Error in derived PartialOrd for structs based on types with incomparable elements. #49650
Description
If a type deriving PartialOrd wraps another type which contains incomparable elements - and therefore only defines an implementation of PartialOrd and not a Ord - the derived implementations of the le and ge functions are flawed.
The leads to a state where the internal type returns false as result of the expressions a <= b and b >= a for two incomparable elements a and b while the wrapper returns true. [playground]
If we look into the attached output of cargo-expand it becomes clear that both implementations ignore the the underlying type only implements PartialOrd and may contain incomparable elements which can't be checked by (a < b) || !(b < a) or (a > b) || !(a > b).
Expanded: Less or Equal
#[inline]
fn le(&self, __arg_0: &StructWithoutOrd) -> bool {
match *__arg_0 {
StructWithoutOrd(ref __self_1_0) => match *self {
StructWithoutOrd(ref __self_0_0) => {
(*__self_0_0) < (*__self_1_0) || !((*__self_1_0) < (*__self_0_0)) && true
}
},
}
}Expanded: Greater or Equal
#[inline]
fn ge(&self, __arg_0: &StructWithoutOrd) -> bool {
match *__arg_0 {
StructWithoutOrd(ref __self_1_0) => match *self {
StructWithoutOrd(ref __self_0_0) => {
(*__self_0_0) > (*__self_1_0) || !((*__self_1_0) > (*__self_0_0)) && true
}
},
}
}