Add Result::map_or_default and Option::map_or_default

[fpervaiz]

Adds Result::map_or_default and Option::map_or_default as discussed extensively at rust-lang/rfcs#3148

[rustbot]

r? @Amanieu

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[Sky9x]

may need rfc approval or an ACP
also needs a tracking issue

implementation LGTM

[tkr-sh]

Thanks a lot for the conversion of the previous RFC into a tracking issue! ❤️

---

Just, for the documentation, I think that something like:

+ by applying function `f` to the contained value if the result is [`Ok`]
- by applying function `f` if the contained is [`Ok`]

( or something like that ) would be better because, with the previous sentence, you don't know if f takes Result<T, E>/Option<T> or T. (and same for Option)

[Amanieu]

Yes, please apply this suggestion too.

[rustbot]

There are merge commits (commits with multiple parents) in your changes. We have a no merge policy so these commits will need to be removed for this pull request to be merged.

You can start a rebase with the following commands:

$ # rebase
$ git pull --rebase https://github.com/rust-lang/rust.git master
$ git push --force-with-lease

The following commits are merge commits:

• 54f885b

[Amanieu]

@fpervaiz Could you please do a rebase to remove merge commits?

I will approve the PR once this is done.

[tkr-sh]

@Amanieu what about #138068 ?

[tkr-sh]

@fpervaiz Could you either do the merge change and #138068 (comment) since the RFC has been accepted or give right of writing to other people on your PR ? Thanks :) !

[tkr-sh]

@Amanieu Do you have the power to make changes to the PR ?
What do we do if the author of the PR doesn't answer anymore ?

[Amanieu]

@tkr-sh Since the author is not responding, you can open a separate PR and I can merge that one. I will then close this one.