The functional record update syntax was used on something other than a struct.
Erroneous code example:
enum PublicationFrequency {
Weekly,
SemiMonthly { days: (u8, u8), annual_special: bool },
}
fn one_up_competitor(competitor_frequency: PublicationFrequency)
-> PublicationFrequency {
match competitor_frequency {
PublicationFrequency::Weekly => PublicationFrequency::SemiMonthly {
days: (1, 15), annual_special: false
},
c @ PublicationFrequency::SemiMonthly{ .. } =>
PublicationFrequency::SemiMonthly {
annual_special: true, ..c // error: functional record update
// syntax requires a struct
}
}
}The functional record update syntax is only allowed for structs (struct-like enum variants don’t qualify, for example). To fix the previous code, rewrite the expression without functional record update syntax:
enum PublicationFrequency {
Weekly,
SemiMonthly { days: (u8, u8), annual_special: bool },
}
fn one_up_competitor(competitor_frequency: PublicationFrequency)
-> PublicationFrequency {
match competitor_frequency {
PublicationFrequency::Weekly => PublicationFrequency::SemiMonthly {
days: (1, 15), annual_special: false
},
PublicationFrequency::SemiMonthly{ days, .. } =>
PublicationFrequency::SemiMonthly {
days, annual_special: true // ok!
}
}
}