Index: src/AST/Decl.hpp
===================================================================
--- src/AST/Decl.hpp	(revision 1387ea0a67f58d42a195b4763adf85f77f4cad16)
+++ src/AST/Decl.hpp	(revision 3cc11113e36bd5d3d127b0782777b020f59fc62e)
@@ -270,8 +270,8 @@
 	: AggregateDecl( loc, name, std::move(attrs), linkage ), kind( kind ) {}
 
-	bool is_coroutine() { return kind == Coroutine; }
-	bool is_generator() { return kind == Generator; }
-	bool is_monitor  () { return kind == Monitor  ; }
-	bool is_thread   () { return kind == Thread   ; }
+	bool is_coroutine() const { return kind == Coroutine; }
+	bool is_generator() const { return kind == Generator; }
+	bool is_monitor  () const { return kind == Monitor  ; }
+	bool is_thread   () const { return kind == Thread   ; }
 
 	const Decl * accept( Visitor & v ) const override { return v.visit( this ); }