pub(crate) fn conversion_expectation(ty: &Type, coerced: bool) -> Option<String>Expand description
The R-facing expectation for a parameter of Rust type ty, for the
message of its Rust conversion failure: '<p>' must be <expected>: ...
(see RTypeCheck::expectation).
Derived from the same type classification as the R-side checks, including
the coerce widening (coerced) and the Missing<T> / Option<T>
wrappers, so the two paths describe an argument the same way. A few types
without an R-side check still have an R-facing expectation
(unchecked_expectation): Either<L, R>, the AsFromStr markers and
tuples. None only for an opaque type (a custom TryFromSexp type, or an
Either with such an arm): the wrapper then asks the type at run time
(rust_conversion_builder::declared_expectation: a derived newtype’s
declared expectation, an Either side by side), else reports
invalid '<p>' argument: <reason>.