Codechange: Make TileIndex a "strong" typedef to give it a distinct type.
This is accomplished by changing it to a single member struct with the appropriate operator overloads to make it all work with not too much source modifications.pull/353/head
Michael Lutz
3 years ago
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4fc055d6e9
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/*
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* This file is part of OpenTTD.
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* OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
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* OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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* See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
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*/
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/** @file strong_typedef_type.hpp Type (helpers) for making a strong typedef that is a distinct type. */
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#ifndef STRONG_TYPEDEF_TYPE_HPP
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#define STRONG_TYPEDEF_TYPE_HPP
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/** Non-templated base for #StrongTypedef for use with type trait queries. */
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struct StrongTypedefBase {};
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/**
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* Templated helper to make a type-safe 'typedef' representing a single POD value.
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* A normal 'typedef' is not distinct from its base type and will be treated as
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* identical in many contexts. This class provides a distinct type that can still
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* be assign from and compared to values of its base type.
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*
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* @note This is meant to be used as a base class, not directly.
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* @tparam T Storage type
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* @tparam Tthis Type of the derived class (i.e. the concrete usage of this class).
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*/
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template <class T, class Tthis>
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struct StrongTypedef : StrongTypedefBase {
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using Type = T;
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T value{}; ///< Backing storage field.
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constexpr StrongTypedef() = default;
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constexpr StrongTypedef(const StrongTypedef &o) = default;
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constexpr StrongTypedef(StrongTypedef &&o) = default;
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constexpr StrongTypedef(const T &value) : value(value) {}
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constexpr Tthis &operator =(const StrongTypedef &rhs) { this->value = rhs.value; return static_cast<Tthis &>(*this); }
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constexpr Tthis &operator =(StrongTypedef &&rhs) { this->value = std::move(rhs.value); return static_cast<Tthis &>(*this); }
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constexpr Tthis &operator =(const T &rhs) { this->value = rhs; return static_cast<Tthis &>(*this); }
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explicit constexpr operator T() const { return this->value; }
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constexpr bool operator ==(const StrongTypedef &rhs) const { return this->value == rhs.value; }
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constexpr bool operator !=(const StrongTypedef &rhs) const { return this->value != rhs.value; }
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constexpr bool operator ==(const T &rhs) const { return this->value == rhs; }
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constexpr bool operator !=(const T &rhs) const { return this->value != rhs; }
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};
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/**
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* Extension of #StrongTypedef with operators for addition and subtraction.
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* @tparam T Storage type
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* @tparam Tthis Type of the derived class (i.e. the concrete usage of this class).
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*/
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template <class T, class Tthis>
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struct StrongIntegralTypedef : StrongTypedef<T, Tthis> {
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using StrongTypedef<T, Tthis>::StrongTypedef;
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constexpr Tthis &operator ++() { this->value++; return static_cast<Tthis &>(*this); }
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constexpr Tthis &operator --() { this->value--; return static_cast<Tthis &>(*this); }
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constexpr Tthis operator ++(int) { auto res = static_cast<Tthis &>(*this); this->value++; return res; }
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constexpr Tthis operator --(int) { auto res = static_cast<Tthis &>(*this); this->value--; return res; }
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constexpr Tthis &operator +=(const Tthis &rhs) { this->value += rhs.value; return *static_cast<Tthis *>(this); }
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constexpr Tthis &operator -=(const Tthis &rhs) { this->value -= rhs.value; return *static_cast<Tthis *>(this); }
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constexpr Tthis operator +(const Tthis &rhs) const { return Tthis{ this->value + rhs.value }; }
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constexpr Tthis operator -(const Tthis &rhs) const { return Tthis{ this->value - rhs.value }; }
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constexpr Tthis operator +(const T &rhs) const { return Tthis{ this->value + rhs }; }
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constexpr Tthis operator -(const T &rhs) const { return Tthis{ this->value - rhs }; }
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};
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#endif /* STRONG_TYPEDEF_TYPE_HPP */
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