Discussion Thread: DIP 1039--Static Arrays with Inferred Length--Community Review Round 1

[Dukc]

On Wednesday, 6 January 2021 at 18:22:32 UTC, Nick Treleaven 
wrote:
> Type inference for parameters with a default argument could be 
> made to work.
>
> auto fun(auto a = [1,2,3].staticArray) {return a;}

Okay that was a bad example. But see Luhrels answer to Jacob.

>> ```
>> int[$] bar(int[2] arr)              // Error: not allowed in 
>> functions declarations
>> {
>>     return arr ~ [3, 4];
>> }
>> ```
>
> causes an error if the return type is specified as int[4].

Why? `arr` is static so the compiler should be able to figure 
that no overflow will ever happen.

>> ```
>> int[] x = something;
>> int y = something[0 .. staticArrFunc(cast(int[$])[1,2,3])];
>> ```
>
> Excellent point, but it isn't just casts, anywhere you use a 
> type (template instantiation) that is within an indexing 
> expression will have this problem.

Yeah, this is just the simplest example that came to mind.