xee-interpreter 0.2.0

// This module matches types for inline functions or type checks
// The convert module is used for checking and converting values for
// external functions declared with xpath_fn

use xee_schema_type::Xs;
use xee_xpath_ast::ast;
use xee_xpath_ast::parse_sequence_type;
use xee_xpath_ast::Namespaces;
use xee_xpath_type::TypeInfo;
use xot::Xot;

use crate::atomic;
use crate::context;
use crate::error;
use crate::function;
use crate::xml;

use super::core::Sequence;
use super::item::Item;
use super::iter::one;
use super::iter::option;

impl Sequence {
    /// Check a type for qee-qt assert-type
    pub fn matches_type<'a>(
        &self,
        s: &str,
        xot: &Xot,
        get_signature: &impl Fn(&function::Function) -> &'a function::Signature,
    ) -> error::Result<bool> {
        let namespaces = Namespaces::default();
        let sequence_type = parse_sequence_type(s, &namespaces)?;
        if self
            .clone()
            .sequence_type_matching(&sequence_type, xot, get_signature)
            .is_ok()
        {
            Ok(true)
        } else {
            Ok(false)
        }
    }

    // sequence type matching for the purposes of instance of
    pub(crate) fn sequence_type_matching<'a>(
        self,
        sequence_type: &ast::SequenceType,
        xot: &Xot,
        get_signature: &impl Fn(&function::Function) -> &'a function::Signature,
    ) -> error::Result<Self> {
        self.sequence_type_matching_convert(
            sequence_type,
            &|atomic, _| Ok(atomic),
            &|function_test, item| item.function_type_matching(function_test, &get_signature),
            xot,
        )
    }

    // sequence type matching, including function conversion rules
    pub(crate) fn sequence_type_matching_function_conversion<'a>(
        self,
        sequence_type: &ast::SequenceType,
        context: &'a context::StaticContext,
        xot: &Xot,
        get_signature: &impl Fn(&function::Function) -> &'a function::Signature,
    ) -> error::Result<Self> {
        self.sequence_type_matching_convert(
            sequence_type,
            &|atomic, xs| Self::cast_or_promote_atomic(atomic, xs, context),
            &|function_test, item| item.function_arity_matching(function_test, &get_signature),
            xot,
        )
    }

    fn cast_or_promote_atomic(
        atom: atomic::Atomic,
        xs: Xs,
        context: &context::StaticContext,
    ) -> error::Result<atomic::Atomic> {
        let atom = if matches!(atom, atomic::Atomic::Untyped(_)) {
            match xs {
                // function conversion rules 3.1.5.2 it says: If the item is of
                // type xs:untypedAtomic and the expected type is
                // namespace-sensitive, a type error [err:XPTY0117] is raised.
                Xs::QName | Xs::Notation => {
                    return Err(error::Error::XPTY0117);
                }
                _ => atom.cast_to_schema_type(xs, context)?,
            }
        } else {
            atom
        };
        atom.type_promote(xs)
    }

    fn sequence_type_matching_convert(
        self,
        t: &ast::SequenceType,
        cast_or_promote_atomic: &impl Fn(atomic::Atomic, Xs) -> error::Result<atomic::Atomic>,
        check_function: &impl Fn(&ast::FunctionTest, &Item) -> error::Result<()>,
        xot: &Xot,
    ) -> error::Result<Self> {
        match t {
            ast::SequenceType::Empty => {
                if self.is_empty() {
                    Ok(self)
                } else {
                    Err(error::Error::XPTY0004)
                }
            }
            ast::SequenceType::Item(occurrence_item) => self.occurrence_item_matching(
                occurrence_item,
                cast_or_promote_atomic,
                check_function,
                xot,
            ),
        }
    }

    fn occurrence_item_matching(
        self,
        occurrence_item: &ast::Item,
        cast_or_promote_atomic: &impl Fn(atomic::Atomic, Xs) -> error::Result<atomic::Atomic>,
        check_function: &impl Fn(&ast::FunctionTest, &Item) -> error::Result<()>,
        xot: &Xot,
    ) -> error::Result<Self> {
        match &occurrence_item.item_type {
            ast::ItemType::AtomicOrUnionType(xs) => self.atomic_occurrence_item_matching(
                occurrence_item,
                cast_or_promote_atomic,
                *xs,
                xot,
            ),
            _ => self.non_atomic_occurrence_item_matching(
                occurrence_item,
                cast_or_promote_atomic,
                check_function,
                xot,
            ),
        }
    }

