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, 18 insertions, 3 deletions

diff --git a/opcode.h b/opcode.h
index b67067536e..c7a304d064 100644
--- a/opcode.h
+++ b/opcode.h
@@ -399,6 +399,9 @@ EXTCONST char* const PL_op_name[] = {
 	"lock",
 	"once",
 	"custom",
+	"reach",
+	"rkeys",
+	"rvalues",
 };
 #endif
 
@@ -772,6 +775,9 @@ EXTCONST char* const PL_op_desc[] = {
 	"lock",
 	"once",
 	"unknown custom operator",
+	"each on reference",
+	"keys on reference",
+	"values on reference",
 };
 #endif
 
@@ -1159,6 +1165,9 @@ EXT Perl_ppaddr_t PL_ppaddr[] /* or perlvars.h */
 	Perl_pp_lock,
 	Perl_pp_once,
 	Perl_unimplemented_op,	/* Perl_pp_custom */
+	Perl_pp_rkeys,	/* Perl_pp_reach */
+	Perl_pp_rkeys,
+	Perl_pp_rkeys,	/* Perl_pp_rvalues */
 }
 #endif
 #ifdef PERL_PPADDR_INITED
@@ -1327,11 +1336,11 @@ EXT Perl_check_t PL_check[] /* or perlvars.h */
 	Perl_ck_null,		/* lslice */
 	Perl_ck_fun,		/* anonlist */
 	Perl_ck_fun,		/* anonhash */
-	Perl_ck_fun,		/* splice */
-	Perl_ck_fun,		/* push */
+	Perl_ck_push,		/* splice */
+	Perl_ck_push,		/* push */
 	Perl_ck_shift,		/* pop */
 	Perl_ck_shift,		/* shift */
-	Perl_ck_fun,		/* unshift */
+	Perl_ck_push,		/* unshift */
 	Perl_ck_sort,		/* sort */
 	Perl_ck_fun,		/* reverse */
 	Perl_ck_grep,		/* grepstart */
@@ -1543,6 +1552,9 @@ EXT Perl_check_t PL_check[] /* or perlvars.h */
 	Perl_ck_rfun,		/* lock */
 	Perl_ck_null,		/* once */
 	Perl_ck_null,		/* custom */
+	Perl_ck_each,		/* reach */
+	Perl_ck_each,		/* rkeys */
+	Perl_ck_each,		/* rvalues */
 }
 #endif
 #ifdef PERL_CHECK_INITED
@@ -1921,6 +1933,9 @@ EXTCONST U32 PL_opargs[] = {
 	0x00007b04,	/* lock */
 	0x00000300,	/* once */
 	0x00000000,	/* custom */
+	0x00001b00,	/* reach */
+	0x00001b08,	/* rkeys */
+	0x00001b08,	/* rvalues */
 };
 #endif