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Add dispatch disambiguation for 'is item'
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This allows for multi routines to distinguish between itemized arguments.

For the sake of simplicity, the parameter trait does not add any new
ParamTypeChecks to the parameter. Instead it is only used as a marker
for disambiguation in multiple dispatch:

    multi sub a(@A is item) { "itemized!" }
    multi sub a(@A) { "array" }

    a [1,2];  # "array"
    a $[1,2]; # "itemized!"

This also works for associatives (${} / {}) and lists ($() / ()).
Sigil-less parameters with Associative or Positional types can also
be disambiguated by 'is item'.

It also works on named parameters. Note that nested-parameters are
currently not parsing with traits at the moment. When they do, this
code will require some adjustment as currently we only use one name
in our name-to-type lookup. Since there was no way to test that it
would work, it has been left for later.
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@ab5tract
ab5tract committed Apr 9, 2024
1 parent d6e8001 commit 11ae695
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Showing 2 changed files with 166 additions and 1 deletion.
2 changes: 2 additions & 0 deletions src/core.c/Associative.rakumod
View file
Expand Up @@ -9,4 +9,6 @@ my role Associative[::TValue = Mu, ::TKey = Str(Any)] {
# method EXISTS-KEY($) { ... }
}

nqp::bindhllsym('Raku', 'Associative', Associative);

# vim: expandtab shiftwidth=4
165 changes: 164 additions & 1 deletion src/vm/moar/dispatchers.nqp
View file
Expand Up @@ -2158,6 +2158,8 @@ sub has-named-args-mismatch($capture, %info) {
my $Positional := nqp::null;
my $PositionalBindFailover := nqp::null;

my $Associative := nqp::null;

# Helper sub to create the dispatch plan.
sub raku-multi-plan(
@candidates, # list of candidates to check
Expand Down Expand Up @@ -2208,6 +2210,7 @@ sub raku-multi-plan(
my $need_type_guard := nqp::list_i;
my $need_conc_guard := nqp::list_i;
my @possibles;
my int $candidates-with-itemizable-params;

my int $done;
my int $cur_idx;
Expand All @@ -2221,6 +2224,12 @@ sub raku-multi-plan(
# An actual candidate
if nqp::isconcrete($cur_candidate) {

# Mark this group for disambigation via is item traits on params
if ! $candidates-with-itemizable-params
&& nqp::atkey($cur_candidate, 'item_disambiguation') {
$candidates-with-itemizable-params := 1
}

# Candidate; does the arity fit? (If not, it drops out on callsite
# shape.)
if $num_args >= nqp::atkey($cur_candidate, 'min_arity')
Expand All @@ -2235,6 +2244,8 @@ sub raku-multi-plan(

my int $type_mismatch;
my int $rwness_mismatch;
my int $positional-params;
my int $associative-params;
my int $i;
while $i < $type_check_count
&& !($type_mismatch +| $rwness_mismatch) {
Expand Down Expand Up @@ -2456,7 +2467,11 @@ sub raku-multi-plan(
unless has-named-args-mismatch($capture, %info) {
nqp::push(@filtered-possibles, %info);
++$need-bind-check
if nqp::existskey(%info, 'bind_check');
if nqp::existskey(%info, 'bind_check')
# bugs in callstatic and callmethod decont
# the value sent into ParamTypeCheck, meaning
# we can't use the VM binder for named args.
&& !$candidates-with-itemizable-params;
my $sub := nqp::atkey(%info, 'sub');
nqp::push(@defaults, %info)
if nqp::can($sub, 'default')
Expand All @@ -2478,6 +2493,12 @@ sub raku-multi-plan(
elsif nqp::elems(@exact-arity) == 1 {
@filtered-possibles := @exact-arity;
}
elsif $candidates-with-itemizable-params
&& 1 == nqp::elems(my @disambiguated
:= itemized-disambiguation($capture, @filtered-possibles))
{
@filtered-possibles := @disambiguated;
}
else {
my $node := MultiDispatchAmbiguous.new();
nqp::isnull($current-head)
Expand Down Expand Up @@ -2533,6 +2554,9 @@ sub raku-multi-plan(
!! nqp::setelems(@possibles, 0);
}

# reset for the next group
$candidates-with-itemizable-params := 0;

# If we're really at the end of the list, we're done
$done := 1
unless nqp::isconcrete(nqp::atpos(@candidates, $cur_idx));
Expand Down Expand Up @@ -2574,6 +2598,143 @@ sub raku-multi-plan(
}
}

