X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=lib%2FMethod%2FGenerate%2FAccessor.pm;h=8c4b19d6acb5a899e59313e37d8132a650df42b5;hb=99f21475b6ad64c2cb8882ab240f04f1165f3159;hp=c9b9dd5c7ce75cea3b84ad58135c1a2cfff175b6;hpb=6d377074a6632b1dd9468ee474040047bec31c7a;p=gitmo%2FMoo.git

diff --git a/lib/Method/Generate/Accessor.pm b/lib/Method/Generate/Accessor.pm
index c9b9dd5..8c4b19d 100644
--- a/lib/Method/Generate/Accessor.pm
+++ b/lib/Method/Generate/Accessor.pm
@@ -1,37 +1,293 @@
 package Method::Generate::Accessor;
 
 use strictures 1;
-use Class::Tiny::_Utils;
-use base qw(Class::Tiny::Object);
+use Moo::_Utils;
+use base qw(Moo::Object);
 use Sub::Quote;
 use B 'perlstring';
+use Scalar::Util 'blessed';
+use overload ();
+use Module::Runtime qw(use_module);
+BEGIN {
+  our $CAN_HAZ_XS =
+    !$ENV{MOO_XS_DISABLE}
+      &&
+    _maybe_load_module('Class::XSAccessor')
+      &&
+    (eval { Class::XSAccessor->VERSION('1.07') })
+  ;
+}
+
+sub _die_overwrite
+{
+  my ($pkg, $method, $type) = @_;
+  die "You cannot overwrite a locally defined method ($method) with @{[ $type || 'an accessor' ]}";
+}
 
