Index: src/ResolvExpr/RenameVars.cc
===================================================================
--- src/ResolvExpr/RenameVars.cc	(revision 2f98fb27b70bc49edf043bbbc1d2c2a23dbc02b8)
+++ src/ResolvExpr/RenameVars.cc	(revision 99da2670a9c3077bcfe60c06fde4a115b84eccae)
@@ -30,4 +30,6 @@
 #include "SynTree/Type.h"          // for Type, TypeInstType, TraitInstType
 #include "SynTree/Visitor.h"       // for acceptAll, maybeAccept
+
+#include "AST/Copy.hpp"
 
 namespace ResolvExpr {
@@ -172,6 +174,8 @@
 
 const ast::Type * renameTyVars( const ast::Type * t ) {
+	ast::Type *tc = ast::deepCopy(t);
 	ast::Pass<RenameVars_new> renamer;
-	return t->accept( renamer );
+//	return t->accept( renamer );
+	return tc->accept( renamer );
 }