    // there is some duplication here for performance reasons; non-atomic
    // occurrence type matching doesn't have to handle casting or promotion

    fn non_atomic_occurrence_item_matching(
        self,
        occurrence_item: &ast::Item,
        cast_or_promote_atomic: &impl Fn(atomic::Atomic, Xs) -> error::Result<atomic::Atomic>,
        check_function: &impl Fn(&ast::FunctionTest, &Item) -> error::Result<()>,
        xot: &Xot,
    ) -> error::Result<Self> {
        match occurrence_item.occurrence {
            ast::Occurrence::One => {
                let one = one(self.iter())?;
                one.non_atomic_item_type_matching(
                    &occurrence_item.item_type,
                    cast_or_promote_atomic,
                    check_function,
                    xot,
                )?;
            }
            ast::Occurrence::Option => {
                let option = option(self.iter())?;
                if let Some(item) = option {
                    item.non_atomic_item_type_matching(
                        &occurrence_item.item_type,
                        cast_or_promote_atomic,
                        check_function,
                        xot,
                    )?;
                }
            }
            ast::Occurrence::Many => {
                match occurrence_item.item_type {
                    ast::ItemType::Item => {
                        // we don't have to do anything, as we already know
                        // all items are items
                    }
                    _ => {
                        for item in self.iter() {
                            item.non_atomic_item_type_matching(
                                &occurrence_item.item_type,
                                cast_or_promote_atomic,
                                check_function,
                                xot,
                            )?;
                        }
                    }
                }
            }
            ast::Occurrence::NonEmpty => {
                if self.is_empty() {
                    return Err(error::Error::XPTY0004);
                }
                match occurrence_item.item_type {
                    ast::ItemType::Item => {
                        // we don't have to do anything, as we already know
                        // all items are items
                    }
                    _ => {
                        for item in self.iter() {
                            item.non_atomic_item_type_matching(
                                &occurrence_item.item_type,
                                cast_or_promote_atomic,
                                check_function,
                                xot,
                            )?;
                        }
                    }
                }
            }
        }
        Ok(self)
    }

    fn atomic_occurrence_item_matching(
        self,
        occurrence_item: &ast::Item,
        cast_or_promote_atomic: &impl Fn(atomic::Atomic, Xs) -> error::Result<atomic::Atomic>,
        xs: Xs,
        xot: &Xot,
    ) -> error::Result<Self> {
        match occurrence_item.occurrence {
            ast::Occurrence::One => {
                let one = one(self.atomized(xot))?;
                let atom = one?.atomic_type_matching(xs, cast_or_promote_atomic)?;
                Ok(atom.into())
            }
            ast::Occurrence::Option => {
                let option = option(self.atomized(xot))?;
                if let Some(atom) = option {
                    let atom = atom?.atomic_type_matching(xs, cast_or_promote_atomic)?;
                    Ok(atom.into())
                } else {
                    Ok(self)
                }
            }
            ast::Occurrence::Many => {
                let mut atoms = Vec::with_capacity(self.len());
                for atom in self.atomized(xot) {
                    atoms.push(atom?.atomic_type_matching(xs, cast_or_promote_atomic)?);
                }
                Ok(atoms.into())
            }
            ast::Occurrence::NonEmpty => {
                if self.is_empty() {
                    return Err(error::Error::XPTY0004);
                }
                let mut atoms = Vec::with_capacity(self.len());
                for atom in self.atomized(xot) {
                    atoms.push(atom?.atomic_type_matching(xs, cast_or_promote_atomic)?);
                }
                Ok(atoms.into())
            }
        }
    }
}

