Applying a code action to a _ hole produces too many suggestions

[mitchellwrosen]

I'm often using code actions to import out-of-scope identifiers. But sometimes I accidentally run a code action on a line that contains both an out-of-scope identifier and an underscore, such as:

TwoWay.twoWay (zipDefnsWith (alignWith _) undefined) conflicts
                             ^^^^^^^^^
                                this is out of scope, and I want HLS to suggest
                                `import Data.Semialign (alignWith)` with a code action.

In this case, the _ on the same line will cause 1800 (!) suggestions that look like

1: replace _ with foo
2: replace _ with bar
...

for (I guess?) every single identifier in scope.

[michaelpj]

Many things weird here:

• GHC shouldn't compute all this stuff
• We should limit the number of things also

Also somewhat unclear why this is happening at all?