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

module FSharp.Compiler.AbstractIL.IL

#nowarn "49"
#nowarn "343" // The type 'ILAssemblyRef' implements 'System.IComparable' explicitly but provides no corresponding override for 'Object.Equals'.
#nowarn "346" // The struct, record or union type 'IlxExtensionType' has an explicit implementation of 'Object.Equals'. ...

open System
open System.Diagnostics
open System.IO
open System.Collections
open System.Collections.Generic
open System.Collections.Concurrent
open System.Runtime.CompilerServices
open System.Reflection
open System.Text
open System.Threading

open FSharp.Compiler.AbstractIL
open FSharp.Compiler.AbstractIL.Diagnostics
open FSharp.Compiler.AbstractIL.Internal
open FSharp.Compiler.AbstractIL.Internal.Library

open Internal.Utilities

let logging = false

let runningOnMono =
#if ENABLE_MONO_SUPPORT
// Officially supported way to detect if we are running on Mono.
// See http://www.mono-project.com/FAQ:_Technical
// "How can I detect if am running in Mono?" section
    try
        System.Type.GetType ("Mono.Runtime") <> null
    with e->
        // Must be robust in the case that someone else has installed a handler into System.AppDomain.OnTypeResolveEvent
        // that is not reliable.
        // This is related to bug 5506--the issue is actually a bug in VSTypeResolutionService.EnsurePopulated which is
        // called by OnTypeResolveEvent. The function throws a NullReferenceException. I'm working with that team to get
        // their issue fixed but we need to be robust here anyway.
        false
#else
    false
#endif

let _ = if logging then dprintn "* warning: Il.logging is on"

let int_order = LanguagePrimitives.FastGenericComparer<int>

let notlazy v = Lazy<_>.CreateFromValue v

/// A little ugly, but the idea is that if a data structure does not
/// contain lazy values then we don't add laziness. So if the thing to map
/// is already evaluated then immediately apply the function.
let lazyMap f (x: Lazy<_>) =
      if x.IsValueCreated then notlazy (f (x.Force())) else lazy (f (x.Force()))

[<RequireQualifiedAccess>]
type PrimaryAssembly =
    | Mscorlib
    | System_Runtime
    | NetStandard

    member this.Name =
        match this with
        | Mscorlib -> "mscorlib"
        | System_Runtime -> "System.Runtime"
        | NetStandard -> "netstandard"
    static member IsSomePrimaryAssembly n =
      n = PrimaryAssembly.Mscorlib.Name
      || n = PrimaryAssembly.System_Runtime.Name
      || n = PrimaryAssembly.NetStandard.Name

// --------------------------------------------------------------------
// Utilities: type names
// --------------------------------------------------------------------

let splitNameAt (nm: string) idx =
    if idx < 0 then failwith "splitNameAt: idx < 0"
    let last = nm.Length - 1
    if idx > last then failwith "splitNameAt: idx > last"
    (nm.Substring (0, idx)),
    (if idx < last then nm.Substring (idx+1, last - idx) else "")

let rec splitNamespaceAux (nm: string) =
    match nm.IndexOf '.' with
    | -1 -> [nm]
    | idx ->
        let s1, s2 = splitNameAt nm idx
        s1 :: splitNamespaceAux s2

/// Global State. All namespace splits ever seen
// ++GLOBAL MUTABLE STATE (concurrency-safe)
let memoizeNamespaceTable = new ConcurrentDictionary<string, string list>()

//  ++GLOBAL MUTABLE STATE (concurrency-safe)
let memoizeNamespaceRightTable = new ConcurrentDictionary<string, string option * string>()


let splitNamespace nm =
    memoizeNamespaceTable.GetOrAdd (nm, splitNamespaceAux)

let splitNamespaceMemoized nm = splitNamespace nm

// ++GLOBAL MUTABLE STATE (concurrency-safe)
let memoizeNamespaceArrayTable =
    Concurrent.ConcurrentDictionary<string, string[]>()

let splitNamespaceToArray nm =
    memoizeNamespaceArrayTable.GetOrAdd (nm, fun nm ->
        let x = Array.ofList (splitNamespace nm)
        x)

let splitILTypeName (nm: string) =
    match nm.LastIndexOf '.' with
    | -1 -> [], nm
    | idx ->
        let s1, s2 = splitNameAt nm idx
        splitNamespace s1, s2

let emptyStringArray = ([| |] : string[])

// Duplicate of comment in import.fs:
//   The type names that flow to the point include the "mangled" type names used for static parameters for provided types.
//   For example,
//       Foo.Bar,"1.0"
//   This is because the ImportSystemType code goes via Abstract IL type references. Ultimately this probably isn't
//   the best way to do things.
let splitILTypeNameWithPossibleStaticArguments (nm: string) =
    let nm, suffix =
        match nm.IndexOf ',' with
        | -1 -> nm, None
        | idx -> let s1, s2 = splitNameAt nm idx in s1, Some s2

    let nsp, nm =
        match nm.LastIndexOf '.' with
        | -1 -> emptyStringArray, nm
        | idx ->
            let s1, s2 = splitNameAt nm idx
            splitNamespaceToArray s1, s2
    nsp, (match suffix with None -> nm | Some s -> nm + "," + s)

(*
splitILTypeNameWithPossibleStaticArguments "Foo" = ([| |], "Foo")
splitILTypeNameWithPossibleStaticArguments "Foo.Bar" = ([| "Foo" |], "Bar")
splitILTypeNameWithPossibleStaticArguments "Foo.Bar,3" = ([| "Foo" |], "Bar, 3")
splitILTypeNameWithPossibleStaticArguments "Foo.Bar," = ([| "Foo" |], "Bar,")
splitILTypeNameWithPossibleStaticArguments "Foo.Bar,\"1.0\"" = ([| "Foo" |], "Bar,\"1.0\"")
splitILTypeNameWithPossibleStaticArguments "Foo.Bar.Bar,\"1.0\"" = ([| "Foo"; "Bar" |], "Bar,\"1.0\"")
*)

let unsplitTypeName (ns, n) =
    match ns with
    | [] -> String.concat "." ns + "." + n
    | _ -> n

let splitTypeNameRightAux (nm: string) =
    let idx = nm.LastIndexOf '.'
    if idx = -1 then None, nm else
    let s1, s2 = splitNameAt nm idx
    Some s1, s2

let splitTypeNameRight nm =
    memoizeNamespaceRightTable.GetOrAdd (nm, splitTypeNameRightAux)

// --------------------------------------------------------------------
// Ordered lists with a lookup table
// --------------------------------------------------------------------

