E0077

Warning name: lexmatch_longest_match

This warning described an earlier experimental form of longest-match lexmatch and is not emitted by the current compiler.

Current lexmatch ... with longest is supported for in-memory String and StringView inputs when its cases use regex constant expressions.

Erroneous example

///|
fn classify(input : String) -> String {
  lexmatch input with longest {
    ("if|[a-z]*" as token) => token.to_owned()
    _ => "other"
  }
}

///|
test {
  inspect(classify("iff"), content="iff")
}

Suggestion

Convert each legacy string pattern to a regex literal. Anchor it at ^, and at $ as well when the case must consume the whole input. Replace a trailing rest binder with after=.

///|
fn classify(input : String) -> String {
  lexmatch input with longest {
    re"^(if|[a-z]*)$" as token => token.to_owned()
    _ => "other"
  }
}

///|
test {
  inspect(classify("iff"), content="iff")
}