<?php

declare(strict_types=1);

namespace Phan\Language;

use Closure;
use Generator;
use Phan\CodeBase;
use Phan\Exception\CodeBaseException;
use Phan\Exception\IssueException;
use Phan\Language\Element\Clazz;
use Phan\Language\Element\FunctionInterface;
use Phan\Language\FQSEN\FullyQualifiedClassName;
use Phan\Language\Type\ArrayType;
use Phan\Language\Type\AssociativeArrayType;
use Phan\Language\Type\BoolType;
use Phan\Language\Type\IterableType;
use Phan\Language\Type\ListType;
use Phan\Language\Type\MixedType;
use Phan\Language\Type\ObjectType;
use Phan\Language\Type\TemplateType;

/**
 * NOTE: there may also be instances of UnionType that are empty, due to the constructor being public
 *
 * @phan-file-suppress PhanUnusedPublicFinalMethodParameter the results don't depend on passed in parameters
 */
final class EmptyUnionType extends UnionType
{
    /**
     * An optional list of types represented by this union
     * @internal
     */
    public function __construct()
    {
        parent::__construct([], true, []);
    }

    /**
     * Use UnionType::empty() instead elsewhere in the codebase.
     */
    protected static function instance(): EmptyUnionType
    {
        static $self = null;
        return $self ?? ($self = new EmptyUnionType());
    }

    /**
     * @return Type[]
     * The list of simple types associated with this
     * union type. Keys are consecutive.
     * @override
     */
    public function getTypeSet(): array
    {
        return [];
    }

    /**
     * Add a type name to the list of types
     * @override
     */
    public function withType(Type $type): UnionType
    {
        return $type->asPHPDocUnionType();
    }

    /**
     * Returns a new union type
     * which removes this type from the list of types,
     * keeping the keys in a consecutive order.
     *
     * Each type in $this->type_set occurs exactly once.
     * @override
     */
    public function withoutType(Type $type): UnionType
    {
        return $this;
    }

    /**
     * @return bool
     * True if this union type contains the given named
     * type.
     * @override
     */
    public function hasType(Type $type): bool
    {
        return false;
    }

    /**
     * Returns a union type which adds the given phpdoc/real types to this type
     * @override
     */
    public function withUnionType(UnionType $union_type): UnionType
    {
        return $union_type->eraseRealTypeSetRecursively();
    }

    /**
     * @return bool
     * True if this type has a type referencing the
     * class context in which it exists such as 'self'
     * or '$this'
     * @override
     */
    public function hasSelfType(): bool
    {
        return false;
    }

    /**
     * @return bool
     * True if this union type has any types that are bool/false/true types
     * @override
     */
    public function hasTypeInBoolFamily(): bool
    {
        return false;
    }

    /**
     * Returns the types for which is_bool($x) would be true.
     *
     * @return UnionType
     * A UnionType with known bool types kept, other types filtered out.
     *
     * @see nonGenericArrayTypes
     */
    public function getTypesInBoolFamily(): UnionType
    {
        return $this;
    }

    /**
     * @param CodeBase $code_base
     * The code base to look up classes against
     *
     * TODO: Defer resolving the template parameters until parse ends. Low priority.
     *
     * @return UnionType[]
     * A map from template type identifiers to the UnionType
     * to replace it with
     */
    public function getTemplateParameterTypeMap(
        CodeBase $code_base
    ): array {
        return [];
    }


    /**
     * @param UnionType[] $template_parameter_type_map
     * A map from template type identifiers to concrete types
     *
     * @return UnionType
     * This UnionType with any template types contained herein
     * mapped to concrete types defined in the given map.
     */
    public function withTemplateParameterTypeMap(
        array $template_parameter_type_map
    ): UnionType {
        return $this;
    }

    /**
     * @return bool
     * True if this union type has any types that are generic
     * types
     * @override
     */
    public function hasTemplateType(): bool
    {
        return false;
    }

    /** @override */
    public function hasTemplateTypeRecursive(): bool
    {
        return false;
    }

    /** @override */
    public function withoutTemplateTypeRecursive(): UnionType
    {
        return $this;
    }

    /** @override */
    public function eraseTemplatesRecursive(): UnionType
    {
        return $this;
    }

    /**
     * @return bool
     * True if this union type has any types that have generic
     * types
     * @override
     */
    public function hasTemplateParameterTypes(): bool
    {
        return false;
    }