impl Item {
    pub(crate) fn non_atomic_item_type_matching(
        self,
        item_type: &ast::ItemType,
        cast_or_promote_atomic: &impl Fn(atomic::Atomic, Xs) -> error::Result<atomic::Atomic>,
        check_function: &impl Fn(&ast::FunctionTest, &Item) -> error::Result<()>,
        xot: &Xot,
    ) -> error::Result<()> {
        match item_type {
            ast::ItemType::Item => {}
            ast::ItemType::AtomicOrUnionType(_) => {
                unreachable!()
            }
            ast::ItemType::KindTest(kind_test) => {
                self.kind_test_matching(kind_test, xot)?;
            }
            ast::ItemType::FunctionTest(function_test) => {
                check_function(function_test, &self)?;
            }
            ast::ItemType::MapTest(map_test) => match map_test {
                ast::MapTest::AnyMapTest => {
                    if !self.is_map() {
                        return Err(error::Error::XPTY0004);
                    }
                }
                ast::MapTest::TypedMapTest(typed_map_test) => {
                    let map = self.to_map()?;
                    for (key, value) in map.entries() {
                        key.clone().atomic_type_matching(
                            typed_map_test.key_type,
                            cast_or_promote_atomic,
                        )?;
                        value.clone().sequence_type_matching_convert(
                            &typed_map_test.value_type,
                            cast_or_promote_atomic,
                            check_function,
                            xot,
                        )?;
                    }
                }
            },
            ast::ItemType::ArrayTest(array_test) => match array_test {
                ast::ArrayTest::AnyArrayTest => {
                    if !self.is_array() {
                        return Err(error::Error::XPTY0004);
                    }
                }
                ast::ArrayTest::TypedArrayTest(typed_array_test) => {
                    let array = self.to_array()?;
                    for sequence in array.iter() {
                        sequence.clone().sequence_type_matching_convert(
                            &typed_array_test.item_type,
                            cast_or_promote_atomic,
                            check_function,
                            xot,
                        )?;
                    }
                }
            },
        }
        Ok(())
    }

    fn kind_test_matching(&self, kind_test: &ast::KindTest, xot: &Xot) -> error::Result<()> {
        match self {
            Item::Node(node) => {
                if xml::kind_test(kind_test, xot, *node) {
                    Ok(())
                } else {
                    Err(error::Error::XPTY0004)
                }
            }
            Item::Atomic(_) => Err(error::Error::XPTY0004),
            Item::Function(_) => Err(error::Error::XPTY0004),
        }
    }

    pub(crate) fn function_arity_matching<'a>(
        &self,
        function_test: &ast::FunctionTest,
        get_signature: &impl Fn(&function::Function) -> &'a function::Signature,
    ) -> error::Result<()> {
        match function_test {
            ast::FunctionTest::AnyFunctionTest => {
                self.to_function()?;
                Ok(())
            }
            ast::FunctionTest::TypedFunctionTest(typed_function_test) => {
                let function = self.to_function()?;
                let signature = get_signature(&function);
                if signature.arity() == typed_function_test.parameter_types.len() {
                    Ok(())
                } else {
                    Err(error::Error::XPTY0004)
                }
            }
        }
    }

    pub(crate) fn function_type_matching<'a>(
        &self,
        function_test: &ast::FunctionTest,
        get_signature: &impl Fn(&function::Function) -> &'a function::Signature,
    ) -> error::Result<()> {
        match function_test {
            ast::FunctionTest::AnyFunctionTest => {
                self.to_function()?;
                Ok(())
            }
            ast::FunctionTest::TypedFunctionTest(typed_function_test) => {
                let function = self.to_function()?;
                let signature = get_signature(&function);
                if signature.arity() != typed_function_test.parameter_types.len() {
                    return Err(error::Error::XPTY0004);
                }
                if Self::function_type_matching_helper(typed_function_test, signature) {
                    Ok(())
                } else {
                    Err(error::Error::XPTY0004)
                }
            }
        }
    }

    fn function_type_matching_helper(
        function_test: &ast::TypedFunctionTest,
        signature: &function::Signature,
    ) -> bool {
        let default_sequence_type = Self::default_sequence_type();
        let function_return_type = signature.return_type().unwrap_or(&default_sequence_type);
        // return type is covariant
        if !function_return_type.subtype(&function_test.return_type) {
            return false;
        }

