Fix f-string boundaries and add more tests

tests/test.py

@@ -244,8 +244,11 @@ b"${test} ${test ${test}aname $$$ $test+nope"
 f"{var}...{arr[123]} normal {var['{'] // 0xff} \"xzcb\" 'xzcb' {var['}'] + 1} text"
 f"{expr1 if True or False else expr2} {None} wow {','.join(c.lower() for c in 'asdf')}"
 f"hello {expr:.2f} yes {(lambda: 0b1)():#03x} lol {var!r}"
-f'brackets: {{ 1 + 2 }} and {{{{ 3 + 4 }}}}'
+f'brackets: {{{ 1 + 2 }}} and {{{{ 3 + 4 }}}}'
 fr'this {that}'
+f"{f'{1+1}'}"
+'{{ }}'
+f"{"{test}"}"  # FIXME: syntax error that should not be highlighted
 
 # Doctests.