From 9dad1d17f08f9969c8f5556db04919cb024b6ea0 Mon Sep 17 00:00:00 2001
From: Jeff Bezanson <jeff.bezanson@gmail.com>
Date: Sun, 15 Apr 2018 13:13:31 -0400
Subject: [PATCH] reserve syntax that could be used for computed field types
 (#18466)

---
 src/julia-syntax.scm | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/julia-syntax.scm b/src/julia-syntax.scm
index ad7b4692c36da..8a7f83e8b7e9d 100644
--- a/src/julia-syntax.scm
+++ b/src/julia-syntax.scm
@@ -862,6 +862,16 @@
                  (if (not (symbol? v))
                      (error (string "field name \"" (deparse v) "\" is not a symbol"))))
                field-names)
+     (for-each (lambda (t)
+                 (if (expr-contains-p (lambda (e)
+                                        (and (pair? e) (eq? (car e) 'call)
+                                             (expr-contains-p (lambda (a) (memq a params))
+                                                              e)))
+                                      t)
+                     (error (string "unsupported field type expression \""
+                                    (deparse t)
+                                    "\""))))
+               field-types)
      `(block
        (scope-block
         (block