Improve return types from async functions

[vbcodec]

Allow to return TaskValue types, or onything what have GetAwaiter method and constructor without parameters. In short similar to C# 7
At minimum allow to use classes that derive from Task or Taks(of ...)

[AnthonyDGreen]

Why?

[AdamSpeight2008]

C# has support for them

[vbcodec]

Why?

For several reasons:

• Customization of behaviour executing async functions. I use async functions together with custom awaiters, that are triggers switched by UI events like clicks. In non-async functions there is need to wait for completion of all async paths excluding those that use these triggers. To perform this there is need to register both tasks and triggers, to some system, that wait for completion., Custom task like types will allow to move that registration code from async functions into these types. Task like types will be somethong like AOP, and allow to simplify async procedures.
• ability to consume task like types created in C# and exposed in libraries
• for speed
• for all other reasons why it was added to C#

[AnthonyDGreen]

• Sounds interesting! Going to need a more detailed example.
• VB can already consume task-like types. Consumption has always been pattern based.
• Need live perf data before using performance/speed as a justification for a language feature.
• "In the other language" isn't a sufficient reason to add it to either.