Parser fails to parse valid Yaml pattern `foo: {abc}`

[nma]

The change in parser from PR https://github.com/goccy/go-yaml/pull/213 introduces a bug. Valid yaml is unable to be parsed.

We found this bug when trying to update from 1.8.9 -> 1.9.0. The latest version of go-yaml still exhibits this bug.

---

The following is valid YAML according to http://yamllint.com/

foo: {abc}

The new parser returns an error. The existing parser in v1.8.9 resolves {abc} as {"abc": null}.

func TestParser(t *testing.T) {
        source := `foo: {abc}`

        _, err := parser.ParseBytes([]byte(source), parser.ParseComments)
        if err != nil {
                t.Errorf("unable to parse yaml: %q, error: %v", source, err)
        }
}

Expected Behaviour: Parser properly tokenizes the valid foo: {abc} source string. Actual Behaviour: Got error.

unable to parse yaml: "foo: {abc}", error: [1:6] unterminated flow mapping
            >  1 | foo: {abc}
                        ^

Other Observations:

Decode seems to work with the right struct field tagging.