RequirementMachine: Add assertion to RewriteSystem::isInMinimizationDomain()

Author: slavapestov

lib/AST/RequirementMachine/RewriteSystem.cpp

@@ -607,6 +607,7 @@ void RewriteSystem::simplifyRightHandSidesAndSubstitutions() {
 bool RewriteSystem::isInMinimizationDomain(
     ArrayRef<const ProtocolDecl *> protos) const {
   assert(protos.size() <= 1);
+  assert(Protos.empty() || !protos.empty());
 
   if (protos.empty() && Protos.empty())
     return true;