Well, for starters, a function with zero arguments/parameters can be value
semantic. For example:
func getMagicNumber() -> UInt64 {
return 0x3A4B1C7539DA4922
}
Dave
> On Sep 24, 2017, at 01:36, Robert Widmann via swift-dev <[email protected]>
> wrote:
>
> Why is the arrow carrying the “Has Value Semantics Bit” rather than it being
> part of a protocol composition on an argument type, or a convention bit on
> the parameter like ‘inout’?
>
> ~Robert Widmann
>
>> On Sep 24, 2017, at 1:12 AM, David Zarzycki <[email protected]
>> <mailto:[email protected]>> wrote:
>>
>> Hi Robert,
>>
>> As a prerequisite to some other hacking I’m doing, I have an experimental
>> implementation of value semantics; where (among other details), all
>> functions have a bit in ExtInfo that denotes whether the function has
>> enforced value semantics or not. As a matter of polish, I’d like the
>> following code to work:
>>
>> // reference semantic context
>> someValueTypeArray.sort({
>> // hasValueSemantics ExtInfo bit propagates from the
>> // parameter type of sort() to the ClosureExpr type
>> })
>>
>> Hence the desire to have the closure’s type be a disjunction between two
>> FunctionTypes, one where the “hasValueSemantics” bit is set, and one where
>> it is not. If there is a better way to do this, I’m open. :-)
>>
>> Thanks,
>> Dave
>>
>>
>>> On Sep 23, 2017, at 20:11, Robert Widmann via swift-dev
>>> <[email protected] <mailto:[email protected]>> wrote:
>>>
>>>
>>>> On Sep 23, 2017, at 3:39 PM, David Zarzycki via swift-dev
>>>> <[email protected] <mailto:[email protected]>> wrote:
>>>>
>>>> Hello,
>>>>
>>>> I’m trying to replace the explicit FunctionType returned by
>>>> visitClosureExpr() in CSGen.cpp with a type variable; and ultimately a
>>>> disjunction of two FunctionTypes with different ExtInfo flags set (one
>>>> favored, one not).
>>>
>>> I really don’t recommend doing this. Even the current late-binding of a
>>> proper function type in closure inference is an artifact of the old
>>> function type representation that needs to go away (you’re probably running
>>> into parameter inference doing weird things which is a symptom of the
>>> larger problem). What does it matter that the two function types have
>>> different ExtInfo? What are you trying to do here?
>>>
>>> ~Robert Widmann
>>>
>>>>
>>>> Thanks,
>>>> Dave
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