    /**
     * @return bool
     * True if this type has a type referencing the
     * class context 'static'.
     * @override
     */
    public function hasStaticType(): bool
    {
        return false;
    }

    /**
     * @return UnionType
     * A new UnionType with any references to 'static' resolved
     * in the given context.
     */
    public function withStaticResolvedInContext(
        Context $context
    ): UnionType {
        return $this;
    }

    /**
     * @return UnionType
     * A new UnionType with any references to 'static' resolved
     * in the given context.
     */
    public function withStaticResolvedInFunctionLike(
        FunctionInterface $function
    ): UnionType {
        return $this;
    }

    /**
     * @return UnionType
     * A new UnionType *plus* any references to 'self' (but not 'static') resolved
     * in the given context.
     */
    public function withAddedClassForResolvedSelf(
        Context $context
    ): UnionType {
        return $this;
    }

    /**
     * @return UnionType
     * A new UnionType with any references to 'self' (but not 'static') resolved
     * in the given context. (the type of 'self' is replaced)
     */
    public function withSelfResolvedInContext(
        Context $context
    ): UnionType {
        return $this;
    }

    /**
     * @return bool
     * True if and only if this UnionType contains
     * the given type and no others.
     * @override
     */
    public function isType(Type $type): bool
    {
        return false;
    }

    /**
     * @return bool
     * True if this UnionType is exclusively native
     * types
     * @override
     */
    public function isNativeType(): bool
    {
        return false;
    }

    /**
     * @return bool
     * True iff this union contains the exact set of types
     * represented in the given union type.
     * @override
     */
    public function isEqualTo(UnionType $union_type): bool
    {
        return $union_type instanceof EmptyUnionType || ($union_type->isEmpty() && !$union_type->isPossiblyUndefined());
    }

    /**
     * @override
     */
    public function isIdenticalTo(UnionType $union_type): bool
    {
        return $union_type->isEmpty() && !$union_type->isPossiblyUndefined() && !$union_type->getRealTypeSet();
    }

    /**
     * @return bool
     * True iff this union contains a type that's also in
     * the other union type.
     */
    public function hasCommonType(UnionType $union_type): bool
    {
        return false;
    }

    /**
     * @return bool - True if not empty and at least one type is NullType or nullable.
     */
    public function containsNullable(): bool
    {
        return false;
    }

    /**
     * @return bool - True if not empty and at least one type is NullType or mixed.
     */
    public function containsNullableOrMixed(): bool
    {
        return false;
    }

    /**
     * @return bool - True if empty or at least one type is NullType or nullable.
     */
    public function containsNullableOrIsEmpty(): bool
    {
        return true;
    }

    public function isNull(): bool
    {
        return false;
    }

    /**
     * @return bool - True if not empty, not possibly undefined, and at least one type is NullType or nullable.
     */
    public function containsNullableOrUndefined(): bool
    {
        return false;
    }

    /** @override */
    public function nonNullableClone(): UnionType
    {
        return $this;
    }

    /** @override */
    public function nullableClone(): UnionType
    {
        return $this;
    }

    /** @override */
    public function withNullableRealTypes(): UnionType
    {
        return $this;
    }

    /** @override */
    public function withIsNullable(bool $is_nullable): UnionType
    {
        return $this;
    }

    /**
     * @return bool - True if type set is not empty and at least one type is NullType or nullable or FalseType or BoolType.
     * (I.e. the type is always falsey, or both sometimes falsey with a non-falsey type it can be narrowed down to)
     * This does not include values such as `IntType`, since there is currently no `NonZeroIntType`.
     * @override
     */
    public function containsFalsey(): bool
    {
        return false;
    }

    /** @override */
    public function nonFalseyClone(): UnionType
    {
        return UnionType::fromFullyQualifiedRealString('non-empty-mixed');
    }

    /**
     * @return bool - True if type set is not empty and at least one type is NullType or nullable or FalseType or BoolType.
     * (I.e. the type is always falsey, or both sometimes falsey with a non-falsey type it can be narrowed down to)
     * This does not include values such as `IntType`, since there is currently no `NonZeroIntType`.
     * @override
     */
    public function containsTruthy(): bool
    {
        return false;
    }

    /** @override */
    public function nonTruthyClone(): UnionType
    {
        return $this;
    }

    /**
     * @return bool - True if type set is not empty and at least one type is BoolType or FalseType
     * @override
     */
    public function containsFalse(): bool
    {
        return false;
    }

