Allow push/pop/keys/etc to act on references

All built-in functions that operate directly on array or hash
containers now also accept hard references to arrays or hashes:

  |----------------------------+---------------------------|
  | Traditional syntax         | Terse syntax              |
  |----------------------------+---------------------------|
  | push @$arrayref, @stuff    | push $arrayref, @stuff    |
  | unshift @$arrayref, @stuff | unshift $arrayref, @stuff |
  | pop @$arrayref             | pop $arrayref             |
  | shift @$arrayref           | shift $arrayref           |
  | splice @$arrayref, 0, 2    | splice $arrayref, 0, 2    |
  | keys %$hashref             | keys $hashref             |
  | keys @$arrayref            | keys $arrayref            |
  | values %$hashref           | values $hashref           |
  | values @$arrayref          | values $arrayref          |
  | ($k,$v) = each %$hashref   | ($k,$v) = each $hashref   |
  | ($k,$v) = each @$arrayref  | ($k,$v) = each $arrayref  |
  |----------------------------+---------------------------|

This allows these built-in functions to act on long dereferencing
chains or on the return value of subroutines without needing to wrap
them in C<@{}> or C<%{}>:

  push @{$obj->tags}, $new_tag;  # old way
  push $obj->tags,    $new_tag;  # new way

  for ( keys %{$hoh->{genres}{artists}} ) {...} # old way
  for ( keys $hoh->{genres}{artists}    ) {...} # new way

For C<push>, C<unshift> and C<splice>, the reference will auto-vivify
if it is not defined, just as if it were wrapped with C<@{}>.

Calling C<keys> or C<values> directly on a reference gives a
substantial performance improvement over explicit dereferencing.

For C<keys>, C<values>, C<each>, when overloaded dereferencing is
present, the overloaded dereference is used instead of dereferencing
the underlying reftype.  Warnings are issued about assumptions made in
the following three ambiguous cases:

  (a) If both %{} and @{} overloading exists, %{} is used
  (b) If %{} overloading exists on a blessed arrayref, %{} is used
  (c) If @{} overloading exists on a blessed hashref, @{} is used

1 files changed, 9 insertions, 0 deletions

diff --git a/proto.h b/proto.h
index 8cc3281f6d..151baf8c0d 100644
--- a/proto.h
+++ b/proto.h
@@ -407,6 +407,12 @@ PERL_CALLCONV OP *	Perl_ck_open(pTHX_ OP *o)
 #define PERL_ARGS_ASSERT_CK_OPEN	\
 	assert(o)
 
+PERL_CALLCONV OP *	Perl_ck_push(pTHX_ OP *o)
+			__attribute__warn_unused_result__
+			__attribute__nonnull__(pTHX_1);
+#define PERL_ARGS_ASSERT_CK_PUSH	\
+	assert(o)
+
 PERL_CALLCONV OP *	Perl_ck_readline(pTHX_ OP *o)
 			__attribute__warn_unused_result__
 			__attribute__nonnull__(pTHX_1);
@@ -3073,6 +3079,7 @@ PERL_CALLCONV OP *	Perl_pp_quotemeta(pTHX);
 PERL_CALLCONV OP *	Perl_pp_rand(pTHX);
 PERL_CALLCONV OP *	Perl_pp_range(pTHX);
 PERL_CALLCONV OP *	Perl_pp_rcatline(pTHX);
+PERL_CALLCONV OP *	Perl_pp_reach(pTHX);
 PERL_CALLCONV OP *	Perl_pp_read(pTHX);
 PERL_CALLCONV OP *	Perl_pp_readdir(pTHX);
 PERL_CALLCONV OP *	Perl_pp_readline(pTHX);
@@ -3093,12 +3100,14 @@ PERL_CALLCONV OP *	Perl_pp_reverse(pTHX);
 PERL_CALLCONV OP *	Perl_pp_rewinddir(pTHX);
 PERL_CALLCONV OP *	Perl_pp_right_shift(pTHX);
 PERL_CALLCONV OP *	Perl_pp_rindex(pTHX);
+PERL_CALLCONV OP *	Perl_pp_rkeys(pTHX);
 PERL_CALLCONV OP *	Perl_pp_rmdir(pTHX);
 PERL_CALLCONV OP *	Perl_pp_rv2av(pTHX);
 PERL_CALLCONV OP *	Perl_pp_rv2cv(pTHX);
 PERL_CALLCONV OP *	Perl_pp_rv2gv(pTHX);
 PERL_CALLCONV OP *	Perl_pp_rv2hv(pTHX);
 PERL_CALLCONV OP *	Perl_pp_rv2sv(pTHX);
+PERL_CALLCONV OP *	Perl_pp_rvalues(pTHX);
 PERL_CALLCONV OP *	Perl_pp_sassign(pTHX);
 PERL_CALLCONV OP *	Perl_pp_say(pTHX);
 PERL_CALLCONV OP *	Perl_pp_scalar(pTHX);