Fix \peek_analysis_map_inline:n for not-expanded tokens (fix #1113)

When followed by an implicit special token, the code saves the
next token using \futurelet, then stringifies the first token and
collects characters until hitting the saved next token.  If that
token was in a "notexpanded" state then the collection loop never
terminated.  Now fixed by simply running \futurelet twice to get
rid of the "notexpanded" state.  One could conceivably want to
keep track of it and restore it.

l3kernel/CHANGELOG.md

@@ -13,8 +13,9 @@ this project uses date-based 'snapshot' version identifiers.
 
 ### Fixed
 - `\peek_analysis_map_inline:n` support for macro parameter characters (issue
-  [\#1109](https://github.com/latex3/latex3/issues/1109)) and for many
-  expandable tokens (issue [\#1110](https://github.com/latex3/latex3/issues/1110))
+  [\#1109](https://github.com/latex3/latex3/issues/1109)), for many expandable
+  tokens (issue [\#1110](https://github.com/latex3/latex3/issues/1110)), and an
+  esoteric case (issue [\#1113](https://github.com/latex3/latex3/issues/1113))
 
 ## [2022-09-28]
 

l3kernel/l3tl-analysis.dtx

@@ -1183,7 +1183,8 @@
 %     \@@_peek_analysis_nonexp:N, \@@_peek_analysis_cs:N,
 %     \@@_peek_analysis_char:N, \@@_peek_analysis_char:w,
 %     \@@_peek_analysis_special:, \@@_peek_analysis_retest:,
-%     \@@_peek_analysis_next:, \@@_peek_analysis_str:,
+%     \@@_peek_analysis_next:, \@@_peek_analysis_nextii:,
+%     \@@_peek_analysis_str:,
 %     \@@_peek_analysis_str:w, \@@_peek_analysis_str:n,
 %     \@@_peek_analysis_active_str:n, \@@_peek_analysis_explicit:n,
 %     \@@_peek_analysis_escape:, \@@_peek_analysis_collect:w,
@@ -1420,6 +1421,8 @@
 %   active character with the same character code as its meaning or as
 %   the escape character).  Now look at the \meta{next token} following
 %   it using a combination of \tn{afterassignment} and \tn{futurelet}.
+%   (In fact look twice to reset an internal \TeX{} flag in case the
+%   \meta{next token} had been hit with \cs{exp_not:N}.)
 %   The syntax of this primitive is \tn{futurelet} \meta{peek token}
 %   \meta{first token} \meta{next token}, and it sets \meta{peek token}
 %   equal to \meta{next token}.  Traditionally, one takes \meta{first
@@ -1436,6 +1439,11 @@
   {
     \tl_if_empty:oT { \tex_the:D \tex_everyeof:D }
       { \tex_everyeof:D { \scan_stop: } }
+    \tex_afterassignment:D \@@_peek_analysis_nextii:
+    \tex_futurelet:D \l_@@_analysis_next_token
+  }
+\cs_new_protected:Npn \@@_peek_analysis_nextii:
+  {
     \tex_afterassignment:D \@@_peek_analysis_str:
     \tex_futurelet:D \l_@@_analysis_next_token
   }