luau/Analysis/src/LValue.cpp

// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
#include "Luau/LValue.h"

#include "Luau/Ast.h"

#include <vector>

namespace Luau
{

bool Field::operator==(const Field& rhs) const
{
    LUAU_ASSERT(parent && rhs.parent);
    return key == rhs.key && (parent == rhs.parent || *parent == *rhs.parent);
}

bool Field::operator!=(const Field& rhs) const
{
    return !(*this == rhs);
}

size_t LValueHasher::operator()(const LValue& lvalue) const
{
    // Most likely doesn't produce high quality hashes, but we're probably ok enough with it.
    // When an evidence is shown that operator==(LValue) is used more often than it should, we can have a look at improving the hash quality.
    size_t acc = 0;
    size_t offset = 0;

    const LValue* current = &lvalue;
    while (current)
    {
        if (auto field = get<Field>(*current))
            acc ^= (std::hash<std::string>{}(field->key) << 1) >> ++offset;
        else if (auto symbol = get<Symbol>(*current))
            acc ^= std::hash<Symbol>{}(*symbol) << 1;
        else
            LUAU_ASSERT(!"Hash not accumulated for this new LValue alternative.");

        current = baseof(*current);
    }

    return acc;
}

const LValue* baseof(const LValue& lvalue)
{
    if (auto field = get<Field>(lvalue))
        return field->parent.get();

    auto symbol = get<Symbol>(lvalue);
    LUAU_ASSERT(symbol);
    return nullptr; // Base of root is null.
}

std::optional<LValue> tryGetLValue(const AstExpr& node)
{
    const AstExpr* expr = &node;
    while (auto e = expr->as<AstExprGroup>())
        expr = e->expr;

    if (auto local = expr->as<AstExprLocal>())
        return Symbol{local->local};
    else if (auto global = expr->as<AstExprGlobal>())
        return Symbol{global->name};
    else if (auto indexname = expr->as<AstExprIndexName>())
    {
        if (auto lvalue = tryGetLValue(*indexname->expr))
            return Field{std::make_shared<LValue>(*lvalue), indexname->index.value};
    }
    else if (auto indexexpr = expr->as<AstExprIndexExpr>())
    {
        if (auto lvalue = tryGetLValue(*indexexpr->expr))
            if (auto string = indexexpr->index->as<AstExprConstantString>())
                return Field{std::make_shared<LValue>(*lvalue), std::string(string->value.data, string->value.size)};
    }

    return std::nullopt;
}

Symbol getBaseSymbol(const LValue& lvalue)
{
    const LValue* current = &lvalue;
    while (auto field = get<Field>(*current))
        current = baseof(*current);

    const Symbol* symbol = get<Symbol>(*current);
    LUAU_ASSERT(symbol);
    return *symbol;
}

void merge(RefinementMap& l, const RefinementMap& r, std::function<TypeId(TypeId, TypeId)> f)
{
    for (const auto& [k, a] : r)
    {
        if (auto it = l.find(k); it != l.end())
            l[k] = f(it->second, a);
        else
            l[k] = a;
    }
}

void addRefinement(RefinementMap& refis, const LValue& lvalue, TypeId ty)
{
    refis[lvalue] = ty;
}

} // namespace Luau