XO0433: a mistyped `to:` or `from:` of `derive Json(via: ...)`

error · reported by the checker

to converts the value to its via type P and cannot fail. from converts a decoded P back; it may fail, and its error’s Display text becomes the decode error’s message at the value’s path (at $.legs[1].amount: invalid amount "12.3.4"), so the error type must implement Display. Change the function’s parameter or result to T and P, or give the error a display method. See core 2.3 and decision 0478.

Example

struct Money {
  minor: Int
} derive Json(via: Int, to: money_minor, from: money_of)

fn money_minor(m: Money) -> Str { "${m.minor}" }

fn money_of(n: Int) -> Money { Money{minor: n} }

Fix

struct Money {
  minor: Int
} derive Json(via: Int, to: money_minor, from: money_of)

fn money_minor(m: Money) -> Int { m.minor }

fn money_of(n: Int) -> Money { Money{minor: n} }

Run xo explain XO0433 for this text in a terminal, or see section 10.6 of the specification.

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XO0433: a mistyped `to:` or `from:` of `derive Json(via: ...)`

Example

Fix