Adjust indentation when using multiple if-let expressions

[DevYeom]

Adjust indentation when using multiple if-let expressions

[ahoppen]

Synced to Apple’s issue tracker as rdar://127922850

[allevato]

We made a fairly conscious decision early on to keep all indentation sizes fixed, rather than offering context-based variant indentations.

It's something we could revisit in the future, but for now, this is by design, and I want to be deliberate about increasing the surface area of the formatter's configurability. Each new setting creates the potential for interactions with other settings, making it harder to reason about.

[DevYeom]

Thanks!