CWG3099 Instantiation of type aliases from alias templates is unspecified

Author: eisenwave

source/templates.tex

@@ -4689,7 +4689,9 @@
 the alias template.
 Any other \grammarterm{template-id}
 that names a specialization of an alias template is
-a \grammarterm{typedef-name} for a type alias.
+a \grammarterm{typedef-name} for a type alias;
+such a \grammarterm{template-id} is ill-formed if
+forming the associated type results in substitution failure.
 \begin{note}
 The alias template name is not deduced from such a type\iref{temp.deduct.type}.
 \end{note}