        for (function_parameter, test_parameter) in signature
            .parameter_types()
            .iter()
            .zip(&function_test.parameter_types)
        {
            let function_parameter = function_parameter
                .as_ref()
                .unwrap_or(&default_sequence_type);
            // parameter is contravariant
            if !test_parameter.subtype(function_parameter) {
                return false;
            }
        }

        true
    }

    fn default_sequence_type() -> ast::SequenceType {
        ast::SequenceType::Item(ast::Item {
            item_type: ast::ItemType::Item,
            occurrence: ast::Occurrence::Many,
        })
    }
}

impl atomic::Atomic {
    fn atomic_type_matching(
        self,
        xs: Xs,
        cast_or_promote_atomic: &impl Fn(atomic::Atomic, Xs) -> error::Result<atomic::Atomic>,
    ) -> error::Result<Self> {
        let atom = cast_or_promote_atomic(self, xs)?;
        let schema_type = atom.schema_type();
        if schema_type.derives_from(xs) || schema_type.matches(xs) {
            Ok(atom)
        } else {
            Err(error::Error::XPTY0004)
        }
    }
}

#[cfg(test)]
mod tests {

    use super::*;

    use ibig::ibig;
    use xee_name::Namespaces;
    use xee_xpath_ast::parse_sequence_type;

    #[test]
    fn test_one_integer() {
        let namespaces = Namespaces::default();
        let sequence_type = parse_sequence_type("xs:integer", &namespaces).unwrap();

        let right_sequence: Sequence = vec![ibig!(1)].into();
        let wrong_amount_sequence: Sequence = vec![ibig!(1), ibig!(2)].into();
        let wrong_type_sequence: Sequence = vec![false].into();
        let xot = Xot::new();

        let right_result = right_sequence.clone().sequence_type_matching(
            &sequence_type,
            &xot,
            &|_| unreachable!(),
        );
        assert_eq!(&right_result.unwrap(), &right_sequence);

        let wrong_amount_result =
            wrong_amount_sequence.sequence_type_matching(&sequence_type, &xot, &|_| unreachable!());
        assert_eq!(wrong_amount_result, Err(error::Error::XPTY0004));
        let wrong_type_result =
            wrong_type_sequence.sequence_type_matching(&sequence_type, &xot, &|_| unreachable!());
        assert_eq!(wrong_type_result, Err(error::Error::XPTY0004));
    }

    #[test]
    fn test_one_long_matches_integer() {
        let namespaces = Namespaces::default();
        let sequence_type = parse_sequence_type("xs:integer", &namespaces).unwrap();

        let right_sequence = Sequence::from(vec![Item::from(1i64)]);
        let wrong_amount_sequence = Sequence::from(vec![Item::from(1i64), Item::from(1i64)]);
        let wrong_type_sequence = Sequence::from(vec![Item::from(atomic::Atomic::from(false))]);
        let xot = Xot::new();

        let right_result = right_sequence.clone().sequence_type_matching(
            &sequence_type,
            &xot,
            &|_| unreachable!(),
        );
        assert_eq!(right_result, Ok(right_sequence));
        let wrong_amount_result =
            wrong_amount_sequence.sequence_type_matching(&sequence_type, &xot, &|_| unreachable!());
        assert_eq!(wrong_amount_result, Err(error::Error::XPTY0004));
        let wrong_type_result =
            wrong_type_sequence.sequence_type_matching(&sequence_type, &xot, &|_| unreachable!());
        assert_eq!(wrong_type_result, Err(error::Error::XPTY0004));
    }

    #[test]
    fn test_one_any_atomic() {
        let namespaces = Namespaces::default();
        let sequence_type = parse_sequence_type("xs:anyAtomicType", &namespaces).unwrap();

        let right_sequence = Sequence::from(vec![Item::from(atomic::Atomic::from(1i64))]);
        let wrong_amount_sequence =
            Sequence::from(vec![Item::from(ibig!(1)), Item::from(ibig!(2))]);
        let right_type_sequence2 = Sequence::from(vec![Item::from(atomic::Atomic::from(false))]);
        let xot = Xot::new();

        let right_result = right_sequence.clone().sequence_type_matching(
            &sequence_type,
            &xot,
            &|_| unreachable!(),
        );
        assert_eq!(right_result, Ok(right_sequence));
        let wrong_amount_result =
            wrong_amount_sequence.sequence_type_matching(&sequence_type, &xot, &|_| unreachable!());
        assert_eq!(wrong_amount_result, Err(error::Error::XPTY0004));
        let right_type_result2 = right_type_sequence2.clone().sequence_type_matching(
            &sequence_type,
            &xot,
            &|_| unreachable!(),
        );
        assert_eq!(right_type_result2, Ok(right_type_sequence2));
    }

