try to fix issue where _numberString is used despite having old value

[pjfanning]

relates to FasterXML/jackson-databind#4917

[cowtowncoder]

Sounds reasonable. But we really need a test or two here, to reproduce the problem and guard against regression. Test in jackson-databind not ideal, but hopefully can be translated to sequence of nextToken()s and number access calls.

[pjfanning]

• the test that I added seems valid enough but actually works without the code fix
• I will continue seeing if I can produce a jackson-core that fails without the change
• this change does seem to work in that it fixes the test in test for issue #4917 jackson-databind#4918

[cowtowncoder]

@pjfanning I think the difference is that thanks to @JsonCreator, number value will be buffered in TokenBuffer and is probably accessed with JsonParser.getNumberValueDeferred() instead of getDecimalValue().

[pjfanning]

@cowtowncoder the test now reproduces the issue - I put a summary in FasterXML/jackson-databind#4918 (comment)