Perform a PropEr check for Erlang/OTP >= 21 (#226)

Erlang/OTP release 21.0 introduced an OTP_RELEASE macro that is
defined to contain the release of the emulator.  Use that macro
for OTP releases >= 21 instead of the (slightly broken, in PropEr)
rebar3 platform_define check.

Author: kostis

include/proper_internal.hrl

@@ -46,13 +46,14 @@
 %% Stacktrace access
 %%------------------------------------------------------------------------------
 
--ifdef(AT_LEAST_21).
--define(STACKTRACE(ErrorType, Error, ErrorStackTrace),
-        ErrorType:Error:ErrorStackTrace ->).
--else.
+-ifndef(OTP_RELEASE).	 %% introduced in 21
+%% cases for Erlang/OTP releases prior to 21
 -define(STACKTRACE(ErrorType, Error, ErrorStackTrace),
         ErrorType:Error ->
             ErrorStackTrace = erlang:get_stacktrace(),).
+-else.  %% -if (?OTP_RELEASE >= 21)
+-define(STACKTRACE(ErrorType, Error, ErrorStackTrace),
+        ErrorType:Error:ErrorStackTrace ->).
 -endif.
 
 %%------------------------------------------------------------------------------

rebar.config

@@ -2,7 +2,7 @@
 %%% -*- coding: utf-8 -*-
 %%% -*- erlang-indent-level: 2 -*-
 %%% -------------------------------------------------------------------
-%%% Copyright 2010-2019 Manolis Papadakis <[email protected]>,
+%%% Copyright 2010-2020 Manolis Papadakis <[email protected]>,
 %%%                     Eirini Arvaniti <[email protected]>
 %%%                 and Kostis Sagonas <[email protected]>
 %%%
@@ -21,8 +21,8 @@
 %%% You should have received a copy of the GNU General Public License
 %%% along with PropEr.  If not, see <http://www.gnu.org/licenses/>.
 
-%%% Author:      Manolis Papadakis
-%%% Description: Options for rebar
+%%% Author(s):   Manolis Papadakis, Kostis Sagonas
+%%% Description: Options for rebar/rebar3
 
 %% WARNING: Our version of rebar does NOT automatically report warnings,
 %% nor does it add erl_opts to eunit_compile_opts.
@@ -38,8 +38,7 @@
 	    report_warnings, {warn_format,1}, warn_export_vars,
 	    warn_obsolete_guard, warn_unused_import,
 	    warn_missing_spec, warn_untyped_record,
-	    {platform_define, "^2", 'AT_LEAST_20'},
-	    {platform_define, "^2[1-9]", 'AT_LEAST_21'}]}.
+	    {platform_define, "^2", 'AT_LEAST_20'}]}.
 
 {post_hooks, [{clean, "./scripts/clean_doc.sh"}]}.