[Bug #19016] SyntaxError with parser error messages

Raise a `SyntaxError` with the parser error message, in the case
reading from a file instead of the `-e` option or standard input. So
syntax_suggest can get the message from the caught error.

ruby.c

@@ -2085,11 +2085,11 @@ process_options(int argc, char **argv, ruby_cmdline_options_t *opt)
     ruby_set_argv(argc, argv);
     process_sflag(&opt->sflag);
 
-    rb_parser_set_context(parser, 0, TRUE);
-
     if (opt->e_script) {
         VALUE progname = rb_progname;
         rb_encoding *eenc;
+        rb_parser_set_context(parser, 0, TRUE);
+
         if (opt->src.enc.index >= 0) {
             eenc = rb_enc_from_index(opt->src.enc.index);
         }
@@ -2114,6 +2114,7 @@ process_options(int argc, char **argv, ruby_cmdline_options_t *opt)
     else {
         VALUE f;
         f = open_load_file(script_name, &opt->xflag);
+        rb_parser_set_context(parser, 0, f == rb_stdin);
         ast = load_file(parser, opt->script_name, f, 1, opt);
     }
     ruby_set_script_name(opt->script_name);

test/ruby/test_exception.rb

@@ -1473,6 +1473,18 @@ def detailed_message(**)
       end;
       pattern = /^<detail\.rb>/
       assert_in_out_err(%W[-r#{dir}/detail -], "1+", [], pattern)
+
+      File.write(File.join(dir, "main.rb"), "#{<<~"begin;"}\n#{<<~'end;'}")
+      begin;
+        1 +
+      end;
+      assert_in_out_err(%W[-r#{dir}/detail #{dir}/main.rb]) do |stdout, stderr,|
+        assert_empty(stdout)
+        assert_not_empty(stderr.grep(pattern))
+        error, = stderr.grep(/unexpected end-of-input/)
+        assert_not_nil(error)
+        assert_match(/<.*unexpected end-of-input.*>/, error)
+      end
     end
   end
 end