mago_codex/ttype/

mod.rs

use std::borrow::Cow;
use std::rc::Rc;
use std::sync::Arc;

use mago_atom::Atom;
use mago_atom::atom;

use crate::metadata::CodebaseMetadata;
use crate::metadata::class_like::ClassLikeMetadata;
use crate::misc::GenericParent;
use crate::ttype::atomic::TAtomic;
use crate::ttype::atomic::array::TArray;
use crate::ttype::atomic::array::keyed::TKeyedArray;
use crate::ttype::atomic::array::list::TList;
use crate::ttype::atomic::generic::TGenericParameter;
use crate::ttype::atomic::iterable::TIterable;
use crate::ttype::atomic::object::TObject;
use crate::ttype::atomic::object::named::TNamedObject;
use crate::ttype::atomic::scalar::TScalar;
use crate::ttype::atomic::scalar::class_like_string::TClassLikeString;
use crate::ttype::atomic::scalar::class_like_string::TClassLikeStringKind;
use crate::ttype::atomic::scalar::int::TInteger;
use crate::ttype::atomic::scalar::string::TString;
use crate::ttype::atomic::scalar::string::TStringCasing;
use crate::ttype::atomic::scalar::string::TStringLiteral;
use crate::ttype::comparator::ComparisonResult;
use crate::ttype::comparator::union_comparator;
use crate::ttype::expander::TypeExpansionOptions;
use crate::ttype::resolution::TypeResolutionContext;
use crate::ttype::shared::ARRAYKEY_ATOMIC;
use crate::ttype::shared::BOOL_ATOMIC;
use crate::ttype::shared::CALLABLE_STRING_ATOMIC;
use crate::ttype::shared::CLASS_STRING_ATOMIC;
use crate::ttype::shared::CLOSED_RESOURCE_ATOMIC;
use crate::ttype::shared::EMPTY_KEYED_ARRAY_ATOMIC;
use crate::ttype::shared::EMPTY_STRING_ATOMIC;
use crate::ttype::shared::ENUM_STRING_ATOMIC;
use crate::ttype::shared::FALSE_ATOMIC;
use crate::ttype::shared::FLOAT_ATOMIC;
use crate::ttype::shared::INT_ATOMIC;
use crate::ttype::shared::INT_FLOAT_ATOMIC_SLICE;
use crate::ttype::shared::INT_STRING_ATOMIC_SLICE;
use crate::ttype::shared::INTERFACE_STRING_ATOMIC;
use crate::ttype::shared::ISSET_FROM_LOOP_MIXED_ATOMIC;
use crate::ttype::shared::LOWERCASE_CALLABLE_STRING_ATOMIC;
use crate::ttype::shared::LOWERCASE_STRING_ATOMIC;
use crate::ttype::shared::MINUS_ONE_INT_ATOMIC;
use crate::ttype::shared::MIXED_ATOMIC;
use crate::ttype::shared::MIXED_CALLABLE_ATOMIC;
use crate::ttype::shared::MIXED_CLOSURE_ATOMIC;
use crate::ttype::shared::MIXED_ITERABLE_ATOMIC;
use crate::ttype::shared::NEGATIVE_INT_ATOMIC;
use crate::ttype::shared::NEVER_ATOMIC;
use crate::ttype::shared::NON_EMPTY_LOWERCASE_STRING_ATOMIC;
use crate::ttype::shared::NON_EMPTY_STRING_ATOMIC;
use crate::ttype::shared::NON_EMPTY_UNSPECIFIED_LITERAL_STRING_ATOMIC;
use crate::ttype::shared::NON_EMPTY_UPPERCASE_STRING_ATOMIC;
use crate::ttype::shared::NON_NEGATIVE_INT_ATOMIC;
use crate::ttype::shared::NON_POSITIVE_INT_ATOMIC;
use crate::ttype::shared::NULL_ATOMIC;
use crate::ttype::shared::NULL_FLOAT_ATOMIC_SLICE;
use crate::ttype::shared::NULL_INT_ATOMIC_SLICE;
use crate::ttype::shared::NULL_OBJECT_ATOMIC_SLICE;
use crate::ttype::shared::NULL_SCALAR_ATOMIC_SLICE;
use crate::ttype::shared::NULL_STRING_ATOMIC_SLICE;
use crate::ttype::shared::NUMERIC_ATOMIC;
use crate::ttype::shared::NUMERIC_STRING_ATOMIC;
use crate::ttype::shared::NUMERIC_TRUTHY_STRING_ATOMIC;
use crate::ttype::shared::OBJECT_ATOMIC;
use crate::ttype::shared::ONE_INT_ATOMIC;
use crate::ttype::shared::OPEN_RESOURCE_ATOMIC;
use crate::ttype::shared::PLACEHOLDER_ATOMIC;
use crate::ttype::shared::POSITIVE_INT_ATOMIC;
use crate::ttype::shared::RESOURCE_ATOMIC;
use crate::ttype::shared::SCALAR_ATOMIC;
use crate::ttype::shared::SIGNUM_RESULT_SLICE;
use crate::ttype::shared::STRING_ATOMIC;
use crate::ttype::shared::TRAIT_STRING_ATOMIC;
use crate::ttype::shared::TRUE_ATOMIC;
use crate::ttype::shared::TRUTHY_LOWERCASE_STRING_ATOMIC;
use crate::ttype::shared::TRUTHY_MIXED_ATOMIC;
use crate::ttype::shared::TRUTHY_STRING_ATOMIC;
use crate::ttype::shared::TRUTHY_UPPERCASE_STRING_ATOMIC;
use crate::ttype::shared::UNSPECIFIED_LITERAL_FLOAT_ATOMIC;
use crate::ttype::shared::UNSPECIFIED_LITERAL_INT_ATOMIC;
use crate::ttype::shared::UNSPECIFIED_LITERAL_STRING_ATOMIC;
use crate::ttype::shared::UPPERCASE_CALLABLE_STRING_ATOMIC;
use crate::ttype::shared::UPPERCASE_STRING_ATOMIC;
use crate::ttype::shared::VOID_ATOMIC;
use crate::ttype::shared::ZERO_INT_ATOMIC;
use crate::ttype::template::TemplateResult;
use crate::ttype::template::inferred_type_replacer;
use crate::ttype::union::TUnion;

pub mod atomic;
pub mod builder;
pub mod cast;
pub mod combination;
pub mod combiner;
pub mod comparator;
pub mod error;
pub mod expander;
pub mod flags;
pub mod resolution;
pub mod shared;
pub mod template;
pub mod union;

/// A reference to a type in the type system, which can be either a union or an atomic type.
#[derive(Clone, Copy, Debug)]
pub enum TypeRef<'a> {
    Union(&'a TUnion),
    Atomic(&'a TAtomic),
}

