Fix issue with iteration of dictionaries

Author: gusty

src/FSharpPlus/Control/Functor.fs

@@ -45,7 +45,7 @@ type Iterate =
     static member Iterate (x: Choice<'T, 'E>       , action) = match x with Choice1Of2 x -> action x | _ -> ()
     static member Iterate (KeyValue(_: 'Key, x: 'T), action) = action x : unit
     static member Iterate (x: Map<'Key,'T>         , action) = Map.iter (const' action) x 
-    static member Iterate (x: Dictionary<'Key, 'T> , action) = Dictionary.iterValues action x
+    static member Iterate (x: IDictionary<'Key, 'T>, action) = Dict.iterValues action x
     static member Iterate (x: _ ResizeArray        , action) = ResizeArray.iter action x
 
     // Restricted

tests/FSharpPlus.Tests/General.fs

@@ -487,6 +487,21 @@ module Functor =
         let nel = zip (NonEmptyList.ofList [1; 2]) (NonEmptyList.ofList ["a"; "b"; "c"])
         CollectionAssert.AreEqual (NonEmptyList.ofList [1,"a"; 2,"b"], nel)
 
+    [<Test>]
+    let iterTests () =
+        let di = new Dictionary<int, int>()
+        di.Add (1, 2)
+        di.Add (3, 4)
+        let id = dict [1, 2; 3, 4]
+        let ir = readOnlyDict [1, 2; 3, 4]
+
+        let r = ResizeArray<string> []
+
+        iter (fun x -> r.Add (string x)) di
+        iter (fun x -> r.Add (string x)) id
+        iter (fun x -> r.Add (string x)) ir
+        CollectionAssert.AreEqual (ResizeArray ["2"; "4"; "2"; "4"], r)
+
 
 
 module Foldable =