[dart-dio] fix issue with multi layered discriminators

[fstotz]

fix for issue issue #15467

When using the dart-dio generator to generate an API with an specs file, which uses multilayered classes with a discriminator at the lowest layer with an discriminator, the generated code tries to map all the values in the middle layer class to all of the subclasses of the lowest layer class.

e.g. classes animal, bird, reptile, turtle, crocodile
The generator runs without an error but there are issues inside of the generated code.
The discriminator mapping inside of the animal class is working fine but the one at reptile uses the same as the one at the animal. This creates a bird and then return it as a bird. This is not allowed in this place because bird is not a subtype of reptile. Since this is a compile error, created by parts of code, which will never be executed, any app using the library is unable is unable to be started.

https://gist.github.com/felixmede/058272bdad39fa14ee30f03e65dbd1df

@jaumard (2018/09) @josh-burton (2019/12) @amondnet (2019/12) @sbu-WBT (2020/12) @kuhnroyal (2020/12) @agilob (2020/12) @ahmednfwela (2021/08)

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[fstotz]

Hi

is there anything I still need to do so that it can be merged?

[ahmednfwela]

@felixmede hi, sorry for not noticing this until now, I will check it

[ahmednfwela]

@felixmede is it possible to also fix this #15517
in this PR?

[ahmednfwela]

@wing328 can you run ci please ?
also is changing the java version ok here?

[wing328]

also is changing the java version ok here?

I guess so. Not sure how that file is used

[fstotz]

@felixmede is it possible to also fix this #15517
in this PR?

This is also fixed now

[ahmednfwela]

@wing328 is this change appropriate for the core generator ?

[fstotz]

Is there anything left to do from my side?

[fstotz]

@ahmednfwela @wing328 ?

[ahmednfwela]

while I can't give a proper review due to not having proper tests, I think it looks ok

[fstotz]

addressed in #23717