RakuAST: change reducecheck to specific ternary handling

Not sure exactly how I'm going to handle ternaries in the
OperatorProperties case yet, but this is a first step towards
being more clear about this rather than burying it in some
obscure general feature that only appears to be used in one
situation in the Raku grammar.

src/Raku/Grammar.nqp

@@ -1274,6 +1274,7 @@ grammar Raku::Grammar is HLL::Grammar does Raku::Common {
 #-------------------------------------------------------------------------------
 # Expression parsing
 
+    # Helper methods for throwing exceptions
     method EXPR-nonassoc($cur, $left, $right) {
         self.typed-panic: 'X::Syntax::NonAssociative',
           :left(~$left), :right(~$right);
@@ -1479,7 +1480,6 @@ grammar Raku::Grammar is HLL::Grammar does Raku::Common {
         my str $opassoc := ~nqp::atkey(%opO, 'assoc');
         my str $key;
         my str $sym;
-        my $reducecheck;
         my $arg;
 
         if $opassoc eq 'unary' {
@@ -1503,8 +1503,12 @@ grammar Raku::Grammar is HLL::Grammar does Raku::Common {
         else { # infix op assoc: left|right|ternary|...
             $op[1] := nqp::pop(@termstack); # right
             $op[0] := nqp::pop(@termstack); # left
-            $reducecheck := nqp::atkey(%opO, 'reducecheck');
-            self."$reducecheck"($op) unless nqp::isnull($reducecheck);
+
+            # we haz a ternary, adjust for that
+            if nqp::atkey(%opO,'ternary') {
+                $op[2] := $op[1];
+                $op[1] := $op<infix><EXPR>;
+            }
             $key := 'INFIX';
         }
         self.'!reduce_with_match'('EXPR', $key, $op);
@@ -2169,7 +2173,7 @@ grammar Raku::Grammar is HLL::Grammar does Raku::Common {
           || <.typed-panic: "X::Syntax::Confused",
                reason => "Confused: Found ?? but no !!">
         ]
-        <O(|%conditional, :reducecheck<ternary>)>
+        <O(|%conditional, :ternary)>
     }
 
     token infix:sym<,>    {