Duration(seconds:) parsing problem

[rocketnik]

There exists a case where the Duration created from an int seconds results in an unexpected value.

Steps to reproduce

• evaluate Duration(seconds: 66666666666666660).inSeconds == 133584280340

This returns true. I would expect it to return false.

I see two options for how this could be resolved:

• The .inSeconds should return the value that was used during initialization.
• Alternatively if the seconds value is not valid (too large) Duration(seconds:) should throw or return null during initialization.

Infos about the environment:

• I ran from Android Studio on ARM Mac on an iOS Simulator

Tooling:

• Dart 3.7.2 (stable) (Tue Mar 11 04:27:50 2025 -0700) on "macos_arm64"
• on macos / Version 15.3.2 (Build 24D81)
• locale is en-DE

[lrhn]

The problem is overflow detection.

The number of seconds by itself is so large that when it's converted to microseconds, it overflows an int-64.

We don't currently try to detect that, because the parameters can be negative too, so a too large number of seconds could be countered by a large negative number of minutes, bringing the final result back into range.

That's probably being too nice. We should check every parameter to ensure it stays within some allowed range, maybe twice the range of DateTime, and then also check that the final sum is in the same range. Then it might be possible to avoid intermediate overflows.

It's complicated by the constructor being const, so there are limits to the logic one can do.
(And different limits depending on whether it's invoked using const or not, since one can use asserts when const invoked, but possibly not when using new, and it's a little tricky to throw at runtime when invoked using new since throw is not a potentially constant expression. (It should be!)
(A proof-of-concept input validation approach: https://dart-review.googlesource.com/c/sdk/+/425060)