Enums not completing in match expressions in VS 17.8.2

1. type in this code, with the last character the `.`:

```
fsharp
type E =
| Aaa = 0
| Bbb = 1
| Ccc = 2

let f(t: E) =
match t with
| E.
```
Expected behaviour: a tooltip pops up allowing the user to select from Aaa, Bbb or Ccc.

2. Type `A`

Expected behaviour: a tooltip popups up allowing the user to select `Aaa`.

Actual behaviour: no completion list shows at either point.


Discriminated unions do not have this problem.

Enums defined in dotnet code and consumed in F# seem to have problem 1 but not problem 2. But I only tested one example (`SqlDataType`).