CFE allows `await voidExpression`.

[lrhn]

The language specification allows void-typed expressions to occur only in an enumerated number of syntactical positions. Those do not include await voidExpression.

If you do:

void foo() {}
void main() {
  await foo();
}

it should be a compile-time error, but it is accepted by both the front-end and the analyzer (the latter with a hint about awaiting a non-future).

The spec says:

The occurrence of an expression of type \VOID{} is a compile-time error unless it is permitted according to one of the following rules.

and then goes on to list the rules which do not include await. So, the code above should be a compile-time error.

[eernstg]

We still agree that it would be nice to make this an error, but we decided that it is not an error (the breakage was more substantial than anticipated). I'll update the language specification to be aligned with this, noting that a tool is very welcome to issue a hint.