The VM is correct. The specification is explicit about this: The argument to a const constructor invocation must be a compile time constant. It is not enough that it is a potential compile-time constant.

The bug here is that dart2js do not report an error.

The analyzer may want to check too.

Shorter example:

class Other {
  final x;
  const Other(this.x);
}
class C {
  final Other other;
  const C(int level) : other = const Other(level);
}
main() => const C(42).other.x;

Removed Area-VM label.
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Changed the title to: "Dart2js does not reports error when using argument to const constructor in const constructor in initializer list".

Adding Lars and Gilad since this is really a question about the language semantics. Clearly, the level parameter is always a compile-time constant if the C constructor is invoked as a const constructor (as in 'const C(42)') but not necessarily if C is invoked using 'new C(x)'.

At some point, we (at least) discussed automatically turning the 'const Other(level)' invocation into 'new Other(level)' when C is invoked as 'new C(x)'.

cc @gbracha.
cc @larsbak.

This comment was originally written by @mhausner

Please don't make this more complicated than it already is.

Also consider the complication that arises if the argument is used in an expression.

class Other {
  final x;
  const Other(this.x);
}
class C {
  final Other other;
  const C(var level) : other = const Other(level + 1);
}

Here level+1 is a compile-time constant only if level is a number, but not if it's some other type.

I agree with comment #­3. We should not be fiddling with these rules at this point.

IIRC, we decided to drop the "turn const Other into new Other" approach to keep things simple.

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Changed the title to: "dart2js: does not reports error when using argument to const constructor in const constructor in initializer list".

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