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carbon-lang/common/ostream.h
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Jon Ross-Perkins cda5f66d22 Refactor NodeCategory to provide a class API (#4004)
Mirroring #4003 for NodeCategory.

Note we template a lot more on NodeCategory's enum, so this is a
slightly more awkward delta.

Also, switch from Enum in KeywordModifierSet to RawEnumType for
consistency with EnumBase. The templating on NodeCategory had me
thinking about that more.
2024-05-29 22:47:50 +00:00

95 lines
3.2 KiB
C++

// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
// Exceptions. See /LICENSE for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
#ifndef CARBON_COMMON_OSTREAM_H_
#define CARBON_COMMON_OSTREAM_H_
#include <concepts>
#include <ostream>
#include <type_traits>
#include "llvm/Support/raw_os_ostream.h"
// Libraries should include this header instead of raw_ostream.
#include "llvm/Support/Compiler.h"
#include "llvm/Support/raw_ostream.h" // IWYU pragma: export
namespace Carbon {
// CRTP base class for printable types. Children (DerivedT) must implement:
// - auto Print(llvm::raw_ostream& out) const -> void
template <typename DerivedT>
class Printable {
// Provides simple printing for debuggers.
LLVM_DUMP_METHOD void Dump() const {
static_cast<const DerivedT*>(this)->Print(llvm::errs());
}
// Supports printing to llvm::raw_ostream.
friend auto operator<<(llvm::raw_ostream& out, const DerivedT& obj)
-> llvm::raw_ostream& {
obj.Print(out);
return out;
}
// Supports printing to std::ostream.
friend auto operator<<(std::ostream& out, const DerivedT& obj)
-> std::ostream& {
llvm::raw_os_ostream raw_os(out);
obj.Print(raw_os);
return out;
}
// Allows GoogleTest and GoogleMock to print pointers by dereferencing them.
// This is important to allow automatic printing of arguments of mocked
// APIs.
friend auto PrintTo(DerivedT* p, std::ostream* out) -> void {
*out << static_cast<const void*>(p);
// Also print the object if non-null.
if (p) {
*out << " pointing to " << *p;
}
}
};
// Returns the result of printing the value.
template <typename T>
inline auto PrintToString(const T& val) -> std::string {
std::string str;
llvm::raw_string_ostream stream(str);
stream << val;
return str;
}
} // namespace Carbon
namespace llvm {
// Injects an `operator<<` overload into the `llvm` namespace which detects LLVM
// types with `raw_ostream` overloads and uses that to map to a `std::ostream`
// overload. This allows LLVM types to be printed to `std::ostream` via their
// `raw_ostream` operator overloads, which is needed both for logging and
// testing.
//
// To make this overload be unusually low priority, it is designed to take even
// the `std::ostream` parameter as a template, and SFINAE disable itself unless
// that template parameter is derived from `std::ostream`. This ensures that an
// *explicit* operator will be preferred when provided. Some LLVM types may have
// this, and so we want to prioritize accordingly.
//
// It would be slightly cleaner for LLVM itself to provide this overload in
// `raw_os_ostream.h` so that we wouldn't need to inject into LLVM's namespace,
// but supporting `std::ostream` isn't a priority for LLVM so we handle it
// locally instead.
template <typename StreamT, typename ClassT>
requires std::derived_from<std::decay_t<StreamT>, std::ostream> &&
(!std::same_as<std::decay_t<ClassT>, raw_ostream>)
auto operator<<(StreamT& standard_out, const ClassT& value) -> StreamT& {
raw_os_ostream(standard_out) << value;
return standard_out;
}
} // namespace llvm
#endif // CARBON_COMMON_OSTREAM_H_