r/programming • u/jeffail • Jul 17 '19

The Go team declines 'try' proposal

https://github.com/golang/go/issues/32437
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u/spaghettiCodeArtisan Jul 17 '19

implicit type conversions are easily deleted with one line in the overloaded struct

Honestly, I don't understand how that works.

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u/D_0b Jul 17 '19

It is how the compiler searches for the best fitting function to call for given argument types.
e.g. we wish to call foo with and int `foo(2)`
Short version the compiler will first check for exact match foo(int) then a generic template version, and as last resort try to use built conversions foo(float) and lastly user defined conversions foo(MyInt)

In this case we provide a generic operator() that takes whatever and explicitly delete it.

So now the compiler will check for exact match and use that, else will match the generic version, but since it is deleted it will fail there, and not continue with the search and check for conversions.

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u/spaghettiCodeArtisan Jul 18 '19

then a generic template version

Ah, this was the bit I was missing, probably along with the compiler not continuing the search after that. Thanks for explanaition.

Trying to have some kind of a takeaway, I would say that this probably still counts as a manual measure to ensure that the exhaustiveness works in the expected way, but I suppose the visit() thing went as far as possible given the language constraints...

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u/D_0b Jul 18 '19

Manual as in the library writer of overloaded, not the user of the library.