Add a new bit to ExtInfo to represent inout results

Move NumParams from ExtInfo to AnyFunctionType to make room in ExtInfo

include/swift/AST/ExtInfo.h

@@ -537,7 +537,8 @@ class ASTExtInfoBuilder {
     DifferentiabilityMaskOffset = 11,
     DifferentiabilityMask = 0x7 << DifferentiabilityMaskOffset,
     SendingResultMask = 1 << 14,
-    NumMaskBits = 15
+    InOutResultMask = 1 << 15,
+    NumMaskBits = 16
   };
 
   static_assert(FunctionTypeIsolation::Mask == 0x7, "update mask manually");
@@ -660,6 +661,8 @@ public:
                                                    globalActor);
   }
 
+  constexpr bool hasInOutResult() const { return bits & InOutResultMask; }
+
   constexpr bool hasSelfParam() const {
     switch (getSILRepresentation()) {
     case SILFunctionTypeRepresentation::Thick:
@@ -782,6 +785,11 @@ public:
         lifetimeDependencies);
   }
 
+  [[nodiscard]] ASTExtInfoBuilder withHasInOutResult() const {
+    return ASTExtInfoBuilder((bits | InOutResultMask), clangTypeInfo,
+                             globalActor, thrownError, lifetimeDependencies);
+  }
+
   void Profile(llvm::FoldingSetNodeID &ID) const {
     ID.AddInteger(bits);
     ID.AddPointer(clangTypeInfo.getType());
@@ -877,6 +885,8 @@ public:
 
   FunctionTypeIsolation getIsolation() const { return builder.getIsolation(); }
 
+  constexpr bool hasInOutResult() const { return builder.hasInOutResult(); }
+
   /// Helper method for changing the representation.
   ///
   /// Prefer using \c ASTExtInfoBuilder::withRepresentation for chaining.

include/swift/AST/Types.h

@@ -407,7 +407,7 @@ class alignas(1 << TypeAlignInBits) TypeBase
   }
 
 protected:
-  enum { NumAFTExtInfoBits = 15 };
+  enum { NumAFTExtInfoBits = 16 };
   enum { NumSILExtInfoBits = 14 };
 
   // clang-format off
@@ -444,8 +444,7 @@ protected:
     HasExtInfo : 1,
     HasClangTypeInfo : 1,
     HasThrownError : 1,
-    HasLifetimeDependencies : 1,
-    NumParams : 15
+    HasLifetimeDependencies : 1
   );
 
   SWIFT_INLINE_BITFIELD_FULL(ArchetypeType, TypeBase, 1+1+16,
@@ -3350,7 +3349,8 @@ END_CAN_TYPE_WRAPPER(DynamicSelfType, Type)
 /// represented at the binary level as a single function pointer.
 class AnyFunctionType : public TypeBase {
   const Type Output;
-  
+  uint16_t NumParams;
+
 public:
   using Representation = FunctionTypeRepresentation;
 
@@ -3611,8 +3611,8 @@ protected:
       Bits.AnyFunctionType.HasThrownError = false;
       Bits.AnyFunctionType.HasLifetimeDependencies = false;
     }
-    Bits.AnyFunctionType.NumParams = NumParams;
-    assert(Bits.AnyFunctionType.NumParams == NumParams && "Params dropped!");
+    this->NumParams = NumParams;
+    assert(this->NumParams == NumParams && "Params dropped!");
     
     if (Info && CONDITIONAL_ASSERT_enabled()) {
       unsigned maxLifetimeTarget = NumParams + 1;
@@ -3650,7 +3650,7 @@ public:
 
   Type getResult() const { return Output; }
   ArrayRef<Param> getParams() const;
-  unsigned getNumParams() const { return Bits.AnyFunctionType.NumParams; }
+  unsigned getNumParams() const { return NumParams; }
 
   GenericSignature getOptGenericSignature() const;
   

lib/Sema/TypeCheckDecl.cpp

@@ -2572,6 +2572,11 @@ InterfaceTypeRequest::evaluate(Evaluator &eval, ValueDecl *D) const {
             infoBuilder.withLifetimeDependencies(*lifetimeDependenceInfo);
       }
 
+      auto *accessor = dyn_cast<AccessorDecl>(AFD);
+      if (accessor && accessor->isMutateAccessor()) {
+        infoBuilder = infoBuilder.withHasInOutResult();
+      }
+
       auto info = infoBuilder.build();
 
       if (sig && !hasSelf) {