    /**
     * @return bool - True if type set is not empty and at least one type is BoolType or TrueType
     * @override
     */
    public function containsTrue(): bool
    {
        return false;
    }

    public function nonFalseClone(): UnionType
    {
        return $this;
    }

    public function nonTrueClone(): UnionType
    {
        return $this;
    }

    public function isExclusivelyNarrowedFormOf(CodeBase $code_base, UnionType $other): bool
    {
        return $other->isEmpty();
    }

    /**
     * @param Type[] $type_list
     * A list of types
     *
     * @return bool
     * True if this union type contains any of the given
     * named types
     */
    public function hasAnyType(array $type_list): bool
    {
        return false;
    }

    /**
     * @return bool
     * True if this type has any subtype of `iterable` type (e.g. Traversable, Array).
     */
    public function hasIterable(): bool
    {
        return false;
    }

    public function iterableTypesStrictCast(CodeBase $code_base): UnionType
    {
        return IterableType::instance(false)->asRealUnionType();
    }

    public function countableTypesStrictCast(CodeBase $code_base): UnionType
    {
        return UnionType::fromFullyQualifiedRealString('array|\Countable');
    }

    public function iterableTypesStrictCastAssumeTraversable(CodeBase $code_base): UnionType
    {
        return IterableType::instance(false)->asRealUnionType();
    }

    /**
     * @return int
     * The number of types in this union type
     */
    public function typeCount(): int
    {
        return 0;
    }

    /**
     * @return bool
     * True if this Union has no types
     */
    public function isEmpty(): bool
    {
        return true;
    }

    /**
     * @return bool
     * True if this Union has no types or is the mixed type
     */
    public function isEmptyOrMixed(): bool
    {
        return true;
    }

    /**
     * @param UnionType $target
     * The type we'd like to see if this type can cast
     * to
     *
     * @param CodeBase $code_base
     * The code base used to expand types
     *
     * @return bool
     * Test to see if this type can be cast to the
     * given type after expanding both union types
     * to include all ancestor types
     *
     * TODO: ensure that this is only called after the parse phase is over.
     */
    public function canCastToExpandedUnionType(
        UnionType $target,
        CodeBase $code_base
    ): bool {
        return true;  // Empty can cast to anything.
    }

    /**
     * @param UnionType $target
     * A type to check to see if this can cast to it
     *
     * @return bool
     * True if this type is allowed to cast to the given type
     * i.e. int->float is allowed  while float->int is not.
     */
    public function canCastToUnionType(
        UnionType $target
    ): bool {
        return true;  // Empty can cast to anything. See parent implementation.
    }

    public function canCastToUnionTypeWithoutConfig(
        UnionType $target
    ): bool {
        return true;  // Empty can cast to anything. See parent implementation.
    }

    /**
     * Precondition: $this->canCastToUnionType() is false.
     *
     * This tells us if it would have succeeded if the source type was not nullable.
     *
     * @internal
     * @override
     */
    public function canCastToUnionTypeIfNonNull(UnionType $target): bool
    {
        return false;
    }

    public function canCastToUnionTypeHandlingTemplates(
        UnionType $target,
        CodeBase $code_base
    ): bool {
        return true;
    }

    /**
     * @return bool
     * True if all types in this union are scalars
     */
    public function isScalar(): bool
    {
        return false;
    }

    /**
     * @return bool
     * True if any types in this union are a printable scalar, or this is the empty union type
     */
    public function hasPrintableScalar(): bool
    {
        return true;
    }

    /**
     * @return bool
     * True if any types in this union are a printable scalar, or this is the empty union type
     */
    public function hasValidBitwiseOperand(): bool
    {
        return true;
    }

    /**
     * @return bool
     * True if this union has array-like types (is of type array, is
     * a generic array, or implements ArrayAccess).
     */
    public function hasArrayLike(): bool
    {
        return false;
    }

    /**
     * @unused-param $code_base
     * @override
     */
    public function asArrayOrArrayAccessSubTypes(CodeBase $code_base): UnionType
    {
        return $this;
    }

    /**
     * @return bool
     * True if this union has array-like types (is of type array, is
     * a generic array, or implements ArrayAccess).
     */
    public function hasGenericArray(): bool
    {
        return false;
    }

    /**
     * @return bool
     * True if this union contains the ArrayAccess type.
     * (Call asExpandedTypes() first to check for subclasses of ArrayAccess)
     */
    public function hasArrayAccess(): bool
    {
        return false;
    }

