Well, I don't follow this line or the comment at all...

You can use pattern bindings in val declarations, like val List(one, two) = List(1, 2)

I'm using quasiquotes to parse the existing source AST and generate more AST. Those support pattern bindings, like

val q"class $className {}" = q"class FooBar {}"
assert(className == tq"FooBar") // tq = the text is parsed as a `Type` rather than a `Term`

When I discard parts of the AST that aren't useful to me by binding them with $_, the compiler lint "Unused pattern variable" is triggered, which cases compile to fail since I'm using -Xfatal-warnings. If I don't bind them, the binding throws a MatchException, as if I had done val List(one) = List(1, 2)