Int64.fromBigInt constructor

Int64.fromBigInt(
  1. BigInt value
)

Builds from an arbitrary signed BigInt, truncating to 64 bits like a wrapping cast — mirrors Int32.fromBigInt / Int128.fromBigInt. BigInt.toUnsigned gives the exact two's-complement bit pattern directly, so this is correct for any magnitude/sign.

Implementation

factory Int64.fromBigInt(BigInt value) =>
    Int64._(Uint64.fromBigInt(value.toUnsigned(64)));