#101666: horrible regex parsing error error [sic]

We were producing a very confusing error when a group name
did not start with an identifier. This patch tries to improve the situation.

diff --git a/pod/perldiag.pod b/pod/perldiag.pod
index 7d85af4..6e78bed 100644 (file)
--- a/pod/perldiag.pod
+++ b/pod/perldiag.pod
@@ -2077,6 +2077,12 @@ has since been undefined.
 (F) A ()-group started with a count.  A count is supposed to follow
 something: a template character or a ()-group.  See L<perlfunc/pack>.
 
+=item Group name must start with a non-digit word character in regex; marked by <-- HERE in m/%s/
+
+(F) Group names must follow the rules for perl identifiers, meaning
+they must start with a non-digit word character. A common cause of
+this error is using (?&0) instead of (?0). See L<perlre>.
+
 =item %s had compilation errors.
 
 (F) The final summary message when a C<perl -c> fails.

diff --git a/regcomp.c b/regcomp.c
index d124034..beb988b 100644 (file)
--- a/regcomp.c
+++ b/regcomp.c
@@ -6871,8 +6871,10 @@ S_reg_scan_name(pTHX_ RExC_state_t *pRExC_state, U32 flags)
            do {
                RExC_parse++;
            } while (isALNUM(*RExC_parse));
+    } else {
+       RExC_parse++; /* so the <- from the vFAIL is after the offending character */
+        vFAIL("Group name must start with a non-digit word character");
     }
-
     if ( flags ) {
         SV* sv_name
            = newSVpvn_flags(name_start, (int)(RExC_parse - name_start),

diff --git a/t/re/pat.t b/t/re/pat.t
index 0728a5a..3cfb363 100644 (file)
--- a/t/re/pat.t
+++ b/t/re/pat.t
@@ -1158,7 +1158,7 @@ use utf8;;
 "abc" =~ qr/(?<$char>abc)/;
 EOP
             utf8::encode($prog);
-            fresh_perl_like($prog, qr!Sequence.* not recognized!, "",
+            fresh_perl_like($prog, qr!Group name must start with a non-digit word character!, "",
                         sprintf("'U+%04X not legal IDFirst'", ord($char)));
         }
     }

