From 96adadce844c554b3bd736b47e2fcaa2dcdddb3d Mon Sep 17 00:00:00 2001
From: Ilya Bylich <ibylich@gmail.com>
Date: Wed, 8 Jan 2020 14:52:18 +0300
Subject: [PATCH] - lexer.rl: fix paren_nest for curly braces (#646)

---
 lib/parser/lexer.rl  |  6 +++++-
 test/parse_helper.rb |  3 +++
 test/test_parser.rb  | 12 ++++++++++++
 3 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/lib/parser/lexer.rl b/lib/parser/lexer.rl
index a310723e3..b3e8a2f46 100644
--- a/lib/parser/lexer.rl
+++ b/lib/parser/lexer.rl
@@ -1064,7 +1064,6 @@ class Parser::Lexer
           emit(:tRCURLY, '}'.freeze, p - 1, p)
           @cond.lexpop
           @cmdarg.lexpop
-          @paren_nest -= 1
         else
           emit(:tSTRING_DEND, '}'.freeze, p - 1, p)
         end
@@ -1079,6 +1078,8 @@ class Parser::Lexer
         fbreak;
       end
     end
+
+    @paren_nest -= 1
   };
 
   action extend_interp_code {
@@ -2165,6 +2166,9 @@ class Parser::Lexer
             emit_do
           end
         end
+        if tok == '{'.freeze
+          @paren_nest += 1
+        end
         @command_start = true
 
         fnext expr_value; fbreak;
diff --git a/test/parse_helper.rb b/test/parse_helper.rb
index 3e5e96a13..e89adb6a6 100644
--- a/test/parse_helper.rb
+++ b/test/parse_helper.rb
@@ -127,6 +127,9 @@ def try_parsing(ast, code, parser, source_maps, version)
 
     assert parser.instance_eval { @lexer }.cmdarg.empty?,
       "(#{version}) expected cmdarg to be empty after parsing"
+
+    assert_equal 0, parser.instance_eval { @lexer.instance_eval { @paren_nest } },
+      "(#{version}) expected paren_nest to be 0 after parsing"
   end
 
   # Use like this:
diff --git a/test/test_parser.rb b/test/test_parser.rb
index a8a20d9b4..ef70b1998 100644
--- a/test/test_parser.rb
+++ b/test/test_parser.rb
@@ -9294,4 +9294,16 @@ def test_pattern_matching_required_parentheses_for_in_match
       %{     ^^ location},
       SINCE_2_7)
   end
+
+  def test_parser_bug_645
+    assert_parses(
+      s(:block,
+        s(:lambda),
+        s(:args,
+          s(:optarg, :arg,
+            s(:hash))), nil),
+      '-> (arg={}) {}',
+      %{},
+      SINCE_1_9)
+  end
 end