/// This is used to store event, property and field maps.
type LazyOrderedMultiMap<'Key, 'Data when 'Key : equality>(keyf : 'Data -> 'Key, lazyItems : Lazy<'Data list>) =

    let quickMap =
        lazyItems |> lazyMap (fun entries ->
            let t = new Dictionary<_, _>(entries.Length, HashIdentity.Structural)
            do entries |> List.iter (fun y ->
                let key = keyf y
                let v =
                    match t.TryGetValue key with
                    | true, v -> v
                    | _ -> []
                t.[key] <- y :: v)
            t)

    member self.Entries() = lazyItems.Force()

    member self.Add y = new LazyOrderedMultiMap<'Key, 'Data>(keyf, lazyItems |> lazyMap (fun x -> y :: x))

    member self.Filter f = new LazyOrderedMultiMap<'Key, 'Data>(keyf, lazyItems |> lazyMap (List.filter f))

    member self.Item
        with get x =
            match quickMap.Force().TryGetValue x with
            | true, v -> v
            | _ -> []


//---------------------------------------------------------------------
// SHA1 hash-signing algorithm. Used to get the public key token from
// the public key.
//---------------------------------------------------------------------


let b0 n = (n &&& 0xFF)
let b1 n = ((n >>> 8) &&& 0xFF)
let b2 n = ((n >>> 16) &&& 0xFF)
let b3 n = ((n >>> 24) &&& 0xFF)


module SHA1 =

    let inline (>>>&) (x: int) (y: int) = int32 (uint32 x >>> y)

    let f(t, b, c, d) =
        if t < 20 then (b &&& c) ||| ((~~~b) &&& d)
        elif t < 40 then b ^^^ c ^^^ d
        elif t < 60 then (b &&& c) ||| (b &&& d) ||| (c &&& d)
        else b ^^^ c ^^^ d

    let [<Literal>] k0to19 = 0x5A827999
    let [<Literal>] k20to39 = 0x6ED9EBA1
    let [<Literal>] k40to59 = 0x8F1BBCDC
    let [<Literal>] k60to79 = 0xCA62C1D6

    let k t =
        if t < 20 then k0to19
        elif t < 40 then k20to39
        elif t < 60 then k40to59
        else k60to79


    type SHAStream =
        { stream: byte[]
          mutable pos: int
          mutable eof: bool }

    let rotLeft32 x n = (x <<< n) ||| (x >>>& (32-n))


    // padding and length (in bits!) recorded at end
    let shaAfterEof sha =
        let n = sha.pos
        let len = sha.stream.Length
        if n = len then 0x80
        else
          let padded_len = (((len + 9 + 63) / 64) * 64) - 8
          if n < padded_len - 8 then 0x0
          elif (n &&& 63) = 56 then int32 ((int64 len * int64 8) >>> 56) &&& 0xff
          elif (n &&& 63) = 57 then int32 ((int64 len * int64 8) >>> 48) &&& 0xff
          elif (n &&& 63) = 58 then int32 ((int64 len * int64 8) >>> 40) &&& 0xff
          elif (n &&& 63) = 59 then int32 ((int64 len * int64 8) >>> 32) &&& 0xff
          elif (n &&& 63) = 60 then int32 ((int64 len * int64 8) >>> 24) &&& 0xff
          elif (n &&& 63) = 61 then int32 ((int64 len * int64 8) >>> 16) &&& 0xff
          elif (n &&& 63) = 62 then int32 ((int64 len * int64 8) >>> 8) &&& 0xff
          elif (n &&& 63) = 63 then (sha.eof <- true; int32 (int64 len * int64 8) &&& 0xff)
          else 0x0

    let shaRead8 sha =
        let s = sha.stream
        let b = if sha.pos >= s.Length then shaAfterEof sha else int32 s.[sha.pos]
        sha.pos <- sha.pos + 1
        b

    let shaRead32 sha =
        let b0 = shaRead8 sha
        let b1 = shaRead8 sha
        let b2 = shaRead8 sha
        let b3 = shaRead8 sha
        let res = (b0 <<< 24) ||| (b1 <<< 16) ||| (b2 <<< 8) ||| b3
        res

    let sha1Hash sha =
        let mutable h0 = 0x67452301
        let mutable h1 = 0xEFCDAB89
        let mutable h2 = 0x98BADCFE
        let mutable h3 = 0x10325476
        let mutable h4 = 0xC3D2E1F0
        let mutable a = 0
        let mutable b = 0
        let mutable c = 0
        let mutable d = 0
        let mutable e = 0
        let w = Array.create 80 0x00
        while (not sha.eof) do
            for i = 0 to 15 do
                w.[i] <- shaRead32 sha
            for t = 16 to 79 do
                w.[t] <- rotLeft32 (w.[t-3] ^^^ w.[t-8] ^^^ w.[t-14] ^^^ w.[t-16]) 1
            a <- h0
            b <- h1
            c <- h2
            d <- h3
            e <- h4
            for t = 0 to 79 do
                let temp = (rotLeft32 a 5) + f (t, b, c, d) + e + w.[t] + k t
                e <- d
                d <- c
                c <- rotLeft32 b 30
                b <- a
                a <- temp
            h0 <- h0 + a
            h1 <- h1 + b
            h2 <- h2 + c
            h3 <- h3 + d
            h4 <- h4 + e
        h0, h1, h2, h3, h4

    let sha1HashBytes s =
        let (_h0, _h1, _h2, h3, h4) = sha1Hash { stream = s; pos = 0; eof = false }   // the result of the SHA algorithm is stored in registers 3 and 4
        Array.map byte [| b0 h4; b1 h4; b2 h4; b3 h4; b0 h3; b1 h3; b2 h3; b3 h3; |]

    let sha1HashInt64 s =
        let (_h0,_h1,_h2,h3,h4) = sha1Hash { stream = s; pos = 0; eof = false }   // the result of the SHA algorithm is stored in registers 3 and 4
        (int64 h3 <<< 32) ||| int64 h4

let sha1HashBytes s = SHA1.sha1HashBytes s
let sha1HashInt64 s = SHA1.sha1HashInt64 s

// --------------------------------------------------------------------
//
// --------------------------------------------------------------------

[<Struct>]
type ILVersionInfo =

    val Major: uint16
    val Minor: uint16
    val Build: uint16
    val Revision: uint16

    new (major, minor, build, revision) =
        { Major = major; Minor = minor; Build = build; Revision = revision }

type Locale = string

[<StructuralEquality; StructuralComparison>]
type PublicKey =

    | PublicKey of byte[]

    | PublicKeyToken of byte[]

    member x.IsKey=match x with PublicKey _ -> true | _ -> false

    member x.IsKeyToken=match x with PublicKeyToken _ -> true | _ -> false

    member x.Key=match x with PublicKey b -> b | _ -> invalidOp "not a key"

    member x.KeyToken=match x with PublicKeyToken b -> b | _ -> invalidOp"not a key token"

    member x.ToToken() =
        match x with
        | PublicKey bytes -> SHA1.sha1HashBytes bytes
        | PublicKeyToken token -> token

    static member KeyAsToken key = PublicKeyToken (PublicKey(key).ToToken())

[<StructuralEquality; StructuralComparison>]
type AssemblyRefData =
    { assemRefName: string
      assemRefHash: byte[] option
      assemRefPublicKeyInfo: PublicKey option
      assemRefRetargetable: bool
      assemRefVersion: ILVersionInfo option
      assemRefLocale: Locale option }

