Update SILGen for mutate accessors

Author: meg-gupta

lib/SILGen/SILGenLValue.cpp

@@ -5706,7 +5706,8 @@ std::optional<ManagedValue>
 SILGenFunction::tryEmitProjectedLValue(SILLocation loc, LValue &&src,
                                        TSanKind tsanKind) {
   assert(src.getAccessKind() == SGFAccessKind::BorrowedAddressRead ||
-         src.getAccessKind() == SGFAccessKind::BorrowedObjectRead);
+         src.getAccessKind() == SGFAccessKind::BorrowedObjectRead ||
+         src.getAccessKind() == SGFAccessKind::Write);
 
   for (auto component = src.begin(); component != src.end(); component++) {
     if (component->get()->getKind() != PathComponent::BorrowMutateKind &&

lib/SILGen/SILGenStmt.cpp

@@ -726,8 +726,8 @@ SILValue SILGenFunction::emitUncheckedGuaranteedConversion(SILValue value) {
 bool SILGenFunction::emitGuaranteedReturn(
     SILLocation loc, Expr *ret, SmallVectorImpl<SILValue> &directResults) {
   auto *afd = cast<AbstractFunctionDecl>(FunctionDC->getAsDecl());
-  assert(cast<AccessorDecl>(afd)->isBorrowAccessor());
-
+  assert(cast<AccessorDecl>(afd)->isBorrowAccessor() ||
+         cast<AccessorDecl>(afd)->isMutateAccessor());
 
   auto emitLoadBorrowFromGuaranteedAddress =
       [&](ManagedValue guaranteedAddress) -> SILValue {
@@ -762,13 +762,25 @@ bool SILGenFunction::emitGuaranteedReturn(
   // Emit return value at +0.
   FormalEvaluationScope scope(*this);
   LValueOptions options;
+
+  if (cast<AccessorDecl>(afd)->isMutateAccessor()) {
+    options = options.forGuaranteedAddressReturn(true);
+  } else {
+    assert(cast<AccessorDecl>(afd)->isBorrowAccessor());
+    if (F.getSelfArgument()->getType().isObject()) {
+      options = options.forGuaranteedReturn(true);
+    } else {
+      options = options.forGuaranteedAddressReturn(true);
+    }
+  }
+
   auto lvalue = emitLValue(ret,
                            F.getSelfArgument()->getType().isObject()
                                ? SGFAccessKind::BorrowedObjectRead
-                               : SGFAccessKind::BorrowedAddressRead,
-                           F.getSelfArgument()->getType().isObject()
-                               ? options.forGuaranteedReturn(true)
-                               : options.forGuaranteedAddressReturn(true));
+                           : cast<AccessorDecl>(afd)->isBorrowAccessor()
+                               ? SGFAccessKind::BorrowedAddressRead
+                               : SGFAccessKind::Write,
+                           options);
 
   // If the accessor is annotated with @_unsafeSelfDependentResultAttr,
   // disable diagnosing the return expression.