Handle vanishing tuples correctly in result planning.

Author: rjmccall

lib/SILGen/ResultPlan.cpp

@@ -584,16 +584,15 @@ class PackTransformResultPlan final : public ResultPlan {
 /// A result plan which produces a larger RValue from a bunch of
 /// components.
 class TupleRValueResultPlan final : public ResultPlan {
-  CanTupleType substType;
-
+  CanType substType;
   SmallVector<ResultPlanPtr, 4> origEltPlans;
 
 public:
   TupleRValueResultPlan(ResultPlanBuilder &builder, AbstractionPattern origType,
-                        CanTupleType substType)
+                        CanType substType)
       : substType(substType) {
     // Create plans for all the elements.
-    origEltPlans.reserve(substType->getNumElements());
+    origEltPlans.reserve(origType.getNumTupleElements());
     origType.forEachTupleElement(substType,
                                  [&](TupleElementGenerator &origElt) {
       AbstractionPattern origEltType = origElt.getOrigType();
@@ -643,7 +642,7 @@ class TupleInitializationResultPlan final : public ResultPlan {
   TupleInitializationResultPlan(ResultPlanBuilder &builder,
                                 Initialization *tupleInit,
                                 AbstractionPattern origType,
-                                CanTupleType substType)
+                                CanType substType)
       : tupleInit(tupleInit) {
     // Get the sub-initializations.
     eltInits = tupleInit->splitIntoTupleElements(builder.SGF, builder.loc,
@@ -1115,7 +1114,7 @@ ResultPlanPtr ResultPlanBuilder::build(Initialization *init,
                                        CanType substType) {
   // Destructure original tuples.
   if (origType.isTuple()) {
-    return buildForTuple(init, origType, cast<TupleType>(substType));
+    return buildForTuple(init, origType, substType);
   }
 
   assert(!origType.isPackExpansion() &&
@@ -1299,13 +1298,17 @@ ResultPlanBuilder::buildScalarIntoPack(SILValue packAddr,
 
 ResultPlanPtr ResultPlanBuilder::buildForTuple(Initialization *init,
                                                AbstractionPattern origType,
-                                               CanTupleType substType) {
+                                               CanType substType) {
   // If we have an initialization, and we can split it, do so.
   if (init && init->canSplitIntoTupleElements()) {
     return ResultPlanPtr(
         new TupleInitializationResultPlan(*this, init, origType, substType));
   }
 
+  auto substTupleType = dyn_cast<TupleType>(substType);
+  bool substHasPackExpansion =
+    (substTupleType && substTupleType.containsPackExpansionType());
+
   // Otherwise, if the tuple contains a pack expansion, we'll need to
   // initialize a single buffer one way or another: either we're giving
   // this to RValue (which wants a single value for tuples with pack
@@ -1319,9 +1322,9 @@ ResultPlanPtr ResultPlanBuilder::buildForTuple(Initialization *init,
   // do that if we're not using lowered addresses because we prefer to
   // build tuples with scalar operations.
   auto &substTL = SGF.getTypeLowering(substType);
-  assert(substTL.isAddressOnly() || !substType.containsPackExpansionType());
+  assert(substTL.isAddressOnly() || !substHasPackExpansion);
   if (substTL.isAddressOnly() &&
-      (substType.containsPackExpansionType() ||
+      (substHasPackExpansion ||
        (init != nullptr && SGF.F.getConventions().useLoweredAddresses()))) {
     // Create a temporary.
     auto temporary = SGF.emitTemporary(loc, substTL);

lib/SILGen/ResultPlan.h

@@ -97,7 +97,7 @@ struct ResultPlanBuilder {
                                SILResultInfo result);
   ResultPlanPtr buildForTuple(Initialization *emitInto,
                               AbstractionPattern origType,
-                              CanTupleType substType);
+                              CanType substType);
   ResultPlanPtr buildForPackExpansion(Optional<MutableArrayRef<InitializationPtr>> inits,
                                       AbstractionPattern origExpansionType,
                                       CanTupleEltTypeArrayRef substTypes);