Revert "Use DmStruct2"

This reverts commit cce7f35.

Author: gusty

src/FSharpPlus/Control/Applicative.fs

@@ -37,7 +37,12 @@ type Apply =
     static member        ``<*>`` ((f: Result<_,'E>     , x: Result<'T,'E>        ), _output: Result<'b,'E>        , [<Optional>]_mthd: Apply) = Result.apply f x : Result<'U,'E>
     static member        ``<*>`` ((f: Choice<_,'E>     , x: Choice<'T,'E>        ), _output: Choice<'b,'E>        , [<Optional>]_mthd: Apply) = Choice.apply f x : Choice<'U,'E>
     static member inline ``<*>`` ((KeyValue(a: 'Key, f), KeyValue(b: 'Key, x: 'T)), _output: KeyValuePair<'Key,'U>, [<Optional>]_mthd: Default3) : KeyValuePair<'Key,'U> = KeyValuePair (Plus.Invoke a b, f x)
-    static member inline ``<*>`` ((_: DmStruct2<'Key, _>, _: DmStruct2<'Key, 'T>) , _output: DmStruct2<'Key,'U>   , [<Optional>]_mthd: Default3) : DmStruct2<'Key,'U> = Unchecked.defaultof<DmStruct2<'Key,'U>>
+    static member inline ``<*>`` ((f: KeyValuePair2<'Key, _>, x: KeyValuePair2<'Key, 'T>), _output: KeyValuePair2<'Key,'U>, [<Optional>]_mthd: Default3) : KeyValuePair2<'Key,'U> =
+        let a = f.Key
+        let b = x.Key
+        let f = f.Value
+        let x = x.Value
+        KeyValuePair2 (Plus.Invoke a b, f x)
 
     static member        ``<*>`` ((f: Map<'Key,_>      , x: Map<'Key,'T>        ) , _output: Map<'Key,'U>         , [<Optional>]_mthd: Apply) : Map<'Key,'U> = Map (seq {
        for KeyValue(k, vf) in f do
@@ -60,7 +65,7 @@ type Apply =
            | true, vx -> dct.Add (k, vf vx)
            | _        -> ()
        dct :> IDictionary<'Key,'U>
-
+    
     static member        ``<*>`` ((f: IReadOnlyDictionary<'Key,_>, x: IReadOnlyDictionary<'Key,'T>) , _output: IReadOnlyDictionary<'Key,'U>  , [<Optional>]_mthd: Apply) : IReadOnlyDictionary<'Key,'U> =
        let dct = Dictionary ()
        for KeyValue(k, vf) in f do
@@ -73,7 +78,7 @@ type Apply =
     static member        ``<*>`` ((f: Expr<'T->'U>, x: Expr<'T>), _output: Expr<'U>, [<Optional>]_mthd: Apply) = Expr.Cast<'U> (Expr.Application (f, x))
     #endif
     static member        ``<*>`` ((f: ('T->'U) ResizeArray, x: 'T ResizeArray), _output: 'U ResizeArray, [<Optional>]_mthd: Apply) = ResizeArray.apply f x : 'U ResizeArray
-
+    
     static member inline Invoke (f: '``Applicative<'T -> 'U>``) (x: '``Applicative<'T>``) : '``Applicative<'U>`` =
         let inline call (mthd : ^M, input1: ^I1, input2: ^I2, output: ^R) =
             ((^M or ^I1 or ^I2 or ^R) : (static member ``<*>`` : (_*_)*_*_ -> _) (input1, input2), output, mthd)

src/FSharpPlus/Control/Functor.fs

@@ -89,7 +89,7 @@ type Map =
     static member Map ((x: Result<_,'E>        , f: 'T->'U), _mthd: Map) = Result.map f x
     static member Map ((x: Choice<_,'E>        , f: 'T->'U), _mthd: Map) = Choice.map f x
     static member Map ((KeyValue(k, x)         , f: 'T->'U), _mthd: Map) = KeyValuePair (k, f x)
-    static member Map ((_: DmStruct2<'T, 'E>   , _: 'T->'U), _mthd: Map) = Unchecked.defaultof<DmStruct2<'U, 'E>>
+    static member Map ((x: KeyValuePair2<_, _> , f: 'T->'U), _mthd: Map) = let k, x = x.Key, x.Value in KeyValuePair2 (k, f x)
     static member Map ((x: Map<'Key,'T>        , f: 'T->'U), _mthd: Map) = Map.map (const' f) x : Map<'Key,'U>
     static member Map ((x: Dictionary<_,_>     , f: 'T->'U), _mthd: Map) = Dictionary.map f x : Dictionary<'Key,'U>
     #if !FABLE_COMPILER

src/FSharpPlus/Internals.fs

@@ -124,7 +124,6 @@ type Either<'t,'u> =
     | Right of 'u
 
 type DmStruct = struct end
-type DmStruct2<'T1, 'T2> = struct end
 
 type KeyValuePair2<'TKey, 'TValue> = struct
     val Key : 'TKey