Allow immediate execution of lambdas with implicit return type

[maxkoshevoi]

Currently immediate execution of lambda with implicit return type throws CS0149: Method name expected. This seems like it should work considering there's no error if I explicitly specify the return type or assign the lambda to a variable first:

List<Task> tasks = [];
string s;

tasks.Add((async () => s = await GetStringAsync())()); // CS0149: Method name expected

tasks.Add(((Func<Task>)(async () => s = await GetStringAsync()))()); // OK

var getTask = async () => s = await GetStringAsync();
tasks.Add(getTask()); // OK

Task<string> GetStringAsync() => throw new NotImplementedException();

Motivation is: I want to add task to a list witch will be awaited with Task.WhenAll later on, and assign variable s with it's result within the same task. Wrapping async () => s = await GetStringAsync() in Task.Run would work as well, but it would create an unnecessary thread

[HaloFour]

See: #4748

Which was considered "universally disliked" by the language design team.

[maxkoshevoi]

I see, thank you. Well we still need some concise syntax to do this. Hope expression blocks will be implemented soon =)

[yaakov-h]

"need" is a strong word here.