// Copyright (c) Microsoft Corporation.  All Rights Reserved.  See License.txt in the project root for license information.

namespace FSharp.Compiler.Symbols

open System.IO

open Internal.Utilities.Library  
open Internal.Utilities.Library.Extras
open FSharp.Core.Printf
open FSharp.Compiler 
open FSharp.Compiler.AbstractIL.Diagnostics 
open FSharp.Compiler.DiagnosticsLogger
open FSharp.Compiler.InfoReader
open FSharp.Compiler.Infos
open FSharp.Compiler.IO 
open FSharp.Compiler.NameResolution
open FSharp.Compiler.Syntax.PrettyNaming
open FSharp.Compiler.Text
open FSharp.Compiler.Text.Range
open FSharp.Compiler.Text.Layout
open FSharp.Compiler.Text.TaggedText
open FSharp.Compiler.Xml
open FSharp.Compiler.TypedTree
open FSharp.Compiler.TypedTreeBasics
open FSharp.Compiler.TypedTreeOps
open FSharp.Compiler.TypeHierarchy
open FSharp.Compiler.TcGlobals 

/// Describe a comment as either a block of text or a file+signature reference into an intellidoc file.
[<RequireQualifiedAccess>]
type FSharpXmlDoc =
    | None
    | FromXmlText of XmlDoc
    | FromXmlFile of dllName: string * xmlSig: string

module EnvMisc2 =
    let maxMembers = GetEnvInteger "FCS_MaxMembersInQuickInfo" 10

[<AutoOpen>]
module internal SymbolHelpers = 

    let rangeOfValRef preferFlag (vref: ValRef) =
        match preferFlag with 
        | None -> vref.Range 
        | Some false -> vref.DefinitionRange 
        | Some true -> vref.SigRange

    let rangeOfEntityRef preferFlag (eref: EntityRef) =
        match preferFlag with 
        | None -> eref.Range 
        | Some false -> eref.DefinitionRange 
        | Some true -> eref.SigRange
   
    let rangeOfPropInfo preferFlag (pinfo: PropInfo) =
        match pinfo with
#if !NO_TYPEPROVIDERS 
        |   ProvidedProp(_, pi, _) -> Construct.ComputeDefinitionLocationOfProvidedItem pi
#endif
        |   _ -> pinfo.ArbitraryValRef |> Option.map (rangeOfValRef preferFlag)

    let rangeOfMethInfo (g: TcGlobals) preferFlag (minfo: MethInfo) = 
        match minfo with
#if !NO_TYPEPROVIDERS 
        |   ProvidedMeth(_, mi, _, _) -> Construct.ComputeDefinitionLocationOfProvidedItem mi
#endif
        |   DefaultStructCtor(_, AppTy g (tcref, _)) -> Some(rangeOfEntityRef preferFlag tcref)
        |   _ -> minfo.ArbitraryValRef |> Option.map (rangeOfValRef preferFlag)

    let rangeOfEventInfo preferFlag (einfo: EventInfo) = 
        match einfo with
#if !NO_TYPEPROVIDERS 
        | ProvidedEvent (_, ei, _) -> Construct.ComputeDefinitionLocationOfProvidedItem ei
#endif
        | _ -> einfo.ArbitraryValRef |> Option.map (rangeOfValRef preferFlag)
      
    let rangeOfUnionCaseInfo preferFlag (ucinfo: UnionCaseInfo) =      
        match preferFlag with 
        | None -> ucinfo.UnionCase.Range 
        | Some false -> ucinfo.UnionCase.DefinitionRange 
        | Some true -> ucinfo.UnionCase.SigRange

    let rangeOfRecdField preferFlag (rField: RecdField) =
        match preferFlag with
        | None -> rField.Range
        | Some false -> rField.DefinitionRange
        | Some true -> rField.SigRange

    let rangeOfRecdFieldInfo preferFlag (rfinfo: RecdFieldInfo) =
        rangeOfRecdField preferFlag rfinfo.RecdField

    let rec rangeOfItem (g: TcGlobals) preferFlag d = 
        match d with
        | Item.Value vref  | Item.CustomBuilder (_, vref) -> Some (rangeOfValRef preferFlag vref)
        | Item.UnionCase(ucinfo, _)     -> Some (rangeOfUnionCaseInfo preferFlag ucinfo)
        | Item.ActivePatternCase apref -> Some (rangeOfValRef preferFlag apref.ActivePatternVal)
        | Item.ExnCase tcref           -> Some tcref.Range
        | Item.AnonRecdField (_,_,_,m) -> Some m
        | Item.RecdField rfinfo        -> Some (rangeOfRecdFieldInfo preferFlag rfinfo)
        | Item.UnionCaseField (UnionCaseInfo (_, ucref), fieldIndex) -> Some (rangeOfRecdField preferFlag (ucref.FieldByIndex(fieldIndex)))
        | Item.Event einfo             -> rangeOfEventInfo preferFlag einfo
        | Item.ILField _               -> None
        | Item.Property(info = pinfos; sourceIdentifierRange = mNameOpt)      ->
            match mNameOpt with
            | Some m -> Some m
            | None -> rangeOfPropInfo preferFlag pinfos.Head 
        | Item.Types(_, tys)     -> tys |> List.tryPick (tryNiceEntityRefOfTyOption >> Option.map (rangeOfEntityRef preferFlag))
        | Item.CustomOperation (_, _, Some minfo)  -> rangeOfMethInfo g preferFlag minfo
        | Item.Trait _ -> None
        | Item.TypeVar (_, tp)  -> Some tp.Range
        | Item.ModuleOrNamespaces modrefs -> modrefs |> List.tryPick (rangeOfEntityRef preferFlag >> Some)
        | Item.MethodGroup(_, minfos, _) 
        | Item.CtorGroup(_, minfos) -> minfos |> List.tryPick (rangeOfMethInfo g preferFlag)
        | Item.ActivePatternResult(APInfo _, _, _, m) -> Some m
        | Item.SetterArg (_, item) -> rangeOfItem g preferFlag item
        | Item.OtherName (range = m) -> Some m
        | Item.CustomOperation (_, _, implOpt) -> implOpt |> Option.bind (rangeOfMethInfo g preferFlag)
        | Item.ImplicitOp (_, {contents = Some(TraitConstraintSln.FSMethSln(vref=vref))}) -> Some vref.Range
        | Item.ImplicitOp _ -> None
        | Item.UnqualifiedType tcrefs -> tcrefs |> List.tryPick (rangeOfEntityRef preferFlag >> Some)
        | Item.DelegateCtor ty 
        | Item.FakeInterfaceCtor ty -> ty |> tryNiceEntityRefOfTyOption |> Option.map (rangeOfEntityRef preferFlag)
        | Item.NewDef _ -> None

