On 07.04.2017 10:21, Daniel Duan via swift-evolution 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?
Although it seems like only an implementation-side problem(i.e. "let's just
improve implementation"), I see a benefits to require type for stored
property *if* it is not obvious what the type is for *reader*. I.e. if we
have something like this, I don't think we should require a type:
struct S {
var x = 0
}
but I do think it will be better to require a type in such cases :
struct S{
var x = something(SomeType(), 123, "123") // can be generic func
}
Daniel Duan _______________________________________________
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