[swift-evolution] [Pitch] Remove type-inference for stored property

Pranshu Goyal pranshu.goyal at novanet.net
Sat Apr 8 00:40:29 CDT 2017

I agree with the sentiment of the proposal, it does add value to overall
efficiency of swift and make things simpler for the swift team, but as
Matthew said a blanket ban will add noise to the code. Also this particular
feature is one of those niceties about swift which makes it very welcoming
to new adopters.

If some middle ground can be proposed to this problem then I think we will
be making a lot of people happy.

On 7 April 2017 at 18:31, Matthew Johnson via swift-evolution <
swift-evolution at swift.org> wrote:

> > On Apr 7, 2017, at 2:21 AM, Daniel Duan via swift-evolution <
> swift-evolution at swift.org> wrote:
> >
> > Hi all,
> >
> > In a discussion about inferring parameter types from default value,
> Slava brought up some performance problems caused by type inference for
> stored properties in side types:
> >
> > https://lists.swift.org/pipermail/swift-evolution/
> Week-of-Mon-20170313/033882.html
> >
> > Towards the end, the post mentioned that some Swift team members
> contemplated requiring types for stored properties in type declarations. I
> think this idea deserves some more attention. Hence this last minute
> idea-floating.
> >
> > In addition to solving a performance headache in implementation,
> there're always the general benefit of making type declartion more explicit
> and readable (clarity for reader should out-weigh pleasure of the author).
> Making the
> > language slightly more consistent (we are not inferring types for
> default parameter values in function anyways).
> >
> > The cons for doing this are obvious too: the inference makes the
> language feels more friendly and is, undoubtedly, a beloved feature for
> many. This would be a source breaking change.
> >
> > Just thought I'd float the idea to gather some quick reaction. What do
> y'all think?
> I’m willing to keep an open mind on this topic but I don’t think wholesale
> banning of inference is the right thing to do.  Here is an example of a
> case where I do not want to give up inference.  When a property is
> initialized inline by calling an initializer of a non-generic type (very
> common) any annotation is strictly redundant.
> struct {
>     let foo = Foo()
> }
> Requiring a type annotation here feels very unnecessary and
> boilerplate-y.  I adds no additional clarity to a reader of the code, only
> noise.  Noise reduces clarity.  Small amounts of unnecessary or redundant
> information such as in an individual stored property declaration are not
> that big a deal.  But on balance they add up quickly and have an
> undesirable impact on the overall clarity of code.
> >
> > Daniel Duan
> > _______________________________________________
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> > swift-evolution at swift.org
> > https://lists.swift.org/mailman/listinfo/swift-evolution
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*Pranshu Goyal*
*iOS Developer*
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