llvm/llvm/include/llvm/ADT/TypeSwitch.h

//===- TypeSwitch.h - Switch functionality for RTTI casting -*- C++ -*-----===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
///
/// \file
///  This file implements the TypeSwitch template, which mimics a switch()
///  statement whose cases are type names.
///
//===-----------------------------------------------------------------------===/

#ifndef LLVM_ADT_TYPESWITCH_H
#define LLVM_ADT_TYPESWITCH_H

#include "llvm/ADT/STLExtras.h"
#include "llvm/Support/Casting.h"
#include <optional>

namespace llvm {
namespace detail {

template <typename DerivedT, typename T> class TypeSwitchBase { … };
} // end namespace detail

/// This class implements a switch-like dispatch statement for a value of 'T'
/// using dyn_cast functionality. Each `Case<T>` takes a callable to be invoked
/// if the root value isa<T>, the callable is invoked with the result of
/// dyn_cast<T>() as a parameter.
///
/// Example:
///  Operation *op = ...;
///  LogicalResult result = TypeSwitch<Operation *, LogicalResult>(op)
///    .Case<ConstantOp>([](ConstantOp op) { ... })
///    .Default([](Operation *op) { ... });
///
template <typename T, typename ResultT = void>
class TypeSwitch : public detail::TypeSwitchBase<TypeSwitch<T, ResultT>, T> { … };

/// Specialization of TypeSwitch for void returning callables.
TypeSwitch<T, void>;
} // end namespace llvm

#endif // LLVM_ADT_TYPESWITCH_H