/// Global state: table of all assembly references keyed by AssemblyRefData.
let AssemblyRefUniqueStampGenerator = new UniqueStampGenerator<AssemblyRefData>()

let isMscorlib data =
    data.assemRefName = "mscorlib"

[<Sealed>]
type ILAssemblyRef(data) =
    let uniqueStamp = AssemblyRefUniqueStampGenerator.Encode data

    member x.Name=data.assemRefName

    member x.Hash=data.assemRefHash

    member x.PublicKey=data.assemRefPublicKeyInfo

    member x.Retargetable=data.assemRefRetargetable

    member x.Version=data.assemRefVersion

    member x.Locale=data.assemRefLocale

    member x.UniqueStamp=uniqueStamp

    override x.GetHashCode() = uniqueStamp

    override x.Equals yobj = ((yobj :?> ILAssemblyRef).UniqueStamp = uniqueStamp)

    interface IComparable with
        override x.CompareTo yobj = compare (yobj :?> ILAssemblyRef).UniqueStamp uniqueStamp

    static member Create (name, hash, publicKey, retargetable, version, locale) =
        ILAssemblyRef
            { assemRefName=name
              assemRefHash=hash
              assemRefPublicKeyInfo=publicKey
              assemRefRetargetable=retargetable
              assemRefVersion=version
              assemRefLocale=locale }

    static member FromAssemblyName (aname: AssemblyName) =

        let locale = None

        let publicKey =
           match aname.GetPublicKey() with
           | null | [| |] ->
               match aname.GetPublicKeyToken() with
               | null | [| |] -> None
               | bytes -> Some (PublicKeyToken bytes)
           | bytes ->
               Some (PublicKey bytes)

        let version =
           match aname.Version with
           | null -> None
           | v -> Some (ILVersionInfo (uint16 v.Major, uint16 v.Minor, uint16 v.Build, uint16 v.Revision))

        let retargetable = aname.Flags = AssemblyNameFlags.Retargetable

        ILAssemblyRef.Create (aname.Name, None, publicKey, retargetable, version, locale)

    member aref.QualifiedName =
        let b = StringBuilder(100)
        let add (s: string) = b.Append s |> ignore
        let addC (s: char) = b.Append s |> ignore
        add aref.Name
        match aref.Version with
        | None -> ()
        | Some (version) ->
            add ", Version="
            add (string (int version.Major))
            add "."
            add (string (int version.Minor))
            add "."
            add (string (int version.Build))
            add "."
            add (string (int version.Revision))
            add ", Culture="
            match aref.Locale with
            | None -> add "neutral"
            | Some b -> add b
            add ", PublicKeyToken="
            match aref.PublicKey with
            | None -> add "null"
            | Some pki ->
                  let pkt = pki.ToToken()
                  let convDigit digit =
                      let digitc =
                          if digit < 10
                          then Convert.ToInt32 '0' + digit
                          else Convert.ToInt32 'a' + (digit - 10)
                      Convert.ToChar digitc
                  for i = 0 to pkt.Length-1 do
                      let v = pkt.[i]
                      addC (convDigit (int32 v / 16))
                      addC (convDigit (int32 v % 16))
            // retargetable can be true only for system assemblies that definitely have Version
            if aref.Retargetable then
                add ", Retargetable=Yes"
        b.ToString()


[<StructuralEquality; StructuralComparison>]
type ILModuleRef =
    { name: string
      hasMetadata: bool
      hash: byte[] option }

    static member Create (name, hasMetadata, hash) =
        { name=name
          hasMetadata= hasMetadata
          hash=hash }

    member x.Name=x.name

    member x.HasMetadata=x.hasMetadata

    member x.Hash=x.hash

[<StructuralEquality; StructuralComparison>]
[<RequireQualifiedAccess>]
type ILScopeRef =
    | Local
    | Module of ILModuleRef
    | Assembly of ILAssemblyRef

    member x.IsLocalRef = match x with ILScopeRef.Local -> true | _ -> false

    member x.IsModuleRef = match x with ILScopeRef.Module _ -> true | _ -> false

    member x.IsAssemblyRef= match x with ILScopeRef.Assembly _ -> true | _ -> false

    member x.ModuleRef = match x with ILScopeRef.Module x -> x | _ -> failwith "not a module reference"

    member x.AssemblyRef = match x with ILScopeRef.Assembly x -> x | _ -> failwith "not an assembly reference"

    member x.QualifiedName =
        match x with
        | ILScopeRef.Local -> ""
        | ILScopeRef.Module mref -> "module "+mref.Name
        | ILScopeRef.Assembly aref -> aref.QualifiedName

type ILArrayBound = int32 option

type ILArrayBounds = ILArrayBound * ILArrayBound

[<StructuralEquality; StructuralComparison>]
type ILArrayShape =

    | ILArrayShape of ILArrayBounds list (* lobound/size pairs *)

    member x.Rank = (let (ILArrayShape l) = x in l.Length)

    static member SingleDimensional = ILArrayShapeStatics.SingleDimensional

    static member FromRank n = if n = 1 then ILArrayShape.SingleDimensional else ILArrayShape (List.replicate n (Some 0, None))


and ILArrayShapeStatics() =

    static let singleDimensional = ILArrayShape [(Some 0, None)]

    static member SingleDimensional = singleDimensional

/// Calling conventions. These are used in method pointer types.
[<StructuralEquality; StructuralComparison; RequireQualifiedAccess>]
type ILArgConvention =
    | Default
    | CDecl
    | StdCall
    | ThisCall
    | FastCall
    | VarArg

[<StructuralEquality; StructuralComparison; RequireQualifiedAccess>]
type ILThisConvention =
    | Instance
    | InstanceExplicit
    | Static

[<StructuralEquality; StructuralComparison>]
type ILCallingConv =

    | Callconv of ILThisConvention * ILArgConvention

    member x.ThisConv = let (Callconv (a, _b)) = x in a

    member x.BasicConv = let (Callconv (_a, b)) = x in b

    member x.IsInstance = match x.ThisConv with ILThisConvention.Instance -> true | _ -> false

    member x.IsInstanceExplicit = match x.ThisConv with ILThisConvention.InstanceExplicit -> true | _ -> false

    member x.IsStatic = match x.ThisConv with ILThisConvention.Static -> true | _ -> false

    static member Instance = ILCallingConvStatics.Instance

    static member Static = ILCallingConvStatics.Static

/// Static storage to amortize the allocation of <c>ILCallingConv.Instance</c> and <c>ILCallingConv.Static</c>.
and ILCallingConvStatics() =

    static let instanceCallConv = Callconv (ILThisConvention.Instance, ILArgConvention.Default)

    static let staticCallConv = Callconv (ILThisConvention.Static, ILArgConvention.Default)

