new unnecessary_map_on_constructor lint

[jonboh]

changelog: [unnecessary_map_on_constructor]: adds lint for cases in which map is not necessary. Some(4).map(myfunction) => Some(myfunction(4))

Closes #6472

Note that the case mentioned in the issue Some(..).and_then(|..| Some(..)) is fixed by a chain of lint changes. This PR completes the last part of that chain.

By bind_instead_of_maplint:
Some(4).and_then(|x| Some(foo(4))) => Some(4).map(|x| foo)

By redundant_closure lint:
Some(4).map(|x| foo) => Some(4).map(fun)

Finally by this PR unnecessary_map_on_constructor:
Some(4).map(fun) => Some(fun(4))

I'm not sure this is the desired behavior for clippy and if it should be addressed in another issue/PR. I'd be up to give it a try if that's the case.

[rustbot]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @Alexendoo (or someone else) soon.

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[bors]

☔ The latest upstream changes (presumably #10692) made this pull request unmergeable. Please resolve the merge conflicts.

[Alexendoo]

Thanks! Looks good, got a couple macro cases but mostly style nits

[jonboh]

Thanks for the comments :), I think I've addressed all issues.

From the Zulip thread I get that the new syntax for the comments in the UI tests is still in the works, I've removed the comments, but if there's already some agreed upon syntax that I can add to be aligned with future practices let me know.

[Alexendoo]

Thanks! just a couple last things I spotted and it looks good. If you could squash the commits too that would be great then it's ready for merging

[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 rebase -i master
$ # delete any merge commits in the editor that appears
$ git push --force-with-lease

The following commits are merge commits:

• 1c67c45

[Alexendoo]

Great, thanks!

@bors r+

[bors]

📌 Commit f136e16 has been approved by Alexendoo

It is now in the queue for this repository.

[bors]

⌛ Testing commit f136e16 with merge cb05701...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: Alexendoo
Pushing cb05701 to master...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: Alexendoo
Pushing cb05701 to master...