    #[test]
    fn test_one_item() {
        let namespaces = Namespaces::default();
        let sequence_type = parse_sequence_type("item()", &namespaces).unwrap();
        let mut xot = Xot::new();
        let root = xot.parse("<doc/>").unwrap();
        let node = xot.document_element(root).unwrap();
        let right_sequence = Sequence::from(vec![Item::from(atomic::Atomic::from(1i64))]);
        let wrong_amount_sequence = Sequence::from(vec![
            Item::from(atomic::Atomic::from(1i64)),
            Item::from(atomic::Atomic::from(2i64)),
        ]);
        let right_type_sequence2 = Sequence::from(vec![Item::from(node)]);

        let right_result = right_sequence.clone().sequence_type_matching(
            &sequence_type,
            &xot,
            &|_| unreachable!(),
        );
        assert_eq!(right_result, Ok(right_sequence));

        let wrong_amount_result =
            wrong_amount_sequence.sequence_type_matching(&sequence_type, &xot, &|_| unreachable!());
        assert_eq!(wrong_amount_result, Err(error::Error::XPTY0004));
        let right_type_result2 = right_type_sequence2.clone().sequence_type_matching(
            &sequence_type,
            &xot,
            &|_| unreachable!(),
        );
        assert_eq!(right_type_result2, Ok(right_type_sequence2));
    }

    #[test]
    fn test_option_integer() {
        let namespaces = Namespaces::default();
        let sequence_type = parse_sequence_type("xs:integer?", &namespaces).unwrap();

        let right_sequence = Sequence::from(vec![Item::from(atomic::Atomic::from(ibig!(1)))]);
        let wrong_amount_sequence =
            Sequence::from(vec![Item::from(ibig!(1)), Item::from(ibig!(2))]);
        let right_empty_sequence = Sequence::default();
        let xot = Xot::new();

        let right_result = right_sequence.clone().sequence_type_matching(
            &sequence_type,
            &xot,
            &|_| unreachable!(),
        );
        assert_eq!(right_result, Ok(right_sequence));
        let wrong_amount_result =
            wrong_amount_sequence.sequence_type_matching(&sequence_type, &xot, &|_| unreachable!());
        assert_eq!(wrong_amount_result, Err(error::Error::XPTY0004));
        let right_empty_result = right_empty_sequence.clone().sequence_type_matching(
            &sequence_type,
            &xot,
            &|_| unreachable!(),
        );
        assert_eq!(right_empty_result, Ok(right_empty_sequence));
    }

    #[test]
    fn test_many_integer() {
        let namespaces = Namespaces::default();
        let sequence_type = parse_sequence_type("xs:integer*", &namespaces).unwrap();

        let right_sequence = Sequence::from(vec![Item::from(atomic::Atomic::from(ibig!(1)))]);
        let right_multi_sequence = Sequence::from(vec![Item::from(ibig!(1)), Item::from(ibig!(2))]);
        let right_empty_sequence = Sequence::default();
        let xot = Xot::new();

        let right_result = right_sequence.clone().sequence_type_matching(
            &sequence_type,
            &xot,
            &|_| unreachable!(),
        );
        assert_eq!(right_result, Ok(right_sequence));

        let right_multi_result = right_multi_sequence.clone().sequence_type_matching(
            &sequence_type,
            &xot,
            &|_| unreachable!(),
        );
        assert_eq!(right_multi_result, Ok(right_multi_sequence));

        let right_empty_result = right_empty_sequence.clone().sequence_type_matching(
            &sequence_type,
            &xot,
            &|_| unreachable!(),
        );
        assert_eq!(right_empty_result, Ok(right_empty_sequence));
    }

