No warning on incomplete pattern matches

Cross-posted from a Stack Overflow question. Please accept my apologies if this is frowned upon, but based on the current answer there, this could be an issue rather than a user error...

Steps to reproduce

1. Open Visual Studio Code with Haskero already installed
2. Add a new Haskell file: Repro.hs
3. Add the following content to the file
4. Press Save

File contents:

module Repro where

foo :: Maybe a -> a
foo (Just x) = x

Expected behaviour

The editor should give a warning to the effect of:

Pattern match(es) are non-exhaustive
In an equation for `foo': Patterns not matched: Nothing

Actual behaviour

Nothing happens. The Problems view just states that:

No problems have been detected in the workspace so far.

More details

The above steps to reproduce are the simplest ones I could think of, but I see the same (lack of) behaviour when I create a full Stack project and make sure that I've run stack build intero in the root of my project directory.

My environment is:

• Windows 10 Pro x64
• Stack version 1.6.3, Git revision b27e629b8c4ce369e3b8273f04db193b060000db (5454 commits) x86_64 hpack-0.20.0
• Visual Studio Code version 1.20.0
• GHC version 8.2.2
• Intero version 0.1.24
• Haskero version 1.3.1