xo-expression: refactor: Lambda/Primitive share FunctionInterface

src/expression/Lambda.cpp

@@ -49,7 +49,7 @@ namespace xo {
                        TypeDescr lambda_type,
                        const std::vector<rp<Variable>> & argv,
                        const ref::rp<Expression> & body)
-            : Expression(exprtype::lambda, lambda_type),
+            : FunctionInterface(exprtype::lambda, lambda_type),
               name_{name},
               argv_{argv},
               body_{body}

src/expression/Variable.cpp

@@ -8,6 +8,7 @@ namespace xo {
         Variable::display(std::ostream & os) const {
             os << "<Variable"
                << xtag("name", name_)
+               << xtag("type", this->valuetype()->short_name())
                << ">";
         } /*display*/
     } /*namespace ast*/