Constant Specification Update 2018

[mit-mit]

This is the feature proposal for request #54. It improved the support for constant expressions, for example the ability to explicitly cast a value in a const expression:

class MyClass {
  final String value;
  const MyClass(Object o) : value = (o is! String) ? "$o" : (o as String);
}

The feature specification is:
https://github.com/dart-lang/language/blob/master/accepted/2.5/constant-update-2018/feature-specification.md

[jodinathan]

"https://dart-review.googlesource.com/c/sdk/+/36220 specified a number of changes to potentially constant and compile-time constant expressions;"

With this will it be possible to use functions in metadata?
eg:

class Foo {
  @Bar(() => 'foobar')
  String myProp;
}

today, the above is not possible, but this is

bar() => 'foobar';
class Foo {
  @Bar(bar)
  String myProp;
}

[lrhn]

@jodinathan
No, there is no change to function literals in the listed changes, only small tweaks to include recently added operators and make the constant evaluation better match Dart 2 type semantics.

You have to do:

String kFooBar() => 'fooBar';
class Foo {
  @Bar(kFooBar)
  String myProp;
}

to tell the compiler that the function is a constant.

[mit-mit]

This shipped in Dart 2.5