Filling type holes can create incomplete signatures due to type variables from context

I have for example the following situation:
```
Found type wildcard ‘_’ standing for ‘R.Dynamic t [Task] -> m ()’
Where: ‘t’, ‘m’ are rigid type variables bound by the type signature for: ...
```
It‘s not an import bug right now, but when `t` and `m` are not declared with `forall t m` and `ScopedTypeVariables` the inserted signature for the type hole will probably fail because it's lacking all constraints for `t` and `m`.

I am not sure what the correct solution is:
* One could possibly look for the right constraints in the code and insert them.
* Another (slightly crazy) possibility would be to offer to refactor used variables to explicit scoped type variables.

As I said this is not urgent and I see that a fix might be hard. Nonetheless I thought having the problem noted somewhere might help.