 sub generate_method {
   my ($self, $into, $name, $spec, $quote_opts) = @_;
+  $spec->{allow_overwrite}++ if $name =~ s/^\+//;
   die "Must have an is" unless my $is = $spec->{is};
-  local $self->{captures} = {};
-  my $body = do {
-    if ($is eq 'ro') {
-      $self->_generate_get($name)
-    } elsif ($is eq 'rw') {
-      $self->_generate_getset($name, $spec)
+  if ($is eq 'ro') {
+    $spec->{reader} = $name unless exists $spec->{reader};
+  } elsif ($is eq 'rw') {
+    $spec->{accessor} = $name unless exists $spec->{accessor}
+      or ( $spec->{reader} and $spec->{writer} );
+  } elsif ($is eq 'lazy') {
+    $spec->{reader} = $name unless exists $spec->{reader};
+    $spec->{lazy} = 1;
+    $spec->{builder} ||= '_build_'.$name unless $spec->{default};
+  } elsif ($is eq 'rwp') {
+    $spec->{reader} = $name unless exists $spec->{reader};
+    $spec->{writer} = "_set_${name}" unless exists $spec->{writer};
+  } elsif ($is ne 'bare') {
+    die "Unknown is ${is}";
+  }
+  if (exists $spec->{builder}) {
+    if(ref $spec->{builder}) {
+      die "Invalid builder for $into->$name - not a method name, coderef or"
+        . " code-convertible object"
+        unless ref $spec->{builder} eq 'CODE'
+        or (blessed($spec->{builder}) and eval { \&{$spec->{builder}} });
+      $spec->{builder_sub} = $spec->{builder};
+      $spec->{builder} = 1;
+    }
+    $spec->{builder} = '_build_'.$name if ($spec->{builder}||0) eq 1;
+    die "Invalid builder for $into->$name - not a valid method name"
+      if $spec->{builder} !~ /\A[A-Za-z_][A-Za-z0-9_]*(?:::[A-Za-z_][A-Za-z0-9_]*)*\z/;
+  }
+  if (($spec->{predicate}||0) eq 1) {
+    $spec->{predicate} = $name =~ /^_/ ? "_has${name}" : "has_${name}";
+  }
+  if (($spec->{clearer}||0) eq 1) {
+    $spec->{clearer} = $name =~ /^_/ ? "_clear${name}" : "clear_${name}";
+  }
+  if (($spec->{trigger}||0) eq 1) {
+    $spec->{trigger} = quote_sub('shift->_trigger_'.$name.'(@_)');
+  }
+
+  for my $setting (qw( isa coerce )) {
+    next if !exists $spec->{$setting};
+    $self->_validate_codulatable($setting, $spec->{$setting}, "$into->$name");
+  }
+
+  if (exists $spec->{default}) {
+    if (!defined $spec->{default} || ref $spec->{default}) {
+      $self->_validate_codulatable('default', $spec->{default}, "$into->$name", 'or a non-ref');
+    }
+  }
+
+  if (exists $spec->{moosify}) {
+    if (ref $spec->{moosify} ne 'ARRAY') {
+      $spec->{moosify} = [$spec->{moosify}];
+    }
+
+    for my $spec (@{$spec->{moosify}}) {
+      $self->_validate_codulatable('moosify', $spec, "$into->$name");
+    }
+  }
+
+  my %methods;
+  if (my $reader = $spec->{reader}) {
+    _die_overwrite($into, $reader, 'a reader')
+      if !$spec->{allow_overwrite} && *{_getglob("${into}::${reader}")}{CODE};
+    if (our $CAN_HAZ_XS && $self->is_simple_get($name, $spec)) {
+      $methods{$reader} = $self->_generate_xs(
+        getters => $into, $reader, $name, $spec
+      );
     } else {
-      die "Unknown is ${is}";
+      $self->{captures} = {};
+      $methods{$reader} =
+        quote_sub "${into}::${reader}"
+          => '    die "'.$reader.' is a read-only accessor" if @_ > 1;'."\n"
+             .$self->_generate_get($name, $spec)
+          => delete $self->{captures}
+        ;
     }
-  };
-  quote_sub
-    "${into}::${name}" => '    '.$body."\n",
-    $self->{captures}, $quote_opts||{}
-  ;
+  }
+  if (my $accessor = $spec->{accessor}) {
+    _die_overwrite($into, $accessor, 'an accessor')
+      if !$spec->{allow_overwrite} && *{_getglob("${into}::${accessor}")}{CODE};
+    if (
+      our $CAN_HAZ_XS
+      && $self->is_simple_get($name, $spec)
+      && $self->is_simple_set($name, $spec)
+    ) {
+      $methods{$accessor} = $self->_generate_xs(
+        accessors => $into, $accessor, $name, $spec
+      );
+    } else {
+      $self->{captures} = {};
+      $methods{$accessor} =
+        quote_sub "${into}::${accessor}"
+          => $self->_generate_getset($name, $spec)
+          => delete $self->{captures}
+        ;
+    }
+  }
+  if (my $writer = $spec->{writer}) {
+    _die_overwrite($into, $writer, 'a writer')
+      if !$spec->{allow_overwrite} && *{_getglob("${into}::${writer}")}{CODE};
+    if (
+      our $CAN_HAZ_XS
+      && $self->is_simple_set($name, $spec)
+    ) {
+      $methods{$writer} = $self->_generate_xs(
+        setters => $into, $writer, $name, $spec
+      );
+    } else {
+      $self->{captures} = {};
+      $methods{$writer} =
+        quote_sub "${into}::${writer}"
+          => $self->_generate_set($name, $spec)
+          => delete $self->{captures}
+        ;
+    }
+  }
+  if (my $pred = $spec->{predicate}) {
+    _die_overwrite($into, $pred, 'a predicate')
+      if !$spec->{allow_overwrite} && *{_getglob("${into}::${pred}")}{CODE};
+    $methods{$pred} =
+      quote_sub "${into}::${pred}" =>
+        '    '.$self->_generate_simple_has('$_[0]', $name, $spec)."\n"
+      ;
+  }
+  if (my $pred = $spec->{builder_sub}) {
+    _install_coderef( "${into}::$spec->{builder}" => $spec->{builder_sub} );
+  }
+  if (my $cl = $spec->{clearer}) {
+    _die_overwrite($into, $cl, 'a clearer')
+      if !$spec->{allow_overwrite} && *{_getglob("${into}::${cl}")}{CODE};
+    $methods{$cl} =
+      quote_sub "${into}::${cl}" => 
+        $self->_generate_simple_clear('$_[0]', $name, $spec)."\n"
+      ;
+  }
+  if (my $hspec = $spec->{handles}) {
+    my $asserter = $spec->{asserter} ||= '_assert_'.$name;
+    my @specs = do {
+      if (ref($hspec) eq 'ARRAY') {
+        map [ $_ => $_ ], @$hspec;
+      } elsif (ref($hspec) eq 'HASH') {
+        map [ $_ => ref($hspec->{$_}) ? @{$hspec->{$_}} : $hspec->{$_} ],
+          keys %$hspec;
+      } elsif (!ref($hspec)) {
+        map [ $_ => $_ ], use_module('Role::Tiny')->methods_provided_by(use_module($hspec))
+      } else {
+        die "You gave me a handles of ${hspec} and I have no idea why";
+      }
+    };
+    foreach my $delegation_spec (@specs) {
+      my ($proxy, $target, @args) = @$delegation_spec;
+      _die_overwrite($into, $proxy, 'a delegation')
+        if !$spec->{allow_overwrite} && *{_getglob("${into}::${proxy}")}{CODE};
+      $self->{captures} = {};
+      $methods{$proxy} =
+        quote_sub "${into}::${proxy}" =>
+          $self->_generate_delegation($asserter, $target, \@args),
+          delete $self->{captures}
+        ;
+    }
+  }
+  if (my $asserter = $spec->{asserter}) {
+    $self->{captures} = {};
+
+
+    $methods{$asserter} =
+      quote_sub "${into}::${asserter}" => $self->_generate_asserter($name, $spec),
+        delete $self->{captures}
+      ;
+  }
+  \%methods;
+}
+
+sub is_simple_attribute {
+  my ($self, $name, $spec) = @_;
+  # clearer doesn't have to be listed because it doesn't
+  # affect whether defined/exists makes a difference
+  !grep $spec->{$_},
+    qw(lazy default builder coerce isa trigger predicate weak_ref);
+}
+
+sub is_simple_get {
+  my ($self, $name, $spec) = @_;
+  !($spec->{lazy} and ($spec->{default} or $spec->{builder}));
+}
+
+sub is_simple_set {
+  my ($self, $name, $spec) = @_;
+  !grep $spec->{$_}, qw(coerce isa trigger weak_ref);
+}
+
+sub has_eager_default {
+  my ($self, $name, $spec) = @_;
+  (!$spec->{lazy} and (exists $spec->{default} or $spec->{builder}));
 }
 
