use TcRef.LogicalName instead of Stamp to calculate completion item hash code...

use TcRef.LogicalName instead of Stamp to calculate completion item hash code while filtering duplicates, letting ItemDisplayPartialEquality.Equals do the job

src/fsharp/symbols/SymbolHelpers.fs

@@ -782,7 +782,7 @@ module internal SymbolHelpers =
             protectAssemblyExploration 1027 (fun () -> 
               match item with 
               | ItemWhereTypIsPreferred ty -> 
-                  if isAppTy g ty then hash (tcrefOfAppTy g ty).Stamp
+                  if isAppTy g ty then hash (tcrefOfAppTy g ty).LogicalName
                   else 1010
               | Item.ILField(ILFieldInfo(_, fld)) -> 
                   System.Runtime.CompilerServices.RuntimeHelpers.GetHashCode fld // hash on the object identity of the AbstractIL metadata blob for the field
@@ -795,12 +795,12 @@ module internal SymbolHelpers =
               | Item.CtorGroup(name, meths) -> name.GetHashCode() + (meths |> List.fold (fun st a -> st + a.ComputeHashCode()) 0)
               | (Item.Value vref | Item.CustomBuilder (_, vref)) -> hash vref.LogicalName
               | Item.ActivePatternCase(APElemRef(_apinfo, vref, idx)) -> hash (vref.LogicalName, idx)
-              | Item.ExnCase(tcref) -> hash tcref.Stamp
+              | Item.ExnCase(tcref) -> hash tcref.LogicalName
               | Item.UnionCase(UnionCaseInfo(_, UCRef(tcref, n)), _) -> hash(tcref.Stamp, n)
               | Item.RecdField(RecdFieldInfo(_, RFRef(tcref, n))) -> hash(tcref.Stamp, n)
               | Item.Event evt -> evt.ComputeHashCode()
               | Item.Property(_name, pis) -> hash (pis |> List.map (fun pi -> pi.ComputeHashCode()))
-              | Item.UnqualifiedType(tcref :: _) -> hash tcref.Stamp
+              | Item.UnqualifiedType(tcref :: _) -> hash tcref.LogicalName
               | _ -> failwith "unreachable") }
 
     let CompletionItemDisplayPartialEquality g =