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[lex.pptoken] Separate out placeholder keywords #7381

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[lex.pptoken] Separate out placeholder keywords #7381

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62 changes: 38 additions & 24 deletions source/lex.tex
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Original file line number Diff line number Diff line change
Expand Up @@ -495,12 +495,10 @@
\indextext{token!preprocessing|(}%
\begin{bnf}
\nontermdef{preprocessing-token}\br
placeholder-keyword\br
header-name\br
import-keyword\br
module-keyword\br
export-keyword\br
identifier\br
pp-number\br
identifier\br
character-literal\br
user-defined-character-literal\br
string-literal\br
Expand All @@ -515,12 +513,15 @@
In this document,
glyphs are used to identify
elements of the basic character set\iref{lex.charset}.
The categories of preprocessing token are: header names,
placeholder tokens produced by preprocessing \tcode{import} and \tcode{module} directives
(\grammarterm{import-keyword}, \grammarterm{module-keyword}, and \grammarterm{export-keyword}),
identifiers, preprocessing numbers, character literals (including user-defined character
literals), string literals (including user-defined string literals), preprocessing
operators and punctuators, and single non-whitespace characters that do not lexically
The categories of preprocessing token are:
placeholder keywords\iref{lex.placeholder},
header names\iref{lex.header},
preprocessing numbers\iref{lex.ppnumber},
identifiers\iref{lex.name},
character literals\iref{lex.ccon} including user-defined character literals,
string literals\iref{lex.string} including user-defined string literals,
preprocessing operators and punctuators\iref{lex.operators}, and
single non-whitespace characters that do not lexically
match the other preprocessing token categories.
If a \unicode{0027}{apostrophe} or a \unicode{0022}{quotation mark} character
matches the last category, the program is ill-formed.
Expand Down Expand Up @@ -548,17 +549,6 @@
shall have the lexical form of a keyword, an identifier, a literal,
or an operator or punctuator.

\pnum
The \grammarterm{import-keyword} is produced
by processing an \keyword{import} directive\iref{cpp.import},
the \grammarterm{module-keyword} is produced
by preprocessing a \keyword{module} directive\iref{cpp.module}, and
the \grammarterm{export-keyword} is produced
by preprocessing either of the previous two directives.
\begin{note}
None has any observable spelling.
\end{note}

\pnum
If the input stream has been parsed into preprocessing tokens up to a
given character:
Expand Down Expand Up @@ -628,6 +618,32 @@
\end{example}
\indextext{token!preprocessing|)}

\rSec1[lex.placeholder]{Placeholder keywords}
\indextext{keyword!placeholder|(}%

\begin{bnf}
\nontermdef{placeholder-keyword}\br
import-keyword\br
module-keyword\br
export-keyword
\end{bnf}

\pnum
Placeholder keywords are produced by preprocessing \keyword{import}
and \keyword{module} directives.
The \grammarterm{import-keyword} is produced
by preprocessing an \keyword{import} directive\iref{cpp.import},
the \grammarterm{module-keyword} is produced
by preprocessing a \keyword{module} directive\iref{cpp.module}, and
the \grammarterm{export-keyword} is produced
by preprocessing either of the previous two directives.

\pnum
\begin{note}
Placeholder keywords do not have any observable spelling.
\end{note}
\indextext{keyword!placeholder|)}%

\rSec1[lex.header]{Header names}

\indextext{header!name|(}%
Expand Down Expand Up @@ -960,9 +976,7 @@
\begin{bnf}
\nontermdef{keyword}\br
\textnormal{any identifier listed in \tref{lex.key}}\br
\grammarterm{import-keyword}\br
\grammarterm{module-keyword}\br
\grammarterm{export-keyword}
\grammarterm{placeholder-keyword}
\end{bnf}

\pnum
Expand Down
4 changes: 2 additions & 2 deletions source/preprocessor.tex
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Original file line number Diff line number Diff line change
Expand Up @@ -796,7 +796,7 @@
\pnum
The \tcode{module} and \tcode{export} (if it exists) preprocessing tokens
are replaced by the \grammarterm{module-keyword} and
\grammarterm{export-keyword} preprocessing tokens respectively.
\grammarterm{export-keyword} placeholder keywords respectively\iref{lex.placeholder}.
\begin{note}
This makes the line no longer a directive
so it is not removed at the end of phase 4.
Expand Down Expand Up @@ -854,7 +854,7 @@
In all three forms of \grammarterm{pp-import},
the \tcode{import} and \tcode{export} (if it exists) preprocessing tokens
are replaced by the \grammarterm{import-keyword} and
\grammarterm{export-keyword} preprocessing tokens respectively.
\grammarterm{export-keyword} placeholder keywords respectively\iref{lex.placeholder}.
\begin{note}
This makes the line no longer a directive
so it is not removed at the end of phase 4.
Expand Down
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