AST: Shave a yak in ProtocolDecl

Author: slavapestov

include/swift/AST/Decl.h

@@ -598,7 +598,7 @@ class alignas(1 << DeclAlignInBits) Decl : public ASTAllocated<Decl> {
     IsComputingSemanticMembers : 1
   );
 
-  SWIFT_INLINE_BITFIELD_FULL(ProtocolDecl, NominalTypeDecl, 1+1+1+1+1+1+1+1+1+1+1+1+1+8,
+  SWIFT_INLINE_BITFIELD_FULL(ProtocolDecl, NominalTypeDecl, 1+1+1+1+1+1+1+1+1+1+1+1+1+1+8,
     /// Whether the \c RequiresClass bit is valid.
     RequiresClassValid : 1,
 
@@ -625,6 +625,9 @@ class alignas(1 << DeclAlignInBits) Decl : public ASTAllocated<Decl> {
     /// Whether we've computed the inherited protocols list yet.
     InheritedProtocolsValid : 1,
 
+    /// Whether we have computed a requirement signature.
+    HasRequirementSignature : 1,
+
     /// Whether we have a lazy-loaded requirement signature.
     HasLazyRequirementSignature : 1,
 
@@ -5126,7 +5129,7 @@ class ProtocolDecl final : public NominalTypeDecl {
 
   /// The generic signature representing exactly the new requirements introduced
   /// by this protocol.
-  std::optional<RequirementSignature> RequirementSig;
+  RequirementSignature RequirementSig;
 
   /// Returns the cached result of \c requiresClass or \c None if it hasn't yet
   /// been computed.
@@ -5435,7 +5438,7 @@ class ProtocolDecl final : public NominalTypeDecl {
 
   /// Has the requirement signature been computed yet?
   bool isRequirementSignatureComputed() const {
-    return RequirementSig.has_value();
+    return Bits.ProtocolDecl.HasRequirementSignature;
   }
 
   void setRequirementSignature(RequirementSignature requirementSig);

lib/AST/Decl.cpp

@@ -6436,6 +6436,8 @@ ProtocolDecl::ProtocolDecl(DeclContext *DC, SourceLoc ProtocolLoc,
   Bits.ProtocolDecl.KnownProtocol = 0;
   Bits.ProtocolDecl.HasAssociatedTypes = 0;
   Bits.ProtocolDecl.HasLazyAssociatedTypes = 0;
+  Bits.ProtocolDecl.HasRequirementSignature = 0;
+  Bits.ProtocolDecl.HasLazyRequirementSignature = 0;
   Bits.ProtocolDecl.ProtocolRequirementsValid = false;
   setTrailingWhereClause(TrailingWhere);
 }
@@ -6682,12 +6684,13 @@ bool ProtocolDecl::isComputingRequirementSignature() const {
 
 void ProtocolDecl::setRequirementSignature(RequirementSignature requirementSig) {
   RequirementSig = requirementSig;
+  Bits.ProtocolDecl.HasRequirementSignature = 1;
 }
 
 void
 ProtocolDecl::setLazyRequirementSignature(LazyMemberLoader *lazyLoader,
                                           uint64_t requirementSignatureData) {
-  assert(!RequirementSig && "requirement signature already set");
+  assert(!isRequirementSignatureComputed() && "requirement signature already set");
 
   auto contextData = static_cast<LazyProtocolData *>(
       getASTContext().getOrCreateLazyContextData(this, lazyLoader));

lib/AST/TypeCheckRequests.cpp

@@ -330,7 +330,7 @@ std::optional<RequirementSignature>
 RequirementSignatureRequest::getCachedResult() const {
   auto proto = std::get<0>(getStorage());
   if (proto->isRequirementSignatureComputed())
-    return *proto->RequirementSig;
+    return proto->RequirementSig;
 
   return std::nullopt;
 }