match arms use ->, not =>

Pitfall 2 of writing Soma, the programming language: a habit from another language, or a rule that surprises, with what the Soma compiler answers and the form to write.

return match x { 1 => "a"  _ => "b" }
// error: match arms use '->', not '=>'

return match x { 1 -> "a"  _ -> "b" }     // `_` is the catch-all arm

=> is lambda syntax (p => p + 1). -> is match arms and signal return types. Don't cross them.