init: replace Result<Success> with Result<void>
Now that Result<T> is actually expected<T, ...>, and the expected
proposal states expected<void, ...> as the way to indicate an expected
object that returns either successfully with no object or an error,
let's move init's Result<Success> to the preferred Result<void>.
Bug: 132145659
Test: boot, init unit tests
Change-Id: Ib2f98396d8e6e274f95a496fcdfd8341f77585ee
diff --git a/init/result.h b/init/result.h
index 984b257..8c1f91e 100644
--- a/init/result.h
+++ b/init/result.h
@@ -14,66 +14,14 @@
* limitations under the License.
*/
-// This file contains classes for returning a successful result along with an optional
-// arbitrarily typed return value or for returning a failure result along with an optional string
-// indicating why the function failed.
-
-// There are 3 classes that implement this functionality and one additional helper type.
-//
-// Result<T> either contains a member of type T that can be accessed using similar semantics as
-// std::optional<T> or it contains a ResultError describing an error, which can be accessed via
-// Result<T>::error().
-//
-// ResultError is a type that contains both a std::string describing the error and a copy of errno
-// from when the error occurred. ResultError can be used in an ostream directly to print its
-// string value.
-//
-// Success is a typedef that aids in creating Result<T> that do not contain a return value.
-// Result<Nothing> is the correct return type for a function that either returns successfully or
-// returns an error value. Returning Nothing() from a function that returns Result<Nothing> is the
-// correct way to indicate that a function without a return type has completed successfully.
-//
-// A successful Result<T> is constructed implicitly from any type that can be implicitly converted
-// to T or from the constructor arguments for T. This allows you to return a type T directly from
-// a function that returns Result<T>.
-//
-// Error and ErrnoError are used to construct a Result<T> that has failed. The Error class takes
-// an ostream as an input and are implicitly cast to a Result<T> containing that failure.
-// ErrnoError() is a helper function to create an Error class that appends ": " + strerror(errno)
-// to the end of the failure string to aid in interacting with C APIs. Alternatively, an errno
-// value can be directly specified via the Error() constructor.
-//
-// ResultError can be used in the ostream when using Error to construct a Result<T>. In this case,
-// the string that the ResultError takes is passed through the stream normally, but the errno is
-// passed to the Result<T>. This can be used to pass errno from a failing C function up multiple
-// callers.
-//
-// ResultError can also directly construct a Result<T>. This is particularly useful if you have a
-// function that return Result<T> but you have a Result<U> and want to return its error. In this
-// case, you can return the .error() from the Result<U> to construct the Result<T>.
-
-// An example of how to use these is below:
-// Result<U> CalculateResult(const T& input) {
-// U output;
-// if (!SomeOtherCppFunction(input, &output)) {
-// return Error() << "SomeOtherCppFunction(" << input << ") failed";
-// }
-// if (!c_api_function(output)) {
-// return ErrnoError() << "c_api_function(" << output << ") failed";
-// }
-// return output;
-// }
-//
-// auto output = CalculateResult(input);
-// if (!output) return Error() << "CalculateResult failed: " << output.error();
-// UseOutput(*output);
-
#pragma once
+// The implementation of this file has moved to android-base. This file remains since historically,
+// these classes were a part of init.
+
#include <android-base/result.h>
using android::base::ErrnoError;
using android::base::Error;
using android::base::Result;
using android::base::ResultError;
-using android::base::Success;