    // Provided type definitions do not have a useful F# CCU for the purposes of goto-definition.
    let computeCcuOfTyconRef (tcref: TyconRef) = 
#if !NO_TYPEPROVIDERS
        if tcref.IsProvided then None else 
#endif
        ccuOfTyconRef tcref

    let ccuOfMethInfo (g: TcGlobals) (minfo: MethInfo) = 
        match minfo with
        | DefaultStructCtor(_, AppTy g (tcref, _)) ->
            computeCcuOfTyconRef tcref

        | _ -> 
            minfo.ArbitraryValRef 
            |> Option.bind ccuOfValRef 
            |> Option.orElseWith (fun () -> minfo.DeclaringTyconRef |> computeCcuOfTyconRef)

    let rec ccuOfItem (g: TcGlobals) d = 
        match d with
        | Item.Value vref
        | Item.CustomBuilder (_, vref) ->
            ccuOfValRef vref 

        | Item.UnionCase(ucinfo, _) ->
            computeCcuOfTyconRef ucinfo.TyconRef

        | Item.ActivePatternCase apref ->
            ccuOfValRef apref.ActivePatternVal

        | Item.ExnCase tcref ->
            computeCcuOfTyconRef tcref

        | Item.RecdField rfinfo ->
            computeCcuOfTyconRef rfinfo.RecdFieldRef.TyconRef

        | Item.UnionCaseField (ucinfo, _) ->
            computeCcuOfTyconRef ucinfo.TyconRef

        | Item.Event einfo ->
            einfo.DeclaringTyconRef |> computeCcuOfTyconRef

        | Item.ILField finfo ->
            finfo.DeclaringTyconRef |> computeCcuOfTyconRef

        | Item.Property(info = pinfos)              -> 
            pinfos |> List.tryPick (fun pinfo -> 
                pinfo.ArbitraryValRef 
                |> Option.bind ccuOfValRef
                |> Option.orElseWith (fun () -> pinfo.DeclaringTyconRef |> computeCcuOfTyconRef))

        | Item.OtherName (container = meth) ->
            match meth with
            | None -> None
            | Some (ArgumentContainer.Method minfo) -> ccuOfMethInfo g minfo
            | Some (ArgumentContainer.Type eref) -> computeCcuOfTyconRef eref

        | Item.MethodGroup(_, minfos, _)
        | Item.CtorGroup(_, minfos) ->
            minfos |> List.tryPick (ccuOfMethInfo g)

        | Item.CustomOperation (_, _, meth) ->
            match meth with
            | None -> None
            | Some minfo -> ccuOfMethInfo g minfo

        | Item.Types(_, tys) ->
            tys |> List.tryPick (tryNiceEntityRefOfTyOption >> Option.bind computeCcuOfTyconRef)

        | Item.FakeInterfaceCtor(ty)
        | Item.DelegateCtor(ty) ->
            ty |> tryNiceEntityRefOfTyOption |> Option.bind computeCcuOfTyconRef

        | Item.ModuleOrNamespaces erefs 
        | Item.UnqualifiedType erefs ->
            erefs |> List.tryPick computeCcuOfTyconRef 

        | Item.SetterArg (_, item) ->
            ccuOfItem g item

        | Item.AnonRecdField (info, _, _, _) ->
            Some info.Assembly

        // This is not expected: you can't directly refer to trait constraints in other assemblies
        | Item.Trait _ -> None

        // This is not expected: you can't directly refer to type variables in other assemblies
        | Item.TypeVar _  -> None

        // This is not expected: you can't directly refer to active pattern result tags in other assemblies
        | Item.ActivePatternResult _  -> None

        // This is not expected: implicit operator references only occur in the current assembly
        | Item.ImplicitOp _  -> None

        // This is not expected: NewDef only occurs within checking
        | Item.NewDef _  -> None

    /// Work out the source file for an item and fix it up relative to the CCU if it is relative.
    let fileNameOfItem (g: TcGlobals) qualProjectDir (m: range) h =
        let file = m.FileName 
        if verbose then dprintf "file stored in metadata is '%s'\n" file
        if not (FileSystem.IsPathRootedShim file) then 
            match ccuOfItem g h with 
            | Some ccu -> 
                Path.Combine(ccu.SourceCodeDirectory, file)
            | None -> 
                match qualProjectDir with 
                | None     -> file
                | Some dir -> Path.Combine(dir, file)
         else file

    let ParamNameAndTypesOfUnaryCustomOperation g minfo = 
        match minfo with 
        | FSMeth(_, _, vref, _) -> 
            let argInfos = ArgInfosOfMember g vref |> List.concat 
            // Drop the first 'seq<T>' argument representing the computation space
            let argInfos = if argInfos.IsEmpty then [] else argInfos.Tail
            [ for ty, argInfo in argInfos do
                  let isPP = HasFSharpAttribute g g.attrib_ProjectionParameterAttribute argInfo.Attribs
                  // Strip the tuple space type of the type of projection parameters
                  let ty = if isPP && isFunTy g ty then rangeOfFunTy g ty else ty
                  yield ParamNameAndType(argInfo.Name, ty) ]
        | _ -> []

    let mkXmlComment thing =
        match thing with
        | Some (Some fileName, xmlDocSig) -> FSharpXmlDoc.FromXmlFile(fileName, xmlDocSig)
        | _ -> FSharpXmlDoc.None

    let GetXmlDocFromLoader (infoReader: InfoReader) xmlDoc =
        match xmlDoc with
        | FSharpXmlDoc.None
        | FSharpXmlDoc.FromXmlText _ -> xmlDoc
        | FSharpXmlDoc.FromXmlFile(dllName, xmlSig) ->
            TryFindXmlDocByAssemblyNameAndSig infoReader (Path.GetFileNameWithoutExtension dllName) xmlSig
            |> Option.map FSharpXmlDoc.FromXmlText
            |> Option.defaultValue xmlDoc

