Index: src/AST/Decl.cpp
===================================================================
--- src/AST/Decl.cpp	(revision 68c9165ba8977f22fd2ed8d7175c671e03359a1a)
+++ src/AST/Decl.cpp	(revision effe5b0a115346c1cb0a5cf1fc5ec1b46392ce80)
@@ -72,8 +72,8 @@
 // --- EnumDecl
 
-bool EnumDecl::valueOf( Decl* enumerator, long long& value ) const {
+bool EnumDecl::valueOf( const Decl * enumerator, long long& value ) const {
 	if ( enumValues.empty() ) {
 		long long crntVal = 0;
-		for ( const Decl* member : members ) {
+		for ( const Decl * member : members ) {
 			const ObjectDecl* field = strict_dynamic_cast< const ObjectDecl* >( member );
 			if ( field->init ) {
Index: src/AST/Decl.hpp
===================================================================
--- src/AST/Decl.hpp	(revision 68c9165ba8977f22fd2ed8d7175c671e03359a1a)
+++ src/AST/Decl.hpp	(revision effe5b0a115346c1cb0a5cf1fc5ec1b46392ce80)
@@ -287,5 +287,5 @@
 
 	/// gets the integer value for this enumerator, returning true iff value found
-	bool valueOf( Decl* enumerator, long long& value ) const;
+	bool valueOf( const Decl * enumerator, long long& value ) const;
 
 	const Decl * accept( Visitor & v ) const override { return v.visit( this ); }
Index: src/AST/Pass.proto.hpp
===================================================================
--- src/AST/Pass.proto.hpp	(revision 68c9165ba8977f22fd2ed8d7175c671e03359a1a)
+++ src/AST/Pass.proto.hpp	(revision effe5b0a115346c1cb0a5cf1fc5ec1b46392ce80)
@@ -109,4 +109,6 @@
 	};
 
+	/// "Short hand" to check if this is a valid previsit function
+	/// Mostly used to make the static_assert look (and print) prettier
 	template<typename pass_t, typename node_t>
 	struct is_valid_previsit {
@@ -117,4 +119,7 @@
 	};
 
+	/// Used by previsit implementation
+	/// We need to reassign the result to 'node', unless the function
+	/// returns void, then we just leave 'node' unchanged
 	template<bool is_void>
 	struct __assign;
@@ -134,4 +139,27 @@
 			node = pass.previsit( node );
 			assertf(node, "Previsit must not return NULL");
+		}
+	};
+
+	/// Used by postvisit implementation
+	/// We need to return the result unless the function
+	/// returns void, then we just return the original node
+	template<bool is_void>
+	struct __return;
+
+	template<>
+	struct __return<true> {
+		template<typename pass_t, typename node_t>
+		static inline const node_t * result( pass_t & pass, const node_t * & node ) {
+			pass.postvisit( node );
+			return node;
+		}
+	};
+
+	template<>
+	struct __return<false> {
+		template<typename pass_t, typename node_t>
+		static inline auto result( pass_t & pass, const node_t * & node ) {
+			return pass.postvisit( node );
 		}
 	};
@@ -174,5 +202,9 @@
 		decltype( pass.postvisit( node ), node->accept( *(Visitor*)nullptr ) )
 	{
-		return pass.postvisit( node );
+		return __return<
+			std::is_void<
+				decltype( pass.postvisit( node ) )
+			>::value
+		>::result( pass, node );
 	}