/// A trait to be implemented by all types in the type system.
pub trait TType {
    /// Returns a vector of child type nodes that this type contains.
    fn get_child_nodes(&self) -> Vec<TypeRef<'_>> {
        vec![]
    }

    /// Returns a vector of all child type nodes, including nested ones.
    fn get_all_child_nodes(&self) -> Vec<TypeRef<'_>> {
        let mut child_nodes = self.get_child_nodes();
        let mut all_child_nodes = Vec::with_capacity(16);

        while let Some(child_node) = child_nodes.pop() {
            let new_child_nodes = match child_node {
                TypeRef::Union(union) => union.get_child_nodes(),
                TypeRef::Atomic(atomic) => atomic.get_child_nodes(),
            };

            all_child_nodes.push(child_node);

            child_nodes.extend(new_child_nodes);
        }

        all_child_nodes
    }

    /// Checks if this type can have intersection types (`&B&S`).
    fn can_be_intersected(&self) -> bool {
        false
    }

    /// Returns a slice of the additional intersection types (`&B&S`), if any. Contains boxed atomic types.
    fn get_intersection_types(&self) -> Option<&[TAtomic]> {
        None
    }

    /// Returns a mutable slice of the additional intersection types (`&B&S`), if any. Contains boxed atomic types.
    fn get_intersection_types_mut(&mut self) -> Option<&mut Vec<TAtomic>> {
        None
    }

    /// Checks if this type has intersection types.
    fn has_intersection_types(&self) -> bool {
        false
    }

    /// Adds an intersection type to this type.
    ///
    /// Returns `true` if the intersection type was added successfully,
    ///  or `false` if this type does not support intersection types.
    fn add_intersection_type(&mut self, _intersection_type: TAtomic) -> bool {
        false
    }

    fn needs_population(&self) -> bool;

    fn is_expandable(&self) -> bool;

    /// Returns true if this type has complex structure that benefits from
    /// multiline formatting when used as a generic parameter.
    fn is_complex(&self) -> bool;

    /// Return a human-readable atom for this type, which is
    /// suitable for use in error messages or debugging.
    ///
    /// The resulting identifier must be unique for the type,
    /// but it does not have to be globally unique.
    fn get_id(&self) -> Atom;

    fn get_pretty_id(&self) -> Atom {
        self.get_pretty_id_with_indent(0)
    }

    fn get_pretty_id_with_indent(&self, indent: usize) -> Atom;
}

/// Implements the `TType` trait for `TypeRef`.
impl<'a> TType for TypeRef<'a> {
    fn get_child_nodes(&self) -> Vec<TypeRef<'a>> {
        match self {
            TypeRef::Union(ttype) => ttype.get_child_nodes(),
            TypeRef::Atomic(ttype) => ttype.get_child_nodes(),
        }
    }

    fn can_be_intersected(&self) -> bool {
        match self {
            TypeRef::Union(ttype) => ttype.can_be_intersected(),
            TypeRef::Atomic(ttype) => ttype.can_be_intersected(),
        }
    }

    fn get_intersection_types(&self) -> Option<&[TAtomic]> {
        match self {
            TypeRef::Union(ttype) => ttype.get_intersection_types(),
            TypeRef::Atomic(ttype) => ttype.get_intersection_types(),
        }
    }

    fn has_intersection_types(&self) -> bool {
        match self {
            TypeRef::Union(ttype) => ttype.has_intersection_types(),
            TypeRef::Atomic(ttype) => ttype.has_intersection_types(),
        }
    }

    fn needs_population(&self) -> bool {
        match self {
            TypeRef::Union(ttype) => ttype.needs_population(),
            TypeRef::Atomic(ttype) => ttype.needs_population(),
        }
    }

    fn is_expandable(&self) -> bool {
        match self {
            TypeRef::Union(ttype) => ttype.is_expandable(),
            TypeRef::Atomic(ttype) => ttype.is_expandable(),
        }
    }

    fn is_complex(&self) -> bool {
        match self {
            TypeRef::Union(ttype) => ttype.is_complex(),
            TypeRef::Atomic(ttype) => ttype.is_complex(),
        }
    }

    fn get_id(&self) -> Atom {
        match self {
            TypeRef::Union(ttype) => ttype.get_id(),
            TypeRef::Atomic(ttype) => ttype.get_id(),
        }
    }

    fn get_pretty_id_with_indent(&self, indent: usize) -> Atom {
        match self {
            TypeRef::Union(ttype) => ttype.get_pretty_id_with_indent(indent),
            TypeRef::Atomic(ttype) => ttype.get_pretty_id_with_indent(indent),
        }
    }
}

impl<'a> From<&'a TUnion> for TypeRef<'a> {
    fn from(reference: &'a TUnion) -> Self {
        TypeRef::Union(reference)
    }
}

impl<'a> From<&'a TAtomic> for TypeRef<'a> {
    fn from(reference: &'a TAtomic) -> Self {
        TypeRef::Atomic(reference)
    }
}

/// Creates a `TUnion` from a `TInteger`, using a canonical static type where possible.
///
/// This function is a key optimization point. It checks if the provided `TInteger`
/// matches a common, reusable form (like "any integer" or "a positive integer").
/// If it does, it returns a zero-allocation `TUnion` that borrows a static,
/// shared instance.
///
/// For specific literal values or ranges that do not have a canonical static
/// representation, it falls back to creating a new, owned `TUnion`, which
/// involves a heap allocation.
#[must_use]
pub fn get_union_from_integer(integer: &TInteger) -> TUnion {
    if integer.is_unspecified() {
        return get_int();
    }

    if integer.is_positive() {
        return get_positive_int();
    }

    if integer.is_negative() {
        return get_negative_int();
    }

    if integer.is_non_negative() {
        return get_non_negative_int();
    }

    if integer.is_non_positive() {
        return get_non_positive_int();
    }

    TUnion::from_single(Cow::Owned(TAtomic::Scalar(TScalar::Integer(*integer))))
}

#[inline]
#[must_use]
pub fn wrap_atomic(tinner: TAtomic) -> TUnion {
    TUnion::from_single(Cow::Owned(tinner))
}

#[inline]
#[must_use]
pub fn get_int() -> TUnion {
    TUnion::from_single(Cow::Borrowed(INT_ATOMIC))
}

#[inline]
#[must_use]
pub fn get_positive_int() -> TUnion {
    TUnion::from_single(Cow::Borrowed(POSITIVE_INT_ATOMIC))
}

#[inline]
#[must_use]
pub fn get_negative_int() -> TUnion {
    TUnion::from_single(Cow::Borrowed(NEGATIVE_INT_ATOMIC))
}

#[inline]
#[must_use]
pub fn get_non_positive_int() -> TUnion {
    TUnion::from_single(Cow::Borrowed(NON_POSITIVE_INT_ATOMIC))
}

