I almost feel like start is better than focus? Ie rather than the change being:

 2 |  val x = implicitly[List[Boolean]] // error
-  |                                   ^
+  |                    ^
   |
 8 |  val value3 = M.pure("ola") // error
-  |                            ^
+  |                     ^

make it:

 2 |  val x = implicitly[List[Boolean]] // error
-  |                                   ^
+  |          ^
   |
 8 |  val value3 = M.pure("ola") // error
-  |                            ^
+  |                 ^

WDYT?

When you put it that way, I like my suggestion for future enhancement, just show me the signature with the holes.

I see there is already similar formatting:

   |I found:
   |
   |    FooT.OrderFFooA[F, A](FooT.OrderFFooA[F, A](/* missing */summon[Order[F[Foo[A]]]]))

I really feel like I'm not so stupid that it should take more than one or two rounds of tests to see which tests failed. I will endeavour [typelevel spelling] to figure out why it can't just summarize at the end and eliminate the scrolling.

Excerpt from my journal during this expedition:

Day 37, I moved the caret to the left, then all the tests expecting // error on a particular line number fail if the caret shifted to the previous line. Moreover, Pixie the test rig is coy about showing me her diff. I must be going mad.

@dwijnand I think my previous comment, that "an improved show-me-the-holes message" is ideal, but I maintain that this delta is an improvement. I'm still very bothered by carets pointing at whitespace.