    /// This function gets the signature to pass to Visual Studio to use its lookup functions for .NET stuff. 
    let rec GetXmlDocHelpSigOfItemForLookup (infoReader: InfoReader) m d =
        let g = infoReader.g
        match d with
        | Item.ActivePatternCase (APElemRef(_, vref, _, _))        
        | Item.Value vref | Item.CustomBuilder (_, vref) -> 
            mkXmlComment (GetXmlDocSigOfValRef g vref)

        | Item.UnionCase  (ucinfo, _) ->
            mkXmlComment (GetXmlDocSigOfUnionCaseRef ucinfo.UnionCaseRef)

        | Item.UnqualifiedType (tcref :: _)
        | Item.ExnCase tcref ->
            mkXmlComment (GetXmlDocSigOfEntityRef infoReader m tcref)

        | Item.RecdField rfinfo ->
            mkXmlComment (GetXmlDocSigOfRecdFieldRef rfinfo.RecdFieldRef)

        | Item.NewDef _ -> FSharpXmlDoc.None

        | Item.ILField finfo ->
            mkXmlComment (GetXmlDocSigOfILFieldInfo infoReader m finfo)

        | Item.FakeInterfaceCtor ty
        | Item.DelegateCtor ty
        | Item.Types(_, ty :: _) ->
            match ty with
            | AbbrevOrAppTy tcref ->
                mkXmlComment (GetXmlDocSigOfEntityRef infoReader m tcref)
            | _ -> FSharpXmlDoc.None

        | Item.CustomOperation (_, _, Some minfo) ->
            mkXmlComment (GetXmlDocSigOfMethInfo infoReader  m minfo)

        | Item.Trait _ -> FSharpXmlDoc.None

        | Item.TypeVar _  -> FSharpXmlDoc.None

        | Item.ModuleOrNamespaces(modref :: _) ->
            mkXmlComment (GetXmlDocSigOfEntityRef infoReader m modref)

        | Item.Property(info = pinfo :: _) ->
            mkXmlComment (GetXmlDocSigOfProp infoReader m pinfo)

        | Item.Event einfo ->
            mkXmlComment (GetXmlDocSigOfEvent infoReader m einfo)

        | Item.MethodGroup(_, minfo :: _, _) ->
            mkXmlComment (GetXmlDocSigOfMethInfo infoReader  m minfo)

        | Item.CtorGroup(_, minfo :: _) ->
            mkXmlComment (GetXmlDocSigOfMethInfo infoReader  m minfo)

        | Item.OtherName(container = Some argContainer) ->
            match argContainer with 
            | ArgumentContainer.Method minfo -> mkXmlComment (GetXmlDocSigOfMethInfo infoReader m minfo)
            | ArgumentContainer.Type tcref -> mkXmlComment (GetXmlDocSigOfEntityRef infoReader m tcref)

        | Item.UnionCaseField (ucinfo, _) ->
            mkXmlComment (GetXmlDocSigOfUnionCaseRef ucinfo.UnionCaseRef)

        | Item.SetterArg (_, item) ->
            GetXmlDocHelpSigOfItemForLookup infoReader m item

        // These do not have entires in XML doc files
        | Item.CustomOperation _
        | Item.OtherName _
        | Item.ActivePatternResult _
        | Item.AnonRecdField _
        | Item.ImplicitOp _

        // These empty lists are not expected to occur
        | Item.CtorGroup (_, [])
        | Item.MethodGroup (_, [], _)
        | Item.Property (info = [])
        | Item.ModuleOrNamespaces []
        | Item.UnqualifiedType []
        | Item.Types(_, []) ->
            FSharpXmlDoc.None

        |> GetXmlDocFromLoader infoReader

    /// Produce an XmlComment with a signature or raw text, given the F# comment and the item
    let GetXmlCommentForItemAux (xmlDoc: XmlDoc option) (infoReader: InfoReader) m d = 
        match xmlDoc with 
        | Some xmlDoc when not xmlDoc.IsEmpty  -> 
            FSharpXmlDoc.FromXmlText xmlDoc
        | _ -> GetXmlDocHelpSigOfItemForLookup infoReader m d

    let GetXmlCommentForMethInfoItem infoReader m d (minfo: MethInfo) = 
        if minfo.HasDirectXmlComment || minfo.XmlDoc.NonEmpty then
            GetXmlCommentForItemAux (Some minfo.XmlDoc) infoReader m d 
        else
            mkXmlComment (GetXmlDocSigOfMethInfo infoReader m minfo)

    let FormatTyparMapping denv (prettyTyparInst: TyparInstantiation) = 
        [ for tp, ty in prettyTyparInst -> 
            wordL (tagTypeParameter ("'" + tp.DisplayName))  ^^ wordL (tagText (FSComp.SR.descriptionWordIs())) ^^ NicePrint.layoutType denv ty  ]

    let (|ItemWhereTypIsPreferred|_|) item = 
        match item with 
        | Item.DelegateCtor ty
        | Item.CtorGroup(_, [DefaultStructCtor(_, ty)])
        | Item.FakeInterfaceCtor ty
        | Item.Types(_, [ty])  -> Some ty
        | _ -> None

    /// Specifies functions for comparing 'Item' objects with respect to the user 
    /// (this means that some values that are not technically equal are treated as equal 
    ///  if this is what we want to show to the user, because we're comparing just the name
    //   for some cases e.g. when using 'fullDisplayTextOfModRef')
    let ItemDisplayPartialEquality g = 
      { new IPartialEqualityComparer<_> with   
          member x.InEqualityRelation item = 
              match item  with 
              | Item.Trait _ -> true
              | Item.Types(_, _ :: _) -> true
              | Item.ILField(_) -> true
              | Item.RecdField _ -> true
              | Item.SetterArg _ -> true
              | Item.TypeVar _ -> true
              | Item.CustomOperation _ -> true
              | Item.ModuleOrNamespaces(_ :: _) -> true
              | Item.MethodGroup _ -> true
              | Item.Value _ | Item.CustomBuilder _ -> true
              | Item.ActivePatternCase _ -> true
              | Item.DelegateCtor _ -> true
              | Item.UnionCase _ -> true
              | Item.ExnCase _ -> true              
              | Item.Event _ -> true
              | Item.Property _ -> true
              | Item.CtorGroup _ -> true
              | Item.UnqualifiedType _ -> true

              // These are never expected to have duplicates in declaration lists etc
              | Item.ActivePatternResult _
              | Item.AnonRecdField _
              | Item.OtherName _
              | Item.FakeInterfaceCtor _
              | Item.ImplicitOp _
              | Item.NewDef _
              | Item.UnionCaseField _

