Implement (try)FindLastSliceIndex

[rzikm]

Closes #574

I was not able to build the test project, so I rely on CI to run them.

[wallymathieu]

@rzikm Hi! What kind of issues around running the tests do you have?

[gusty]

@rzikm That's fine, I also rely mostly in CIs run. You can keep adding commits, I will squash in the end.

Also, if you want to run them locally do it in Release mode, I don't think they will compile in DEBUG mode due to an old F# compiler bug.

PS: Looking at the test results, it seems to me that the Fable implementation you did is wrong.

[rzikm]

@rzikm Hi! What kind of issues around running the tests do you have?

I was hitting the DEBUG compiler bug gusty mentioned.

I also got snagged because there is more than one WrappedListD type and I added a function to only one of them. Maybe there is a room for internal cleanup?

[gusty]

I also got snagged because there is more than one WrappedListD type and I added a function to only one of them. Maybe there is a room for internal cleanup?

AFAIK There's only one, which is in General.fs line 70

The main purpose of these types was to test overloads paths, but @wallymathieu recently added a better mechanism for it in #557

Still these wrapper types are sometimes useful to perform some tests as they are user-defined classes.

Independently from that, cleanups are always welcome, but then you have to consider either doing them in a separate PR or in a separate commit and then squash all the other unrelated commits.

My advice is a separate commit so you can draft it first and we can give early feedback.

BTW: when doing a separate PR or opening a new issue please mention me because somehow I never managed to get notifications for them until I participate.

[rzikm]

AFAIK There's only one, which is in General.fs line 70

The other one is in

FSharpPlus/tests/FSharpPlusFable.Tests/FSharpTests/General/Util.fs

Line 67 in 54ffdcc

type WrappedListD<'s> = WrappedListD of 's list with

[gusty]

Oh, but those are Fable tests.
Fable tests are independent, they have their own set of wrappers.

We can unify some stuff, but sometimes it gets complicated.

[gusty]

This seems to be ready to merge. The failure in appveyor is a transient one.

[gusty]

Looks good to me. Just 2 nits.
In fact, there's room for optimizations by using ListCollector and possibly ArrayCollector, but to be fair, the same would apply to findSliceIndex, so it's better to leave both for a separate PR.

Thanks for this contribution !