Fix leak of AST when Ripper#compile_error jumps

For example, the following script leaks:

    class MyRipper < Ripper
      def initialize(src, &blk)
        super(src)
        @blk = blk
      end

      def compile_error(msg) = @blk.call(msg)
    end

    def call_parse = MyRipper.new("/") { |msg| return msg }.parse

    10.times do
      100_000.times do
        call_parse
      end

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

Before:

    93952
    169040
    244224
    318784
    394432
    468224
    544048
    618560
    693776
    768384

After:

    19776
    19776
    20352
    20880
    20912
    21408
    21328
    21152
    21472
    20944

parse.y

@@ -15608,6 +15608,10 @@ rb_ruby_parser_free(void *ptr)
     struct parser_params *p = (struct parser_params*)ptr;
     struct local_vars *local, *prev;
 
+    if (p->ast) {
+        rb_ast_free(p->ast);
+    }
+
 #ifndef RIPPER
     if (p->tokens) {
         rb_parser_ary_free(p, p->tokens);

test/ripper/test_parser_events.rb

@@ -1743,4 +1743,26 @@ class TestRipper::ParserEvents < Test::Unit::TestCase
     parse('case 0; in {a:}; end', :on_hshptn) {thru_hshptn = true}
     assert_equal true, thru_hshptn
   end
+
+  def test_return_out_of_compile_error_no_memory_leak
+    assert_no_memory_leak(%w(-rripper), "#{<<~'begin;'}", "#{<<~'end;'}", rss: true)
+      class MyRipper < Ripper
+        def initialize(src, &blk)
+          super(src)
+          @blk = blk
+        end
+
+        def compile_error(msg) = @blk.call(msg)
+      end
+
+      def call_parse = MyRipper.new("/") { |msg| return msg }.parse
+
+      # Check that call_parse does return a syntax error
+      raise "call_parse should return a syntax error" unless call_parse
+    begin;
+      100_000.times do
+        call_parse
+      end
+    end;
+  end
 end if ripper_test