CWG3032 Template argument disambiguation

Author: eisenwave

source/templates.tex

@@ -715,10 +715,15 @@
 
 \begin{bnf}
 \nontermdef{template-argument}\br
+  template-argument-name\br
   constant-expression\br
-  type-id\br
-  \opt{nested-name-specifier} template-name\br
-  nested-name-specifier \terminal{template} template-name
+  type-id
+\end{bnf}
+
+\begin{bnf}
+\nontermdef{template-argument-name}\br
+  \opt{nested-name-specifier} identifier\br
+  nested-name-specifier \terminal{template} identifier
 \end{bnf}
 
 \pnum
@@ -888,6 +893,11 @@
 \end{codeblock}
 \end{example}
 
+\pnum
+The component names of a \grammarterm{template-argument-name} are
+those of its \grammarterm{nested-name-specifier} (if any) and
+its \grammarterm{identifier}.
+
 \pnum
 A \grammarterm{template-id} or \grammarterm{splice-specialization-specifier}
 is \defnx{valid}{\idxgram{template-id}!valid} if
@@ -1051,6 +1061,29 @@
 the $n^\text{th}$ template argument is a pack expansion
 whose pattern is the name of the template parameter pack.
 
+\pnum
+If a \grammarterm{template-argument} $A$
+matches the form \grammarterm{template-argument-name},
+it is interpreted as such;
+the identifier is looked up and its meaning is determined as follows:
+\begin{itemize}
+\item
+If lookup finds an injected-class-name\iref{temp.local}, then:
+\begin{itemize}
+\item When $A$ is for a type template template parameter,
+$A$ denotes the corresponding class template.
+\item Otherwise, it denotes a \grammarterm{type-name}.
+\end{itemize}
+\item
+Otherwise, if lookup finds a template,
+$A$ denotes that template.
+\item
+Otherwise, if lookup finds a type alias or a type,
+$A$ denotes the underlying type and is interpreted as a \grammarterm{type-id}.
+\item
+Otherwise, $A$ is interpreted as an expression.
+\end{itemize}
+
 \pnum
 In a
 \grammarterm{template-argument},