    /**
     * @return bool
     * True if this union contains the Traversable type.
     * (Call asExpandedTypes() first to check for subclasses of Traversable)
     */
    public function hasTraversable(): bool
    {
        return false;
    }

    /**
     * @return bool
     * True if this union type represents types that are
     * array-like, and nothing else (e.g. can't be null).
     * If any of the array-like types are nullable, this returns false.
     */
    public function isExclusivelyArrayLike(): bool
    {
        return false;
    }

    /**
     * @return bool
     * True if this union type represents types that are arrays
     * or generic arrays, but nothing else.
     * @override
     */
    public function isExclusivelyArray(): bool
    {
        return false;
    }

    /**
     * @return UnionType
     * Get the subset of types which are not native
     */
    public function nonNativeTypes(): UnionType
    {
        return $this;
    }

    /**
     * A memory efficient way to create a UnionType from a filter operation.
     * If this the filter preserves everything, returns $this instead
     */
    public function makeFromFilter(Closure $cb): UnionType
    {
        return $this;  // filtering empty results in empty
    }

    /**
     * @param Context $context
     * The context in which we're resolving this union
     * type.
     *
     * @return Generator<FullyQualifiedClassName>
     * @suppress PhanTypeMismatchGeneratorYieldValue (deliberate empty stub code)
     *
     * A list of class FQSENs representing the non-native types
     * associated with this UnionType
     *
     * @throws CodeBaseException
     * An exception is thrown if a non-native type does not have
     * an associated class
     *
     * @throws IssueException
     * An exception is thrown if static is used as a type outside of an object
     * context
     *
     * TODO: Add a method to ContextNode to directly get FQSEN instead?
     * @suppress PhanImpossibleCondition deliberately making a generator yielding nothing
     */
    public function asClassFQSENList(
        Context $context
    ): Generator {
        if (false) {
            yield;
        }
    }

    /**
     * @param CodeBase $code_base
     * The code base in which to find classes
     *
     * @param Context $context
     * The context in which we're resolving this union
     * type.
     *
     * @return Generator<Clazz>
     *
     * A list of classes representing the non-native types
     * associated with this UnionType
     *
     * @throws CodeBaseException
     * An exception is thrown if a non-native type does not have
     * an associated class
     *
     * @throws IssueException
     * An exception is thrown if static is used as a type outside of an object
     * context
     *
     * @suppress PhanEmptyYieldFrom this is deliberate
     */
    public function asClassList(
        CodeBase $code_base,
        Context $context
    ): Generator {
        yield from [];
    }

    /**
     * Takes "a|b[]|c|d[]|e" and returns "a|c|e"
     *
     * @return UnionType
     * A UnionType with generic array types filtered out
     *
     * @override
     */
    public function nonGenericArrayTypes(): UnionType
    {
        return $this;
    }

    /**
     * Takes "a|b[]|c|d[]|e" and returns "b[]|d[]"
     *
     * @return UnionType
     * A UnionType with generic array types kept, other types filtered out.
     *
     * @see nonGenericArrayTypes
     */
    public function genericArrayTypes(): UnionType
    {
        return $this;
    }

    /**
     * Takes "MyClass|int|array|?object" and returns "MyClass|?object"
     *
     * @return UnionType
     * A UnionType with known object types kept, other types filtered out.
     *
     * @see nonGenericArrayTypes
     */
    public function objectTypes(): UnionType
    {
        return $this;
    }

    public function objectTypesStrict(): UnionType
    {
        return ObjectType::instance(false)->asRealUnionType();
    }

    public function objectTypesStrictAllowEmpty(): UnionType
    {
        return $this;
    }

    /**
     * Takes "MyClass|int|array|?object" and returns "MyClass|?object"
     *
     * @return UnionType
     * A UnionType with known object types kept, other types filtered out.
     *
     * @see nonGenericArrayTypes
     */
    public function objectTypesWithKnownFQSENs(): UnionType
    {
        return $this;
    }

    /**
     * Returns true if objectTypes would be non-empty.
     */
    public function hasObjectTypes(): bool
    {
        return false;
    }

    /**
     * Returns the types for which is_scalar($x) would be true.
     * This means null/nullable is removed.
     * Takes "MyClass|int|?bool|array|?object" and returns "int|bool"
     * Takes "?MyClass" and returns an empty union type.
     *
     * @return UnionType
     * A UnionType with known scalar types kept, other types filtered out.
     *
     * @see nonGenericArrayTypes
     */
    public function scalarTypes(): UnionType
    {
        return $this;
    }

