This patch mechanically replaces None with std::nullopt where the
compiler would warn if None were deprecated. The intent is to reduce
the amount of manual work required in migrating from Optional to
std::optional.
This is part of an effort to migrate from llvm::Optional to
std::optional:
https://discourse.llvm.org/t/deprecating-llvm-optional-x-hasvalue-getvalue-getvalueor/63716
This change makes it possible to extract iOS-to-another-platform version mappings from `VersionMap` in the `SDKSettings.json` file in Darwin SDKs, for example, `iOS_watchOS` and `iOS_tvOS`.
This code was originally authored by Alex Lorenz.
rdar://81491680
Differential Revision: https://reviews.llvm.org/D116615