              // These are not expected to occur
              | Item.Types(_, [])
              | Item.ModuleOrNamespaces [] -> false

              //| _ -> false
              
          member x.Equals(item1, item2) = 
            // This may explore assemblies that are not in the reference set.
            // In this case just bail out and assume items are not equal
            protectAssemblyExploration false (fun () -> 
              let equalHeadTypes(ty1, ty2) =
                  match tryTcrefOfAppTy g ty1 with
                  | ValueSome tcref1 ->
                    match tryTcrefOfAppTy g ty2 with
                    | ValueSome tcref2 -> tyconRefEq g tcref1 tcref2
                    | _ -> typeEquiv g ty1 ty2
                  | _ -> typeEquiv g ty1 ty2

              ItemsAreEffectivelyEqual g item1 item2 || 

              // Much of this logic is already covered by 'ItemsAreEffectivelyEqual'
              match item1, item2 with 
              | Item.DelegateCtor ty1, Item.DelegateCtor ty2 -> equalHeadTypes(ty1, ty2)
              | Item.Types(dn1, ty1 :: _), Item.Types(dn2, ty2 :: _) ->
                  // Bug 4403: We need to compare names as well, because 'int' and 'Int32' are physically the same type, but we want to show both
                  dn1 = dn2 && equalHeadTypes(ty1, ty2) 
              
              // Prefer a type to a DefaultStructCtor, a DelegateCtor and a FakeInterfaceCtor 
              | ItemWhereTypIsPreferred ty1, ItemWhereTypIsPreferred ty2 -> equalHeadTypes(ty1, ty2) 

              | Item.ExnCase tcref1, Item.ExnCase tcref2 -> tyconRefEq g tcref1 tcref2
              | Item.ILField(fld1), Item.ILField(fld2) ->
                  ILFieldInfo.ILFieldInfosUseIdenticalDefinitions fld1 fld2
              | Item.CustomOperation (_, _, Some minfo1), Item.CustomOperation (_, _, Some minfo2) -> 
                    MethInfo.MethInfosUseIdenticalDefinitions minfo1 minfo2
              | Item.TypeVar (nm1, tp1), Item.TypeVar (nm2, tp2) -> 
                    (nm1 = nm2) && typarRefEq tp1 tp2
              | Item.ModuleOrNamespaces(modref1 :: _), Item.ModuleOrNamespaces(modref2 :: _) -> fullDisplayTextOfModRef modref1 = fullDisplayTextOfModRef modref2
              | Item.SetterArg(id1, _), Item.SetterArg(id2, _) -> Range.equals id1.idRange id2.idRange && id1.idText = id2.idText
              | Item.MethodGroup(_, meths1, _), Item.MethodGroup(_, meths2, _) -> 
                  Seq.zip meths1 meths2 |> Seq.forall (fun (minfo1, minfo2) ->
                    MethInfo.MethInfosUseIdenticalDefinitions minfo1 minfo2)
              | (Item.Value vref1 | Item.CustomBuilder (_, vref1)), (Item.Value vref2 | Item.CustomBuilder (_, vref2)) -> 
                  valRefEq g vref1 vref2
              | Item.ActivePatternCase(APElemRef(_apinfo1, vref1, idx1, _)), Item.ActivePatternCase(APElemRef(_apinfo2, vref2, idx2, _)) ->
                  idx1 = idx2 && valRefEq g vref1 vref2
              | Item.UnionCase(UnionCaseInfo(_, ur1), _), Item.UnionCase(UnionCaseInfo(_, ur2), _) -> 
                  g.unionCaseRefEq ur1 ur2
              | Item.RecdField(RecdFieldInfo(_, RecdFieldRef(tcref1, n1))), Item.RecdField(RecdFieldInfo(_, RecdFieldRef(tcref2, n2))) -> 
                  (tyconRefEq g tcref1 tcref2) && (n1 = n2) // there is no direct function as in the previous case
              | Item.Property(info = pi1s), Item.Property(info = pi2s) -> 
                  (pi1s, pi2s) ||> List.forall2 (fun pi1 pi2 -> PropInfo.PropInfosUseIdenticalDefinitions pi1 pi2)
              | Item.Event evt1, Item.Event evt2 -> 
                  EventInfo.EventInfosUseIdenticalDefinitions evt1 evt2
              | Item.AnonRecdField(anon1, _, i1, _), Item.AnonRecdField(anon2, _, i2, _) ->
                 anonInfoEquiv anon1 anon2 && i1 = i2
              | Item.Trait traitInfo1, Item.Trait traitInfo2 ->
                 (traitInfo1.MemberLogicalName = traitInfo2.MemberLogicalName)
              | Item.CtorGroup(_, meths1), Item.CtorGroup(_, meths2) ->
                  (meths1, meths2)
                  ||> List.forall2 (fun minfo1 minfo2 -> MethInfo.MethInfosUseIdenticalDefinitions minfo1 minfo2)
              | Item.UnqualifiedType tcrefs1, Item.UnqualifiedType tcrefs2 ->
                  (tcrefs1, tcrefs2)
                  ||> List.forall2 (fun tcref1 tcref2 -> tyconRefEq g tcref1 tcref2)
              | Item.Types(_, [AbbrevOrAppTy tcref1]), Item.UnqualifiedType([tcref2]) -> tyconRefEq g tcref1 tcref2
              | Item.UnqualifiedType([tcref1]), Item.Types(_, [AbbrevOrAppTy tcref2]) -> tyconRefEq g tcref1 tcref2
              | _ -> false)
              