    /**
     * Returns the types for which is_callable($x) would be true.
     * TODO: Check for __invoke()?
     * Takes "Closure|false" and returns "Closure"
     * Takes "?MyClass" and returns an empty union type.
     *
     * @return UnionType
     * A UnionType with known callable types kept, other types filtered out.
     *
     * @see nonGenericArrayTypes
     */
    public function callableTypes(): UnionType
    {
        return $this;
    }

    /**
     * Returns true if this has one or more callable types
     * TODO: Check for __invoke()?
     * Takes "Closure|false" and returns true
     * Takes "?MyClass" and returns false
     *
     * @return bool
     * A UnionType with known callable types kept, other types filtered out.
     *
     * @see self::callableTypes()
     *
     * @override
     */
    public function hasCallableType(): bool
    {
        return false;  // has no types
    }

    /**
     * Returns the types for which is_int($x) would be true.
     *
     * @return UnionType
     * A UnionType with known int types kept, other types filtered out.
     *
     * @see nonGenericArrayTypes
     */
    public function intTypes(): UnionType
    {
        return $this;
    }

    public function floatTypes(): UnionType
    {
        return $this;
    }

    /**
     * Returns the types for which is_string($x) would be true.
     *
     * @return UnionType
     * A UnionType with known string types kept, other types filtered out.
     *
     * @see nonGenericArrayTypes
     */
    public function stringTypes(): UnionType
    {
        return $this;
    }

    public function isExclusivelyStringTypes(): bool
    {
        return true;
    }

    /**
     * Returns the types for which is_numeric($x) is possibly true.
     *
     * @return UnionType
     * A UnionType with known numeric types kept, other types filtered out.
     *
     * @see nonGenericArrayTypes
     */
    public function numericTypes(): UnionType
    {
        return $this;
    }

    /**
     * Returns true if every type in this type is callable.
     * TODO: Check for __invoke()?
     * Takes "callable" and returns true
     * Takes "callable|false" and returns false
     *
     * @return bool
     * A UnionType with known callable types kept, other types filtered out.
     *
     * @see nonGenericArrayTypes
     */
    public function isExclusivelyCallable(): bool
    {
        return true; // !$this->hasTypeMatchingCallback(empty)
    }

    /**
     * Takes "a|b[]|c|d[]|e|array|ArrayAccess" and returns "a|c|e|ArrayAccess"
     *
     * @return UnionType
     * A UnionType with generic types(as well as the non-generic type "array")
     * filtered out.
     *
     * @see nonGenericArrayTypes
     */
    public function nonArrayTypes(): UnionType
    {
        return $this;
    }

    public function arrayTypes(): UnionType
    {
        return $this;
    }

    /**
     * @return bool
     * True if this is exclusively generic types
     */
    public function isGenericArray(): bool
    {
        return false;  // empty
    }

    /**
     * @return bool
     * True if any of the types in this UnionType made $matcher_callback return true
     */
    public function hasTypeMatchingCallback(Closure $matcher_callback): bool
    {
        return false;
    }

    public function hasRealTypeMatchingCallback(Closure $matcher_callback): bool
    {
        return false;
    }

    public function hasPhpdocOrRealTypeMatchingCallback(Closure $matcher_callback): bool
    {
        return false;
    }

    /**
     * @return bool
     * True if all of the types in this UnionType made $matcher_callback return true
     */
    public function allTypesMatchCallback(Closure $matcher_callback): bool
    {
        return true;
    }

    /**
     * @return Type|false
     * Returns the first type in this UnionType made $matcher_callback return true
     */
    public function findTypeMatchingCallback(Closure $matcher_callback)
    {
        return false;  // empty, no types
    }

    /**
     * Takes "a|b[]|c|d[]|e" and returns "b|d"
     *
     * @return UnionType
     * The subset of types in this
     */
    public function genericArrayElementTypes(bool $add_real_types = false): UnionType
    {
        return $this; // empty
    }

    /**
     * Takes "b|d[]" and returns "b[]|d[][]"
     *
     * @param int $key_type
     * Corresponds to the type of the array keys. Set this to a GenericArrayType::KEY_* constant.
     *
     * @return UnionType
     * The subset of types in this
     */
    public function elementTypesToGenericArray(int $key_type): UnionType
    {
        return $this;
    }

