letIntOrNone function

Option<int> letIntOrNone(dynamic input)

Converts input to int, returning None on failure.

Returns None for NaN, Infinity, -Infinity, and any value outside the signed 64-bit integer range — converting these via num.toInt() would throw UnsupportedError or silently saturate.

Supported types:

• Any sync Outcome chain.
• String
• num
• double
• int
• String

Implementation

Option<int> letIntOrNone(dynamic input) {
  return letNumOrNone(input).flatMap((n) {
    if (n is int) {
      // dart2js quirk: every integer-valued double satisfies `is int`,
      // including `double.infinity` and out-of-range doubles. On the VM and
      // WASM the two types are disjoint, but on dart2js they collapse into a
      // single JS-Number — so we apply the same finite + int64-range guards
      // we use on a raw double whenever the runtime additionally reports the
      // value as a double (true only on dart2js).
      if (n is double) {
        if (!n.isFinite) return const None();
        if (n >= 9223372036854775808.0 || n < -9223372036854775808.0) {
          return const None();
        }
      }
      return Some(n);
    }
    final d = n.toDouble();
    if (!d.isFinite) return const None();
    // int64 bounds. 9.223372036854776e18 is the smallest double > int64.max,
    // and -9.223372036854776e18 is the largest double < int64.min, so we
    // reject values at or beyond those magnitudes.
    if (d >= 9223372036854775808.0 || d < -9223372036854775808.0) {
      return const None();
    }
    return Some(d.toInt());
  });
}