From e2b192f7d5b4f0e2133bb6cf03cfc609258826be Mon Sep 17 00:00:00 2001
From: Kazuhiro NISHIYAMA <zn@mbf.nifty.com>
Date: Sun, 15 Dec 2019 14:47:36 +0900
Subject: [PATCH] rand(beginless_range) raise Errno::EDOM instead of TypeError

same as `rand(endless_range)`

Before:
```
$ ruby -e 'rand(..1)'
Traceback (most recent call last):
	2: from -e:1:in `<main>'
	1: from -e:1:in `rand'
-e:1:in `-': nil can't be coerced into Integer (TypeError)
```

After:
```
$ ruby -e 'rand(..1)'
Traceback (most recent call last):
	1: from -e:1:in `<main>'
-e:1:in `rand': Numerical argument out of domain (Errno::EDOM)
```
---
 random.c               | 6 ++++--
 test/ruby/test_rand.rb | 1 +
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/random.c b/random.c
index f72abb0a6c..68b47bcf1b 100644
--- a/random.c
+++ b/random.c
@@ -1043,9 +1043,11 @@ random_s_bytes(VALUE obj, VALUE len)
 static VALUE
 range_values(VALUE vmax, VALUE *begp, VALUE *endp, int *exclp)
 {
-    VALUE end;
+    VALUE beg, end;
 
-    if (!rb_range_values(vmax, begp, &end, exclp)) return Qfalse;
+    if (!rb_range_values(vmax, &beg, &end, exclp)) return Qfalse;
+    if (begp) *begp = beg;
+    if (NIL_P(beg)) return Qnil;
     if (endp) *endp = end;
     if (NIL_P(end)) return Qnil;
     return rb_check_funcall_default(end, id_minus, 1, begp, Qfalse);
diff --git a/test/ruby/test_rand.rb b/test/ruby/test_rand.rb
index ab9a1837f6..939d17bdf7 100644
--- a/test/ruby/test_rand.rb
+++ b/test/ruby/test_rand.rb
@@ -400,6 +400,7 @@ END
     assert_raise(Errno::EDOM, Errno::ERANGE) { r.rand(1.0 / 0.0) }
     assert_raise(Errno::EDOM, Errno::ERANGE) { r.rand(0.0 / 0.0) }
     assert_raise(Errno::EDOM) {r.rand(1..)}
+    assert_raise(Errno::EDOM) {r.rand(..1)}
 
     r = Random.new(0)
     assert_in_delta(1.5488135039273248, r.rand(1.0...2.0), 0.0001, '[ruby-core:24655]')