    /**
     * @param Closure(Type):Type $closure
     * A closure mapping `Type` to `Type`
     *
     * @return UnionType
     * A new UnionType with each type mapped through the
     * given closure
     * @override
     */
    public function asMappedUnionType(Closure $closure): UnionType
    {
        return $this;  // empty
    }

    public function asMappedListUnionType(Closure $closure): UnionType
    {
        return $this;  // empty
    }

    /**
     * @param Closure(UnionType):UnionType $closure
     * @override
     */
    public function withMappedElementTypes(Closure $closure): UnionType
    {
        return $this;
    }

    /**
     * @param int $key_type
     * Corresponds to the type of the array keys. Set this to a GenericArrayType::KEY_* constant.
     *
     * @return UnionType
     * Get a new type for each type in this union which is
     * the generic array version of this type. For instance,
     * 'int|float' will produce 'int[]|float[]'.
     *
     * If $this is an empty UnionType, this method will produce an empty UnionType
     */
    public function asGenericArrayTypes(int $key_type): UnionType
    {
        return $this;  // empty
    }

    public function asListTypes(): UnionType
    {
        return $this;
    }

    /**
     * @return UnionType
     * Get a non-empty union type with a new type for each type in this union which is
     * the generic array version of this type. For instance,
     * 'int|float' will produce 'int[]|float[]'.
     *
     * If $this is an empty UnionType, this method will produce 'array<KeyT,mixed>'
     */
    public function asNonEmptyGenericArrayTypes(int $key_type): UnionType
    {
        static $cache = [];
        return ($cache[$key_type] ?? ($cache[$key_type] = MixedType::instance(false)->asGenericArrayType($key_type)->asRealUnionType()));
    }

    public function asNonEmptyAssociativeArrayTypes(int $key_type): UnionType
    {
        static $cache = [];
        return ($cache[$key_type] ?? ($cache[$key_type] = AssociativeArrayType::fromElementType(MixedType::instance(false), false, $key_type)->asRealUnionType()));
    }

    /**
     * @unused-param $can_reduce_size
     */
    public function withAssociativeArrays(bool $can_reduce_size): UnionType
    {
        return $this;
    }

    public function withIntegerKeyArraysAsLists(): UnionType
    {
        return $this;
    }

    public function asNonEmptyListTypes(): UnionType
    {
        static $type = null;
        return ($type ?? ($type = ListType::fromElementType(MixedType::instance(false), false)->asRealUnionType()));
    }

    /**
     * @param CodeBase $code_base
     * The code base to use in order to find super classes, etc.
     *
     * @param int $recursion_depth
     * This thing has a tendency to run-away on me. This tracks
     * how bad I messed up by seeing how far the expanded types
     * go
     *
     * @return UnionType
     * Expands all class types to all inherited classes returning
     * a superset of this type.
     */
    public function asExpandedTypes(
        CodeBase $code_base,
        int $recursion_depth = 0
    ): UnionType {
        return $this;
    }

    /**
     * @param CodeBase $code_base
     * The code base to use in order to find super classes, etc.
     *
     * @param int $recursion_depth
     * This thing has a tendency to run-away on me. This tracks
     * how bad I messed up by seeing how far the expanded types
     * go
     *
     * @return UnionType
     * Expands all class types to all inherited classes returning
     * a superset of this type.
     */
    public function asExpandedTypesPreservingTemplate(
        CodeBase $code_base,
        int $recursion_depth = 0
    ): UnionType {
        return $this;
    }

    public function replaceWithTemplateTypes(UnionType $template_union_type): UnionType
    {
        return $template_union_type->eraseRealTypeSetRecursively();
    }

    public function hasTypeWithFQSEN(Type $other): bool
    {
        return false;
    }

    public function getTypesWithFQSEN(Type $other): UnionType
    {
        return $this;
    }

    /**
     * As per the Serializable interface
     *
     * @return string
     * A serialized representation of this type
     *
     * @see \Serializable
     */
    public function serialize(): string
    {
        return '';
    }

    /**
     * @return string
     * A human-readable string representation of this union
     * type
     */
    public function __toString(): string
    {
        return '';
    }

    /**
     * @return UnionType - A normalized version of this union type (May or may not be the same object, if no modifications were made)
     *
     * The following normalization rules apply
     *
     * 1. If one of the types is null or nullable, convert all types to nullable and remove "null" from the union type
     * 2. If both "true" and "false" (possibly nullable) coexist, or either coexists with "bool" (possibly nullable),
     *    then remove "true" and "false"
     */
    public function asNormalizedTypes(): UnionType
    {
        return $this;
    }

    public function hasTopLevelArrayShapeTypeInstances(): bool
    {
        return false;
    }