          member x.GetHashCode item =
            // This may explore assemblies that are not in the reference set.
            // In this case just bail out and use a random hash code
            protectAssemblyExploration 1027 (fun () -> 
              match item with 
              | ItemWhereTypIsPreferred ty -> 
                  match tryTcrefOfAppTy g ty with
                  | ValueSome tcref -> hash tcref.LogicalName
                  | _ -> 1010
              | Item.ILField(fld) ->
                  fld.ComputeHashCode()
              | Item.TypeVar (nm, _tp) -> hash nm
              | Item.CustomOperation (_, _, Some minfo) -> minfo.ComputeHashCode()
              | Item.CustomOperation (_, _, None) -> 1
              | Item.ModuleOrNamespaces(modref :: _) -> hash (fullDisplayTextOfModRef modref)          
              | Item.SetterArg(id, _) -> hash (id.idRange, id.idText)
              | Item.MethodGroup(_, meths, _) -> meths |> List.fold (fun st a -> st + a.ComputeHashCode()) 0
              | 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.LogicalName
              | Item.UnionCase(UnionCaseInfo(_, UnionCaseRef(tcref, n)), _) -> hash(tcref.Stamp, n)
              | Item.RecdField(RecdFieldInfo(_, RecdFieldRef(tcref, n))) -> hash(tcref.Stamp, n)
              | Item.AnonRecdField(anon, _, i, _) -> hash anon.SortedNames[i]
              | Item.Trait traitInfo -> hash traitInfo.MemberLogicalName
              | Item.Event evt -> evt.ComputeHashCode()
              | Item.Property(info = pis) -> hash (pis |> List.map (fun pi -> pi.ComputeHashCode()))
              | Item.UnqualifiedType(tcref :: _) -> hash tcref.LogicalName

              // These are not expected to occur, see InEqualityRelation and ItemWhereTypIsPreferred
              | Item.ActivePatternResult _
              | Item.AnonRecdField _
              | Item.OtherName _
              | Item.FakeInterfaceCtor _
              | Item.ImplicitOp _
              | Item.NewDef _
              | Item.UnionCaseField _
              | Item.UnqualifiedType _
              | Item.Types _
              | Item.DelegateCtor _
              | Item.ModuleOrNamespaces [] -> 0
              ) }
    
    /// Remove all duplicate items
    let RemoveDuplicateItems g (items: ItemWithInst list) =     
        if isNil items then items else
        items |> IPartialEqualityComparer.partialDistinctBy (IPartialEqualityComparer.On (fun item -> item.Item) (ItemDisplayPartialEquality g))

    let IsExplicitlySuppressed (g: TcGlobals) (item: Item) = 
        // This may explore assemblies that are not in the reference set.
        // In this case just assume the item is not suppressed.
        protectAssemblyExploration true (fun () -> 
            match item with 
            | Item.Types(it, [ty]) -> 
                match tryTcrefOfAppTy g ty with
                | ValueSome tcr1 ->
                    g.suppressed_types 
                    |> List.exists (fun supp ->
                        let generalizedSupp = generalizedTyconRef g supp
                        // check the display name is precisely the one we're suppressing
                        match tryTcrefOfAppTy g generalizedSupp with
                        | ValueSome tcr2 ->
                            it = supp.DisplayName &&
                            // check if they are the same logical type (after removing all abbreviations) 
                            tyconRefEq g tcr1 tcr2
                        | _ -> false) 
                | _ -> false
            | _ -> false)

    /// Filter types that are explicitly suppressed from the IntelliSense (such as uppercase "FSharpList", "Option", etc.)
    let RemoveExplicitlySuppressed (g: TcGlobals) (items: ItemWithInst list) =
        items |> List.filter (fun item -> not (IsExplicitlySuppressed g item.Item))

    let SimplerDisplayEnv denv = 
        { denv with shortConstraints=true
                    showStaticallyResolvedTyparAnnotations=false
                    abbreviateAdditionalConstraints=false
                    suppressNestedTypes=true
                    maxMembers=Some EnvMisc2.maxMembers }

    let rec FullNameOfItem g item = 
        let denv = DisplayEnv.Empty g
        match item with
        | Item.ImplicitOp(_, { contents = Some(TraitConstraintSln.FSMethSln(vref=vref)) })
        | Item.Value vref | Item.CustomBuilder (_, vref) -> fullDisplayTextOfValRef vref
        | Item.UnionCase (ucinfo, _) -> fullDisplayTextOfUnionCaseRef  ucinfo.UnionCaseRef
        | Item.ActivePatternResult(apinfo, _ty, idx, _) -> apinfo.DisplayNameByIdx idx
        | Item.ActivePatternCase apref -> FullNameOfItem g (Item.Value apref.ActivePatternVal)  + "." + apref.DisplayName
        | Item.ExnCase ecref -> fullDisplayTextOfExnRef ecref 
        | Item.AnonRecdField(anon, _argTys, i, _) -> anon.DisplayNameByIdx i
        | Item.RecdField rfinfo -> fullDisplayTextOfRecdFieldRef  rfinfo.RecdFieldRef
        | Item.NewDef id -> id.idText
        | Item.ILField finfo -> buildString (fun os -> NicePrint.outputType denv os finfo.ApparentEnclosingType; bprintf os ".%s" finfo.FieldName)
        | Item.Event einfo -> buildString (fun os -> NicePrint.outputTyconRef denv os einfo.DeclaringTyconRef; bprintf os ".%s" einfo.EventName)
        | Item.Property(info = pinfo :: _) -> buildString (fun os -> NicePrint.outputTyconRef denv os pinfo.DeclaringTyconRef; bprintf os ".%s" pinfo.PropertyName)
        | Item.CustomOperation (customOpName, _, _) -> customOpName
        | Item.CtorGroup(_, minfo :: _) -> buildString (fun os -> NicePrint.outputTyconRef denv os minfo.DeclaringTyconRef)
        | Item.MethodGroup(_, _, Some minfo) -> buildString (fun os -> NicePrint.outputTyconRef denv os minfo.DeclaringTyconRef; bprintf os ".%s" minfo.DisplayName)        
        | Item.MethodGroup(_, minfo :: _, _) -> buildString (fun os -> NicePrint.outputTyconRef denv os minfo.DeclaringTyconRef; bprintf os ".%s" minfo.DisplayName)        
        | Item.UnqualifiedType (tcref :: _) -> buildString (fun os -> NicePrint.outputTyconRef denv os tcref)
        | Item.FakeInterfaceCtor ty 
        | Item.DelegateCtor ty 
        | Item.Types(_, ty :: _) -> 
            match tryTcrefOfAppTy g ty with
            | ValueSome tcref -> buildString (fun os -> NicePrint.outputTyconRef denv os tcref)
            | _ -> ""
        | Item.Trait traitInfo -> traitInfo.MemberLogicalName
        | Item.ModuleOrNamespaces(modref :: _ as modrefs) ->
            let definiteNamespace = modrefs |> List.forall (fun modref -> modref.IsNamespace)
            if definiteNamespace then fullDisplayTextOfModRef modref else modref.DisplayName
        | Item.TypeVar _
        | Item.OtherName _ -> item.DisplayName
        | Item.SetterArg (_, item) -> FullNameOfItem g item
        | Item.ImplicitOp(id, _) -> id.idText
        | Item.UnionCaseField (UnionCaseInfo (_, ucref), fieldIndex) -> ucref.FieldByIndex(fieldIndex).DisplayName
        // unreachable 
        | Item.UnqualifiedType([]) 
        | Item.Types(_, []) 
        | Item.CtorGroup(_, []) 
        | Item.MethodGroup(_, [], _) 
        | Item.ModuleOrNamespaces []
        | Item.Property(info = []) -> ""

