[swift-evolution] Revisiting SE-0110

[Gwendal Roué]

Wait, there's more!
> When passing a closure with a single underscore argument ({ _ in ...}) to a function expecting multiple arguments, the compiler may error after migration with:
> 
>     error: cannot convert value of type '(_) -> ()' to expected argument
>     type
> (32301091)
> Workaround: To fix the error, change the single argument to the correct number of arguments
> 
> such as { (_,_) in ...}
> 
> 
> 
> When passing a closure to map with two function arguments, the compiler may after migration error with:
> 
>        error: 'map' produces '[T]', not the expected contextual result type
>        '<TYPE>'
> (32432752)
> Workaround: Change the closure signature to accept a tuple argument of two elements when
> 
> using map. 
> 

Gwendal

> Le 6 juin 2017 à 06:36, Gwendal Roué <gwendal.roue at gmail.com> a écrit :
> 
> http://adcdownload.apple.com/WWDC_2017/Xcode_9_beta/Xcode_9_beta_Release_Notes.pdf <http://adcdownload.apple.com/WWDC_2017/Xcode_9_beta/Xcode_9_beta_Release_Notes.pdf>
> 
>> The migrator does not properly distinquish between single-tuple and multiple-argument function types as described in SE–0110, causing additional mismatched type errors with the closure types that are passed to Standard Library functions expecting tuple objects. (32431899)
>> 
>> Workaround: Manually fix the closure types to accept values of tuples instead of separate argument values.
>> 
>> 
>> 
>> When using $0 and $1 in a closure that is passed to a function expecting a closure with a single tuple argument, the compiler may error after migration with:
>> 
>>     error: closure tuple parameter '(TYPE, TYPE)' does not support
>>     destructuring with implicit parameters
>> (32489893)
>> 
>> Workaround: Change $0 and $1 references to $0.0 and $0.1 respectively. 
>> 
> Where are the firemen?
> 
> Gwendal
> 

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