    static member Instance = instanceCallConv

    static member Static = staticCallConv

type ILBoxity =
    | AsObject
    | AsValue

// IL type references have a pre-computed hash code to enable quick lookup tables during binary generation.
[<CustomEquality; CustomComparison; StructuredFormatDisplay("{DebugText}")>]
type ILTypeRef =
    { trefScope: ILScopeRef
      trefEnclosing: string list
      trefName: string
      hashCode : int
      mutable asBoxedType: ILType }

    static member Create (scope, enclosing, name) =
        let hashCode = hash scope * 17 ^^^ (hash enclosing * 101 <<< 1) ^^^ (hash name * 47 <<< 2)
        { trefScope=scope
          trefEnclosing=enclosing
          trefName=name
          hashCode=hashCode
          asBoxedType = Unchecked.defaultof<_> }

    member x.Scope = x.trefScope

    member x.Enclosing = x.trefEnclosing

    member x.Name = x.trefName

    member x.ApproxId = x.hashCode

    member x.AsBoxedType (tspec: ILTypeSpec) =
        if isNil tspec.tspecInst then
            let v = x.asBoxedType
            match box v with
            | null ->
               let r = ILType.Boxed tspec
               x.asBoxedType <- r
               r
            | _ -> v
        else
            ILType.Boxed tspec

    override x.GetHashCode() = x.hashCode

    override x.Equals yobj =
         let y = (yobj :?> ILTypeRef)
         (x.ApproxId = y.ApproxId) &&
         (x.Scope = y.Scope) &&
         (x.Name = y.Name) &&
         (x.Enclosing = y.Enclosing)

    interface IComparable with

        override x.CompareTo yobj =
            let y = (yobj :?> ILTypeRef)
            let c = compare x.ApproxId y.ApproxId
            if c <> 0 then c else
            let c = compare x.Scope y.Scope
            if c <> 0 then c else
            let c = compare x.Name y.Name
            if c <> 0 then c else
            compare x.Enclosing y.Enclosing

    member tref.FullName = String.concat "." (tref.Enclosing @ [tref.Name])

    member tref.BasicQualifiedName =
        (String.concat "+" (tref.Enclosing @ [ tref.Name ] )).Replace(",", @"\,")

    member tref.AddQualifiedNameExtension basic =
        let sco = tref.Scope.QualifiedName
        if sco = "" then basic else String.concat ", " [basic;sco]

    member tref.QualifiedName =
        tref.AddQualifiedNameExtension tref.BasicQualifiedName

    /// For debugging
    [<DebuggerBrowsable(DebuggerBrowsableState.Never)>]
    member x.DebugText = x.ToString()

    /// For debugging
    override x.ToString() = x.FullName


and [<StructuralEquality; StructuralComparison; StructuredFormatDisplay("{DebugText}")>]
    ILTypeSpec =
    { tspecTypeRef: ILTypeRef
      /// The type instantiation if the type is generic.
      tspecInst: ILGenericArgs }

    member x.TypeRef=x.tspecTypeRef

    member x.Scope=x.TypeRef.Scope

    member x.Enclosing=x.TypeRef.Enclosing

    member x.Name=x.TypeRef.Name

    member x.GenericArgs=x.tspecInst

    static member Create (tref, inst) = { tspecTypeRef =tref; tspecInst=inst }

    member x.BasicQualifiedName =
        let tc = x.TypeRef.BasicQualifiedName
        if isNil x.GenericArgs then
            tc
        else
            tc + "[" + String.concat "," (x.GenericArgs |> List.map (fun arg -> "[" + arg.QualifiedName + "]")) + "]"

    member x.AddQualifiedNameExtension basic =
        x.TypeRef.AddQualifiedNameExtension basic

    member x.FullName=x.TypeRef.FullName

    /// For debugging
    [<DebuggerBrowsable(DebuggerBrowsableState.Never)>]
    member x.DebugText = x.ToString()

    override x.ToString() = x.TypeRef.ToString() + if isNil x.GenericArgs then "" else "<...>"

and [<RequireQualifiedAccess; StructuralEquality; StructuralComparison; StructuredFormatDisplay("{DebugText}")>]
    ILType =
    | Void
    | Array of ILArrayShape * ILType
    | Value of ILTypeSpec
    | Boxed of ILTypeSpec
    | Ptr of ILType
    | Byref of ILType
    | FunctionPointer of ILCallingSignature
    | TypeVar of uint16
    | Modified of bool * ILTypeRef * ILType

    member x.BasicQualifiedName =
        match x with
        | ILType.TypeVar n -> "!" + string n
        | ILType.Modified (_, _ty1, ty2) -> ty2.BasicQualifiedName
        | ILType.Array (ILArrayShape s, ty) -> ty.BasicQualifiedName + "[" + String(',', s.Length-1) + "]"
        | ILType.Value tr | ILType.Boxed tr -> tr.BasicQualifiedName
        | ILType.Void -> "void"
        | ILType.Ptr _ty -> failwith "unexpected pointer type"
        | ILType.Byref _ty -> failwith "unexpected byref type"
        | ILType.FunctionPointer _mref -> failwith "unexpected function pointer type"

    member x.AddQualifiedNameExtension basic =
        match x with
        | ILType.TypeVar _n -> basic
        | ILType.Modified (_, _ty1, ty2) -> ty2.AddQualifiedNameExtension basic
        | ILType.Array (ILArrayShape(_s), ty) -> ty.AddQualifiedNameExtension basic
        | ILType.Value tr | ILType.Boxed tr -> tr.AddQualifiedNameExtension basic
        | ILType.Void -> failwith "void"
        | ILType.Ptr _ty -> failwith "unexpected pointer type"
        | ILType.Byref _ty -> failwith "unexpected byref type"
        | ILType.FunctionPointer _mref -> failwith "unexpected function pointer type"

    member x.QualifiedName =
        x.AddQualifiedNameExtension(x.BasicQualifiedName)

    member x.TypeSpec =
        match x with
        | ILType.Boxed tr | ILType.Value tr -> tr
        | _ -> invalidOp "not a nominal type"

    member x.Boxity =
        match x with
        | ILType.Boxed _ -> AsObject
        | ILType.Value _ -> AsValue
        | _ -> invalidOp "not a nominal type"

    member x.TypeRef =
        match x with
        | ILType.Boxed tspec | ILType.Value tspec -> tspec.TypeRef
        | _ -> invalidOp "not a nominal type"

    member x.IsNominal =
        match x with
        | ILType.Boxed _ | ILType.Value _ -> true
        | _ -> false

    member x.GenericArgs =
        match x with
        | ILType.Boxed tspec | ILType.Value tspec -> tspec.GenericArgs
        | _ -> []

    member x.IsTyvar =
        match x with
        | ILType.TypeVar _ -> true | _ -> false

