- lexer.rl: fix paren_nest for curly braces (#646)

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;

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:

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