From 33296501241d80df3dec8ee422bf8743558258af Mon Sep 17 00:00:00 2001
From: Doug Rohrer <doug@therohrers.org>
Date: Tue, 4 Oct 2016 17:10:40 -0400
Subject: Fix reference to automatic `undefined` field declared types.

In 8ce35b287fb50a6845fccf6a13c672aae303dc91 automatic insertion of `undefined` for record fields without initializers was removed, but this was not noted in the documentation. Add a warning about this change using similar verbiage as the original docs.
---
 system/doc/reference_manual/typespec.xml | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

(limited to 'system')

diff --git a/system/doc/reference_manual/typespec.xml b/system/doc/reference_manual/typespec.xml
index 1899efd5f3..4421529dda 100644
--- a/system/doc/reference_manual/typespec.xml
+++ b/system/doc/reference_manual/typespec.xml
@@ -409,11 +409,13 @@
       The initial values for fields are to be compatible
       with (that is, a member of) the corresponding types.
       This is checked by the compiler and results in a compilation error
-      if a violation is detected. For fields without initial values,
-      the singleton type <c>'undefined'</c> is added to all declared types.
-      In other words, the following two record declarations have identical 
-      effects:
+      if a violation is detected. 
     </p>
+    <warning>
+      <p>In previous (pre-19) versions of Erlang, for fields without initial values,
+      the singleton type <c>'undefined'</c> was added to all declared types.
+      In other words, the following two record declarations had identical 
+      effects:</p>
     <pre>
   -record(rec, {f1 = 42 :: integer(),
                 f2      :: float(),
@@ -423,9 +425,10 @@
                 f2      :: 'undefined' | float(),
                 f3      :: 'undefined' | 'a' | 'b'}).</pre>
     <p>
-      For this reason, it is recommended that records contain initializers, 
-      whenever possible.
+      This is no longer the case. If you require <c>'undefined'</c> in your record field
+      type, you must explicitly add it to the typespec, as in the 2nd example.
     </p>
+    </warning>
     <p>
       Any record, containing type information or not, once defined, 
       can be used as a type using the following syntax:
-- 
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