    #[test]
    fn test_many_node() {
        let namespaces = Namespaces::default();
        let sequence_type = parse_sequence_type("node()*", &namespaces).unwrap();

        let mut xot = Xot::new();
        let doc = xot.parse(r#"<doc><a attr="Attr">A</a><b/></doc>"#).unwrap();
        let doc = xot.document_element(doc).unwrap();
        let a = xot.first_child(doc).unwrap();
        let b = xot.next_sibling(a).unwrap();
        let text = xot.first_child(a).unwrap();
        let attr = xot
            .attributes(a)
            .get_node(xot.name("attr").unwrap())
            .unwrap();

        let right_sequence = Sequence::from(vec![
            Item::from(doc),
            Item::from(a),
            Item::from(b),
            Item::from(text),
            Item::from(attr),
        ]);

        let wrong_sequence = Sequence::from(vec![Item::from(ibig!(1))]);

        let right_result = right_sequence.clone().sequence_type_matching(
            &sequence_type,
            &xot,
            &|_| unreachable!(),
        );
        assert_eq!(right_result, Ok(right_sequence));

        let wrong_result =
            wrong_sequence.sequence_type_matching(&sequence_type, &xot, &|_| unreachable!());
        assert_eq!(wrong_result, Err(error::Error::XPTY0004));
    }

    #[test]
    fn test_many_element() {
        let namespaces = Namespaces::default();
        let sequence_type = parse_sequence_type("element()*", &namespaces).unwrap();

        let mut xot = Xot::new();
        let doc = xot.parse(r#"<doc><a attr="Attr">A</a><b/></doc>"#).unwrap();
        let doc = xot.document_element(doc).unwrap();
        let a = xot.first_child(doc).unwrap();
        let b = xot.next_sibling(a).unwrap();
        let text = xot.first_child(a).unwrap();
        let attr = xot
            .attributes(a)
            .get_node(xot.name("attr").unwrap())
            .unwrap();

        let right_sequence = Sequence::from(vec![Item::from(doc), Item::from(a), Item::from(b)]);

        let wrong_sequence_text = Sequence::from(vec![Item::from(text)]);
        let wrong_sequence_attr = Sequence::from(vec![Item::from(attr)]);

        let right_result = right_sequence.clone().sequence_type_matching(
            &sequence_type,
            &xot,
            &|_| unreachable!(),
        );
        assert_eq!(right_result, Ok(right_sequence));

        let wrong_result =
            wrong_sequence_text.sequence_type_matching(&sequence_type, &xot, &|_| unreachable!());
        assert_eq!(wrong_result, Err(error::Error::XPTY0004));
        let wrong_result =
            wrong_sequence_attr.sequence_type_matching(&sequence_type, &xot, &|_| unreachable!());
        assert_eq!(wrong_result, Err(error::Error::XPTY0004));
    }

    #[test]
    fn test_many_atomized_promote() {
        let namespaces = Namespaces::default();
        let sequence_type = parse_sequence_type("xs:double*", &namespaces).unwrap();

        // integers count as decimals, so should be promoted to a double
        let right_sequence = Sequence::from(vec![Item::from(ibig!(1)), Item::from(ibig!(2))]);

        let static_context = context::StaticContext::default();
        let xot = Xot::new();
        let right_result = right_sequence.sequence_type_matching_function_conversion(
            &sequence_type,
            &static_context,
            &xot,
            &|_| unreachable!(),
        );
        // atomization has changed the result sequence
        assert_eq!(
            right_result,
            Ok(Sequence::from(vec![
                Item::from(atomic::Atomic::from(1f64)),
                Item::from(atomic::Atomic::from(2f64)),
            ]))
        );
    }