    /// Output the description of a language item
    let rec GetXmlCommentForItem (infoReader: InfoReader) m item = 
        let g = infoReader.g
        match item with
        | Item.ImplicitOp(_, sln) ->
            match sln.Value with
            | Some(TraitConstraintSln.FSMethSln(vref=vref)) ->
                GetXmlCommentForItem infoReader m (Item.Value vref)
            | Some (TraitConstraintSln.ILMethSln _)
            | Some (TraitConstraintSln.FSRecdFieldSln _)
            | Some (TraitConstraintSln.FSAnonRecdFieldSln _)
            | Some (TraitConstraintSln.ClosedExprSln _)
            | Some TraitConstraintSln.BuiltInSln
            | None ->
                GetXmlCommentForItemAux None infoReader m item

        | Item.Value vref | Item.CustomBuilder (_, vref) ->            
            let doc = if valRefInThisAssembly g.compilingFSharpCore vref || vref.XmlDoc.NonEmpty then Some vref.XmlDoc else None
            GetXmlCommentForItemAux doc infoReader m item

        | Item.UnionCase(ucinfo, _) -> 
            let doc = if tyconRefUsesLocalXmlDoc g.compilingFSharpCore ucinfo.TyconRef || ucinfo.UnionCase.XmlDoc.NonEmpty then Some ucinfo.UnionCase.XmlDoc else None
            GetXmlCommentForItemAux doc infoReader m item

        | Item.ActivePatternCase apref -> 
            let doc = Some apref.ActivePatternVal.XmlDoc
            GetXmlCommentForItemAux doc infoReader m item

        | Item.ExnCase ecref -> 
            let doc = if tyconRefUsesLocalXmlDoc g.compilingFSharpCore ecref || ecref.XmlDoc.NonEmpty then Some ecref.XmlDoc else None
            GetXmlCommentForItemAux doc infoReader m item

        | Item.RecdField rfinfo ->
            let tcref = rfinfo.TyconRef
            let doc =
                if tyconRefUsesLocalXmlDoc g.compilingFSharpCore tcref || tcref.XmlDoc.NonEmpty then
                    if tcref.IsFSharpException then
                        Some tcref.XmlDoc
                    else
                        Some rfinfo.RecdField.XmlDoc
                else
                    None
            GetXmlCommentForItemAux doc infoReader m item

        | Item.Event einfo ->
            let doc = if einfo.HasDirectXmlComment || einfo.XmlDoc.NonEmpty then Some einfo.XmlDoc else None
            GetXmlCommentForItemAux doc infoReader m item

        | Item.Property(info = pinfos) -> 
            let pinfo = pinfos.Head
            let doc = if pinfo.HasDirectXmlComment || pinfo.XmlDoc.NonEmpty then Some pinfo.XmlDoc else None
            GetXmlCommentForItemAux doc infoReader m item

        | Item.CustomOperation (_, _, Some minfo) 
        | Item.CtorGroup(_, minfo :: _) 
        | Item.MethodGroup(_, minfo :: _, _) ->
            GetXmlCommentForMethInfoItem infoReader m item minfo

        | Item.Types(_, tys) ->
            let doc =
                match tys with
                | AbbrevOrAppTy tcref :: _ ->
                    if tyconRefUsesLocalXmlDoc g.compilingFSharpCore tcref || tcref.XmlDoc.NonEmpty then
                        Some tcref.XmlDoc
                    else
                        None
                | _ -> None
            GetXmlCommentForItemAux doc infoReader m item

        | Item.UnqualifiedType(tcrefs) ->
            let doc =
                match tcrefs with
                | tcref :: _ ->
                    if tyconRefUsesLocalXmlDoc g.compilingFSharpCore tcref || tcref.XmlDoc.NonEmpty then
                        Some tcref.XmlDoc
                    else
                        None
                | _ -> None
            GetXmlCommentForItemAux doc infoReader m item

        | Item.ModuleOrNamespaces(modref :: _ as modrefs) -> 
            let definiteNamespace = modrefs |> List.forall (fun modref -> modref.IsNamespace)
            if not definiteNamespace then
                let doc = if entityRefInThisAssembly g.compilingFSharpCore modref || modref.XmlDoc.NonEmpty  then Some modref.XmlDoc else None
                GetXmlCommentForItemAux doc infoReader m item
            else
                GetXmlCommentForItemAux None infoReader m item

        | Item.OtherName (container = argContainer) ->
            let doc =
                match argContainer with
                | Some(ArgumentContainer.Method minfo) ->
                    if minfo.HasDirectXmlComment || minfo.XmlDoc.NonEmpty  then Some minfo.XmlDoc else None 
                | Some(ArgumentContainer.Type tcref) ->
                    if tyconRefUsesLocalXmlDoc g.compilingFSharpCore tcref || tcref.XmlDoc.NonEmpty  then Some tcref.XmlDoc else None
                | _ -> None
            GetXmlCommentForItemAux doc infoReader m item

        | Item.UnionCaseField (ucinfo, _) ->
            let doc =
                if tyconRefUsesLocalXmlDoc g.compilingFSharpCore ucinfo.TyconRef || ucinfo.UnionCase.XmlDoc.NonEmpty then
                    Some ucinfo.UnionCase.XmlDoc
                else
                    None
            GetXmlCommentForItemAux doc infoReader m item

        | Item.SetterArg (_, item) -> 
            GetXmlCommentForItem infoReader m item
        
