Use countType and add an additional tuple check

Author: Sima Nerush

lib/Sema/CSSimplify.cpp

@@ -7754,12 +7754,17 @@ ConstraintSystem::matchTypes(Type type1, Type type2, ConstraintKind kind,
     // number of elements, record a fix.
     auto *loc = getConstraintLocator(locator);
     if (loc->isLastElement<LocatorPathElt::ApplyArgToParam>()) {
-      if (auto paramPack = simplifyType(type2, flags)->getAs<PackType>()) {
-        if (type1->getAs<TupleType>()->getNumElements() ==
-            paramPack->getNumElements()) {
-          if (recordFix(DestructureTupleToMatchPackExpansionParameter::create(
-                  *this, paramPack, loc))) {
-            return getTypeMatchFailure(loc);
+      if (auto packExpansion = type2->getAs<PackExpansionType>()) {
+        auto countType = simplifyType(packExpansion->getCountType(), flags);
+        if (auto paramPack = countType->getAs<PackType>()) {
+          if (auto *tuple = type1->getAs<TupleType>()) {
+            if (tuple->getNumElements() == paramPack->getNumElements()) {
+              if (recordFix(
+                      DestructureTupleToMatchPackExpansionParameter::create(
+                          *this, paramPack, loc))) {
+                return getTypeMatchFailure(loc);
+              }
+            }
           }
         }
       }