Implement IReadOnlyDictionary for dict

[cartermp]

The return value of dict is a readonly view of the underlying dictionary, so it should implement IReadonlyDictionary<'TKey, 'TValue>.

[dsyme]

+1

[dsyme]

@cartermp We should check that all IReadOnly* are implemented wherever possible in FSharp.Core. We held off doing that for too long.

[cartermp]

Created suggestion here: fsharp/fslang-suggestions#624

Happy to fill out the RFC as well.

[dsyme]

@cartermp Super, marked as approved :)

[manofstick]

How about wrapping in a type which contains the collection of interfaces so that it advertises what it has rather than requiring a blind cast?

type Dict<'key, 'value> =
    interface IDictionary<'key, 'value>
    interface IReadOnlyDictionary<'key, 'value>

let dict : seq<'key*'value> -> Dict<'key, 'value>

Hmmm, probably no good because it is an API change, but something to mull over...

[cartermp]

Closing in favor of the RFC and language proposal