#[inline]
#[must_use]
pub fn get_non_negative_int() -> TUnion {
    TUnion::from_single(Cow::Borrowed(NON_NEGATIVE_INT_ATOMIC))
}

#[inline]
#[must_use]
pub fn get_non_zero_int() -> TUnion {
    TUnion::from_vec(vec![
        TAtomic::Scalar(TScalar::Integer(TInteger::negative())),
        TAtomic::Scalar(TScalar::Integer(TInteger::positive())),
    ])
}

#[inline]
#[must_use]
pub fn get_unspecified_literal_int() -> TUnion {
    TUnion::from_single(Cow::Borrowed(UNSPECIFIED_LITERAL_INT_ATOMIC))
}

#[inline]
#[must_use]
pub fn get_unspecified_literal_float() -> TUnion {
    TUnion::from_single(Cow::Borrowed(UNSPECIFIED_LITERAL_FLOAT_ATOMIC))
}

#[inline]
#[must_use]
pub fn get_int_range(from: Option<i64>, to: Option<i64>) -> TUnion {
    let atomic = match (from, to) {
        (Some(from), Some(to)) => TAtomic::Scalar(TScalar::Integer(TInteger::Range(from, to))),
        (Some(from), None) => {
            if 0 == from {
                return get_non_negative_int();
            }

            if 1 == from {
                return get_positive_int();
            }

            TAtomic::Scalar(TScalar::Integer(TInteger::From(from)))
        }
        (None, Some(to)) => {
            if 0 == to {
                return get_non_positive_int();
            }

            if -1 == to {
                return get_negative_int();
            }

            TAtomic::Scalar(TScalar::Integer(TInteger::To(to)))
        }
        (None, None) => return get_int(),
    };

    TUnion::from_single(Cow::Owned(atomic))
}

/// Returns a zero-allocation `TUnion` for the type `-1|0|1`.
#[inline]
#[must_use]
pub fn get_signum_result() -> TUnion {
    TUnion::new(Cow::Borrowed(SIGNUM_RESULT_SLICE))
}

/// Returns a zero-allocation `TUnion` for the integer literal `1`.
#[inline]
#[must_use]
pub fn get_one_int() -> TUnion {
    TUnion::from_single(Cow::Borrowed(ONE_INT_ATOMIC))
}

/// Returns a zero-allocation `TUnion` for the integer literal `0`.
#[inline]
#[must_use]
pub fn get_zero_int() -> TUnion {
    TUnion::from_single(Cow::Borrowed(ZERO_INT_ATOMIC))
}

/// Returns a zero-allocation `TUnion` for the integer literal `-1`.
#[inline]
#[must_use]
pub fn get_minus_one_int() -> TUnion {
    TUnion::from_single(Cow::Borrowed(MINUS_ONE_INT_ATOMIC))
}

#[inline]
#[must_use]
pub fn get_literal_int(value: i64) -> TUnion {
    if value == 0 {
        return get_zero_int();
    }

    if value == 1 {
        return get_one_int();
    }

    if value == -1 {
        return get_minus_one_int();
    }

    TUnion::from_single(Cow::Owned(TAtomic::Scalar(TScalar::literal_int(value))))
}

#[inline]
#[must_use]
pub fn get_int_or_float() -> TUnion {
    TUnion::new(Cow::Borrowed(INT_FLOAT_ATOMIC_SLICE))
}

#[inline]
#[must_use]
pub fn get_int_or_string() -> TUnion {
    TUnion::new(Cow::Borrowed(INT_STRING_ATOMIC_SLICE))
}

#[inline]
#[must_use]
pub fn get_nullable_int() -> TUnion {
    TUnion::new(Cow::Borrowed(NULL_INT_ATOMIC_SLICE))
}

#[inline]
#[must_use]
pub fn get_nullable_float() -> TUnion {
    TUnion::new(Cow::Borrowed(NULL_FLOAT_ATOMIC_SLICE))
}

#[inline]
#[must_use]
pub fn get_nullable_object() -> TUnion {
    TUnion::new(Cow::Borrowed(NULL_OBJECT_ATOMIC_SLICE))
}

#[inline]
#[must_use]
pub fn get_nullable_string() -> TUnion {
    TUnion::new(Cow::Borrowed(NULL_STRING_ATOMIC_SLICE))
}

#[inline]
#[must_use]
pub fn get_string() -> TUnion {
    TUnion::from_single(Cow::Borrowed(STRING_ATOMIC))
}

/// Returns a zero-allocation `TUnion` for a `string` with the specified properties.
///
/// This function maps all possible boolean property combinations to a canonical,
/// static `TAtomic` instance, avoiding heap allocations for common string types.
#[must_use]
pub fn get_string_with_props(
    is_numeric: bool,
    is_truthy: bool,
    is_non_empty: bool,
    is_callable: bool,
    casing: TStringCasing,
) -> TUnion {
    if is_callable {
        return match casing {
            TStringCasing::Lowercase => TUnion::from_single(Cow::Borrowed(LOWERCASE_CALLABLE_STRING_ATOMIC)),
            TStringCasing::Uppercase => TUnion::from_single(Cow::Borrowed(UPPERCASE_CALLABLE_STRING_ATOMIC)),
            TStringCasing::Unspecified => TUnion::from_single(Cow::Borrowed(CALLABLE_STRING_ATOMIC)),
        };
    }

    let atomic_ref = match (is_numeric, is_truthy, is_non_empty, casing) {
        // is_numeric = true
        (true, true, _, _) => NUMERIC_TRUTHY_STRING_ATOMIC,
        (true, false, _, _) => NUMERIC_STRING_ATOMIC,
        // is_numeric = false, is_truthy = true
        (false, true, _, TStringCasing::Unspecified) => TRUTHY_STRING_ATOMIC,
        (false, true, _, TStringCasing::Uppercase) => TRUTHY_UPPERCASE_STRING_ATOMIC,
        (false, true, _, TStringCasing::Lowercase) => TRUTHY_LOWERCASE_STRING_ATOMIC,
        // is_numeric = false, is_truthy = false
        (false, false, false, TStringCasing::Unspecified) => STRING_ATOMIC,
        (false, false, false, TStringCasing::Uppercase) => UPPERCASE_STRING_ATOMIC,
        (false, false, false, TStringCasing::Lowercase) => LOWERCASE_STRING_ATOMIC,
        (false, false, true, TStringCasing::Unspecified) => NON_EMPTY_STRING_ATOMIC,
        (false, false, true, TStringCasing::Uppercase) => NON_EMPTY_UPPERCASE_STRING_ATOMIC,
        (false, false, true, TStringCasing::Lowercase) => NON_EMPTY_LOWERCASE_STRING_ATOMIC,
    };

