(alx-0014r6-F) Refactor syntax of diagnostic directives

Signed-off-by: Alejandro Colomar <[email protected]>

Author: alejandro-colomar

source/preprocessor.tex

@@ -53,8 +53,7 @@
     define-directive\br
     undef-directive\br
     line-directive\br
-    \terminal{\# error \ } \opt{pp-tokens} new-line\br
-    \terminal{\# warning} \opt{pp-tokens} new-line\br
+    diagnostic-directive\br
     \terminal{\# pragma } \opt{pp-tokens} new-line\br
     \terminal{\# }new-line
 \end{bnf}
@@ -2155,6 +2154,12 @@
 \indextext{preprocessing directive!warning}%
 \indextext{\idxcode{\#error}|see{preprocessing directive, error}}
 
+\begin{bnf}
+\nontermdef{diagnostic-directive}\br
+    \terminal{\# error \ } \opt{pp-tokens} new-line\br
+    \terminal{\# warning} \opt{pp-tokens} new-line\br
+\end{bnf}
+
 \pnum
 A preprocessing directive of the form
 \begin{ncsimplebnf}