 sub _generate_get {
-  my ($self, $name) = @_;
-  $self->_generate_simple_get('$_[0]', $name);
+  my ($self, $name, $spec) = @_;
+  my $simple = $self->_generate_simple_get('$_[0]', $name, $spec);
+  if ($self->is_simple_get($name, $spec)) {
+    $simple;
+  } else {
+    $self->_generate_use_default(
+      '$_[0]', $name, $spec,
+      $self->_generate_simple_has('$_[0]', $name, $spec),
+    );
+  }
+}
+
+sub _generate_simple_has {
+  my ($self, $me, $name) = @_;
+  "exists ${me}->{${\perlstring $name}}";
+}
+
+sub _generate_simple_clear {
+  my ($self, $me, $name) = @_;
+  "    delete ${me}->{${\perlstring $name}}\n"
+}
+
+sub generate_get_default {
+  my $self = shift;
+  $self->{captures} = {};
+  my $code = $self->_generate_get_default(@_);
+  ($code, delete $self->{captures});
+}
+
+sub _generate_use_default {
+  my ($self, $me, $name, $spec, $test) = @_;
+  my $get_value = $self->_generate_get_default($me, $name, $spec);
+  if ($spec->{coerce}) {
+    $get_value = $self->_generate_coerce(
+      $name, $get_value,
+      $spec->{coerce}
+    )
+  }
+  $test." ? \n"
+  .$self->_generate_simple_get($me, $name, $spec)."\n:"
+  .($spec->{isa}
+    ? "    do {\n      my \$value = ".$get_value.";\n"
+      ."      ".$self->_generate_isa_check($name, '$value', $spec->{isa}).";\n"
+      ."      ".$self->_generate_simple_set($me, $name, $spec, '$value')."\n"
+      ."    }\n"
+    : '    ('.$self->_generate_simple_set($me, $name, $spec, $get_value).")\n");
+}
+
+sub _generate_get_default {
+  my ($self, $me, $name, $spec) = @_;
+  if (exists $spec->{default}) {
+    ref $spec->{default}
+      ? $self->_generate_call_code($name, 'default', $me, $spec->{default})
+      : perlstring $spec->{default};
+  }
+  else {
+    "${me}->${\$spec->{builder}}"
+  }
 }
 
 sub generate_simple_get {
-  shift->_generate_simple_get(@_);
+  my ($self, @args) = @_;
+  $self->_generate_simple_get(@args);
 }
 
