Restore condition with non-generic type parameter (#2173)

* test

* add TLongIdent option to TyparSupportsMember

* format :)

* DRY - new helper function: colSurr

* format

* Remove blank lines

Co-authored-by: nojaf <florian.verdonck@outlook.com>

src/Fantomas.Tests/FunctionDefinitionTests.fs

@@ -935,7 +935,7 @@ let ``space before ^ SRTP type is required in function call, 984`` () =
     formatSourceString
         false
         """
-let inline deserialize< ^a when ( ^a or FromJsonDefaults) : (static member FromJson :  ^a -> Json< ^a>)> json =
+let inline deserialize< ^a when ^a: (static member FromJson: ^a -> Json< ^a >)> json =
     json |> Json.parse |> Json.deserialize< ^a>
 """
         config
@@ -947,6 +947,23 @@ let inline deserialize< ^a when ^a: (static member FromJson: ^a -> Json< ^a >)>
     json |> Json.parse |> Json.deserialize< ^a>
 """
 
+[<Test>]
+let ``SRTP or condition with non-generic type, 2168`` () =
+    formatSourceString
+        false
+        """
+let inline deserialize< ^a when ( ^a or FromJsonDefaults) : (static member FromJson :  ^a -> Json< ^a>)> json =
+    json |> Json.parse |> Json.deserialize< ^a>
+"""
+        config
+    |> prepend newline
+    |> should
+        equal
+        """
+let inline deserialize< ^a when (^a or FromJsonDefaults): (static member FromJson: ^a -> Json< ^a >)> json =
+    json |> Json.parse |> Json.deserialize< ^a>
+"""
+
 [<Test>]
 let ``equals sign between hash directives, 1218`` () =
     formatSourceString

src/Fantomas/CodePrinter.fs

@@ -527,12 +527,16 @@ and genExprSepEqPrependType
         +> sepSpaceOrIndentAndNlnIfExpressionExceedsPageWidth (genExpr astContext e)
 
 and genTyparList astContext tps =
-    ifElse
-        (List.atMostOne tps)
-        (col wordOr tps (genTypar astContext))
-        (sepOpenT
-         +> col wordOr tps (genTypar astContext)
-         +> sepCloseT)
+    colSurr sepOpenT sepCloseT wordOr tps (genTypar astContext)
+
+and genTypeSupportMember astContext st =
+    match st with
+    | SynType.Var (td, _) -> genTypar astContext td
+    | TLongIdent s -> !-s
+    | _ -> !- ""
+
+and genTypeSupportMemberList astContext tps =
+    colSurr sepOpenT sepCloseT wordOr tps (genTypeSupportMember astContext)
 
 and genTypeAndParam astContext typeName (tds: SynTyparDecls option) tcs =
     let types openSep tds tcs closeSep =
@@ -4533,7 +4537,7 @@ and genTypeConstraint astContext node =
         genTypar astContext tp -- " :> "
         +> genType astContext false t
     | TyparSupportsMember (tps, msg) ->
-        genTyparList astContext tps
+        genTypeSupportMemberList astContext tps
         +> sepColon
         +> sepOpenT
         +> genMemberSig astContext msg

src/Fantomas/Context.fs

@@ -599,6 +599,19 @@ let internal colPreEx f2 f1 (c: seq<'T>) f (ctx: Context) =
     else
         colEx f1 c f (f2 ctx)
 
+/// Similar to col, but apply two more functions fStart, fEnd at the beginning and the end if the input sequence is bigger thn one item
+let internal colSurr fStart fEnd f1 (c: list<'T>) f (ctx: Context) =
+    if Seq.isEmpty c then
+        ctx
+    else
+        (col f1 c f
+         |> fun g ->
+             if (List.moreThanOne c) then
+                 fStart +> g +> fEnd
+             else
+                 g)
+            ctx
+
 /// If there is a value, apply f and f' accordingly, otherwise do nothing
 let internal opt (f': Context -> _) o f (ctx: Context) =
     match o with

src/Fantomas/SourceParser.fs

@@ -1605,7 +1605,8 @@ let (|TyparSingle|TyparDefaultsToType|TyparSubtypeOfType|TyparSupportsMember|Typ
         TyparSupportsMember(
             List.choose
                 (function
-                | SynType.Var (tp, _) -> Some tp
+                | SynType.Var _ as v -> Some v
+                | TLongIdent _ as i -> Some i
                 | _ -> None)
                 tps,
             msg