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[red-knot] feat: implement all rich comparison operators #13635

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[red-knot] feat: implement all rich comparison operators #13635

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61 changes: 51 additions & 10 deletions crates/red_knot_python_semantic/src/types/infer.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2604,13 +2604,32 @@ impl<'db> TypeInferenceBuilder<'db> {
Type::IntLiteral(i64::from(b)),
),
// Lookup the rich comparison `__dunder__` methods on instances
(Type::Instance(left_class_ty), Type::Instance(right_class_ty)) => match op {
ast::CmpOp::Lt => {
perform_rich_comparison(self.db, left_class_ty, right_class_ty, "__lt__")
}
// TODO: implement mapping from `ast::CmpOp` to rich comparison methods
_ => Some(Type::Todo),
},
(Type::Instance(left_class_ty), Type::Instance(right_class_ty)) => {
let dunder_name = match op {
ast::CmpOp::Lt => "__lt__",
ast::CmpOp::LtE => "__le__",
ast::CmpOp::Eq => "__eq__",
ast::CmpOp::NotEq => "__ne__",
ast::CmpOp::Gt => "__gt__",
ast::CmpOp::GtE => "__ge__",
ast::CmpOp::In => "__contains__",
ast::CmpOp::NotIn => "__contains__",
ast::CmpOp::Is | ast::CmpOp::IsNot => {
return Some(builtins_symbol_ty(self.db, "bool").to_instance(self.db))
}
};
perform_rich_comparison(self.db, left_class_ty, right_class_ty, dunder_name).map(
|ty| {
// `not in` is a special case as it's the negation of `__contains__`, and
// it always returns a bool (not an arbitrary type).
if matches!(op, ast::CmpOp::NotIn) {
ty.bool(self.db).negate().into_type(self.db)
} else {
ty
}
},
)
}
// TODO: handle more types
_ => Some(Type::Todo),
}
Expand Down Expand Up @@ -3148,7 +3167,6 @@ fn perform_rich_comparison<'db>(
//
// TODO: the reflected dunder actually has priority if the r.h.s. is a strict subclass of the
// l.h.s.
// TODO: `object.__ne__` will call `__eq__` if `__ne__` is not defined

let dunder = left.class_member(db, dunder_name);
if !dunder.is_unbound() {
Expand All @@ -3159,8 +3177,31 @@ fn perform_rich_comparison<'db>(
.return_ty(db);
}

// TODO: reflected dunder -- (==, ==), (!=, !=), (<, >), (>, <), (<=, >=), (>=, <=)
None
let reflected_dunder_name = match dunder_name {
"__eq__" => "__eq__", // (==, ==)
"__ne__" => "__ne__", // (==, ==)
"__lt__" => "__ge__", // (<, >=)
"__gt__" => "__le__", // (>, <=)
"__le__" => "__gt__", // (<=, >)
"__ge__" => "__lt__", // (>=, <)
_ => return None,
};
let dunder = right.class_member(db, reflected_dunder_name);
if !dunder.is_unbound() {
return dunder
.call(db, &[Type::Instance(left), Type::Instance(right)])
.return_ty(db);
}

// Special case: `object.__ne__` (default implementation) will call `__eq__` if not defined.
if dunder_name == "__ne__" {
// While `__eq__` can be any type, `object.__eq__` is implemented as a bool, which means
// we'll error on any implementation that returns a non-bool type.
perform_rich_comparison(db, left, right, "__eq__")
.map(|ty| ty.bool(db).negate().into_type(db))
} else {
None
}
}

#[cfg(test)]
Expand Down
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