    /** @override */
    public function hasArrayShapeOrLiteralTypeInstances(): bool
    {
        return false;
    }

    /** @override */
    public function hasArrayShapeTypeInstances(): bool
    {
        return false;
    }

    /** @override */
    public function hasMixedType(): bool
    {
        return false;
    }

    /** @override */
    public function withFlattenedArrayShapeTypeInstances(): UnionType
    {
        return $this;
    }

    /** @override */
    public function withPossiblyEmptyArrays(): UnionType
    {
        return $this;
    }

    /** @override */
    public function withFlattenedTopLevelArrayShapeTypeInstances(): UnionType
    {
        return $this;
    }

    /** @override */
    public function withFlattenedArrayShapeOrLiteralTypeInstances(): UnionType
    {
        return $this;
    }

    public function hasPossiblyObjectTypes(): bool
    {
        return false;
    }

    public function isExclusivelyBoolTypes(): bool
    {
        return false;
    }

    public function generateUniqueId(): string
    {
        return '';
    }

    public function hasTopLevelNonArrayShapeTypeInstances(): bool
    {
        return false;
    }

    public function shouldBeReplacedBySpecificTypes(): bool
    {
        return true;
    }

    /**
     * @param int|string|float|bool $field_key
     */
    public function withoutArrayShapeField($field_key): UnionType
    {
        return $this;
    }

    public function withoutSubclassesOf(CodeBase $code_base, Type $object_type): UnionType
    {
        return $this;
    }

    public function canAnyTypeStrictCastToUnionType(CodeBase $code_base, UnionType $target, bool $allow_casting = true): bool
    {
        return true;
    }

    public function canStrictCastToUnionType(CodeBase $code_base, UnionType $target): bool
    {
        return true;
    }

    public function hasArray(): bool
    {
        return false;
    }

    public function hasClassWithToStringMethod(CodeBase $code_base, Context $context): bool
    {
        return false;
    }

    public function isExclusivelyGenerators(): bool
    {
        return false;
    }

    /** @suppress PhanThrowTypeAbsentForCall */
    public function asGeneratorTemplateType(): Type
    {
        return Type::fromFullyQualifiedString('\Generator');
    }

    /**
     * @unused-param $code_base
     * @override
     */
    public function iterableKeyUnionType(CodeBase $code_base): UnionType
    {
        return $this;
    }

    /**
     * @unused-param $code_base
     * @override
     */
    public function iterableValueUnionType(CodeBase $code_base): UnionType
    {
        return $this;
    }

    /**
     * @return Generator<Type,Type>
     * @suppress PhanTypeMismatchGeneratorYieldValue (deliberate empty stub code)
     * @suppress PhanTypeMismatchGeneratorYieldKey (deliberate empty stub code)
     * @suppress PhanImpossibleCondition
     */
    public function getReferencedClasses(): Generator
    {
        if (false) {
            yield;
        }
    }

    public function hasIntType(): bool
    {
        return false;
    }

    public function hasNonNullIntType(): bool
    {
        return false;
    }

    public function isExclusivelyRealFloatTypes(): bool
    {
        return false;
    }

    public function isNonNullIntType(): bool
    {
        return false;
    }

    public function isNonNullIntOrFloatType(): bool
    {
        return false;
    }

    public function isNonNullNumberType(): bool
    {
        return false;
    }

    public function hasStringType(): bool
    {
        return false;
    }

    public function hasNonNullStringType(): bool
    {
        return false;
    }

    public function isNonNullStringType(): bool
    {
        return false;
    }

    public function hasLiterals(): bool
    {
        return false;
    }

    public function asNonLiteralType(): UnionType
    {
        return $this;
    }

    public function applyUnaryMinusOperator(): UnionType
    {
        return UnionType::fromFullyQualifiedRealString('int|float');
    }

    public function applyUnaryBitwiseNotOperator(): UnionType
    {
        return UnionType::fromFullyQualifiedPHPDocAndRealString('int', 'int|string');
    }

    public function applyUnaryPlusOperator(): UnionType
    {
        return UnionType::fromFullyQualifiedRealString('int|float');
    }

    public function applyUnaryNotOperator(): UnionType
    {
        return UnionType::fromFullyQualifiedRealString('bool');
    }

    public function applyBoolCast(): UnionType
    {
        return UnionType::fromFullyQualifiedRealString('bool');
    }