        // In all these cases, there is no direct XML documentation from F# comments
        | Item.MethodGroup (_, [], _)
        | Item.CtorGroup (_, [])
        | Item.ModuleOrNamespaces []
        | Item.Types (_, [])
        | Item.CustomOperation (_, _, None)
        | Item.UnqualifiedType []
        | Item.TypeVar _
        | Item.Trait _
        | Item.AnonRecdField _
        | Item.ActivePatternResult _
        | Item.NewDef _
        | Item.ILField _
        | Item.FakeInterfaceCtor _
        | Item.DelegateCtor _ ->
        //|  _ ->
            GetXmlCommentForItemAux None infoReader m item

        |> GetXmlDocFromLoader infoReader

    let IsAttribute (infoReader: InfoReader) item =
        try
            let g = infoReader.g
            let amap = infoReader.amap
            match item with
            | Item.Types(_, TType_app(tcref, _, _) :: _)
            | Item.UnqualifiedType(tcref :: _) ->
                let ty = generalizedTyconRef g tcref
                ExistsHeadTypeInEntireHierarchy g amap range0 ty g.tcref_System_Attribute
            | _ -> false
        with _ -> false

#if !NO_TYPEPROVIDERS

    /// Determine if an item is a provided type 
    let (|ItemIsProvidedType|_|) g item =
        match item with
        | Item.Types(_name, tys) ->
            match tys with
            | [AppTy g (tcref, _typeInst)] ->
                if tcref.IsProvidedErasedTycon || tcref.IsProvidedGeneratedTycon then
                    Some tcref
                else
                    None
            | _ -> None
        | _ -> None

    /// Determine if an item is a provided type that has static parameters
    let (|ItemIsProvidedTypeWithStaticArguments|_|) m g item =
        match item with
        | Item.Types(_name, tys) ->
            match tys with
            | [AppTy g (tcref, _typeInst)] ->
                if tcref.IsProvidedErasedTycon || tcref.IsProvidedGeneratedTycon then
                    let typeBeforeArguments = 
                        match tcref.TypeReprInfo with 
                        | TProvidedTypeRepr info -> info.ProvidedType
                        | _ -> failwith "unreachable"
                    let staticParameters = typeBeforeArguments.PApplyWithProvider((fun (typeBeforeArguments, provider) -> typeBeforeArguments.GetStaticParameters provider), range=m) 
                    let staticParameters = staticParameters.PApplyArray(id, "GetStaticParameters", m)
                    Some staticParameters
                else
                    None
            | _ -> None
        | _ -> None

    let (|ItemIsProvidedMethodWithStaticArguments|_|) item =
        match item with
        // Prefer the static parameters from the uninstantiated method info
        | Item.MethodGroup(_, _, Some minfo) ->
            match minfo.ProvidedStaticParameterInfo  with 
            | Some (_, staticParameters) -> Some staticParameters
            | _ -> None
        | Item.MethodGroup(_, [minfo], _) ->
            match minfo.ProvidedStaticParameterInfo  with 
            | Some (_, staticParameters) -> Some staticParameters
            | _ -> None
        | _ -> None

    /// Determine if an item has static arguments
    let (|ItemIsWithStaticArguments|_|) m g item =
        match item with
        | ItemIsProvidedTypeWithStaticArguments m g staticParameters -> Some staticParameters
        | ItemIsProvidedMethodWithStaticArguments staticParameters -> Some staticParameters
        | _ -> None

#endif

    /// Get the "F1 Keyword" associated with an item, for looking up documentation help indexes on the web
    let rec GetF1Keyword (g: TcGlobals) item = 

        let getKeywordForMethInfo (minfo : MethInfo) =
            match minfo with 
            | FSMeth(_, _, vref, _) ->
                match vref.TryDeclaringEntity with
                | Parent tcref ->
                    (tcref |> ticksAndArgCountTextOfTyconRef) + "." + vref.CompiledName g.CompilerGlobalState |> Some
                | ParentNone -> None
                
            | ILMeth (_, minfo, _) ->
                let typeString = minfo.DeclaringTyconRef |> ticksAndArgCountTextOfTyconRef
                let paramString =
                    let nGenericParams = minfo.RawMetadata.GenericParams.Length 
                    if nGenericParams > 0 then "``"+(nGenericParams.ToString()) else ""
                sprintf "%s.%s%s" typeString minfo.RawMetadata.Name paramString |> Some

            | DefaultStructCtor _  -> None
#if !NO_TYPEPROVIDERS
            | ProvidedMeth _ -> None
#endif
             
        match item with
        | Item.Value vref | Item.CustomBuilder (_, vref) -> 
            let v = vref.Deref
            if v.IsModuleBinding && v.HasDeclaringEntity then
                let tyconRef = v.DeclaringEntity
                let paramsString =
                    match v.Typars with
                    |   [] -> ""
                    |   l -> "``"+(List.length l).ToString() 
                
                sprintf "%s.%s%s" (tyconRef |> ticksAndArgCountTextOfTyconRef) (v.CompiledName g.CompilerGlobalState) paramsString |> Some
            else
                None

        | Item.ActivePatternCase apref ->
            GetF1Keyword g (Item.Value apref.ActivePatternVal)

        | Item.UnionCase(ucinfo, _) ->
            (ucinfo.TyconRef |> ticksAndArgCountTextOfTyconRef) + "."+ucinfo.DisplayName |> Some

        | Item.RecdField rfi ->
            (rfi.TyconRef |> ticksAndArgCountTextOfTyconRef) + "." + rfi.DisplayName |> Some
        
        | Item.AnonRecdField _ -> None
        
        | Item.ILField finfo ->
             match finfo with 
             | ILFieldInfo(tinfo, fdef) -> 
                 (tinfo.TyconRefOfRawMetadata |> ticksAndArgCountTextOfTyconRef) + "." + fdef.Name |> Some
#if !NO_TYPEPROVIDERS
             | ProvidedField _ -> None
#endif
        | Item.Types(_, AppTy g (tcref, _) :: _) 
        | Item.DelegateCtor(AppTy g (tcref, _))
        | Item.FakeInterfaceCtor(AppTy g (tcref, _))
        | Item.UnqualifiedType (tcref :: _)
        | Item.ExnCase tcref -> 
            // strip off any abbreviation
            match generalizedTyconRef g tcref with 
            | AppTy g (tcref, _)  -> Some (ticksAndArgCountTextOfTyconRef tcref)
            | _ -> None

