Deparse: detect hh changes properly

The hack to check whether the hint hash has changed doesn’t work.  One
actually has to iterate through the hash.  Since declare_hinthash does
that already, just call it.

The change to declare_hinthash to return an empty list instead of ''
is one of those theoretical speed-ups.  It results in one less state-
ment and two fewer method calls in its caller.

2 files changed, 14 insertions, 5 deletions

diff --git a/dist/B-Deparse/Deparse.pm b/dist/B-Deparse/Deparse.pm
index c7bdec4249..ed5493b0f7 100644
--- a/dist/B-Deparse/Deparse.pm
+++ b/dist/B-Deparse/Deparse.pm
@@ -1451,11 +1451,12 @@ sub pp_nextstate {
 	$self->{'hints'} = $hints;
     }
 
-    # hack to check that the hint hash hasn't changed
     if ($] > 5.009 &&
-	"@{[sort %{$self->{'hinthash'} || {}}]}"
-	ne "@{[sort %{$op->hints_hash->HASH || {}}]}") {
-	push @text, declare_hinthash($self->{'hinthash'}, $op->hints_hash->HASH, $self->{indent_size});
+	@text != push @text, declare_hinthash(
+	    $self->{'hinthash'}, $op->hints_hash->HASH,
+	    $self->{indent_size}
+	)
+    ) {
 	$self->{'hinthash'} = $op->hints_hash->HASH;
     }
 
@@ -1527,7 +1528,7 @@ sub declare_hinthash {
 	    push @decls, qq(delete \$^H{'$key'};);
 	}
     }
-    @decls or return '';
+    @decls or return;
     return join("\n" . (" " x $indent), "BEGIN {", @decls) . "\n}\n";
 }
 
diff --git a/dist/B-Deparse/t/deparse.t b/dist/B-Deparse/t/deparse.t
index d47498cf59..a4284ef33f 100644
--- a/dist/B-Deparse/t/deparse.t
+++ b/dist/B-Deparse/t/deparse.t
@@ -809,3 +809,11 @@ BEGIN { $^H{'foo'} = undef; }
 }
 BEGIN { $^H{q[']} = '('; }
 print $_;
+####
+# hint hash changes that serialise the same way with sort %hh
+BEGIN { $^H{'a'} = 'b'; }
+{
+ BEGIN { $^H{'b'} = 'a'; delete $^H{'a'}; }
+ print $_;
+}
+print $_;