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[basic.pre,basic.link] Clarify 'declaration of entity' vs. namespace-alias #4833

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[basic.pre,basic.link] Clarify 'declaration of entity' vs. namespace-alias #4833

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23 changes: 19 additions & 4 deletions source/basic.tex
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Original file line number Diff line number Diff line change
Expand Up @@ -85,9 +85,16 @@
The interpretation of a \grammarterm{for-range-declaration} produces
one or more of the above\iref{stmt.ranged}.
\end{note}
An entity $E$ is denoted by the name (if any)
that is introduced by a declaration of $E$ or
by a \grammarterm{typedef-name} introduced by a declaration specifying $E$.
An entity $E$ is denoted by
\begin{itemize}
\item
the name (if any) that is introduced by a declaration of $E$, or
\item
a \grammarterm{typedef-name} introduced by a declaration specifying $E$, or
\item
a \grammarterm{namespace-alias} introduced by
a \grammarterm{namespace-alias-definition} denoting $E$.
\end{itemize}

\pnum
A \defn{variable} is introduced by the
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they both declare names with external linkage.
\end{itemize}
\begin{note}
There are other circumstances in which declarations declare the same entity%
An \grammarterm{alias-declaration}\iref{dcl.typedef},
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@xmh0511 xmh0511 Aug 23, 2021 •
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How about using type = struct A{};? Moreover, since alias-declaration does not declare any entity why doesn't the declaration with typedef specifier do?

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It's true that an alias-declaration can contain a declaration of an entity, but I think it's clear here that it is the direct effect of the top-most declaration that is in question.

I'm not sure I understand the second question, although note that the paragraph begins by "enabling" names for linkage for purposes.

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I think alias-declaration and declaration specified with typedef should have the same treatment since they are merely different ways to declare the identifier to be a typedef-name. In line 2690, we just say alias-declaration but do not mention the declaration with typedef specifier, it's the second question.

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Why not add this note instead to [basic.pre]/5 (changed above), perhaps phrased as

A typedef-name or namespace-alias is not itself an entity. A using-declarator does not introduce an entity.

? I think namespace-alias-definition is then covered by implication. (The non-parallelism in that wording results from the lack of a pseudo-grammar term like using-name to distinguish identifiers with such a declaration, which I regard as no great omission.)

If we prefer to leave it here, I think it goes better after the "other circumstances" note (which is more directly related to the paragraph).

a \grammarterm{using-declarator}\iref{namespace.udecl}, or
a \grammarterm{namespace-alias-definition}\iref{namespace.alias}
does not declare any entities;
a \grammarterm{typedef-name} or \grammarterm{namespace-alias}
is not an entity\iref{basic.pre}.
\end{note}
\begin{note}
There are other circumstances in which declarations declare the same entity
\iref{dcl.link,temp.type,temp.spec.partial}.
\end{note}

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