        // Pathological cases of the above
        | Item.Types _ 
        | Item.DelegateCtor _
        | Item.FakeInterfaceCtor _
        | Item.UnqualifiedType [] -> 
            None

        | Item.ModuleOrNamespaces modrefs -> 
            match modrefs with 
            | modref :: _ -> 
                // namespaces from type providers need to be handled separately because they don't have compiled representation
                // otherwise we'll fail at tast.fs
                match modref.Deref.TypeReprInfo with
#if !NO_TYPEPROVIDERS                
                | TProvidedNamespaceRepr _ -> 
                    modref.CompilationPathOpt
                    |> Option.bind (fun path ->
                        // works similar to generation of xml-docs at tastops.fs, probably too similar
                        // TODO: check if this code can be implemented using xml-doc generation functionality
                        let prefix = path.AccessPath |> Seq.map fst |> String.concat "."
                        let fullName = if prefix = "" then modref.CompiledName else prefix + "." + modref.CompiledName
                        Some fullName
                        )
#endif
                | _ -> modref.Deref.CompiledRepresentationForNamedType.FullName |> Some
            | [] ->  None // Pathological case of the above

        | Item.Property(info = pinfo :: _) -> 
            match pinfo with 
            | FSProp(_, _, Some vref, _) 
            | FSProp(_, _, _, Some vref) -> 
                // per spec, extension members in F1 keywords are qualified with definition class
                match vref.TryDeclaringEntity with 
                | Parent tcref ->
                    (tcref |> ticksAndArgCountTextOfTyconRef)+"."+vref.PropertyName|> Some                     
                | ParentNone -> None

            | ILProp(ILPropInfo(tinfo, pdef)) -> 
                let tcref = tinfo.TyconRefOfRawMetadata
                (tcref |> ticksAndArgCountTextOfTyconRef)+"."+pdef.Name |> Some
            | FSProp _ -> None
#if !NO_TYPEPROVIDERS
            | ProvidedProp _ -> None
#endif
        | Item.Property(info = []) -> None // Pathological case of the above
                   
        | Item.Event einfo -> 
            match einfo with 
            | ILEvent _  ->
                let tcref = einfo.DeclaringTyconRef
                (tcref |> ticksAndArgCountTextOfTyconRef)+"."+einfo.EventName |> Some
            | FSEvent(_, pinfo, _, _) ->
                match pinfo.ArbitraryValRef with 
                | Some vref ->
                   // per spec, members in F1 keywords are qualified with definition class
                   match vref.TryDeclaringEntity with 
                   | Parent tcref -> (tcref |> ticksAndArgCountTextOfTyconRef)+"."+vref.PropertyName|> Some                     
                   | ParentNone -> None
                | None -> None
#if !NO_TYPEPROVIDERS
            | ProvidedEvent _ -> None 
#endif
        | Item.CtorGroup(_, minfos) ->
            match minfos with 
            | [] -> None
            | FSMeth(_, _, vref, _) :: _ ->
                   match vref.TryDeclaringEntity with
                   | Parent tcref -> (tcref |> ticksAndArgCountTextOfTyconRef) + ".#ctor"|> Some
                   | ParentNone -> None
#if !NO_TYPEPROVIDERS
            | ProvidedMeth _ :: _ -> None
#endif
            | minfo :: _ ->
                let tcref = minfo.DeclaringTyconRef
                (tcref |> ticksAndArgCountTextOfTyconRef)+".#ctor" |> Some
        | Item.CustomOperation (_, _, Some minfo) -> getKeywordForMethInfo minfo
        | Item.MethodGroup(_, _, Some minfo) -> getKeywordForMethInfo minfo
        | Item.MethodGroup(_, minfo :: _, _) -> getKeywordForMethInfo minfo
        | Item.SetterArg (_, propOrField) -> GetF1Keyword g propOrField 
        | Item.MethodGroup(_, [], _) 
        | Item.CustomOperation (_, _, None)   // "into"
        | Item.NewDef _ // "let x$yz = ..." - no keyword
        | Item.OtherName _ // no keyword on named parameters 
        | Item.Trait _
        | Item.UnionCaseField _
        | Item.TypeVar _ 
        | Item.ImplicitOp _
        | Item.ActivePatternResult _ // "let (|Foo|Bar|) = .. Fo$o ..." - no keyword
            ->  None

    /// Select the items that participate in a MethodGroup.
    //
    // NOTE: This is almost identical to SelectMethodGroupItems and
    // should be merged, and indeed is only used on the TypeCheckInfo::GetMethodsAsSymbols path, which is unused by
    // the VS integration.
    let SelectMethodGroupItems2 g (m: range) (item: ItemWithInst) : ItemWithInst list =
        ignore m
        match item.Item with 
        | Item.MethodGroup(nm, minfos, orig) ->
            minfos |> List.map (fun minfo -> { Item = Item.MethodGroup(nm, [minfo], orig); TyparInstantiation = item.TyparInstantiation })
        | Item.CtorGroup(nm, cinfos) ->
            cinfos |> List.map (fun minfo -> { Item = Item.CtorGroup(nm, [minfo]); TyparInstantiation = item.TyparInstantiation }) 
        | Item.FakeInterfaceCtor _
        | Item.DelegateCtor _ -> [item]
        | Item.NewDef _ 
        | Item.ILField _ -> []
        | Item.Event _ -> []
        | Item.RecdField rfinfo -> if isForallFunctionTy g rfinfo.FieldType then [item] else []
        | Item.Value v -> if isForallFunctionTy g v.Type then [item] else []
        | Item.UnionCase(ucr, _) -> if not ucr.UnionCase.IsNullary then [item] else []
        | Item.ExnCase ecr -> if isNil (recdFieldsOfExnDefRef ecr) then [] else [item]
        | Item.Property(info = pinfos) -> 
            let pinfo = List.head pinfos 
            if pinfo.IsIndexer then [item] else []
#if !NO_TYPEPROVIDERS
        | ItemIsWithStaticArguments m g _ -> [item] // we pretend that provided-types-with-static-args are method-like in order to get ParamInfo for them
#endif
        | Item.CustomOperation(_name, _helpText, _minfo) -> [item]
        | Item.Trait _ -> [item]
        | Item.TypeVar _ -> []
        | Item.CustomBuilder _ -> []
        // These are not items that can participate in a method group
        | Item.TypeVar _
        | Item.CustomBuilder _
        | Item.ActivePatternCase _
        | Item.AnonRecdField _
        | Item.OtherName _
        | Item.ImplicitOp _
        | Item.ModuleOrNamespaces _
        | Item.SetterArg _
        | Item.Types _
        | Item.UnionCaseField _
        | Item.UnqualifiedType _
        | Item.ActivePatternResult _ -> []
