Analyzer doesn't allow ! selector in constants

[sgrekhov]

The below works well in VM but produces an error in the analyzer.

const answer = "42"!; // Analyzer error. Const variables must be initialized with a constant value.

main() {
  print(answer);
}

Constant expression allows ! selector, therefore, I believe, it's an analyzer issue.

@lrhn @eernstg please confirm.

Dart SDK version: 3.7.0-274.0.dev (dev) (Thu Dec 19 20:06:50 2024 -0800) on "windows_x64"

[lrhn]

I'd be fine with ! being a constant expression. However, I didn't find it in the "Constant Objects" section of the NNBD specification. Was it added later @eernstg?

(I did find a section saying that the section on as checks being covariant should be changed to'

\item An expression of the form \code{$e$\,\,as\,\,$T$} or \code{$e$\,\,is\,\,$T$} is potentially constant if $e$ is a potentially constant expression and $T$ is a potentially constant type expression, and it is further constant if $e$ is constant.

That should also say "and $T$ is constant" at the end.)