    /** @return null */
    public function asSingleScalarValueOrNull()
    {
        return null;
    }

    public function asSingleScalarValueOrNullOrSelf()
    {
        return $this;
    }

    public function asValueOrNullOrSelf()
    {
        return $this;
    }

    public function asStringScalarValues(): array
    {
        return [];
    }

    public function asIntScalarValues(): array
    {
        return [];
    }

    public function asScalarValues(bool $strict = false): ?array
    {
        return [];
    }

    public function containsDefiniteNonObjectType(): bool
    {
        return false;
    }

    public function containsDefiniteNonObjectAndNonClassType(): bool
    {
        return false;
    }

    public function containsDefiniteNonCallableType(): bool
    {
        return false;
    }

    public function hasPossiblyCallableType(): bool
    {
        return true;
    }

    public function getTypeAfterIncOrDec(): UnionType
    {
        return $this;
    }

    public function getTemplateTypeExtractorClosure(CodeBase $code_base, TemplateType $template_type): ?Closure
    {
        return null;
    }

    public function usesTemplateType(TemplateType $template_type): bool
    {
        return false;
    }

    public function isVoidType(): bool
    {
        return false;
    }

    public function withRealType(Type $type): UnionType
    {
        return $type->asRealUnionType();
    }

    public function getRealTypeSet(): array
    {
        return [];
    }

    public function hasRealTypeSet(): bool
    {
        return false;
    }

    public function eraseRealTypeSet(): UnionType
    {
        return $this;
    }

    public function eraseRealTypeSetRecursively(): UnionType
    {
        return $this;
    }

    public function hasAnyTypeOverlap(CodeBase $code_base, UnionType $other): bool
    {
        return true;
    }

    public function hasAnyWeakTypeOverlap(UnionType $other): bool
    {
        return true;
    }

    public function canCastToDeclaredType(CodeBase $code_base, Context $context, UnionType $other): bool
    {
        return true;
    }

    /**
     * @param ?list<Type> $real_type_set
     */
    public function withRealTypeSet(?array $real_type_set): UnionType
    {
        if (!$real_type_set) {
            return $this;
        }
        return UnionType::of($real_type_set, $real_type_set);
    }

    public function getRealUnionType(): UnionType
    {
        return $this;
    }

    public function asRealUnionType(): UnionType
    {
        return $this;
    }

    public function arrayTypesStrictCast(): UnionType
    {
        return ArrayType::instance(false)->asRealUnionType();
    }

    public function arrayTypesStrictCastAllowEmpty(): UnionType
    {
        return $this;
    }

    public function boolTypes(): UnionType
    {
        return BoolType::instance(false)->asRealUnionType();
    }

    public function scalarTypesStrict(bool $allow_empty = false): UnionType
    {
        if ($allow_empty) {
            return $this;
        }
        return UnionType::fromFullyQualifiedRealString('int|float|string|bool');
    }

    public function isExclusivelyRealTypes(): bool
    {
        return false;
    }

    public function getDebugRepresentation(): string
    {
        return '(empty union type)';
    }

    public function canPossiblyCastToClass(CodeBase $code_base, Type $class_type): bool
    {
        return true;
    }

    public function isExclusivelySubclassesOf(CodeBase $code_base, Type $class_type): bool
    {
        return false;
    }

    /**
     * Returns true if this type has types for which `+expr` isn't an integer.
     */
    public function hasTypesCoercingToNonInt(): bool
    {
        return true;
    }

    public function isEmptyArrayShape(): bool
    {
        return false;
    }

    public function hasSubtypeOf(UnionType $type): bool
    {
        return true;
    }

    public function isStrictSubtypeOf(CodeBase $code_base, UnionType $type): bool
    {
        return true;
    }

    public function isDefinitelyUndefined(): bool
    {
        return false;
    }

    public function convertUndefinedToNullable(): UnionType
    {
        return $this;
    }

    public function classStringTypes(): UnionType
    {
        return $this;
    }

    public function classStringOrObjectTypes(): UnionType
    {
        return $this;
    }

    /**
     * @return Generator<Type> no types.
     * @suppress PhanImpossibleCondition
     * @suppress PhanTypeMismatchGeneratorYieldValue
     */
    public function getTypesRecursively(): Generator
    {
        if (false) {
            yield;
        }
    }
}
