Analyzer issue in case of constant constructor and mixin application

[sgrekhov]

The code below produces an error in the analyzer but works without any issue in VM.

class C {
  const C();
}

mixin M on C {
  static const M instance = MC(); // Analyzer error.  The constructor being called isn't a const constructor.
}

class MC = C with M;

main() {
  print(M.instance); 
}

According to the Dart language specification (12.3 Mixin Application) if C has a constant constructor and M declares no instance variables then default constructor of MC is also a constant constructor. So, I believe, that CFE is right here and the analyzer produces a wrong error. Please confirm.

If Sq is a generative const constructor, and MC does not declare any instance variables, Cq is also a const constructor

Dart SDK version: 3.7.0-264.0.dev (dev) (Wed Dec 18 00:02:57 2024 -0800) on "windows_x64"

[sgrekhov]

Interesting that the static member is important here.

class C {
  const C();
}

mixin M on C {
  static const M instance = const MC(); // Analyzer Error

class MC = C with M;

main() {
  M mc = const MC(); // Analyzer error
  print(mc);
}

But without the static member the current behavior is:

class C {
  const C();
}

mixin M on C {
  //static const M instance = const MC();
}

class MC = C with M;

main() {
  M mc = const MC(); // No error
  print(mc);
}

[lrhn]

Can confirm.
The constructor of MC is not a "default constructor", just a normal forwarding constructor of a mixin application.
A mixin application class has a forwarding constructor for each generative constructor of its superclass. If the superclass constructor is const and the mixin declares no instance variables, then the forwarding constructor is also const.

Seems the analyzer drops the const if the mixin declares a static variable too.