From a0df9ab3d7c9b301f717eaea2455613d60d3dec3 Mon Sep 17 00:00:00 2001
From: Hans Bolinder <hasse@erlang.org>
Date: Wed, 12 May 2010 09:44:28 +0000
Subject: OTP-8629 stdlib: prepare erl_parse.yrl for future extension

---
 lib/stdlib/src/erl_parse.yrl | 5 +++++
 1 file changed, 5 insertions(+)

(limited to 'lib/stdlib')

diff --git a/lib/stdlib/src/erl_parse.yrl b/lib/stdlib/src/erl_parse.yrl
index 69807aad83..5287f55e59 100644
--- a/lib/stdlib/src/erl_parse.yrl
+++ b/lib/stdlib/src/erl_parse.yrl
@@ -112,6 +112,7 @@ type_guards -> type_guard ',' type_guards : ['$1'|'$3'].
 
 type_guard -> atom '(' top_types ')'      : {type, ?line('$1'), constraint,
                                              ['$1', '$3']}.
+type_guard -> var '::' top_type           : build_def('$1', '$3').
 
 top_types -> top_type                     : ['$1'].
 top_types -> top_type ',' top_types       : ['$1'|'$3'].
@@ -597,6 +598,10 @@ find_arity_from_specs([Spec|_]) ->
     {type, _, 'fun', [{type, _, product, Args},_]} = Fun,
     length(Args).
 
+build_def(LHS, Types) ->
+    IsSubType = {atom, ?line(LHS), is_subtype},
+    {type, ?line(LHS), constraint, [IsSubType, [LHS, Types]]}.
+
 lift_unions(T1, {type, _La, union, List}) ->
     {type, ?line(T1), union, [T1|List]};
 lift_unions(T1, T2) ->
-- 
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