Index: src/Validate/ForallPointerDecay.cpp
===================================================================
--- src/Validate/ForallPointerDecay.cpp	(revision a55649200b5601ebf0ca0b430984b9546e7bed94)
+++ src/Validate/ForallPointerDecay.cpp	(revision 48a91e270c570a6f6635a022d7dfafbbd208229b)
@@ -70,9 +70,5 @@
 		AssertionList assertions;
 		// Substitute trait decl parameters for instance parameters.
-		ast::TypeSubstitution sub(
-			inst->base->params.begin(),
-			inst->base->params.end(),
-			inst->params.begin()
-		);
+		ast::TypeSubstitution sub( inst->base->params, inst->params );
 		for ( const ast::ptr<ast::Decl> & decl : inst->base->members ) {
 			ast::ptr<ast::DeclWithType> copy =