    TUnion::from_single(Cow::Borrowed(atomic_ref))
}

#[inline]
#[must_use]
pub fn get_literal_class_string(value: Atom) -> TUnion {
    TUnion::from_single(Cow::Owned(TAtomic::Scalar(TScalar::ClassLikeString(TClassLikeString::literal(value)))))
}

#[inline]
#[must_use]
pub fn get_class_string() -> TUnion {
    TUnion::from_single(Cow::Borrowed(CLASS_STRING_ATOMIC))
}

#[inline]
#[must_use]
pub fn get_class_string_of_type(constraint: TAtomic) -> TUnion {
    TUnion::from_single(Cow::Owned(TAtomic::Scalar(TScalar::ClassLikeString(TClassLikeString::class_string_of_type(
        constraint,
    )))))
}

#[inline]
#[must_use]
pub fn get_interface_string() -> TUnion {
    TUnion::from_single(Cow::Borrowed(INTERFACE_STRING_ATOMIC))
}

#[inline]
#[must_use]
pub fn get_interface_string_of_type(constraint: TAtomic) -> TUnion {
    TUnion::from_single(Cow::Owned(TAtomic::Scalar(TScalar::ClassLikeString(
        TClassLikeString::interface_string_of_type(constraint),
    ))))
}

#[inline]
#[must_use]
pub fn get_enum_string() -> TUnion {
    TUnion::from_single(Cow::Borrowed(ENUM_STRING_ATOMIC))
}

#[inline]
#[must_use]
pub fn get_enum_string_of_type(constraint: TAtomic) -> TUnion {
    TUnion::from_single(Cow::Owned(TAtomic::Scalar(TScalar::ClassLikeString(TClassLikeString::enum_string_of_type(
        constraint,
    )))))
}

#[inline]
#[must_use]
pub fn get_trait_string() -> TUnion {
    TUnion::from_single(Cow::Borrowed(TRAIT_STRING_ATOMIC))
}

#[inline]
#[must_use]
pub fn get_trait_string_of_type(constraint: TAtomic) -> TUnion {
    TUnion::from_single(Cow::Owned(TAtomic::Scalar(TScalar::ClassLikeString(TClassLikeString::trait_string_of_type(
        constraint,
    )))))
}

#[inline]
#[must_use]
pub fn get_literal_string(value: Atom) -> TUnion {
    TUnion::from_single(Cow::Owned(TAtomic::Scalar(TScalar::literal_string(value))))
}

#[inline]
#[must_use]
pub fn get_float() -> TUnion {
    TUnion::from_single(Cow::Borrowed(FLOAT_ATOMIC))
}

#[inline]
#[must_use]
pub fn get_literal_float(v: f64) -> TUnion {
    TUnion::from_single(Cow::Owned(TAtomic::Scalar(TScalar::literal_float(v))))
}

#[inline]
#[must_use]
pub fn get_mixed() -> TUnion {
    TUnion::from_single(Cow::Borrowed(MIXED_ATOMIC))
}

#[inline]
#[must_use]
pub fn get_truthy_mixed() -> TUnion {
    TUnion::from_single(Cow::Borrowed(TRUTHY_MIXED_ATOMIC))
}

#[inline]
#[must_use]
pub fn get_isset_from_mixed_mixed() -> TUnion {
    TUnion::from_single(Cow::Borrowed(ISSET_FROM_LOOP_MIXED_ATOMIC))
}

#[must_use]
pub fn get_mixed_maybe_from_loop(from_loop_isset: bool) -> TUnion {
    if from_loop_isset { get_isset_from_mixed_mixed() } else { get_mixed() }
}

#[inline]
#[must_use]
pub fn get_never() -> TUnion {
    TUnion::from_single(Cow::Borrowed(NEVER_ATOMIC))
}

#[inline]
#[must_use]
pub fn get_resource() -> TUnion {
    TUnion::from_single(Cow::Borrowed(RESOURCE_ATOMIC))
}

#[inline]
#[must_use]
pub fn get_closed_resource() -> TUnion {
    TUnion::from_single(Cow::Borrowed(CLOSED_RESOURCE_ATOMIC))
}

#[inline]
#[must_use]
pub fn get_open_resource() -> TUnion {
    TUnion::from_single(Cow::Borrowed(OPEN_RESOURCE_ATOMIC))
}

#[inline]
#[must_use]
pub fn get_placeholder() -> TUnion {
    TUnion::from_single(Cow::Borrowed(PLACEHOLDER_ATOMIC))
}

#[inline]
#[must_use]
pub fn get_void() -> TUnion {
    TUnion::from_single(Cow::Borrowed(VOID_ATOMIC))
}

#[inline]
#[must_use]
pub fn get_null() -> TUnion {
    TUnion::from_single(Cow::Borrowed(NULL_ATOMIC))
}

#[inline]
#[must_use]
pub fn get_undefined_null() -> TUnion {
    let mut null = TUnion::from_single(Cow::Borrowed(NULL_ATOMIC));
    null.set_possibly_undefined(true, None);
    null
}

#[inline]
#[must_use]
pub fn get_arraykey() -> TUnion {
    TUnion::from_single(Cow::Borrowed(ARRAYKEY_ATOMIC))
}

#[inline]
#[must_use]
pub fn get_bool() -> TUnion {
    TUnion::from_single(Cow::Borrowed(BOOL_ATOMIC))
}

#[inline]
#[must_use]
pub fn get_false() -> TUnion {
    TUnion::from_single(Cow::Borrowed(FALSE_ATOMIC))
}

#[inline]
#[must_use]
pub fn get_true() -> TUnion {
    TUnion::from_single(Cow::Borrowed(TRUE_ATOMIC))
}

#[inline]
#[must_use]
pub fn get_object() -> TUnion {
    TUnion::from_single(Cow::Borrowed(OBJECT_ATOMIC))
}

#[inline]
#[must_use]
pub fn get_numeric() -> TUnion {
    TUnion::from_single(Cow::Borrowed(NUMERIC_ATOMIC))
}

#[inline]
#[must_use]
pub fn get_callable_string() -> TUnion {
    TUnion::from_single(Cow::Borrowed(CALLABLE_STRING_ATOMIC))
}

pub fn get_numeric_string() -> TUnion {
    TUnion::from_single(Cow::Borrowed(NUMERIC_STRING_ATOMIC))
}

#[inline]
#[must_use]
pub fn get_lowercase_string() -> TUnion {
    TUnion::from_single(Cow::Borrowed(LOWERCASE_STRING_ATOMIC))
}

#[inline]
#[must_use]
pub fn get_non_empty_lowercase_string() -> TUnion {
    TUnion::from_single(Cow::Borrowed(NON_EMPTY_LOWERCASE_STRING_ATOMIC))
}

#[inline]
#[must_use]
pub fn get_uppercase_string() -> TUnion {
    TUnion::from_single(Cow::Borrowed(UPPERCASE_STRING_ATOMIC))
}

