Improve error messages for $' or @' followed by .' or -'.

Previously, for this special case of an invalid reference, the
usual "symbol not found in production:" was printed.  However,
because the symbol name was parsed as the empty string, that
message was followed immediately by a newline instead of a symbol
name.  In reality, this is a syntax error, so the reference is
invalid regardless of the symbols actually appearing in the
production.  Discussed at
<http://lists.gnu.org/archive/html/bison-patches/2011-01/msg00012.html>.
* src/scan-code.l (parse_ref): Report the above case as a syntax
error.  Other than that, continue to handle this case like any
other invalid reference that Bison manages to parse because
"possibly meant" messages can still be helpful to the user.
* tests/named-refs.at ($ or @ followed by . or -): New test group.
(cherry picked from commit 5c9efc755e)

ChangeLog

@@ -1,3 +1,20 @@
+2011-01-09  Joel E. Denny  <joeldenny@joeldenny.org>
+
+	Improve error messages for `$' or `@' followed by `.' or `-'.
+	Previously, for this special case of an invalid reference, the
+	usual "symbol not found in production:" was printed.  However,
+	because the symbol name was parsed as the empty string, that
+	message was followed immediately by a newline instead of a symbol
+	name.  In reality, this is a syntax error, so the reference is
+	invalid regardless of the symbols actually appearing in the
+	production.  Discussed at
+	<http://lists.gnu.org/archive/html/bison-patches/2011-01/msg00012.html>.
+	* src/scan-code.l (parse_ref): Report the above case as a syntax
+	error.  Other than that, continue to handle this case like any
+	other invalid reference that Bison manages to parse because
+	"possibly meant" messages can still be helpful to the user.
+	* tests/named-refs.at ($ or @ followed by . or -): New test group.
+
 2011-01-08  Joel E. Denny  <joeldenny@joeldenny.org>
 
 	doc: don't use @acronym.

src/scan-code.l

@@ -620,7 +620,17 @@ parse_ref (char *cp, symbol_list *rule, int rule_length,
         complain_at_indent (text_loc, &indent, _("invalid reference: %s"),
                             quote (text));
         indent += SUB_INDENT;
-        if (midrule_rhs_index)
+        if (len == 0)
+          {
+            location sym_loc = text_loc;
+            sym_loc.start.column += 1;
+            sym_loc.end = sym_loc.start;
+            const char *format =
+              _("syntax error after `%c', expecting integer, letter,"
+                " `_', `[', or `$'");
+            complain_at_indent (sym_loc, &indent, format, dollar_or_at);
+          }
+        else if (midrule_rhs_index)
           {
             const char *format =
               _("symbol not found in production before $%d: %.*s");

tests/named-refs.at

@@ -561,3 +561,32 @@ test.y:57.8-17: invalid reference: `$<aa>[sym]'
 test.y:54.1-57.21:  symbol not found in production: sym
 ]])
 AT_CLEANUP
+
+#######################################################################
+
+AT_SETUP([[$ or @ followed by . or -]])
+AT_DATA([[test.y]],
+[[
+%%
+start:
+  .field { $.field; }
+| -field { @-field; }
+| 'a'    { @.field; }
+| 'a'    { $-field; }
+;
+.field: ;
+-field: ;
+]])
+AT_BISON_CHECK([[test.y]], [[1]], [],
+[[test.y:4.12-18: invalid reference: `$.field'
+test.y:4.13:        syntax error after `$', expecting integer, letter, `_', `@<:@', or `$'
+test.y:4.3-8:       possibly meant: $[.field] at $1
+test.y:5.12-18: invalid reference: `@-field'
+test.y:5.13:        syntax error after `@', expecting integer, letter, `_', `@<:@', or `$'
+test.y:5.3-8:       possibly meant: @[-field] at $1
+test.y:6.12-18: invalid reference: `@.field'
+test.y:6.13:        syntax error after `@', expecting integer, letter, `_', `@<:@', or `$'
+test.y:7.12-18: invalid reference: `$-field'
+test.y:7.13:        syntax error after `$', expecting integer, letter, `_', `@<:@', or `$'
+]])
+AT_CLEANUP