Eval fails in certain situations (eval "{'...")

On Sun, 20 Jul 1997 16:02:05 MDT, Dave Carrigan wrote:
>Eval will fail in the following situation:
>
>- eval'ing a string
>- the string represents an anonymous hash
>- the first key of the anon hash is single quoted, and contains an
>  embedded single quote escaped with a backslash
>- using the form `` $ref = eval $string ''
>
>The MLDBM module uses this form of eval all the time, so the above
>situation actually has the potential to occur quite often.

>$string2 = "{'a\\'' => 'foo', 'b' => 'bar', 'c' => 'bat'}";

That is one of the cases where the note in perlref (about
disambiguating braces not preceded by anything else) applies.

However, in this particular case, the code that recognizes if
a literal string is the first thing inside the curlies is not
doing a thorough job of it.  The attached patch should cure
it.

Note that you'll still need to write C<eval "{ $a => 'foo' }">
as C<eval "+{ $a => 'foo' }"> if you want it to evaluate as a
hashref.  Perl only auto-disambiguates if the first thing in
the curlies is a literal string followed by a comma or =>.

I'll change MLDBM to conform, for the next release.

p5p-msgid: 199707211753.NAA14940@aatma.engin.umich.edu

1 files changed, 36 insertions, 1 deletions

diff --git a/t/comp/term.t b/t/comp/term.t
index b248e9b161..eb9968003e 100755
--- a/t/comp/term.t
+++ b/t/comp/term.t
@@ -4,7 +4,7 @@
 
 # tests that aren't important enough for base.term
 
-print "1..14\n";
+print "1..22\n";
 
 $x = "\\n";
 print "#1\t:$x: eq " . ':\n:' . "\n";
@@ -33,3 +33,38 @@ if ("$foo[1]b" eq "2b") { print "ok 12\n";} else {print "not ok 12\n";}
 if ("@foo[0..1]b" eq "1 2b") { print "ok 13\n";} else {print "not ok 13\n";}
 $" = '::';
 if ("@foo[0..1]b" eq "1::2b") { print "ok 14\n";} else {print "not ok 14\n";}
+
+# test if C<eval "{...}"> distinguishes between blocks and hashrefs
+
+$a = "{ '\\'' , 'foo' }";
+$a = eval $a;
+if (ref($a) eq 'HASH') {print "ok 15\n";} else {print "not ok 15\n";}
+
+$a = "{ '\\\\\\'abc' => 'foo' }";
+$a = eval $a;
+if (ref($a) eq 'HASH') {print "ok 16\n";} else {print "not ok 16\n";}
+
+$a = "{'a\\\n\\'b','foo'}";
+$a = eval $a;
+if (ref($a) eq 'HASH') {print "ok 17\n";} else {print "not ok 17\n";}
+
+$a = "{'\\\\\\'\\\\'=>'foo'}";
+$a = eval $a;
+if (ref($a) eq 'HASH') {print "ok 18\n";} else {print "not ok 18\n";}
+
+$a = "{q,a'b,,'foo'}";
+$a = eval $a;
+if (ref($a) eq 'HASH') {print "ok 19\n";} else {print "not ok 19\n";}
+
+$a = "{q[[']]=>'foo'}";
+$a = eval $a;
+if (ref($a) eq 'HASH') {print "ok 20\n";} else {print "not ok 20\n";}
+
+# needs disambiguation if first term is a variable
+$a = "+{ \$a , 'foo'}";
+$a = eval $a;
+if (ref($a) eq 'HASH') {print "ok 21\n";} else {print "not ok 21\n";}
+
+$a = "+{ \$a=>'foo'}";
+$a = eval $a;
+if (ref($a) eq 'HASH') {print "ok 22\n";} else {print "not ok 22\n";}