E4099

A trait is used in context where a type is needed.

Erroneous example

// `Show` is a trait, not a type

///|
fn f(_ : Show) -> Unit {

}

Suggestion

If you want to refer to a trait object type, use the syntax &Trait instead.

///|
fn f(_ : &Show) -> Unit {

}

///|
test {
  ignore(f)
}