

overflow whenever either lhs or rhs are opposite signs and the abs sum is >u64::MAX

repro:

    let a = BigDecimal::new(bigdecimal::num_bigint::BigInt::from(1), i64::MIN);
    let b = BigDecimal::new(bigdecimal::num_bigint::BigInt::from(1), 1);
    let _ = a == b;

Found during fuzzing near/borsh-rs#91 (comment)