std.conv:to that does not throw?

[Kyle Ingraham]

Does D have a 'try' `std.conv:to` that does not throw if it 
fails? Something like:
```D
string input = "9";
int output;
auto parsed = input.tryTo!int(output);
```

`std.conv:to` is super flexible and does exactly what I need. 
However, hitting an exception for conversion failures really 
slows down my code. A conversion failure wouldn't be an exception 
for my use case. I'm trying to write web application route 
constraint code like what's [available in 
C#](https://github.com/dotnet/aspnetcore/blob/main/src/Http/Routing/src/Constraints/IntRouteConstraint.cs#L53). There, code like `Int.TryParse` is used to figure out whether a string meets a route constraint.

`std.conv:to` is almost perfect with it's flexibility across 
types. I'm just hoping I've missed the version that doesn't throw.