Return type of "async () => {}" is displayed as "void"

[kasugaiasuka]

There seems to be something wrong with the handling of async function objects.

Steps to Reproduce

1. Write the following code.
2. Open the ts-type-expand panel.
3. Point foo.

const foo = async () => { };

Expected
ts-type-expand displays the return type of foo as Promise<void>.

Actual
It displays this type as void.

Additional info
const bar= async (): Promise<void> => { }; will be displayed as any.

[d-kimuson]

Thanks for the report !
I was able to reproduce it by trying it in my environment. I'll fix it.

[d-kimuson]

fixed in #99

[d-kimuson]

#99 merged.