    /// For debugging
    [<DebuggerBrowsable(DebuggerBrowsableState.Never)>]
    member x.DebugText = x.ToString()

    override x.ToString() = x.QualifiedName

and [<StructuralEquality; StructuralComparison>]
    ILCallingSignature =
    { CallingConv: ILCallingConv
      ArgTypes: ILTypes
      ReturnType: ILType }

and ILGenericArgs = list<ILType>

and ILTypes = list<ILType>

let mkILCallSig (cc, args, ret) = { ArgTypes=args; CallingConv=cc; ReturnType=ret}

let mkILBoxedType (tspec: ILTypeSpec) = tspec.TypeRef.AsBoxedType tspec

[<StructuralEquality; StructuralComparison; StructuredFormatDisplay("{DebugText}")>]
type ILMethodRef =
    { mrefParent: ILTypeRef
      mrefCallconv: ILCallingConv
      mrefGenericArity: int
      mrefName: string
      mrefArgs: ILTypes
      mrefReturn: ILType }

    member x.DeclaringTypeRef = x.mrefParent

    member x.CallingConv = x.mrefCallconv

    member x.Name = x.mrefName

    member x.GenericArity = x.mrefGenericArity

    member x.ArgCount = List.length x.mrefArgs

    member x.ArgTypes = x.mrefArgs

    member x.ReturnType = x.mrefReturn

    member x.CallingSignature = mkILCallSig (x.CallingConv, x.ArgTypes, x.ReturnType)

    static member Create (a, b, c, d, e, f) =
        { mrefParent=a; mrefCallconv=b; mrefName=c; mrefGenericArity=d; mrefArgs=e; mrefReturn=f }

    /// For debugging
    [<DebuggerBrowsable(DebuggerBrowsableState.Never)>]
    member x.DebugText = x.ToString()

    override x.ToString() = x.DeclaringTypeRef.ToString() + "::" + x.Name + "(...)"

[<StructuralEquality; StructuralComparison; StructuredFormatDisplay("{DebugText}")>]
type ILFieldRef =
    { DeclaringTypeRef: ILTypeRef
      Name: string
      Type: ILType }

    /// For debugging
    [<DebuggerBrowsable(DebuggerBrowsableState.Never)>]
    member x.DebugText = x.ToString()

    override x.ToString() = x.DeclaringTypeRef.ToString() + "::" + x.Name

[<StructuralEquality; StructuralComparison; StructuredFormatDisplay("{DebugText}")>]
type ILMethodSpec =
    { mspecMethodRef: ILMethodRef

      mspecDeclaringType: ILType

      mspecMethodInst: ILGenericArgs }

    static member Create (a, b, c) = { mspecDeclaringType=a; mspecMethodRef=b; mspecMethodInst=c }

    member x.MethodRef = x.mspecMethodRef

    member x.DeclaringType=x.mspecDeclaringType

    member x.GenericArgs=x.mspecMethodInst

    member x.Name=x.MethodRef.Name

    member x.CallingConv=x.MethodRef.CallingConv

    member x.GenericArity = x.MethodRef.GenericArity

    member x.FormalArgTypes = x.MethodRef.ArgTypes

    member x.FormalReturnType = x.MethodRef.ReturnType

    /// For debugging
    [<DebuggerBrowsable(DebuggerBrowsableState.Never)>]
    member x.DebugText = x.ToString()

    override x.ToString() = x.MethodRef.ToString() + "(...)"

[<StructuralEquality; StructuralComparison; StructuredFormatDisplay("{DebugText}")>]
type ILFieldSpec =
    { FieldRef: ILFieldRef
      DeclaringType: ILType }

    member x.FormalType = x.FieldRef.Type

    member x.Name = x.FieldRef.Name

    member x.DeclaringTypeRef = x.FieldRef.DeclaringTypeRef

    /// For debugging
    [<DebuggerBrowsable(DebuggerBrowsableState.Never)>]
    member x.DebugText = x.ToString()

    override x.ToString() = x.FieldRef.ToString()

// --------------------------------------------------------------------
// Debug info.
// --------------------------------------------------------------------

type ILGuid = byte[]

type ILPlatform =
    | X86
    | AMD64
    | IA64

type ILSourceDocument =
    { sourceLanguage: ILGuid option
      sourceVendor: ILGuid option
      sourceDocType: ILGuid option
      sourceFile: string }

    static member Create (language, vendor, docType, file) =
        { sourceLanguage=language
          sourceVendor=vendor
          sourceDocType=docType
          sourceFile=file }

    member x.Language=x.sourceLanguage

    member x.Vendor=x.sourceVendor

    member x.DocumentType=x.sourceDocType

    member x.File=x.sourceFile

[<StructuralEquality; StructuralComparison; StructuredFormatDisplay("{DebugText}")>]
type ILSourceMarker =
    { sourceDocument: ILSourceDocument
      sourceLine: int
      sourceColumn: int
      sourceEndLine: int
      sourceEndColumn: int }

    static member Create (document, line, column, endLine, endColumn) =
        { sourceDocument=document
          sourceLine=line
          sourceColumn=column
          sourceEndLine=endLine
          sourceEndColumn=endColumn }

    member x.Document=x.sourceDocument

    member x.Line=x.sourceLine

    member x.Column=x.sourceColumn

    member x.EndLine=x.sourceEndLine

    member x.EndColumn=x.sourceEndColumn

    /// For debugging
    [<DebuggerBrowsable(DebuggerBrowsableState.Never)>]
    member x.DebugText = x.ToString()

    override x.ToString() = sprintf "(%d, %d)-(%d, %d)" x.Line x.Column x.EndLine x.EndColumn

type ILAttribElem =
  | String of string option
  | Bool of bool
  | Char of char
  | SByte of int8
  | Int16 of int16
  | Int32 of int32
  | Int64 of int64
  | Byte of uint8
  | UInt16 of uint16
  | UInt32 of uint32
  | UInt64 of uint64
  | Single of single
  | Double of double
  | Null
  | Type of ILType option
  | TypeRef of ILTypeRef option
  | Array of ILType * ILAttribElem list

type ILAttributeNamedArg = (string * ILType * bool * ILAttribElem)

[<RequireQualifiedAccess; StructuralEquality; StructuralComparison; StructuredFormatDisplay("{DebugText}")>]
type ILAttribute =
    | Encoded of method: ILMethodSpec * data: byte[] * elements: ILAttribElem list
    | Decoded of method: ILMethodSpec * fixedArgs: ILAttribElem list * namedArgs: ILAttributeNamedArg list

    member x.Method =
        match x with
        | Encoded (method, _, _)
        | Decoded (method, _, _) -> method

    member x.Elements =
        match x with
        | Encoded (_, _, elements) -> elements
        | Decoded (_, fixedArgs, namedArgs) -> fixedArgs @ (namedArgs |> List.map (fun (_, _, _, e) -> e))

    member x.WithMethod (method: ILMethodSpec) =
        match x with
        | Encoded (_, data, elements) -> Encoded (method, data, elements)
        | Decoded (_, fixedArgs, namedArgs) -> Decoded (method, fixedArgs, namedArgs)

    /// For debugging
    [<DebuggerBrowsable(DebuggerBrowsableState.Never)>]
    member x.DebugText = x.ToString()

    override x.ToString() = x.Method.ToString() + "(...)"