#[inline]
#[must_use]
pub fn get_non_empty_uppercase_string() -> TUnion {
    TUnion::from_single(Cow::Borrowed(NON_EMPTY_UPPERCASE_STRING_ATOMIC))
}

#[inline]
#[must_use]
pub fn get_non_empty_string() -> TUnion {
    TUnion::from_single(Cow::Borrowed(NON_EMPTY_STRING_ATOMIC))
}

#[inline]
#[must_use]
pub fn get_empty_string() -> TUnion {
    TUnion::from_single(Cow::Borrowed(&EMPTY_STRING_ATOMIC))
}

#[inline]
#[must_use]
pub fn get_truthy_string() -> TUnion {
    TUnion::from_single(Cow::Borrowed(TRUTHY_STRING_ATOMIC))
}

#[inline]
#[must_use]
pub fn get_unspecified_literal_string() -> TUnion {
    TUnion::from_single(Cow::Borrowed(UNSPECIFIED_LITERAL_STRING_ATOMIC))
}

#[inline]
#[must_use]
pub fn get_non_empty_unspecified_literal_string() -> TUnion {
    TUnion::from_single(Cow::Borrowed(NON_EMPTY_UNSPECIFIED_LITERAL_STRING_ATOMIC))
}

#[inline]
#[must_use]
pub fn get_scalar() -> TUnion {
    TUnion::from_single(Cow::Borrowed(SCALAR_ATOMIC))
}

#[inline]
#[must_use]
pub fn get_nullable_scalar() -> TUnion {
    TUnion::new(Cow::Borrowed(NULL_SCALAR_ATOMIC_SLICE))
}

#[inline]
#[must_use]
pub fn get_mixed_iterable() -> TUnion {
    TUnion::from_single(Cow::Borrowed(&MIXED_ITERABLE_ATOMIC))
}

#[inline]
#[must_use]
pub fn get_empty_keyed_array() -> TUnion {
    TUnion::from_single(Cow::Borrowed(&EMPTY_KEYED_ARRAY_ATOMIC))
}

#[inline]
#[must_use]
pub fn get_mixed_list() -> TUnion {
    get_list(get_mixed())
}

#[inline]
#[must_use]
pub fn get_mixed_keyed_array() -> TUnion {
    get_keyed_array(get_arraykey(), get_mixed())
}

#[inline]
#[must_use]
pub fn get_mixed_callable() -> TUnion {
    TUnion::from_single(Cow::Borrowed(&MIXED_CALLABLE_ATOMIC))
}

#[inline]
#[must_use]
pub fn get_mixed_closure() -> TUnion {
    TUnion::from_single(Cow::Borrowed(&MIXED_CLOSURE_ATOMIC))
}

#[inline]
#[must_use]
pub fn get_named_object(name: Atom, type_resolution_context: Option<&TypeResolutionContext>) -> TUnion {
    if let Some(type_resolution_context) = type_resolution_context
        && let Some(defining_entities) = type_resolution_context.get_template_definition(name)
    {
        let first = &defining_entities[0];
        return wrap_atomic(TAtomic::Scalar(TScalar::ClassLikeString(TClassLikeString::Generic {
            kind: TClassLikeStringKind::Class,
            parameter_name: name,
            defining_entity: first.defining_entity,
            constraint: Arc::new((*(first.constraint.get_single())).clone()),
        })));
    }

    wrap_atomic(TAtomic::Object(TObject::Named(TNamedObject::new(name))))
}

#[inline]
#[must_use]
pub fn get_iterable(key_parameter: TUnion, value_parameter: TUnion) -> TUnion {
    wrap_atomic(TAtomic::Iterable(TIterable::new(Arc::new(key_parameter), Arc::new(value_parameter))))
}

#[inline]
#[must_use]
pub fn get_list(element_type: TUnion) -> TUnion {
    wrap_atomic(TAtomic::Array(TArray::List(TList::new(Arc::new(element_type)))))
}

#[inline]
#[must_use]
pub fn get_non_empty_list(element_type: TUnion) -> TUnion {
    wrap_atomic(TAtomic::Array(TArray::List(TList::new_non_empty(Arc::new(element_type)))))
}

#[inline]
#[must_use]
pub fn get_keyed_array(key_parameter: TUnion, value_parameter: TUnion) -> TUnion {
    wrap_atomic(TAtomic::Array(TArray::Keyed(TKeyedArray::new_with_parameters(
        Arc::new(key_parameter),
        Arc::new(value_parameter),
    ))))
}

#[inline]
#[must_use]
pub fn add_optional_union_type(base_type: TUnion, maybe_type: Option<&TUnion>, codebase: &CodebaseMetadata) -> TUnion {
    if let Some(type_2) = maybe_type {
        add_union_type(base_type, type_2, codebase, combiner::CombinerOptions::default())
    } else {
        base_type
    }
}

/// Reference-counted variant of [`add_optional_union_type`].
#[must_use]
pub fn add_optional_union_type_rc(
    base_type: &Rc<TUnion>,
    maybe_type: Option<&TUnion>,
    codebase: &CodebaseMetadata,
) -> Rc<TUnion> {
    match maybe_type {
        Some(type_2) => {
            Rc::new(add_union_type((**base_type).clone(), type_2, codebase, combiner::CombinerOptions::default()))
        }
        None => Rc::clone(base_type),
    }
}

#[inline]
#[must_use]
pub fn combine_optional_union_types(
    type_1: Option<&TUnion>,
    type_2: Option<&TUnion>,
    codebase: &CodebaseMetadata,
) -> TUnion {
    match (type_1, type_2) {
        (Some(type_1), Some(type_2)) => {
            combine_union_types(type_1, type_2, codebase, combiner::CombinerOptions::default())
        }
        (Some(type_1), None) => type_1.clone(),
        (None, Some(type_2)) => type_2.clone(),
        (None, None) => get_mixed(),
    }
}

/// Reference-counted variant of [`combine_union_types`].
#[inline]
#[must_use]
pub fn combine_union_types_rc(
    type_1: &Rc<TUnion>,
    type_2: &Rc<TUnion>,
    codebase: &CodebaseMetadata,
    options: combiner::CombinerOptions,
) -> Rc<TUnion> {
    if Rc::ptr_eq(type_1, type_2) {
        return Rc::clone(type_1);
    }