 sub _generate_simple_get {
@@ -41,31 +297,68 @@ sub _generate_simple_get {
 }
 
 sub _generate_set {
-  my ($self, $name, $value, $spec) = @_;
-  my $simple = $self->_generate_simple_set($name, $value);
-  my ($trigger, $isa_check) = @{$spec}{qw(trigger isa)};
-  return $simple unless $trigger or $isa_check;
-  my $code = 'do {';
-  if ($isa_check) {
-    $code .= ' '.$self->_generate_isa_check($name, '$_[1]', $isa_check).';';
-  }
-  if ($trigger) {
-    my $fire = $self->_generate_trigger($name, '$_[0]', '$value', $trigger);
-    $code .=
-      ' my $value = '.$simple.'; '.$fire.'; '
-      .'$value';
+  my ($self, $name, $spec) = @_;
+  if ($self->is_simple_set($name, $spec)) {
+    $self->_generate_simple_set('$_[0]', $name, $spec, '$_[1]');
   } else {
-    $code .= ' '.$simple;
+    my ($coerce, $trigger, $isa_check) = @{$spec}{qw(coerce trigger isa)};
+    my $value_store = '$_[0]';
+    my $code;
+    if ($coerce) {
+      $value_store = '$value';
+      $code = "do { my (\$self, \$value) = \@_;\n"
+        ."        \$value = "
+        .$self->_generate_coerce($name, $value_store, $coerce).";\n";
+    }
+    else {
+      $code = "do { my \$self = shift;\n";
+    }
+    if ($isa_check) {
+      $code .= 
+        "        ".$self->_generate_isa_check($name, $value_store, $isa_check).";\n";
+    }
+    my $simple = $self->_generate_simple_set('$self', $name, $spec, $value_store);
+    if ($trigger) {
+      my $fire = $self->_generate_trigger($name, '$self', $value_store, $trigger);
+      $code .=
+        "        ".$simple.";\n        ".$fire.";\n"
+        ."        $value_store;\n";
+    } else {
+      $code .= "        ".$simple.";\n";
+    }
+    $code .= "      }";
+    $code;
   }
-  $code .= ' }';
-  return $code;
 }
 
+sub generate_coerce {
+  my $self = shift;
+  $self->{captures} = {};
+  my $code = $self->_generate_coerce(@_);
+  ($code, delete $self->{captures});
+}
+
+sub _attr_desc {
+  my ($name, $init_arg) = @_;
+  return perlstring($name) if !defined($init_arg) or $init_arg eq $name;
+  return perlstring($name).' (constructor argument: '.perlstring($init_arg).')';
+}
+
+sub _generate_coerce {
+  my ($self, $name, $value, $coerce, $init_arg) = @_;
+  $self->_generate_die_prefix(
+    $name,
+    "coercion",
+    $init_arg,
+    $self->_generate_call_code($name, 'coerce', "${value}", $coerce)
+  );
+}
+ 
 sub generate_trigger {
   my $self = shift;
-  local $self->{captures} = {};
+  $self->{captures} = {};
   my $code = $self->_generate_trigger(@_);
-  return ($code, $self->{captures});
+  ($code, delete $self->{captures});
 }
 
 sub _generate_trigger {
@@ -74,46 +367,254 @@ sub _generate_trigger {
 }
 
 sub generate_isa_check {
-  my $self = shift;
-  local $self->{captures} = {};
-  my $code = $self->_generate_isa_check(@_);
-  return ($code, $self->{captures});
+  my ($self, @args) = @_;
+  $self->{captures} = {};
+  my $code = $self->_generate_isa_check(@args);
+  ($code, delete $self->{captures});
+}
+
+sub _generate_die_prefix {
+  my ($self, $name, $prefix, $init_arg, $inside) = @_;
+  
+  $self->{captures}{'$__DIE__'} ||= \ sub {
+    our ($CurrentArgument, $CurrentAttribute, $CurrentStep, $OrigSigDie);
+    $OrigSigDie ||= sub { die $_[0] };
+    
+    $OrigSigDie->(
+      qq[$CurrentStep for "$CurrentAttribute"]
+      . ($CurrentArgument && ($CurrentArgument ne $CurrentAttribute)
+        ? qq[ (constructor argument: "$CurrentArgument")]
+        : "")
+      . qq[ failed: $_[0]]
+    );
+  };
+  
+  "do {\n"
+  .'  local $Method::Generate::Accessor::CurrentArgument = '
+    . B::perlstring($init_arg) . ";\n"
+  .'  local $Method::Generate::Accessor::CurrentAttribute = '
+    . B::perlstring($name) . ";\n"
+  .'  local $Method::Generate::Accessor::CurrentStep = '
+    . B::perlstring($prefix) . ";\n"
+  .'  local $Method::Generate::Accessor::OrigSigDie = $SIG{__DIE__};'."\n"
+  .'  local $SIG{__DIE__} = $__DIE__;'."\n"
+  .$inside
+  ."}\n"
 }
 
