86 lines
3.6 KiB
C
86 lines
3.6 KiB
C
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//===-- raw-ostream.h - Support for printing using raw_ostream --*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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// This file is not part of gtest, but extends it to support LLVM libraries.
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// This is not a public API for testing - it's a detail of LLVM's gtest.
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//
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// gtest allows providing printers for custom types by defining operator<<.
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// In LLVM, operator<< usually takes llvm:raw_ostream& instead of std::ostream&.
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//
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// This file defines a template printable(V), which returns a version of V that
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// can be streamed into a std::ostream.
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//
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// This interface is chosen so that in the default case (printable(V) is V),
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// the main gtest code calls operator<<(OS, V) itself. gtest-printers carefully
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// controls the lookup to enable fallback printing (see testing::internal2).
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//===----------------------------------------------------------------------===//
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#ifndef GTEST_INCLUDE_GTEST_INTERNAL_CUSTOM_RAW_OSTREAM_H_
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#define GTEST_INCLUDE_GTEST_INTERNAL_CUSTOM_RAW_OSTREAM_H_
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namespace llvm_gtest {
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// StreamSwitch is a trait that tells us how to stream a T into a std::ostream.
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// By default, we just stream the T directly. We'll specialize this later.
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template <typename T, typename Enable = void> struct StreamSwitch {
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static const T& printable(const T& V) { return V; }
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};
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// printable() returns a version of its argument that can be streamed into a
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// std::ostream. This may be the argument itself, or some other representation.
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template <typename T> decltype(auto) printable(const T &V) {
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// We delegate to the trait, to allow partial specialization.
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return StreamSwitch<T>::printable(V);
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}
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} // namespace llvm_gtest
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// If raw_ostream support is enabled, we specialize for types with operator<<
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// that takes a raw_ostream.
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#if !GTEST_NO_LLVM_SUPPORT
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#include "llvm/ADT/Optional.h"
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#include "llvm/Support/raw_os_ostream.h"
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#include "llvm/Support/raw_ostream.h"
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#include <ostream>
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namespace llvm_gtest {
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// The printable() of a raw_ostream-enabled type T is a RawStreamProxy<T>.
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// It uses raw_os_ostream to write the wrapped value to a std::ostream.
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template <typename T>
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struct RawStreamProxy {
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const T& V;
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friend std::ostream &operator<<(std::ostream &S, const RawStreamProxy<T> &V) {
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llvm::raw_os_ostream OS(S);
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OS << V.V;
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return S;
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}
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};
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// We enable raw_ostream treatment if `(raw_ostream&) << (const T&)` is valid.
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// We don't want implicit conversions on the RHS (e.g. to bool!), so "consume"
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// the possible conversion by passing something convertible to const T& instead.
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template <typename T> struct ConvertibleTo { operator T(); };
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template <typename T>
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struct StreamSwitch<T, decltype((void)(std::declval<llvm::raw_ostream &>()
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<< ConvertibleTo<const T &>()))> {
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static const RawStreamProxy<T> printable(const T &V) { return {V}; }
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};
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// llvm::Optional has a template operator<<, which means it will not accept any
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// implicit conversions, so we need to special-case it here.
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template <typename T>
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struct StreamSwitch<llvm::Optional<T>,
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decltype((void)(std::declval<llvm::raw_ostream &>()
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<< std::declval<llvm::Optional<T>>()))> {
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static const RawStreamProxy<llvm::Optional<T>>
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printable(const llvm::Optional<T> &V) {
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return {V};
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}
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};
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} // namespace llvm_gtest
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#endif // !GTEST_NO_LLVM_SUPPORT
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#endif // GTEST_INCLUDE_GTEST_INTERNAL_CUSTOM_RAW_OSTREAM_H_
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