Function value_error 

pub fn value_error(name: &str, expected: &str, got: &str, cause: Error) -> Error

Name the type a whole-value conversion failed on: a newtype (type N = T on the Teal side) whose inner conversion refused what arrived. The alias is what the Teal side declared, so it is the name the reader looks for: a FieldError from inside (the inner type is a record, an enum, or another alias) is re-rooted at the alias — Label.y: expected number, got nil, Wrap: expected one of .. — and a plain mismatch becomes N: expected T, got <type>.