[<NoEquality; NoComparison; Struct>]
type ILAttributes(array : ILAttribute[]) =

    member x.AsArray = array

    member x.AsList = x.AsArray |> Array.toList

[<NoEquality; NoComparison>]
type ILAttributesStored =

    /// Computed by ilread.fs based on metadata index
    | Reader of (int32 -> ILAttribute[])

    /// Already computed
    | Given of ILAttributes

    member x.GetCustomAttrs metadataIndex =
       match x with
       | Reader f -> ILAttributes (f metadataIndex)
       | Given attrs -> attrs

let emptyILCustomAttrs = ILAttributes [| |]

let mkILCustomAttrsFromArray (attrs: ILAttribute[]) = if attrs.Length = 0 then emptyILCustomAttrs else ILAttributes attrs

let mkILCustomAttrs l = match l with [] -> emptyILCustomAttrs | _ -> mkILCustomAttrsFromArray (List.toArray l)

let emptyILCustomAttrsStored = ILAttributesStored.Given emptyILCustomAttrs

let storeILCustomAttrs (attrs: ILAttributes) = if attrs.AsArray.Length = 0 then emptyILCustomAttrsStored else ILAttributesStored.Given attrs

let mkILCustomAttrsReader f = ILAttributesStored.Reader f

type ILCodeLabel = int

// --------------------------------------------------------------------
// Instruction set.
// --------------------------------------------------------------------

type ILBasicType =
  | DT_R
  | DT_I1
  | DT_U1
  | DT_I2
  | DT_U2
  | DT_I4
  | DT_U4
  | DT_I8
  | DT_U8
  | DT_R4
  | DT_R8
  | DT_I
  | DT_U
  | DT_REF

[<StructuralEquality; StructuralComparison; RequireQualifiedAccess>]
type ILToken =
  | ILType of ILType
  | ILMethod of ILMethodSpec
  | ILField of ILFieldSpec

[<StructuralEquality; StructuralComparison; RequireQualifiedAccess>]
type ILConst =
  | I4 of int32
  | I8 of int64
  | R4 of single
  | R8 of double

type ILTailcall =
  | Tailcall
  | Normalcall

type ILAlignment =
  | Aligned
  | Unaligned1
  | Unaligned2
  | Unaligned4

type ILVolatility =
  | Volatile
  | Nonvolatile

type ILReadonly =
  | ReadonlyAddress
  | NormalAddress

type ILVarArgs = ILTypes option

[<StructuralEquality; StructuralComparison>]
type ILComparisonInstr =
  | BI_beq
  | BI_bge
  | BI_bge_un
  | BI_bgt
  | BI_bgt_un
  | BI_ble
  | BI_ble_un
  | BI_blt
  | BI_blt_un
  | BI_bne_un
  | BI_brfalse
  | BI_brtrue


[<StructuralEquality; NoComparison>]
type ILInstr =
    | AI_add
    | AI_add_ovf
    | AI_add_ovf_un
    | AI_and
    | AI_div
    | AI_div_un
    | AI_ceq
    | AI_cgt
    | AI_cgt_un
    | AI_clt
    | AI_clt_un
    | AI_conv of ILBasicType
    | AI_conv_ovf of ILBasicType
    | AI_conv_ovf_un of ILBasicType
    | AI_mul
    | AI_mul_ovf
    | AI_mul_ovf_un
    | AI_rem
    | AI_rem_un
    | AI_shl
    | AI_shr
    | AI_shr_un
    | AI_sub
    | AI_sub_ovf
    | AI_sub_ovf_un
    | AI_xor
    | AI_or
    | AI_neg
    | AI_not
    | AI_ldnull
    | AI_dup
    | AI_pop
    | AI_ckfinite
    | AI_nop
    | AI_ldc of ILBasicType * ILConst
    | I_ldarg of uint16
    | I_ldarga of uint16
    | I_ldind of ILAlignment * ILVolatility * ILBasicType
    | I_ldloc of uint16
    | I_ldloca of uint16
    | I_starg of uint16
    | I_stind of ILAlignment * ILVolatility * ILBasicType
    | I_stloc of uint16

    | I_br of ILCodeLabel
    | I_jmp of ILMethodSpec
    | I_brcmp of ILComparisonInstr * ILCodeLabel
    | I_switch of ILCodeLabel list
    | I_ret

    | I_call of ILTailcall * ILMethodSpec * ILVarArgs
    | I_callvirt of ILTailcall * ILMethodSpec * ILVarArgs
    | I_callconstraint of ILTailcall * ILType * ILMethodSpec * ILVarArgs
    | I_calli of ILTailcall * ILCallingSignature * ILVarArgs
    | I_ldftn of ILMethodSpec
    | I_newobj of ILMethodSpec * ILVarArgs

    | I_throw
    | I_endfinally
    | I_endfilter
    | I_leave of ILCodeLabel
    | I_rethrow

    | I_ldsfld of ILVolatility * ILFieldSpec
    | I_ldfld of ILAlignment * ILVolatility * ILFieldSpec
    | I_ldsflda of ILFieldSpec
    | I_ldflda of ILFieldSpec
    | I_stsfld of ILVolatility * ILFieldSpec
    | I_stfld of ILAlignment * ILVolatility * ILFieldSpec
    | I_ldstr of string
    | I_isinst of ILType
    | I_castclass of ILType
    | I_ldtoken of ILToken
    | I_ldvirtftn of ILMethodSpec

    | I_cpobj of ILType
    | I_initobj of ILType
    | I_ldobj of ILAlignment * ILVolatility * ILType
    | I_stobj of ILAlignment * ILVolatility * ILType
    | I_box of ILType
    | I_unbox of ILType
    | I_unbox_any of ILType
    | I_sizeof of ILType

    | I_ldelem of ILBasicType
    | I_stelem of ILBasicType
    | I_ldelema of ILReadonly * bool * ILArrayShape * ILType
    | I_ldelem_any of ILArrayShape * ILType
    | I_stelem_any of ILArrayShape * ILType
    | I_newarr of ILArrayShape * ILType
    | I_ldlen

    | I_mkrefany of ILType
    | I_refanytype
    | I_refanyval of ILType

    | I_break
    | I_seqpoint of ILSourceMarker

    | I_arglist

    | I_localloc
    | I_cpblk of ILAlignment * ILVolatility
    | I_initblk of ILAlignment * ILVolatility

    (* FOR EXTENSIONS, e.g. MS-ILX *)
    | EI_ilzero of ILType
    | EI_ldlen_multi of int32 * int32


[<RequireQualifiedAccess>]
type ILExceptionClause =
    | Finally of (ILCodeLabel * ILCodeLabel)
    | Fault of (ILCodeLabel * ILCodeLabel)
    | FilterCatch of (ILCodeLabel * ILCodeLabel) * (ILCodeLabel * ILCodeLabel)
    | TypeCatch of ILType * (ILCodeLabel * ILCodeLabel)

[<RequireQualifiedAccess; NoEquality; NoComparison>]
type ILExceptionSpec =
    { Range: (ILCodeLabel * ILCodeLabel)
      Clause: ILExceptionClause }

