Removed Type-Defect label.
Added Type-Enhancement, Area-Language, Triaged labels.

Conditional expressions are constant if there subexpressions are constant. This addresses the metadata scenario.

Conditional asserts are a bit different, since an assert is never constant. I'd argue that a good implementation will reduce thing like DEBUG? assert(predicate : null; to nothing if DEBUG is false.

The same holds for whole blocks of code within if statements. All of which is similar to some of the alternatives you mention. It seems to come down to "i'm used to C# and I want it that way'.
So I'm closing this bug.

Added WontFix label.

We should reopen this.
With Flutter we have both IOS/Android as target.

The problem is doing as followed:

if (platform === TargetPlaform.android) {
  return RaisedButton(...)
}
else {
  return CupertinoButton(...)
}

will not work with tree shaking.

You can use -t to run different lib/main_xxx.dart files like shown in https://stackoverflow.com/a/47438620/217408.
This should work well with tree-shaking.

Yeah that's what I do.

But it causes frustration for many others. https://medium.com/flutter-io/do-flutter-apps-dream-of-platform-aware-widgets-7d7ed7b4624d

I quickly skimmed though the doc but couldn't see anything about frustration.
Would you mind copying a citation?

In the comments there's a

Yup, agree with you guys, I feel flutter can only succeed if we don’t have to write platform specific widgets since it then requires you to study both material design guidelines and iOS ones thoroughly.

This is also an argument regularly used against flutter coming from RN Developers.

I am preparing a medium article on the -t part.

But I still think this issue would make things easier

Overlall, the simple fact that this article got 1k6 claps when it actually breaks tree shaking reveals that the community is looking for a solution.

I'm not against it and it's not my call anyway.
I just tried to get at the core of what this is required for or what it would make more convenient.
Your last comment should make that clear.
I don't know if Dart team members monitor comments on closed issues.
Perhaps it's better to create a new issue with the new motivation and perhaps a link to this issue.