Can not use `await` in Dart expression evaluation

[grouma]

When using await in a Dart expression, you'll get the following error:

CompilationError: 'await' can only be used in 'async' or 'async*' methods.

[annagrin]

Frontend issue: dart-lang/sdk#45454

But I am not sure if fixing it will not open some can of worms:) Can easily imagine deadlocking the debugger by waiting on something that needs the debugger to continue to complete...

[annagrin]

See explanations in the comments of:
dart-lang/sdk#44999