 sub _generate_isa_check {
-  my ($self, $name, $value, $check) = @_;
-  $self->_generate_call_code($name, 'isa_check', $value, $check);
+  my ($self, $name, $value, $check, $init_arg) = @_;
+  $self->_generate_die_prefix(
+    $name,
+    "isa check",
+    $init_arg,
+    $self->_generate_call_code($name, 'isa_check', $value, $check)
+  );
 }
 
 sub _generate_call_code {
   my ($self, $name, $type, $values, $sub) = @_;
+  $sub = \&{$sub} if blessed($sub);  # coderef if blessed
   if (my $quoted = quoted_from_sub($sub)) {
+    my $local = 1;
+    if ($values eq '@_' || $values eq '$_[0]') {
+      $local = 0;
+      $values = '@_';
+    }
     my $code = $quoted->[1];
-    my $at_ = 'local @_ = ('.$values.');';
     if (my $captures = $quoted->[2]) {
       my $cap_name = qq{\$${type}_captures_for_${name}};
       $self->{captures}->{$cap_name} = \$captures;
-      return "do {\n".'      '.$at_."\n"
-        .Sub::Quote::capture_unroll($cap_name, $captures, 6)
-        ."     ${code}\n    }";
+      Sub::Quote::inlinify(
+        $code, $values, Sub::Quote::capture_unroll($cap_name, $captures, 6), $local
+      );
+    } else {
+      Sub::Quote::inlinify($code, $values, undef, $local);
+    }
+  } else {
+    my $cap_name = qq{\$${type}_for_${name}};
+    $self->{captures}->{$cap_name} = \$sub;
+    "${cap_name}->(${values})";
+  }
+}
+
+sub generate_populate_set {
+  my $self = shift;
+  $self->{captures} = {};
+  my $code = $self->_generate_populate_set(@_);
+  ($code, delete $self->{captures});
+}
+
+sub _generate_populate_set {
+  my ($self, $me, $name, $spec, $source, $test, $init_arg) = @_;
+  if ($self->has_eager_default($name, $spec)) {
+    my $get_indent = ' ' x ($spec->{isa} ? 6 : 4);
+    my $get_default = $self->_generate_get_default(
+                        '$new', $_, $spec
+                      );
+    my $get_value = 
+      defined($spec->{init_arg})
+        ? "(\n${get_indent}  ${test}\n${get_indent}   ? ${source}\n${get_indent}   : "
+            .$get_default
+            ."\n${get_indent})"
+        : $get_default;
+    if ($spec->{coerce}) {
+      $get_value = $self->_generate_coerce(
+        $name, $get_value,
+        $spec->{coerce}, $init_arg
+      )
     }
-    return 'do { local @_ = ('.$values.'); '.$code.' }';
+    ($spec->{isa}
+      ? "    {\n      my \$value = ".$get_value.";\n      "
+        .$self->_generate_isa_check(
+          $name, '$value', $spec->{isa}, $init_arg
+        ).";\n"
+        .'      '.$self->_generate_simple_set($me, $name, $spec, '$value').";\n"
+        ."    }\n"
+      : '    '.$self->_generate_simple_set($me, $name, $spec, $get_value).";\n"
+    )
+    .($spec->{trigger}
+      ? '    '
+        .$self->_generate_trigger(
+          $name, $me, $self->_generate_simple_get($me, $name, $spec),
+          $spec->{trigger}
+        )." if ${test};\n"
+      : ''
+    );
+  } else {
+    "    if (${test}) {\n"
+      .($spec->{coerce}
+        ? "      $source = "
+          .$self->_generate_coerce(
+            $name, $source,
+            $spec->{coerce}, $init_arg
+          ).";\n"
+        : ""
+      )
+      .($spec->{isa}
+        ? "      "
+          .$self->_generate_isa_check(
+            $name, $source, $spec->{isa}, $init_arg
+          ).";\n"
+        : ""
+      )
+      ."      ".$self->_generate_simple_set($me, $name, $spec, $source).";\n"
+      .($spec->{trigger}
+        ? "      "
+          .$self->_generate_trigger(
+            $name, $me, $self->_generate_simple_get($me, $name, $spec),
+            $spec->{trigger}
+          ).";\n"
+        : ""
+      )
+      ."    }\n";
   }
-  my $cap_name = qq{\$${type}_for_${name}};
-  $self->{captures}->{$cap_name} = \$sub;
-  return "${cap_name}->(${values})";
+}
+
+sub _generate_core_set {
+  my ($self, $me, $name, $spec, $value) = @_;
+  my $name_str = perlstring $name;
+  "${me}->{${name_str}} = ${value}";
 }
 
