From a58b4eee25b79432d98a1c665edaf5ec0a054b2e Mon Sep 17 00:00:00 2001
From: Nobuyoshi Nakada <nobu@ruby-lang.org>
Date: Tue, 12 Nov 2019 17:14:10 +0900
Subject: Warn on `...` at EOL

---
 parse.y                  | 3 +++
 test/ruby/test_syntax.rb | 7 +++++++
 2 files changed, 10 insertions(+)

diff --git a/parse.y b/parse.y
index 0bda2d2db0..6d0564476d 100644
--- a/parse.y
+++ b/parse.y
@@ -9235,6 +9235,9 @@ parser_yylex(struct parser_params *p)
 	switch (c = nextc(p)) {
 	  case '.':
 	    if ((c = nextc(p)) == '.') {
+		if (p->lex.paren_nest == 0 && looking_at_eol_p(p)) {
+		    rb_warn0("... at EOL, should be parenthesized?");
+		}
 		return is_beg ? tBDOT3 : tDOT3;
 	    }
 	    pushback(p, c);
diff --git a/test/ruby/test_syntax.rb b/test/ruby/test_syntax.rb
index ba479fa459..622017be83 100644
--- a/test/ruby/test_syntax.rb
+++ b/test/ruby/test_syntax.rb
@@ -986,6 +986,13 @@ eom
     assert_syntax_error('0...%q.', /unterminated string/, bug10957)
   end
 
+  def test_range_at_eol
+    assert_warn(/\.\.\. at EOL/) {eval("1...\n2")}
+    assert_warn('') {eval("(1...)")}
+    assert_warn('') {eval("(1...\n2)")}
+    assert_warn('') {eval("{a: 1...\n2}")}
+  end
+
   def test_too_big_nth_ref
     bug11192 = '[ruby-core:69393] [Bug #11192]'
     assert_warn(/too big/, bug11192) do
-- 
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