Optimize simple mappings with binds and/or sequentials before single yield

[brianrourkeboll]

Description

Followup to #16832, #16948, #17067.

• Optimize simple mappings when the body of the mapping has let-bindings and/or unit-typed sequential expressions before a single explicit or implicit yield. (Noticed in FS-1135 implementation - random functions for collections #17277 (comment).)

Before, with #16832, #16948, #17067, etc., when xs was a list (or an array, or an integral range, depending), an expression like this would get optimized to a fast while-loop

[for x in xs ->lety= z
x + y
]

as would

[for x in xs doyieldlety= z in x + y
]

but this would not

[for x in xs dolety= z
yield x + y
]

nor would

[for x in xs dolety= z
x + y
]

Now, the latter two are optimized as well.

Checklist

• Test cases added.
• Release notes entry updated.

Notes

• This isn't a new optimization; it just ensures that the existing optimizations are applied in more scenarios.
• I should probably come back someday and redo these emitted IL tests to be more systematic, comprehensive, and descriptively-named — maybe an approach similar to that taken in Some more active pattern error message improvements + tests #17186 would help, although there would be far more combinations at play here...

[github-actions]

❗ Release notes required

---

✅ Found changes and release notes in following paths:

Change path	Release notes path	Description
src/Compiler	docs/release-notes/.FSharp.Compiler.Service/9.0.100.md

[psfinaki]

Good stuff, thanks for further tuning the optimization!

[vzarytovskii]

Nice, thanks!