    #[test]
    fn test_many_cast_untyped() {
        let namespaces = Namespaces::default();
        let sequence_type = parse_sequence_type("xs:integer*", &namespaces).unwrap();

        let mut xot = Xot::new();
        let doc = xot.parse(r#"<doc><a>1</a><b>2</b></doc>"#).unwrap();
        let doc = xot.document_element(doc).unwrap();
        let a = xot.first_child(doc).unwrap();
        let b = xot.next_sibling(a).unwrap();

        let right_sequence = Sequence::from(vec![Item::from(a), Item::from(b)]);

        let static_context = context::StaticContext::default();

        let right_result = right_sequence.sequence_type_matching_function_conversion(
            &sequence_type,
            &static_context,
            &xot,
            &|_| unreachable!(),
        );
        // atomization has changed the result sequence
        assert_eq!(
            right_result,
            Ok(Sequence::from(vec![
                Item::from(atomic::Atomic::from(ibig!(1))),
                Item::from(atomic::Atomic::from(ibig!(2))),
            ]))
        );
    }

    #[test]
    fn test_any_function_test() {
        let namespaces = Namespaces::default();
        let sequence_type = parse_sequence_type("function(*)", &namespaces).unwrap();
        let function =
            function::StaticFunctionData::new(function::StaticFunctionId(1), vec![]).into();
        let right_sequence = Sequence::from(vec![Item::Function(function)]);

        let signature = function::Signature::new(
            vec![Some(
                parse_sequence_type("xs:integer", &namespaces).unwrap(),
            )],
            Some(parse_sequence_type("xs:integer", &namespaces).unwrap()),
        );

        let xot = Xot::new();

        let right_result =
            right_sequence
                .clone()
                .sequence_type_matching(&sequence_type, &xot, &|_| &signature);
        assert_eq!(&right_result.unwrap(), &right_sequence);
    }

    #[test]
    fn test_function_test_same_parameters() {
        let namespaces = Namespaces::default();
        let sequence_type =
            parse_sequence_type("function(xs:integer) as xs:integer", &namespaces).unwrap();
        let function =
            function::StaticFunctionData::new(function::StaticFunctionId(1), vec![]).into();
        let right_sequence = Sequence::from(vec![Item::Function(function)]);

        let signature = function::Signature::new(
            vec![Some(
                parse_sequence_type("xs:integer", &namespaces).unwrap(),
            )],
            Some(parse_sequence_type("xs:integer", &namespaces).unwrap()),
        );

        let xot = Xot::new();

        let right_result =
            right_sequence
                .clone()
                .sequence_type_matching(&sequence_type, &xot, &|_| &signature);
        assert_eq!(&right_result.unwrap(), &right_sequence);
    }

    #[test]
    fn test_function_test_derived_parameters() {
        let namespaces = Namespaces::default();
        let sequence_type =
            parse_sequence_type("function(xs:integer) as xs:integer", &namespaces).unwrap();
        let function =
            function::StaticFunctionData::new(function::StaticFunctionId(1), vec![]).into();
        let right_sequence = Sequence::from(vec![Item::Function(function)]);

        let signature = function::Signature::new(
            vec![Some(
                parse_sequence_type("xs:integer", &namespaces).unwrap(),
            )],
            Some(parse_sequence_type("xs:integer", &namespaces).unwrap()),
        );

        let xot = Xot::new();

        let right_result =
            right_sequence
                .clone()
                .sequence_type_matching(&sequence_type, &xot, &|_| &signature);
        assert_eq!(&right_result.unwrap(), &right_sequence);
    }

    #[test]
    fn test_function_test_wrong_arity() {
        let namespaces = Namespaces::default();
        let sequence_type =
            parse_sequence_type("function(xs:integer) as xs:integer", &namespaces).unwrap();
        let function =
            function::StaticFunctionData::new(function::StaticFunctionId(1), vec![]).into();
        let wrong_sequence = Sequence::from(vec![Item::Function(function)]);

        let signature = function::Signature::new(
            vec![
                Some(parse_sequence_type("xs:integer", &namespaces).unwrap()),
                Some(parse_sequence_type("xs:integer", &namespaces).unwrap()),
            ],
            Some(parse_sequence_type("xs:integer", &namespaces).unwrap()),
        );

        let xot = Xot::new();

        let wrong_result =
            wrong_sequence
                .clone()
                .sequence_type_matching(&sequence_type, &xot, &|_| &signature);
        assert_eq!(wrong_result, Err(error::Error::XPTY0004));
    }
}