[clang] NFC: introduce UnsignedOrNone as a replacement for std::optional<unsigned> (#134142)

This introduces a new class 'UnsignedOrNone', which models a lite
version of `std::optional<unsigned>`, but has the same size as
'unsigned'.

This replaces most uses of `std::optional<unsigned>`, and similar
schemes utilizing 'int' and '-1' as sentinel.

Besides the smaller size advantage, this is simpler to serialize, as its
internal representation is a single unsigned int as well.

1 files changed, 1 insertions, 1 deletions

diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index 84f7f2b..f27be5f 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -4267,7 +4267,7 @@ public:
       auto ID = Writer.GetDeclRef(DeclForLocalLookup);
 
       if (isModuleLocalDecl(D)) {
-        if (std::optional<unsigned> PrimaryModuleHash =
+        if (UnsignedOrNone PrimaryModuleHash =
                 getPrimaryModuleHash(D->getOwningModule())) {
           auto Key = std::make_pair(D->getDeclName(), *PrimaryModuleHash);
           auto Iter = ModuleLocalDeclsMap.find(Key);