Several offsetting bugs both broke the caching of `ObjCInterfaceAndImplementationRequest` and caused it to usually miss. Fix this whole painful mess. Also has collateral improvements to simple_display().
An @_objcImpl extension with no category name *should* implement not only the class’s main @interface, but also any class extension @interfaces. Start making this true by making ObjCInterfaceAndImplementationRequest return all of these decls as the interfaces for such an implementation.
This commit doesn’t actually change Sema or IRGen to process the extra interfaces, so it’s NFC.
This reduces the memory overhead of objcImpl from one word per Decl to one bit per Decl, at the cost of making cache lookups slightly slower (but it will only be consulted once for non-objcImpl decls, which is by far the most common case).
This is phase-1 of switching from llvm::Optional to std::optional in the
next rebranch. llvm::Optional was removed from upstream LLVM, so we need
to migrate off rather soon. On Darwin, std::optional, and llvm::Optional
have the same layout, so we don't need to be as concerned about ABI
beyond the name mangling. `llvm::Optional` is only returned from one
function in
```
getStandardTypeSubst(StringRef TypeName,
bool allowConcurrencyManglings);
```
It's the return value, so it should not impact the mangling of the
function, and the layout is the same as `std::optional`, so it should be
mostly okay. This function doesn't appear to have users, and the ABI was
already broken 2 years ago for concurrency and no one seemed to notice
so this should be "okay".
I'm doing the migration incrementally so that folks working on main can
cherry-pick back to the release/5.9 branch. Once 5.9 is done and locked
away, then we can go through and finish the replacement. Since `None`
and `Optional` show up in contexts where they are not `llvm::None` and
`llvm::Optional`, I'm preparing the work now by going through and
removing the namespace unwrapping and making the `llvm` namespace
explicit. This should make it fairly mechanical to go through and
replace llvm::Optional with std::optional, and llvm::None with
std::nullopt. It's also a change that can be brought onto the
release/5.9 with minimal impact. This should be an NFC change.