diff --git a/t/re/re_tests b/t/re/re_tests
index 327f585..318ef89 100644 (file)
--- a/t/re/re_tests
+++ b/t/re/re_tests
@@ -481,7 +481,7 @@ a(?:b|(c|e){1,2}?|d)+?(.)   ace     y       $1$2    ce
 (?<!c)b        cb      n       -       -
 (?<!c)b        b       y       -       -
 (?<!c)b        b       y       $&      b
-(?<%)b -       c       -       Sequence (?<%...) not recognized
+(?<%)b -       c       -       Group name must start with a non-digit word character
 (?:..)*a       aba     y       $&      aba
 (?:..)*?a      aba     y       $&      a
 ^(?:b|a(?=(.)))*\1     abc     y       $&      ab
@@ -1082,8 +1082,8 @@ X(?<=foo.)[YZ]    ..XfooXY..      y       pos     8
 (?P<n>foo|bar|baz)(?P<m>[ew]+) snofooewa       yM      $+{m}   ew      miniperl cannot load Tie::Hash::NamedCapture
 (?P<n>foo)|(?P<n>bar)|(?P<n>baz)       snofooewa       yM      $+{n}   foo     miniperl cannot load Tie::Hash::NamedCapture
 (?P<n>foo)(??{ $+{n} })        snofooefoofoowaa        yM      $+{n}   foo     miniperl cannot load Tie::Hash::NamedCapture
-(?P<=n>foo|bar|baz)    snofooewa       c       -       Sequence (?P<=...) not recognized
-(?P<!n>foo|bar|baz)    snofooewa       c       -       Sequence (?P<!...) not recognized
+(?P<=n>foo|bar|baz)    snofooewa       c       -       Group name must start with a non-digit word character
+(?P<!n>foo|bar|baz)    snofooewa       c       -       Group name must start with a non-digit word character
 (?PX<n>foo|bar|baz)    snofooewa       c       -       Sequence (?PX<...) not recognized
 /(?'n'foo|bar|baz)/    snofooewa       y       $1      foo
 /(?'n'foo|bar|baz)/    snofooewa       yM      $+{n}   foo     miniperl cannot load Tie::Hash::NamedCapture
@@ -1262,14 +1262,14 @@ a*(*F)  aaaab   n       -       -
 /(?<_>foo) \k<_>/      ..foo foo..     yM      $+{_}   foo     miniperl cannot load Tie::Hash::NamedCapture
 /(?'_0_'foo) \k'_0_'/  ..foo foo..     yM      $+{_0_} foo     miniperl cannot load Tie::Hash::NamedCapture
 /(?<_0_>foo) \k<_0_>/  ..foo foo..     yM      $+{_0_} foo     miniperl cannot load Tie::Hash::NamedCapture
-/(?'0'foo) bar/        ..foo bar..     c       -       Sequence (?'
-/(?<0>foo) bar/        ..foo bar..     c       -       Sequence (?<
-/(?'12'foo) bar/       ..foo bar..     c       -       Sequence (?'
-/(?<12>foo) bar/       ..foo bar..     c       -       Sequence (?<
-/(?'1a'foo) bar/       ..foo bar..     c       -       Sequence (?'
-/(?<1a>foo) bar/       ..foo bar..     c       -       Sequence (?<
-/(?''foo) bar/ ..foo bar..     c       -       Sequence (?''
-/(?<>foo) bar/ ..foo bar..     c       -       Sequence (?<>
+/(?'0'foo) bar/        ..foo bar..     c       -       Group name must start with a non-digit word character
+/(?<0>foo) bar/        ..foo bar..     c       -       Group name must start with a non-digit word character
+/(?'12'foo) bar/       ..foo bar..     c       -       Group name must start with a non-digit word character
+/(?<12>foo) bar/       ..foo bar..     c       -       Group name must start with a non-digit word character
+/(?'1a'foo) bar/       ..foo bar..     c       -       Group name must start with a non-digit word character
+/(?<1a>foo) bar/       ..foo bar..     c       -       Group name must start with a non-digit word character
+/(?''foo) bar/ ..foo bar..     c       -       Group name must start with a non-digit word character
+/(?<>foo) bar/ ..foo bar..     c       -       Group name must start with a non-digit word character
 /foo \k'n'/    foo foo c       -       Reference to nonexistent named group
 /foo \k<n>/    foo foo c       -       Reference to nonexistent named group
 /foo \k'a1'/   foo foo c       -       Reference to nonexistent named group
@@ -1278,14 +1278,14 @@ a*(*F)  aaaab   n       -       -
 /foo \k<_>/    foo foo c       -       Reference to nonexistent named group
 /foo \k'_0_'/  foo foo c       -       Reference to nonexistent named group
 /foo \k<_0_>/  foo foo c       -       Reference to nonexistent named group
-/foo \k'0'/    foo foo c       -       Sequence \\k'
-/foo \k<0>/    foo foo c       -       Sequence \\k<
-/foo \k'12'/   foo foo c       -       Sequence \\k'
-/foo \k<12>/   foo foo c       -       Sequence \\k<
-/foo \k'1a'/   foo foo c       -       Sequence \\k'
-/foo \k<1a>/   foo foo c       -       Sequence \\k<
-/foo \k''/     foo foo c       -       Sequence \\k'
-/foo \k<>/     foo foo c       -       Sequence \\k<
+/foo \k'0'/    foo foo c       -       Group name must start with a non-digit word character
+/foo \k<0>/    foo foo c       -       Group name must start with a non-digit word character
+/foo \k'12'/   foo foo c       -       Group name must start with a non-digit word character
+/foo \k<12>/   foo foo c       -       Group name must start with a non-digit word character
+/foo \k'1a'/   foo foo c       -       Group name must start with a non-digit word character
+/foo \k<1a>/   foo foo c       -       Group name must start with a non-digit word character
+/foo \k''/     foo foo c       -       Group name must start with a non-digit word character
+/foo \k<>/     foo foo c       -       Group name must start with a non-digit word character
 /(?<as>as) (\w+) \k<as> (\w+)/ as easy as pie  y       $1-$2-$3        as-easy-pie
 
 # \g{...} with a name as the argument 

diff --git a/t/re/reg_mesg.t b/t/re/reg_mesg.t
index b86fd41..0241cd5 100644 (file)
--- a/t/re/reg_mesg.t
+++ b/t/re/reg_mesg.t
@@ -50,8 +50,7 @@ my @death =
  '/(?/' => 'Sequence (? incomplete in regex; marked by {#} in m/(?{#}/',
 
  '/(?;x/' => 'Sequence (?;...) not recognized in regex; marked by {#} in m/(?;{#}x/',
- '/(?<;x/' => 'Sequence (?<;...) not recognized in regex; marked by {#} in m/(?<;{#}x/',
-
+ '/(?<;x/' => 'Group name must start with a non-digit word character in regex; marked by {#} in m/(?<;{#}x/',
  '/(?\ix/' => 'Sequence (?\...) not recognized in regex; marked by {#} in m/(?\{#}ix/',
  '/(?\mx/' => 'Sequence (?\...) not recognized in regex; marked by {#} in m/(?\{#}mx/',
  '/(?\:x/' => 'Sequence (?\...) not recognized in regex; marked by {#} in m/(?\{#}:x/',