    Rc::new(combine_union_types(type_1, type_2, codebase, options))
}

#[inline]
#[must_use]
pub fn combine_union_types(
    type_1: &TUnion,
    type_2: &TUnion,
    codebase: &CodebaseMetadata,
    options: combiner::CombinerOptions,
) -> TUnion {
    if type_1 == type_2 {
        return type_1.clone();
    }

    let mut combined_type = if type_1.is_never() || type_1.is_never_template() {
        type_2.clone()
    } else if type_2.is_never() || type_2.is_never_template() {
        type_1.clone()
    } else if type_1.is_vanilla_mixed() && type_2.is_vanilla_mixed() {
        get_mixed()
    } else {
        let mut all_atomic_types = type_1.types.to_vec();
        all_atomic_types.extend(type_2.types.iter().cloned());

        let mut result = TUnion::from_vec(combiner::combine(all_atomic_types, codebase, options));

        if type_1.had_template() && type_2.had_template() {
            result.set_had_template(true);
        }

        if type_1.reference_free() && type_2.reference_free() {
            result.set_reference_free(true);
        }

        result
    };

    if type_1.possibly_undefined() || type_2.possibly_undefined() {
        combined_type.set_possibly_undefined(true, None);
    }

    if type_1.possibly_undefined_from_try() || type_2.possibly_undefined_from_try() {
        combined_type.set_possibly_undefined_from_try(true);
    }

    if type_1.ignore_falsable_issues() || type_2.ignore_falsable_issues() {
        combined_type.set_ignore_falsable_issues(true);
    }

    combined_type
}

#[inline]
#[must_use]
pub fn add_union_type(
    mut base_type: TUnion,
    other_type: &TUnion,
    codebase: &CodebaseMetadata,
    options: combiner::CombinerOptions,
) -> TUnion {
    if &base_type != other_type {
        base_type.types = if base_type.is_vanilla_mixed() && other_type.is_vanilla_mixed() {
            base_type.types
        } else {
            combine_union_types(&base_type, other_type, codebase, options).types
        };

        if !other_type.had_template() {
            base_type.set_had_template(false);
        }

        if !other_type.reference_free() {
            base_type.set_reference_free(false);
        }
    }

    if other_type.possibly_undefined() {
        base_type.set_possibly_undefined(true, None);
    }
    if other_type.possibly_undefined_from_try() {
        base_type.set_possibly_undefined_from_try(true);
    }
    if other_type.ignore_falsable_issues() {
        base_type.set_ignore_falsable_issues(true);
    }
    if other_type.ignore_nullable_issues() {
        base_type.set_ignore_nullable_issues(true);
    }

    base_type
}

#[must_use]
pub fn intersect_union_types(type_1: &TUnion, type_2: &TUnion, codebase: &CodebaseMetadata) -> Option<TUnion> {
    if type_1 == type_2 {
        return Some(type_1.clone());
    }

    if type_1.is_never() || type_2.is_never() {
        return Some(get_never());
    }

    let mut intersection_performed = false;

    if type_1.is_mixed() {
        if type_2.is_mixed() {
            return Some(get_mixed());
        }

        return Some(type_2.clone());
    } else if type_2.is_mixed() {
        return Some(type_1.clone());
    }

    let mut intersected_atomic_types = vec![];
    for type_1_atomic in type_1.types.iter() {
        for type_2_atomic in type_2.types.iter() {
            if let Some(intersection_atomic) =
                intersect_atomic_types(type_1_atomic, type_2_atomic, codebase, &mut intersection_performed)
            {
                intersected_atomic_types.push(intersection_atomic);
            }
        }
    }

    let mut combined_type: Option<TUnion> = None;
    if !intersected_atomic_types.is_empty() {
        let combined_vec = combiner::combine(intersected_atomic_types, codebase, combiner::CombinerOptions::default());
        if !combined_vec.is_empty() {
            combined_type = Some(TUnion::from_vec(combined_vec));
        }
    }

    // If atomic-level intersection didn't yield a result, check for subtyping at the union level.
    if !intersection_performed {
        if union_comparator::is_contained_by(
            codebase,
            type_1,
            type_2,
            false,
            false,
            false,
            &mut ComparisonResult::default(),
        ) {
            intersection_performed = true;
            combined_type = Some(type_1.clone());
        } else if union_comparator::is_contained_by(
            codebase,
            type_2,
            type_1,
            false,
            false,
            false,
            &mut ComparisonResult::default(),
        ) {
            intersection_performed = true;
            combined_type = Some(type_2.clone());
        }
    }

    if let Some(mut final_type) = combined_type {
        final_type.set_possibly_undefined(
            type_1.possibly_undefined() && type_2.possibly_undefined(),
            Some(type_1.possibly_undefined_from_try() && type_2.possibly_undefined_from_try()),
        );
        final_type.set_ignore_falsable_issues(type_1.ignore_falsable_issues() && type_2.ignore_falsable_issues());
        final_type.set_ignore_nullable_issues(type_1.ignore_nullable_issues() && type_2.ignore_nullable_issues());

        return Some(final_type);
    }

    if !intersection_performed && type_1.get_id() != type_2.get_id() {
        return None;
    }

    None
}

/// This is the core logic used by `intersect_union_types`.
fn intersect_atomic_types(
    type_1: &TAtomic,
    type_2: &TAtomic,
    codebase: &CodebaseMetadata,
    intersection_performed: &mut bool,
) -> Option<TAtomic> {
    if let (TAtomic::Scalar(TScalar::Integer(t1_int)), TAtomic::Scalar(TScalar::Integer(t2_int))) = (type_1, type_2) {
        let (min1, max1) = t1_int.get_bounds();
        let (min2, max2) = t2_int.get_bounds();

        let new_min = match (min1, min2) {
            (Some(m1), Some(m2)) => Some(m1.max(m2)),
            (Some(m), None) | (None, Some(m)) => Some(m),
            (None, None) => None,
        };

        let new_max = match (max1, max2) {
            (Some(m1), Some(m2)) => Some(m1.min(m2)),
            (Some(m), None) | (None, Some(m)) => Some(m),
            (None, None) => None,
        };

        let intersected_int = if let (Some(min), Some(max)) = (new_min, new_max) {
            if min > max {
                return None;
            }

            if min == max { TInteger::Literal(min) } else { TInteger::Range(min, max) }
        } else if let Some(min) = new_min {
            TInteger::From(min)
        } else if let Some(max) = new_max {
            TInteger::To(max)
        } else {
            TInteger::Unspecified
        };

