luau/Analysis/include/Luau/Unifier2.h

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// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
#pragma once
#include "Luau/DenseHash.h"
#include "Luau/NotNull.h"
#include <optional>
#include <vector>
#include <utility>
namespace Luau
{
using TypeId = const struct Type*;
using TypePackId = const struct TypePackVar*;
struct BuiltinTypes;
struct InternalErrorReporter;
struct Scope;
struct TypeArena;
enum class OccursCheckResult
{
Pass,
Fail
};
struct Unifier2
{
NotNull<TypeArena> arena;
NotNull<BuiltinTypes> builtinTypes;
NotNull<InternalErrorReporter> ice;
int recursionCount = 0;
int recursionLimit = 0;
Unifier2(NotNull<TypeArena> arena, NotNull<BuiltinTypes> builtinTypes, NotNull<InternalErrorReporter> ice);
/** Attempt to commit the subtype relation subTy <: superTy to the type
* graph.
*
* @returns true if successful.
*
* Note that incoherent types can and will successfully be unified. We stop
* when we *cannot know* how to relate the provided types, not when doing so
* would narrow something down to never or broaden it to unknown.
*
* Presently, the only way unification can fail is if we attempt to bind one
* free TypePack to another and encounter an occurs check violation.
*/
bool unify(TypeId subTy, TypeId superTy);
// TODO think about this one carefully. We don't do unions or intersections of type packs
bool unify(TypePackId subTp, TypePackId superTp);
std::optional<TypeId> generalize(NotNull<Scope> scope, TypeId ty);
private:
/**
* @returns simplify(left | right)
*/
TypeId mkUnion(TypeId left, TypeId right);
/**
* @returns simplify(left & right)
*/
TypeId mkIntersection(TypeId left, TypeId right);
// Returns true if needle occurs within haystack already. ie if we bound
// needle to haystack, would a cyclic TypePack result?
OccursCheckResult occursCheck(DenseHashSet<TypePackId>& seen, TypePackId needle, TypePackId haystack);
};
} // namespace Luau