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
GCC warning:
```
/llvm-project/clang/lib/APINotes/APINotesYAMLCompiler.cpp:574:6: warning: ‘void {anonymous}::Module::dump()’ defined but not used [-Wunused-function]
574 | void Module::dump() {
| ^~~~~~
```
_Nullable_result generally like _Nullable, except when being imported into a
swift async method. rdar://70106409
Differential revision: https://reviews.llvm.org/D92495
This adds the skeleton of the YAML Compiler for APINotes. This change
only adds the YAML IO model for the API Notes along with a new testing
tool `apinotes-test` which can be used to verify that can round trip the
YAML content properly. It provides the basis for the future work which
will add a binary serialization and deserialization format to the data
model.
This is based on the code contributed by Apple at
https://github.com/llvm/llvm-project-staging/tree/staging/swift/apinotes.
Differential Revision: https://reviews.llvm.org/D88859
Reviewed By: Gabor Marton
Kazu Hirata