        *intersection_performed = true;
        return Some(TAtomic::Scalar(TScalar::Integer(intersected_int)));
    }

    let t1_union = TUnion::from_atomic(type_1.clone());
    let t2_union = TUnion::from_atomic(type_2.clone());

    let mut narrower_type = None;
    let mut wider_type = None;

    if union_comparator::is_contained_by(
        codebase,
        &t2_union,
        &t1_union,
        false,
        false,
        false,
        &mut ComparisonResult::default(),
    ) {
        narrower_type = Some(type_2);
        wider_type = Some(type_1);
    } else if union_comparator::is_contained_by(
        codebase,
        &t1_union,
        &t2_union,
        false,
        false,
        false,
        &mut ComparisonResult::default(),
    ) {
        narrower_type = Some(type_1);
        wider_type = Some(type_2);
    }

    if let (Some(narrower), Some(wider)) = (narrower_type, wider_type) {
        *intersection_performed = true;
        let mut result = narrower.clone();

        if narrower.can_be_intersected() && wider.can_be_intersected() {
            let mut wider_clone = wider.clone();
            if let Some(types) = wider_clone.get_intersection_types_mut() {
                types.clear();
            }
            result.add_intersection_type(wider_clone);

            if let Some(wider_intersections) = wider.get_intersection_types() {
                for i_type in wider_intersections {
                    result.add_intersection_type(i_type.clone());
                }
            }
        }
        return Some(result);
    }

    if let (TAtomic::Scalar(TScalar::String(s1)), TAtomic::Scalar(TScalar::String(s2))) = (type_1, type_2) {
        if let (Some(v1), Some(v2)) = (&s1.get_known_literal_value(), &s2.get_known_literal_value())
            && v1 != v2
        {
            return None;
        }

        let combined = TAtomic::Scalar(TScalar::String(TString {
            is_numeric: s1.is_numeric || s2.is_numeric,
            is_truthy: s1.is_truthy || s2.is_truthy,
            is_non_empty: s1.is_non_empty || s2.is_non_empty,
            is_callable: false,
            casing: match (s1.casing, s2.casing) {
                (TStringCasing::Lowercase, TStringCasing::Lowercase) => TStringCasing::Lowercase,
                (TStringCasing::Uppercase, TStringCasing::Uppercase) => TStringCasing::Uppercase,
                _ => TStringCasing::Unspecified,
            },
            literal: if s1.is_literal_origin() && s2.is_literal_origin() {
                Some(TStringLiteral::Unspecified)
            } else {
                None
            },
        }));
        *intersection_performed = true;
        return Some(combined);
    }

    if type_1.can_be_intersected() && type_2.can_be_intersected() {
        if let (TAtomic::Object(TObject::Named(n1)), TAtomic::Object(TObject::Named(n2))) = (type_1, type_2)
            && let (Some(c1), Some(c2)) = (codebase.get_class_like(&n1.name), codebase.get_class_like(&n2.name))
            && !c1.kind.is_interface()
            && !c1.kind.is_trait()
            && !c2.kind.is_interface()
            && !c2.kind.is_trait()
        {
            return None;
        }

        let mut result = type_1.clone();
        result.add_intersection_type(type_2.clone());
        if let Some(intersections) = type_2.get_intersection_types() {
            for i in intersections {
                result.add_intersection_type(i.clone());
            }
        }

        *intersection_performed = true;
        return Some(result);
    }

    None
}

pub fn get_iterable_parameters(atomic: &TAtomic, codebase: &CodebaseMetadata) -> Option<(TUnion, TUnion)> {
    if let Some(generator_parameters) = atomic.get_generator_parameters() {
        let mut key_type = generator_parameters.0;
        let mut value_type = generator_parameters.1;

        expander::expand_union(codebase, &mut key_type, &TypeExpansionOptions::default());
        expander::expand_union(codebase, &mut value_type, &TypeExpansionOptions::default());

        return Some((key_type, value_type));
    }

    let parameters = 'parameters: {
        match atomic {
            TAtomic::Iterable(iterable) => {
                let mut key_type = iterable.get_key_type().clone();
                let mut value_type = iterable.get_value_type().clone();

                expander::expand_union(codebase, &mut key_type, &TypeExpansionOptions::default());
                expander::expand_union(codebase, &mut value_type, &TypeExpansionOptions::default());

                Some((key_type, value_type))
            }
            TAtomic::Array(array_type) => {
                let (mut key_type, mut value_type) = get_array_parameters(array_type, codebase);

                expander::expand_union(codebase, &mut key_type, &TypeExpansionOptions::default());
                expander::expand_union(codebase, &mut value_type, &TypeExpansionOptions::default());

                Some((key_type, value_type))
            }
            TAtomic::Object(object) => {
                let name = object.get_name()?;
                let traversable = atom("traversable");
                let iterator = atom("iterator");
                let iterator_aggregate = atom("iteratoraggregate");

                let class_metadata = codebase.get_class_like(&name)?;
                if !codebase.is_instance_of(&class_metadata.name, &traversable) {
                    break 'parameters None;
                }

                let is_iterator_interface = name == iterator || name == traversable || name == iterator_aggregate;
                if !is_iterator_interface
                    && codebase.is_instance_of(&class_metadata.name, &iterator)
                    && let (Some(key_type), Some(value_type)) = (
                        get_iterator_method_return_type(codebase, name, "key"),
                        get_iterator_method_return_type(codebase, name, "current"),
                    )
                {
                    let contains_generic_param = |t: &TUnion| t.types.iter().any(atomic::TAtomic::is_generic_parameter);

                    if !key_type.is_mixed()
                        && !value_type.is_mixed()
                        && !contains_generic_param(&key_type)
                        && !contains_generic_param(&value_type)
                    {
                        return Some((key_type, value_type));
                    }
                }

                let traversable_metadata = codebase.get_class_like(&traversable)?;
                let key_template = traversable_metadata.template_types.get_index(0).map(|(name, _)| *name)?;
                let value_template = traversable_metadata.template_types.get_index(1).map(|(name, _)| *name)?;

                let key_type = get_specialized_template_type(
                    codebase,
                    key_template,
                    traversable,
                    class_metadata,
                    object.get_type_parameters(),
                )
                .unwrap_or_else(get_mixed);

                let value_type = get_specialized_template_type(
                    codebase,
                    value_template,
                    traversable,
                    class_metadata,
                    object.get_type_parameters(),
                )
                .unwrap_or_else(get_mixed);

                Some((key_type, value_type))
            }
            _ => None,
        }
    };

    if let Some((key_type, value_type)) = parameters {
        return Some((key_type, value_type));
    }

    if let Some(intersection_types) = atomic.get_intersection_types() {
        for intersection_type in intersection_types {
            if let Some((key_type, value_type)) = get_iterable_parameters(intersection_type, codebase) {
                return Some((key_type, value_type));
            }
        }
    }

    None
}

#[must_use]
pub fn get_array_parameters(array_type: &TArray, codebase: &CodebaseMetadata) -> (TUnion, TUnion) {
    match array_type {
        TArray::Keyed(keyed_data) => {
            let mut key_types = vec![];
            let mut value_param;

            if let Some((key_param, value_p)) = &keyed_data.parameters {
                key_types.extend(key_param.types.iter().cloned());
                value_param = (**value_p).clone();
            } else {
                key_types.push(TAtomic::Never);
                value_param = get_never();
            }

            if let Some(known_items) = &keyed_data.known_items {
                for (key, (_, item_type)) in known_items {
                    key_types.push(key.to_atomic());
                    value_param =
                        add_union_type(value_param, item_type, codebase, combiner::CombinerOptions::default());
                }
            }

            if key_types.is_empty() {
                key_types.push(TAtomic::Never);
            }

            let combined_key_types = combiner::combine(key_types, codebase, combiner::CombinerOptions::default());
            let key_param_union = TUnion::from_vec(combined_key_types);

