Index: src/SynTree/AggregateDecl.cc
===================================================================
--- src/SynTree/AggregateDecl.cc	(revision 4ef08f76a55ae935c3aff3e628469cb6618b8ca8)
+++ src/SynTree/AggregateDecl.cc	(revision 6fbe9a5fd01aa79d7b7dd2fbf7e7b4656c1b7bc7)
@@ -21,4 +21,5 @@
 #include "Common/utility.h"      // for printAll, cloneAll, deleteAll
 #include "Declaration.h"         // for AggregateDecl, TypeDecl, Declaration
+#include "Expression.h"
 #include "Initializer.h"
 #include "LinkageSpec.h"         // for Spec, linkageName, Cforall
@@ -88,4 +89,17 @@
 const char * StructDecl::typeString() const { return aggrString( kind ); }
 
+StructInstType * StructDecl::makeInst( std::list< Expression * > const & new_parameters ) {
+	std::list< Expression * > copy_parameters;
+	cloneAll( new_parameters, copy_parameters );
+	return makeInst( move( copy( copy_parameters ) ) );
+}
+
+StructInstType * StructDecl::makeInst( std::list< Expression * > && new_parameters ) {
+	assert( parameters.size() == new_parameters.size() );
+	StructInstType * type = new StructInstType( noQualifiers, this );
+	type->parameters = std::move( new_parameters );
+	return type;
+}
+
 const char * UnionDecl::typeString() const { return aggrString( Union ); }
 
Index: src/SynTree/Declaration.h
===================================================================
--- src/SynTree/Declaration.h	(revision 4ef08f76a55ae935c3aff3e628469cb6618b8ca8)
+++ src/SynTree/Declaration.h	(revision 6fbe9a5fd01aa79d7b7dd2fbf7e7b4656c1b7bc7)
@@ -306,4 +306,8 @@
 	bool is_thread   () { return kind == Thread   ; }
 
+	// Make a type instance of this declaration.
+	StructInstType * makeInst( std::list< Expression * > const & parameters );
+	StructInstType * makeInst( std::list< Expression * > && parameters );
+
 	virtual StructDecl * clone() const override { return new StructDecl( *this ); }
 	virtual void accept( Visitor & v ) override { v.visit( this ); }