E4180

E4180#

Compiler diagnostic name: unsupported_match_strategy.

Unsupported lexmatch match strategy.

lexmatch only supports the default first-match strategy and the explicit longest strategy. Other strategy names are rejected.

Erroneous example#

The following example asks for an unsupported shortest strategy:

///|
fn classify(input : String) -> String {
  lexmatch input with shortest {
    "if" => "keyword"
    _ => "identifier"
  }
}

///|
test {
  ignore(classify)
}

MoonBit will report an error.

Suggestion#

Rewrite the code with a regex match expression when a single boolean check is enough, or use lexmatch ... with longest for longest-match case selection:

///|
fn classify(input : String) -> String {
  if input =~ re"^if$" {
    "keyword"
  } else {
    "identifier"
  }
}

///|
test {
  inspect(classify("if"), content="keyword")
  inspect(classify("gift"), content="identifier")
}
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