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45 lines
1.2 KiB
C++
45 lines
1.2 KiB
C++
// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
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// Exceptions. See /LICENSE for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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#ifndef EXECUTABLE_SEMANTICS_SYNTAX_BISON_WRAP_H_
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#define EXECUTABLE_SEMANTICS_SYNTAX_BISON_WRAP_H_
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#include <optional>
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#include "common/check.h"
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namespace Carbon {
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// Bison requires that types be default initializable for use with its variant
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// semantics. This wraps arbitrary types to support a default constructor, while
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// still requiring they be properly initialized.
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template <typename T>
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class BisonWrap {
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public:
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// Assigning a value initializes the wrapper.
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auto operator=(T&& rhs) -> BisonWrap& {
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val_ = std::move(rhs);
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return *this;
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}
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// Support transparent conversion to the wrapped type.
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operator T() { return Release(); }
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// Deliberately releases the contained value. Errors if not initialized.
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// Called directly in parser.ypp when releasing pairs.
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auto Release() -> T {
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CHECK(val_.has_value());
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T ret = std::move(*val_);
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val_.reset();
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return ret;
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}
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private:
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std::optional<T> val_;
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};
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} // namespace Carbon
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#endif // EXECUTABLE_SEMANTICS_SYNTAX_BISON_WRAP_H_
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