 sub _generate_simple_set {
-  my ($self, $name, $value) = @_;
+  my ($self, $me, $name, $spec, $value) = @_;
   my $name_str = perlstring $name;
-  "\$_[0]->{${name_str}} = ${value}";
+  my $simple = $self->_generate_core_set($me, $name, $spec, $value);
+
+  if ($spec->{weak_ref}) {
+    require Scalar::Util;
+    my $get = $self->_generate_simple_get($me, $name, $spec);
+
+    # Perl < 5.8.3 can't weaken refs to readonly vars
+    # (e.g. string constants). This *can* be solved by:
+    #
+    #Internals::SetReadWrite($foo);
+    #Scalar::Util::weaken ($foo);
+    #Internals::SetReadOnly($foo);
+    #
+    # but requires XS and is just too damn crazy
+    # so simply throw a better exception
+    my $weak_simple = "do { Scalar::Util::weaken(${simple}); no warnings 'void'; $get }";
+    Moo::_Utils::lt_5_8_3() ? <<"EOC" : $weak_simple;
+      eval { Scalar::Util::weaken($simple); 1 }
+        ? do { no warnings 'void'; $get }
+        : do {
+          if( \$@ =~ /Modification of a read-only value attempted/) {
+            require Carp;
+            Carp::croak( sprintf (
+              'Reference to readonly value in "%s" can not be weakened on Perl < 5.8.3',
+              $name_str,
+            ) );
+          } else {
+            die \$@;
+          }
+        }
+EOC
+  } else {
+    $simple;
+  }
 }
 
 sub _generate_getset {
   my ($self, $name, $spec) = @_;
-  q{(@_ > 1 ? }.$self->_generate_set($name, q{$_[1]}, $spec)
-    .' : '.$self->_generate_get($name).')';
+  q{(@_ > 1}."\n      ? ".$self->_generate_set($name, $spec)
+    ."\n      : ".$self->_generate_get($name, $spec)."\n    )";
+}
+
+sub _generate_asserter {
+  my ($self, $name, $spec) = @_;
+
+  "do {\n"
+   ."  my \$val = ".$self->_generate_get($name, $spec).";\n"
+   ."  unless (".$self->_generate_simple_has('$_[0]', $name, $spec).") {\n"
+   .qq!    die "Attempted to access '${name}' but it is not set";\n!
+   ."  }\n"
+   ."  \$val;\n"
+   ."}\n";
+}
+sub _generate_delegation {
+  my ($self, $asserter, $target, $args) = @_;
+  my $arg_string = do {
+    if (@$args) {
+      # I could, I reckon, linearise out non-refs here using perlstring
+      # plus something to check for numbers but I'm unsure if it's worth it
+      $self->{captures}{'@curries'} = $args;
+      '@curries, @_';
+    } else {
+      '@_';
+    }
+  };
+  "shift->${asserter}->${target}(${arg_string});";
+}
+
+sub _generate_xs {
+  my ($self, $type, $into, $name, $slot) = @_;
+  Class::XSAccessor->import(
+    class => $into,
+    $type => { $name => $slot },
+    replace => 1,
+  );
+  $into->can($name);
+}
+
+sub default_construction_string { '{}' }
+
+sub _validate_codulatable {
+  my ($self, $setting, $value, $into, $appended) = @_;
+  my $invalid = "Invalid $setting '" . overload::StrVal($value)
+    . "' for $into not a coderef";
+  $invalid .= " $appended" if $appended;
+
+  unless (ref $value and (ref $value eq 'CODE' or blessed($value))) {
+    die "$invalid or code-convertible object";
+  }
+
+  unless (eval { \&$value }) {
+    die "$invalid and could not be converted to a coderef: $@";
+  }
+
+  1;
 }
 
 1;