# Helper sub to disambiguate candidates that may have itemization requirements
sub itemized-disambiguation($capture, $candidates) {
my int $num-candidates := nqp::elems($candidates);

my @capture-item-assoc := nqp::list_i;
my @capture-item-pos := nqp::list_i;
my $num-capture-args := nqp::captureposelems($capture);
my int $x;
while $x < $num-capture-args {
my $arg := nqp::captureposarg($capture, $x);
if nqp::iscont($arg) {
if nqp::istype($arg,
nqp::ifnull($Associative, $Associative := nqp::gethllsym('Raku', 'Associative')))
{
nqp::push_i(@capture-item-assoc, $x);
} elsif nqp::istype($arg,
nqp::ifnull($Positional, $Positional := nqp::gethllsym('Raku', 'MD_Pos')))
{
nqp::push_i(@capture-item-pos, $x);
}
}
++$x;
}

my %capture-named-item-assoc := nqp::hash;
my %capture-named-item-pos := nqp::hash;
if my %nameds := nqp::capturenamedshash($capture) {
my $iter := nqp::iterator(%nameds);
while $iter {
my $pair := nqp::shift($iter);
my $arg-name := nqp::iterkey_s($pair);
my $arg := nqp::iterval($pair);
if nqp::iscont($arg) {
if nqp::istype($arg,
nqp::ifnull($Associative, $Associative := nqp::gethllsym('Raku', 'Associative')))
{
nqp::bindkey(
%capture-named-item-assoc,
$arg-name, 1
);
} elsif nqp::istype($arg,
nqp::ifnull($Positional, $Positional := nqp::gethllsym('Raku', 'MD_Pos')))
{
nqp::bindkey(
%capture-named-item-pos,
$arg-name, 1
);
}
}
}
}

my int $z := 0;
my $candidate;
while $z < $num-candidates {
$candidate := nqp::atpos($candidates, $z);
my $signature := nqp::atkey($candidate, 'signature');
my @params := nqp::getattr($signature, Signature, '@!params');

my %cand-named-item-assoc := nqp::hash;
my %cand-named-item-pos := nqp::hash;

my @cand-item-assoc := nqp::list_i;
my @cand-item-pos := nqp::list_i;
my $num-cand-params := nqp::elems(@params);
my @cand-types := nqp::atkey($candidate, 'types');
my %named-types := nqp::atkey($candidate, 'named_types');
my int $y;
while $y < $num-cand-params {
my $param := nqp::atpos(@params, $y);
my int $is-named-param := $param.named;
my $type := $is-named-param
?? nqp::atkey(%named-types, $param.usage-name)
!! nqp::atpos(@cand-types, $y);
if $param.is-item {
if nqp::istype($type,
nqp::ifnull($Associative, $Associative := nqp::gethllsym('Raku', 'Associative')))
{
$is-named-param
?? nqp::bindkey(%cand-named-item-assoc, $param.usage-name, 1)
!! nqp::push_i(@cand-item-assoc, $y);
} elsif nqp::istype($type,
nqp::ifnull($Positional, $Positional := nqp::gethllsym('Raku', 'MD_Pos')))
{
$is-named-param
?? nqp::bindkey(%cand-named-item-pos, $param.usage-name, 1)
!! nqp::push_i(@cand-item-pos, $y);
}
}
++$y;
}

# when all counts are 0, the perfect-match will be the non-itemized signature
if (my int $num-assoc := nqp::elems(@capture-item-assoc)) == nqp::elems(@cand-item-assoc)
&& (my int $num-pos := nqp::elems(@capture-item-pos)) == nqp::elems(@cand-item-pos)
&& (my int $named-assoc := nqp::elems(%capture-named-item-assoc)) == nqp::elems(%cand-named-item-assoc)
&& (my int $named-pos := nqp::elems(%capture-named-item-pos)) == nqp::elems(%cand-named-item-pos)
{
my int $perfect-match := 1;
my int $z;
while $z < $num-assoc {
$perfect-match := $perfect-match
&& nqp::atpos_i(@capture-item-assoc, $z) == nqp::atpos_i(@cand-item-assoc, $z);
++$z;
}

$z := 0 if $z;
while $perfect-match && $z < $num-pos {
$perfect-match := $perfect-match
&& nqp::atpos_i(@capture-item-pos, $z) == nqp::atpos_i(@cand-item-pos, $z);
++$z;
}

if $named-assoc > 0 {
my $iter := nqp::iterator(%capture-named-item-assoc);
while $iter {
$perfect-match := $perfect-match
&& nqp::atkey(%cand-named-item-assoc, nqp::iterkey_s(nqp::shift($iter)));
}
}

if $named-pos > 0 {
my $iter := nqp::iterator(%capture-named-item-pos);
while $iter {
$perfect-match := $perfect-match
&& nqp::atkey(%cand-named-item-pos, nqp::iterkey_s(nqp::shift($iter)));
}
}

# for a well constructed multi, there should only be one candidate that is a perfect match.
return [ $candidate ] if $perfect-match;
}
++$z;
}
[]
}

# Helper sub to return a Raku Capture for the given VM capture
sub form-raku-capture($capture) {
my $raku-capture := nqp::create(Capture);
Expand Down Expand Up @@ -2681,6 +2842,8 @@ nqp::register('raku-multi-core',
my $target := nqp::captureposarg($capture, 0);
my @candidates := $target.dispatch_order;

$NAME := $target.name;

# Drop the first argument, to get just the arguments to dispatch on,
# and then produce a multi-dispatch plan. Decide what to do based
# upon it
Expand Down

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