Index: src/GenPoly/SpecializeNew.cpp
===================================================================
--- src/GenPoly/SpecializeNew.cpp	(revision 474a170607306d8a8de9d85a373aa6a5efa1554f)
+++ src/GenPoly/SpecializeNew.cpp	(revision 0c840fc175421beff77fdd02802dd0b5c1da973c)
@@ -112,7 +112,8 @@
 	using namespace ResolvExpr;
 	ast::OpenVarSet openVars, closedVars;
-	ast::AssertionSet need, have;
-	findOpenVars( formalType, openVars, closedVars, need, have, FirstClosed );
-	findOpenVars( actualType, openVars, closedVars, need, have, FirstOpen );
+	ast::AssertionSet need, have; // unused
+	ast::TypeEnvironment env; // unused
+	// findOpenVars( formalType, openVars, closedVars, need, have, FirstClosed );
+	findOpenVars( actualType, openVars, closedVars, need, have, env, FirstOpen );
 	for ( const ast::OpenVarSet::value_type & openVar : openVars ) {
 		const ast::Type * boundType = subs->lookup( openVar.first );
@@ -124,4 +125,7 @@
 			if ( closedVars.find( *inst ) == closedVars.end() ) {
 				return true;
+			}
+			else {
+				assertf(false, "closed: %s", inst->name.c_str());
 			}
 		// Otherwise, the variable is bound to a concrete type.