Feature request: compile time assertions

[dnfield]

I would really like to be able to write code like this:

/// A class used only in debug mode.
@pragma('unretained', const bool.fromEnvironment('dart.vm.product'))
class DebugInformationHolder {}

class Foo {
  @pragma('unretained', const bool.fromEnvironment('dart.vm.product') || const bool.fromEnrivonment('dart.vm.profile'))
  bool _debugSomethingOrOther = true;
}

I would like this annotation to be able to be applied to methods, constructors, fields, getters/setters, or class definitions. I am not really concerned with whether it is a pragma or its own annotation.

I would like this annotation to do nothing at runtime, but trigger a compile time error if annotated code ended up in the final binary (e.g. after the VM optimizer pass in gen_snapshot). Ideally, it would also show the call graph(s) that led to that code being retained.

This is a similar request to #28113, but I want this to trigger compilation errors, not analysis warnings.

This is a similar request to #35303, but I want this to trigger compilation errors, since I should never be referring to this code at all in release mode and I don't even want placeholder objects.

These errors should be ignorable in cases where a library writer has annotated something but an application author decides to explicitly invoke it in the forbidden mode anyway.