Fix memory leak when parsing invalid hash symbol

For example:

    10.times do
      100_000.times do
        eval('{"\xC3": 1}')
      rescue EncodingError
      end

      puts `ps -o rss= -p #{$$}`
    end

Before:

    32032
    48464
    66112
    84192
    100592
    117520
    134096
    150656
    167168
    183760

After:

    17120
    17120
    17120
    17120
    18560
    18560
    18560
    18560
    18560
    18560

1 files changed, 15 insertions, 0 deletions

diff --git a/test/ruby/test_syntax.rb b/test/ruby/test_syntax.rb
index 854fd46027..a3aa823cdc 100644
--- a/test/ruby/test_syntax.rb
+++ b/test/ruby/test_syntax.rb
@@ -1365,6 +1365,21 @@ eom
     assert_valid_syntax 'p :foo, {proc do end => proc do end, b: proc do end}', bug13073
   end
 
+  def test_invalid_symbol_in_hash_memory_leak
+    assert_no_memory_leak([], "#{<<-'begin;'}", "#{<<-'end;'}", rss: true)
+      str = '{"\xC3": 1}'.force_encoding("UTF-8")
+      code = proc do
+        eval(str)
+        raise "unreachable"
+      rescue EncodingError
+      end
+
+      1_000.times(&code)
+    begin;
+      1_000_000.times(&code)
+    end;
+  end
+
   def test_do_after_local_variable
     obj = Object.new
     def obj.m; yield; end