rename AssignRef to Reference

php7/php7.go

@@ -4223,7 +4223,7 @@ yydefault:
 		yyDollar = yyS[yypt-4 : yypt+1]
 		//line php7/php7.y:1512
 		{
-			yyVAL.node = assign.NewAssignRef(yyDollar[1].node, yyDollar[4].node)
+			yyVAL.node = assign.NewReference(yyDollar[1].node, yyDollar[4].node)
 			positions.AddPosition(yyVAL.node, positionBuilder.NewNodesPosition(yyDollar[1].node, yyDollar[4].node))
 			comments.AddComments(yyVAL.node, comments[yyDollar[1].node])
 		}

php7/php7.y

@@ -1510,7 +1510,7 @@ expr_without_variable:
         }
     |   variable '=' '&' expr
         {
-            $$ = assign.NewAssignRef($1, $4)
+            $$ = assign.NewReference($1, $4)
             positions.AddPosition($$, positionBuilder.NewNodesPosition($1, $4))
             comments.AddComments($$, comments[$1])
         }

php7/php7_test.go

@@ -2890,7 +2890,7 @@ CAD;
 				},
 			},
 			&stmt.Expression{
-				Expr: &assign.AssignRef{
+				Expr: &assign.Reference{
 					Variable:   &expr.Variable{VarName: &node.Identifier{Value: "a"}},
 					Expression: &expr.Variable{VarName: &node.Identifier{Value: "b"}},
 				},