Do not allow identifiers that start with a dash.

This cleans up our previous fixes for a bug whereby Bison
discarded `.field' in `$-1.field'.  The previous fixes were less
restrictive about where a dash could appear in an identifier, but
the restrictions were hard to explain.  That bug was reported and
this final fix was originally suggested by Paul Hilfinger.  This
also fixes a remaining bug reported by Paul Eggert whereby Bison
parses `%token ID -123' as `%token ID - 123' and handles `-' as an
identifier.  Now, `-' cannot be an identifier.  Discussed in
threads beginning at
<http://lists.gnu.org/archive/html/bug-bison/2011-01/msg00000.html>,
<http://lists.gnu.org/archive/html/bug-bison/2011-01/msg00004.html>.
* NEWS (2.5): Update entry describing the dash extension to
grammar symbol names.  Also, move that entry before the named
references entry because the latter mentions the former.
* doc/bison.texinfo (Symbol): Update documentation for symbol
names.  As suggested by Paul Eggert, mention the effect of periods
and dashes on named references.
(Decl Summary): Update documentation for unquoted %define values,
which, as a side effect, can no longer start with dashes either.
* src/scan-code.l (id): Implement.
* src/scan-gram.l (id): Implement.
* tests/actions.at (Exotic Dollars): Extend test group to exercise
bug reported by Paul Hilfinger.
* tests/input.at (Symbols): Update test group, and extend to
exercise bug reported by Paul Eggert.
* tests/named-refs.at (Stray symbols in brackets): Update test
group.
($ or @ followed by . or -): Likewise.
* tests/regression.at (Invalid inputs): Likewise.
(cherry picked from commit 82f3355eaf)

tests/actions.at

@@ -158,6 +158,52 @@ AT_PARSER_CHECK([./input], 0,
 [[15
 ]])
 
+# Make sure that fields after $n or $-n are parsed correctly.  At one
+# point while implementing dashes in symbol names, we were dropping
+# fields after $-n.
+AT_DATA_GRAMMAR([[input.y]],
+[[
+%{
+# include <stdio.h>
+  static int yylex (void);
+  static void yyerror (char const *msg);
+  typedef struct { int val; } stype;
+# define YYSTYPE stype
+%}
+
+%%
+start: one two { $$.val = $1.val + $2.val; } sum ;
+one: { $$.val = 1; } ;
+two: { $$.val = 2; } ;
+sum: { printf ("%d\n", $0.val + $-1.val + $-2.val); } ;
+
+%%
+
+static int
+yylex (void)
+{
+  return 0;
+}
+
+static void
+yyerror (char const *msg)
+{
+  fprintf (stderr, "%s\n", msg);
+}
+
+int
+main (void)
+{
+  return yyparse ();
+}
+]])
+
+AT_BISON_CHECK([[-o input.c input.y]])
+AT_COMPILE([[input]])
+AT_PARSER_CHECK([[./input]], [[0]],
+[[6
+]])
+
 AT_CLEANUP
 
 

tests/input.at

@@ -658,17 +658,20 @@ AT_BISON_CHECK([-o input.c input.y])
 AT_COMPILE([input.o], [-c input.c])
 
 
-# Periods and dashes are genuine letters, they can start identifiers.
-# Digits cannot.
+# Periods are genuine letters, they can start identifiers.
+# Digits and dashes cannot.
 AT_DATA_GRAMMAR([input.y],
 [[%token .GOOD
          -GOOD
          1NV4L1D
+         -123
 %%
-start: .GOOD -GOOD
+start: .GOOD GOOD
 ]])
 AT_BISON_CHECK([-o input.c input.y], [1], [],
-[[input.y:11.10-16: invalid identifier: `1NV4L1D'
+[[input.y:10.10: invalid character: `-'
+input.y:11.10-16: invalid identifier: `1NV4L1D'
+input.y:12.10: invalid character: `-'
 ]])
 
 AT_CLEANUP

tests/named-refs.at

@@ -446,13 +446,14 @@ AT_SETUP([Stray symbols in brackets])
 AT_DATA_GRAMMAR([test.y],
 [[
 %%
-start: foo[ /* aaa */ *&-+ ] bar
+start: foo[ /* aaa */ *&-.+ ] bar
   { s = $foo; }
 ]])
 AT_BISON_CHECK([-o test.c test.y], 1, [],
 [[test.y:11.23: invalid character in bracketed name: `*'
 test.y:11.24: invalid character in bracketed name: `&'
-test.y:11.26: invalid character in bracketed name: `+'
+test.y:11.25: invalid character in bracketed name: `-'
+test.y:11.27: invalid character in bracketed name: `+'
 ]])
 AT_CLEANUP
 
@@ -570,23 +571,27 @@ 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 $1
-test.y:5.12-18: invalid reference: `@-field'
+test.y:5.12-18: invalid reference: `@.field'
 test.y:5.13:        syntax error after `@', expecting integer, letter, `_', `@<:@', or `$'
-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_DATA([[test.y]],
+[[
+%%
+start:
+  'a' { $-field; }
+| 'b' { @-field; }
+;
+]])
+AT_BISON_CHECK([[test.y]], [[0]], [],
+[[test.y:4.9: warning: stray `$'
+test.y:5.9: warning: stray `@'
 ]])
 AT_CLEANUP

tests/regression.at

@@ -392,7 +392,8 @@ input.y:3.14: invalid character: `}'
 input.y:4.1: invalid character: `%'
 input.y:4.2: invalid character: `&'
 input.y:5.1-17: invalid directive: `%a-does-not-exist'
-input.y:6.1-2: invalid directive: `%-'
+input.y:6.1: invalid character: `%'
+input.y:6.2: invalid character: `-'
 input.y:7.1-8.0: missing `%}' at end of file
 input.y:7.1-8.0: syntax error, unexpected %{...%}
 ]])