Index: src/Virtual/ExpandCasts.cc
===================================================================
--- src/Virtual/ExpandCasts.cc	(revision ccbc65c42005605b9878e400666970218d61d502)
+++ src/Virtual/ExpandCasts.cc	(revision 01865fb2bd5249a71fe41e9769e5bb5833723bc2)
@@ -362,4 +362,5 @@
 }
 
+/// Copy newType, but give the copy the params of the oldType.
 ast::StructInstType * polyCopy(
 		ast::StructInstType const * oldType,