> On Nov 9, 2017, at 9:37 AM, Sam Warner via swift-evolution
> <swift-evolution@swift.org> wrote:
>
> I accept the motivation for this change, although I would mention that:
> - in 2.5 years on a ~200k lines of Swift project
> - we've seen a plenty of instances of `flatMap` used where `map` would have
> been sufficient, but
> - we've never burned time on tracking down the sort of compiler issue
> described by the author in the Motivation. As I say, the argument is fair,
> but I am questioning how frequently this problem occurs.
>
> I can't speak to the previous attempts to solve this problem, but I'd add my
> voice to anyone advocating solving this by having a compiler warning when
> `flatMap` is used redundantly(?).
>
> If this proposal were to be accepted, I'd also question the choice of
> `filterMap` as a name. This name is presumably shorthand for
> `filterNonesAndMap`, which conveniently ignores the following:
> - `flatMap` may be used on a sequence-of-sequences to flatten our to a
> single-dimensional sequence.
> - `flatMap` may be used on other 'box' types, e.g. on an optional:
> `Optional<String>("foo").flatMap { .some($0 + "bar") }` or on the common
> `Result` type.
>
> Any re-naming of one `flatMap` should take these other uses into account, as
> they share conceptual details.
>
> Thanks,
>
> Sam
This proposal only proposes renaming the “filterNonesAndMap” variant (though
that name is misleading, it would be “filterNonesAfterMapping” if anything);
the other uses of flatMap will remain unchanged.
-BJ
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