implement :$var colonpair syntax

Also adds a single test.

Author: moritz

src/NQP/Actions.pm

@@ -420,11 +420,16 @@ class NQP::Actions is HLL::Actions {
     }
 
     method colonpair($/) {
-        my $past := $<circumfix>
-                    ?? $<circumfix>[0].ast
-                    !! PAST::Val.new( :value( !$<not> ) );
-        $past.named( ~$<identifier> );
-        make $past;
+        if $<variable> {
+            $<variable>.ast.named(~$<variable><desigilname>);
+            make $<variable>.ast;
+        } else {
+            my $past := $<circumfix>
+                        ?? $<circumfix>[0].ast
+                        !! PAST::Val.new( :value( !$<not> ) );
+            $past.named( ~$<identifier> );
+            make $past;
+        }
     }
 
     method variable($/) {

src/NQP/Grammar.pm

@@ -286,6 +286,7 @@ grammar NQP::Grammar is HLL::Grammar {
         | $<not>='!' <identifier>
         | <identifier> <circumfix>?
         | <circumfix>
+        | <variable>
         ]
     }
 

t/nqp/23-named-args.t

@@ -2,7 +2,7 @@
 
 # test named parameters and arguments
 
-plan(4);
+plan(5);
 
 sub f1 ($x, :$y) { $x - $y; }
 say('ok ', f1(2, :y(1)), ' # named args passable');
@@ -16,5 +16,8 @@ say('ok ', f3(:y(2), :x(5)), ' # args reorderable');
 sub f4 ($w, $x, :$y, :$z) { $w + $x + $y + $z; }
 say('ok ', f4(:z(2), -3, :y(1), 4), ' # named/positional intermixable');
 
+my $y := 5;
+say('ok ', f1(10, :$y), ' - :$x colonpair syntax');
+
 
 # XXX: test mandatory named args are actually mandatory