/// Indicates that a particular local variable has a particular source
/// language name within a given set of ranges. This does not effect local
/// variable numbering, which is global over the whole method.
[<RequireQualifiedAccess; NoEquality; NoComparison>]
type ILLocalDebugMapping =
    { LocalIndex: int
      LocalName: string }

[<RequireQualifiedAccess; NoEquality; NoComparison>]
type ILLocalDebugInfo =
    { Range: (ILCodeLabel * ILCodeLabel)
      DebugMappings: ILLocalDebugMapping list }

[<RequireQualifiedAccess; NoEquality; NoComparison>]
type ILCode =
    { Labels: Dictionary<ILCodeLabel, int>
      Instrs: ILInstr[]
      Exceptions: ILExceptionSpec list
      Locals: ILLocalDebugInfo list }

[<RequireQualifiedAccess; NoComparison; NoEquality>]
type ILLocal =
    { Type: ILType
      IsPinned: bool
      DebugInfo: (string * int * int) option }

type ILLocals = list<ILLocal>

[<RequireQualifiedAccess; NoEquality; NoComparison>]
type ILMethodBody =
    { IsZeroInit: bool
      MaxStack: int32
      NoInlining: bool
      AggressiveInlining: bool
      Locals: ILLocals
      Code: ILCode
      SourceMarker: ILSourceMarker option }

[<RequireQualifiedAccess>]
type ILMemberAccess =
    | Assembly
    | CompilerControlled
    | FamilyAndAssembly
    | FamilyOrAssembly
    | Family
    | Private
    | Public

[<RequireQualifiedAccess; StructuralEquality; StructuralComparison>]
type ILFieldInit =
    | String of string
    | Bool of bool
    | Char of uint16
    | Int8 of int8
    | Int16 of int16
    | Int32 of int32
    | Int64 of int64
    | UInt8 of uint8
    | UInt16 of uint16
    | UInt32 of uint32
    | UInt64 of uint64
    | Single of single
    | Double of double
    | Null

// --------------------------------------------------------------------
// Native Types, for marshalling to the native C interface.
// These are taken directly from the ILASM syntax, and don't really
// correspond yet to the ECMA Spec (Partition II, 7.4).
// --------------------------------------------------------------------

[<RequireQualifiedAccess; StructuralEquality; StructuralComparison>]
type ILNativeType =
    | Empty
    | Custom of ILGuid * string * string * byte[] (* guid, nativeTypeName, custMarshallerName, cookieString *)
    | FixedSysString of int32
    | FixedArray of int32
    | Currency
    | LPSTR
    | LPWSTR
    | LPTSTR
    | LPUTF8STR
    | ByValStr
    | TBSTR
    | LPSTRUCT
    | Struct
    | Void
    | Bool
    | Int8
    | Int16
    | Int32
    | Int64
    | Single
    | Double
    | Byte
    | UInt16
    | UInt32
    | UInt64
    | Array of ILNativeType option * (int32 * int32 option) option (* optional idx of parameter giving size plus optional additive i.e. num elems *)
    | Int
    | UInt
    | Method
    | AsAny
    | BSTR
    | IUnknown
    | IDispatch
    | Interface
    | Error
    | SafeArray of ILNativeVariant * string option
    | ANSIBSTR
    | VariantBool

and
  [<RequireQualifiedAccess; StructuralEquality; StructuralComparison>]
  ILNativeVariant =
    | Empty
    | Null
    | Variant
    | Currency
    | Decimal
    | Date
    | BSTR
    | LPSTR
    | LPWSTR
    | IUnknown
    | IDispatch
    | SafeArray
    | Error
    | HRESULT
    | CArray
    | UserDefined
    | Record
    | FileTime
    | Blob
    | Stream
    | Storage
    | StreamedObject
    | StoredObject
    | BlobObject
    | CF
    | CLSID
    | Void
    | Bool
    | Int8
    | Int16
    | Int32
    | Int64
    | Single
    | Double
    | UInt8
    | UInt16
    | UInt32
    | UInt64
    | PTR
    | Array of ILNativeVariant
    | Vector of ILNativeVariant
    | Byref of ILNativeVariant
    | Int
    | UInt

[<RequireQualifiedAccess; StructuralEquality; StructuralComparison>]
type ILSecurityAction =
    | Request
    | Demand
    | Assert
    | Deny
    | PermitOnly
    | LinkCheck
    | InheritCheck
    | ReqMin
    | ReqOpt
    | ReqRefuse
    | PreJitGrant
    | PreJitDeny
    | NonCasDemand
    | NonCasLinkDemand
    | NonCasInheritance
    | LinkDemandChoice
    | InheritanceDemandChoice
    | DemandChoice

[<RequireQualifiedAccess; StructuralEquality; StructuralComparison>]
type ILSecurityDecl =
    | ILSecurityDecl of ILSecurityAction * byte[]

[<NoEquality; NoComparison; Struct>]
type ILSecurityDecls (array : ILSecurityDecl[]) =
    member x.AsArray = array
    member x.AsList = x.AsArray |> Array.toList

[<NoEquality; NoComparison>]
type ILSecurityDeclsStored =

    /// Computed by ilread.fs based on metadata index
    | Reader of (int32 -> ILSecurityDecl[])

    /// Already computed
    | Given of ILSecurityDecls

    member x.GetSecurityDecls metadataIndex =
       match x with
       | Reader f -> ILSecurityDecls(f metadataIndex)
       | Given attrs -> attrs

let emptyILSecurityDecls = ILSecurityDecls [| |]

let emptyILSecurityDeclsStored = ILSecurityDeclsStored.Given emptyILSecurityDecls

let mkILSecurityDecls l = match l with [] -> emptyILSecurityDecls | _ -> ILSecurityDecls (Array.ofList l)

let storeILSecurityDecls (x: ILSecurityDecls) = if x.AsArray.Length = 0 then emptyILSecurityDeclsStored else ILSecurityDeclsStored.Given x

let mkILSecurityDeclsReader f = ILSecurityDeclsStored.Reader f

[<RequireQualifiedAccess>]
type PInvokeCharBestFit =
    | UseAssembly
    | Enabled
    | Disabled

[<RequireQualifiedAccess>]
type PInvokeThrowOnUnmappableChar =
    | UseAssembly
    | Enabled
    | Disabled

[<RequireQualifiedAccess>]
type PInvokeCallingConvention =
    | None
    | Cdecl
    | Stdcall
    | Thiscall
    | Fastcall
    | WinApi

[<RequireQualifiedAccess>]
type PInvokeCharEncoding =
    | None
    | Ansi
    | Unicode
    | Auto

[<RequireQualifiedAccess; NoComparison; NoEquality>]
type PInvokeMethod =
    { Where: ILModuleRef
      Name: string
      CallingConv: PInvokeCallingConvention
      CharEncoding: PInvokeCharEncoding
      NoMangle: bool
      LastError: bool
      ThrowOnUnmappableChar: PInvokeThrowOnUnmappableChar
      CharBestFit: PInvokeCharBestFit }

