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[basic.lookup.unqual] Clarify conversion-function-id components lookup #5191

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[basic.lookup.unqual] Clarify conversion-function-id components lookup #5191

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14 changes: 8 additions & 6 deletions source/basic.tex
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Original file line number Diff line number Diff line change
Expand Up @@ -1777,13 +1777,15 @@
such a name undergoes unqualified name lookup from the point where it appears.

\pnum
An unqualified name that is a component name\iref{expr.prim.id.unqual} of
Lookup for an unqualified name $U$
that is a component name\iref{expr.prim.id.unqual} of
a \grammarterm{type-specifier} or \grammarterm{ptr-operator} of
a \grammarterm{conversion-type-id} is looked up in the same fashion
as the \grammarterm{conversion-function-id} in which it appears.
If that lookup finds nothing, it undergoes unqualified name lookup;
in each case, only names
that denote types or templates whose specializations are types are considered.
a \grammarterm{conversion-type-id} $T$ considers only names
that denote types or templates whose specializations are types.
If $T$ appears in a \grammarterm{conversion-function-id} that is a qualified name
whose lookup context\iref{basic.lookup.qual} is a class $S$,
lookup for $U$ performs a search in the scope associated with $S$;
if that lookup finds nothing, $U$ undergoes unqualified name lookup.
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I think it would be clearer to say "[…]; otherwise, or if that lookup finds nothing, […]". It's true that the general "Unless otherwise specified" from the previous paragraph ought to apply, but it tends to sound like the alternative is that the name is not looked up at all.

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It's true that the general "Unless otherwise specified" from the previous paragraph ought to apply, but it tends to sound like the alternative is that the name is not looked up at all.

To me, the previous paragraph clearly applies to unqualified \grammarterm{conversion-function-id} :/
May I not apply the proposed change, please?

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This paragraph is about an unqualified U, looked up separately from the conversion-function-id that contains it. I want to avoid the (nonsensical) suggestion that, if T does not appear in the given context, U is not looked up at all.

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@languagelawyer languagelawyer Feb 22, 2022 •
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This paragraph is about an unqualified U, looked up separately from the conversion-function-id that contains it.

Yeah, right, but whatever, the previous paragraph applies to other unqualified names (which are not mentioned in this paragraphs) (and in any other paragraphs-exceptions).

I want to avoid the (nonsensical) suggestion that, if T does not appear in the given context, U is not looked up at all.

I don't see how is it possible. I mean, not only the previous paragraph, but also the previous sentence suggest that such U s are looked up:

Lookup for an unqualified name U that is ... of a conversion-type-id T considers only names that ... If T appears in a conversion-function-id ...

If U is not looked up when T doesn't appear in conversion-function-id, there is no reason these sentences are in this and not the opposite order

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@opensdh opensdh Feb 22, 2022 •
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I don't insist on a change; it just strikes me as a trip hazard for the reader to say "If X, then Y; if Y does nothing, Z." and have Z also happen when X doesn't obtain.

\begin{example}
\begin{codeblock}
struct T1 { struct U { int i; }; };
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