I think Associative Array should throw Exception

[Jesse Phillips]

On Thursday, 3 September 2020 at 15:12:14 UTC, Steven 
Schveighoffer wrote:
> int[int] aa;
> aa[4] = 5;
> auto b = aa[4];
>
> How is this code broken? It's valid, will never throw, and 
> there's no reason that we should break it by adding an 
> exception into the mix.
>

int foo() nothrow {
     return "1".to!int;
}

The following code is valid, will never throw, why does the 
compiler prevent it?