intellij-elm also shows just a small red squiggly after the = in type alias Foo =. In general, it seems to highlight a very small portion exactly where (it considers) the syntax error is. That’s really nice!
Another thing that helps in intellij is that unresolved variables (misspelled, not defined yet, not imported yet) are not underlined with squiggles. Instead, they are in bold and red font – that’s not as “screaming” as squiggles.
Actually, it’s pretty nice to easily see the difference between different kinds of errors at a glance:
- Syntax error: Small squiggly at a very specific place
- Unresolved reference: Bold and red
- Type error: Big squiggly around a full expression
Maybe the VSCode extension can steal some of that!
(I like errors as I type, but sometimes it gets annoying when a very big expression gets squigglified and the whole screen is red 
I sometimes do tricks like adding |> x at the end temporarily, so that the error switches to just highlighting x as undefined.)