[swift-evolution] Making capturing semantics of local

[Howard Lovatt]

The issues raised about local capture by local (inner) functions are valid,
likewise the discussion about the @nonescaping annotation are also valid.

Rather than expand local function syntax why not deprecate local functions
completely and add the @nonescaping annotation to local closures following
the argument syntax, e.g. the running example:


    class A {
        func foo() {
            let local: @nonescaping () -> void = {
                bar() // Capture of self does not need to be explicit in
the closure because it is non-escaping.
            }
            local()
        }
        func bar() { ... }
    }

This is a simpler and more powerful solution (I think others have pretty
much suggested the same thing in this forum but have not explicitly said
get rid of local functions).

  -- Howard.

On 27 October 2017 at 08:16, Mike Kluev via swift-evolution <
swift-evolution at swift.org> wrote:

> On 26 October 2017 at 20:24, David Hart <david at hartbit.com> wrote:
>
>> I don’t see how this makes any sense or be possible:
>>
>> * It doesn’t make sense for me because local is not a member function of
>> A.
>> * It would cause ambiguity when trying to call another member function
>> with the same name as the local function.
>>
>
> in the escaping contexts, "self." is currently required before the
> instance members (**).
> the idea is to require it before some local functions as well, recursively
> analysing what these local functions do (at the compile time).
>
> /* local */ foo() {
>     bar()
>     variable = 1
> }
>
> ...
> self.foo()
>
> // self is required because the compiler knows what's inside, and if it
> were to put the content inline that would be:
>
> // inlining foo pseudo code:
>      self.bar()
>      self.variable = 1
>
> hence the compiler can figure out that in this case "self" is required
> before foo()
>
> on the other hand:
>
> /* local */ poo() {
>     print("doesnt not capture anything")
> }
>
> here, if compiler were to use poo in the escaping context it would not
> require "self." before it.
>
> this decision (whether to require "self." on not) can be on the use side.
>
> (**) FTM, the normal instance methods that do not capture anything may as
> well not require "self." before them in escaping contexts:
>
> /* non local */ baz() {
>     print("doesn't capture anything")
> }
>
> Mike
>
>
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>
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