[perl #126209] [BUG] LTA error message for $hash assignment with missing comma

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This used to work somehow:
  ugexe | star: my @z = (^3).map: {$_}; my $x = { :a(1) :b(@z) }
camelia | star-m 2015.03: ( no output )

But now it gives a cryptic error message:
  ugexe | m: my @z = (^3).map: {$_}; my $x = { :a(1) :b(@z) }
camelia | rakudo-moar 1ed1ea: OUTPUT«===SORRY!===␤Unknown QAST node type NQPMu␤»