            (key_param_union, value_param)
        }
        TArray::List(list_data) => {
            let mut key_types = vec![];
            let mut value_type = (*list_data.element_type).clone();

            if let Some(known_elements) = &list_data.known_elements {
                for (key_idx, (_, element_type)) in known_elements {
                    key_types.push(TAtomic::Scalar(TScalar::literal_int(*key_idx as i64)));

                    value_type =
                        combine_union_types(element_type, &value_type, codebase, combiner::CombinerOptions::default());
                }
            }

            if key_types.is_empty() || !value_type.is_never() {
                if value_type.is_never() {
                    key_types.push(TAtomic::Never);
                } else {
                    key_types.push(TAtomic::Scalar(TScalar::Integer(TInteger::non_negative())));
                }
            }

            let key_type =
                TUnion::from_vec(combiner::combine(key_types, codebase, combiner::CombinerOptions::default()));

            (key_type, value_type)
        }
    }
}

#[must_use]
pub fn get_iterable_value_parameter(atomic: &TAtomic, codebase: &CodebaseMetadata) -> Option<TUnion> {
    if let Some(generator_parameters) = atomic.get_generator_parameters() {
        return Some(generator_parameters.1);
    }

    let parameter = match atomic {
        TAtomic::Iterable(iterable) => Some(iterable.get_value_type().clone()),
        TAtomic::Array(array_type) => Some(get_array_value_parameter(array_type, codebase)),
        TAtomic::Object(object) => {
            let name = object.get_name()?;
            let traversable = atom("traversable");

            let class_metadata = codebase.get_class_like(&name)?;
            if !codebase.is_instance_of(&class_metadata.name, &traversable) {
                return None;
            }

            let traversable_metadata = codebase.get_class_like(&traversable)?;
            let value_template = traversable_metadata.template_types.get_index(1).map(|(name, _)| *name)?;

            get_specialized_template_type(
                codebase,
                value_template,
                traversable,
                class_metadata,
                object.get_type_parameters(),
            )
        }
        _ => None,
    };

    if let Some(value_param) = parameter {
        return Some(value_param);
    }

    if let Some(intersection_types) = atomic.get_intersection_types() {
        for intersection_type in intersection_types {
            if let Some(value_param) = get_iterable_value_parameter(intersection_type, codebase) {
                return Some(value_param);
            }
        }
    }

    None
}

#[must_use]
pub fn get_array_value_parameter(array_type: &TArray, codebase: &CodebaseMetadata) -> TUnion {
    match array_type {
        TArray::Keyed(keyed_data) => {
            let mut value_param;

            if let Some((_, value_p)) = &keyed_data.parameters {
                value_param = (**value_p).clone();
            } else {
                value_param = get_never();
            }

            if let Some(known_items) = &keyed_data.known_items {
                for (_, item_type) in known_items.values() {
                    value_param =
                        combine_union_types(item_type, &value_param, codebase, combiner::CombinerOptions::default());
                }
            }

            value_param
        }
        TArray::List(list_data) => {
            let mut value_param = (*list_data.element_type).clone();

            if let Some(known_elements) = &list_data.known_elements {
                for (_, element_type) in known_elements.values() {
                    value_param =
                        combine_union_types(element_type, &value_param, codebase, combiner::CombinerOptions::default());
                }
            }

            value_param
        }
    }
}

/// Resolves a generic template from an ancestor class in the context of a descendant class.
///
/// This function correctly traverses the pre-calculated inheritance map to determine the
/// concrete type of a template parameter.
#[must_use]
pub fn get_specialized_template_type(
    codebase: &CodebaseMetadata,
    template_name: Atom,
    template_defining_class_id: Atom,
    instantiated_class_metadata: &ClassLikeMetadata,
    instantiated_type_parameters: Option<&[TUnion]>,
) -> Option<TUnion> {
    let defining_class_metadata = codebase.get_class_like(&template_defining_class_id)?;

    if defining_class_metadata.name == instantiated_class_metadata.name {
        let index = instantiated_class_metadata.get_template_index_for_name(template_name)?;

        let Some(instantiated_type_parameters) = instantiated_type_parameters else {
            let template = instantiated_class_metadata.get_template_type(template_name)?;
            let mut result = template.constraint.clone();

            expander::expand_union(codebase, &mut result, &TypeExpansionOptions::default());

            return Some(result);
        };

        let mut result = instantiated_type_parameters.get(index).cloned()?;

        expander::expand_union(codebase, &mut result, &TypeExpansionOptions::default());

        return Some(result);
    }

    let template = defining_class_metadata.get_template_type(template_name)?;
    let template_union = wrap_atomic(TAtomic::GenericParameter(TGenericParameter {
        parameter_name: template_name,
        defining_entity: template.defining_entity,
        constraint: Arc::new(template.constraint.clone()),
        intersection_types: None,
    }));

    let mut template_result = TemplateResult::default();
    for (defining_class, template_parameters) in &instantiated_class_metadata.template_extended_parameters {
        for (parameter_name, parameter_type) in template_parameters {
            template_result.add_lower_bound(
                *parameter_name,
                GenericParent::ClassLike(*defining_class),
                parameter_type.clone(),
            );
        }
    }

    let mut template_type = inferred_type_replacer::replace(&template_union, &template_result, codebase);
    if let Some(type_parameters) = instantiated_type_parameters {
        let mut template_result = TemplateResult::default();
        for (i, parameter_type) in type_parameters.iter().enumerate() {
            if let Some(parameter_name) = instantiated_class_metadata.get_template_name_for_index(i) {
                template_result.add_lower_bound(
                    parameter_name,
                    GenericParent::ClassLike(instantiated_class_metadata.name),
                    parameter_type.clone(),
                );
            }
        }

        if !template_result.lower_bounds.is_empty() {
            template_type = inferred_type_replacer::replace(&template_type, &template_result, codebase);
        }
    }

    expander::expand_union(codebase, &mut template_type, &TypeExpansionOptions::default());

    Some(template_type)
}

fn get_iterator_method_return_type(codebase: &CodebaseMetadata, class_name: Atom, method_name: &str) -> Option<TUnion> {
    let method = codebase.get_declaring_method(&class_name, method_name)?;
    let return_type_meta = method.return_type_metadata.as_ref()?;
    let mut return_type = return_type_meta.type_union.clone();
    expander::expand_union(codebase, &mut return_type, &TypeExpansionOptions::default());
    Some(return_type)
}