[<RequireQualifiedAccess; NoEquality; NoComparison>]
type ILParameter =
    { Name: string option
      Type: ILType
      Default: ILFieldInit option
      Marshal: ILNativeType option
      IsIn: bool
      IsOut: bool
      IsOptional: bool
      CustomAttrsStored: ILAttributesStored
      MetadataIndex: int32 }

    member x.CustomAttrs = x.CustomAttrsStored.GetCustomAttrs x.MetadataIndex

type ILParameters = list<ILParameter>

[<RequireQualifiedAccess; NoEquality; NoComparison>]
type ILReturn =
    { Marshal: ILNativeType option
      Type: ILType
      CustomAttrsStored: ILAttributesStored
      MetadataIndex: int32 }

    member x.CustomAttrs = x.CustomAttrsStored.GetCustomAttrs x.MetadataIndex

    member x.WithCustomAttrs(customAttrs) = { x with CustomAttrsStored = storeILCustomAttrs customAttrs }

type ILOverridesSpec =
    | OverridesSpec of ILMethodRef * ILType

    member x.MethodRef = let (OverridesSpec (mr, _ty)) = x in mr

    member x.DeclaringType = let (OverridesSpec (_mr, ty)) = x in ty

type ILMethodVirtualInfo =
    { IsFinal: bool
      IsNewSlot: bool
      IsCheckAccessOnOverride: bool
      IsAbstract: bool }

type MethodKind =
    | Static
    | Cctor
    | Ctor
    | NonVirtual
    | Virtual of ILMethodVirtualInfo

[<RequireQualifiedAccess>]
type MethodBody =
    | IL of ILMethodBody
    | PInvoke of PInvokeMethod (* platform invoke to native *)
    | Abstract
    | Native
    | NotAvailable

type ILLazyMethodBody =
    | ILLazyMethodBody of Lazy<MethodBody >

    member x.Contents = let (ILLazyMethodBody mb) = x in mb.Force()

[<RequireQualifiedAccess>]
type MethodCodeKind =
    | IL
    | Native
    | Runtime

let mkMethBodyAux mb = ILLazyMethodBody (notlazy mb)

let mkMethBodyLazyAux mb = ILLazyMethodBody mb

let typesOfILParams (ps: ILParameters) : ILTypes = ps |> List.map (fun p -> p.Type)

[<StructuralEquality; StructuralComparison>]
type ILGenericVariance =
    | NonVariant
    | CoVariant
    | ContraVariant

[<NoEquality; NoComparison; StructuredFormatDisplay("{DebugText}")>]
type ILGenericParameterDef =
    { Name: string
      Constraints: ILTypes
      Variance: ILGenericVariance
      HasReferenceTypeConstraint: bool
      HasNotNullableValueTypeConstraint: bool
      HasDefaultConstructorConstraint: bool
      CustomAttrsStored : ILAttributesStored
      MetadataIndex: int32 }

    member x.CustomAttrs = x.CustomAttrsStored.GetCustomAttrs x.MetadataIndex

    /// For debugging
    [<DebuggerBrowsable(DebuggerBrowsableState.Never)>]
    member x.DebugText = x.ToString()

    override x.ToString() = x.Name

type ILGenericParameterDefs = ILGenericParameterDef list

let memberAccessOfFlags flags =
    let f = (flags &&& 0x00000007)
    if f = 0x00000001 then ILMemberAccess.Private
    elif f = 0x00000006 then ILMemberAccess.Public
    elif f = 0x00000004 then ILMemberAccess.Family
    elif f = 0x00000002 then ILMemberAccess.FamilyAndAssembly
    elif f = 0x00000005 then ILMemberAccess.FamilyOrAssembly
    elif f = 0x00000003 then ILMemberAccess.Assembly
    else ILMemberAccess.CompilerControlled

let convertMemberAccess (ilMemberAccess: ILMemberAccess) =
    match ilMemberAccess with
    | ILMemberAccess.Public -> MethodAttributes.Public
    | ILMemberAccess.Private -> MethodAttributes.Private
    | ILMemberAccess.Assembly -> MethodAttributes.Assembly
    | ILMemberAccess.FamilyAndAssembly -> MethodAttributes.FamANDAssem
    | ILMemberAccess.CompilerControlled -> MethodAttributes.PrivateScope
    | ILMemberAccess.FamilyOrAssembly -> MethodAttributes.FamORAssem
    | ILMemberAccess.Family -> MethodAttributes.Family

let inline conditionalAdd condition flagToAdd source = if condition then source ||| flagToAdd else source &&& ~~~flagToAdd

let NoMetadataIdx = -1

[<NoComparison; NoEquality>]
type ILMethodDef (name: string, attributes: MethodAttributes, implAttributes: MethodImplAttributes, callingConv: ILCallingConv,
                  parameters: ILParameters, ret: ILReturn, body: ILLazyMethodBody, isEntryPoint: bool, genericParams: ILGenericParameterDefs,
                  securityDeclsStored: ILSecurityDeclsStored, customAttrsStored: ILAttributesStored, metadataIndex: int32) =

    new (name, attributes, implAttributes, callingConv, parameters, ret, body, isEntryPoint, genericParams, securityDecls, customAttrs) =
       ILMethodDef (name, attributes, implAttributes, callingConv, parameters, ret, body, isEntryPoint, genericParams,
                    storeILSecurityDecls securityDecls, storeILCustomAttrs customAttrs, NoMetadataIdx)

    // The captured data - remember the object will be as large as the data captured by these members
    member __.Name = name

    member __.Attributes = attributes

    member __.ImplAttributes = implAttributes

    member __.CallingConv = callingConv

    member __.Parameters = parameters

    member __.Return = ret

    member __.Body = body

    member __.SecurityDeclsStored = securityDeclsStored

    member __.IsEntryPoint = isEntryPoint

    member __.GenericParams = genericParams

    member __.CustomAttrsStored = customAttrsStored

    member __.MetadataIndex = metadataIndex

    member x.With (?name: string, ?attributes: MethodAttributes, ?implAttributes: MethodImplAttributes,
                   ?callingConv: ILCallingConv, ?parameters: ILParameters, ?ret: ILReturn,
                   ?body: ILLazyMethodBody, ?securityDecls: ILSecurityDecls, ?isEntryPoint: bool,
                   ?genericParams: ILGenericParameterDefs, ?customAttrs: ILAttributes) =

        ILMethodDef (name = defaultArg name x.Name,
                     attributes = defaultArg attributes x.Attributes,
                     implAttributes = defaultArg implAttributes x.ImplAttributes,
                     callingConv = defaultArg callingConv x.CallingConv,
                     parameters = defaultArg parameters x.Parameters,
                     ret = defaultArg ret x.Return,
                     body = defaultArg body x.Body,
                     securityDecls = (match securityDecls with None -> x.SecurityDecls | Some attrs -> attrs),
                     isEntryPoint = defaultArg isEntryPoint x.IsEntryPoint,
                     genericParams = defaultArg genericParams x.GenericParams,
                     customAttrs=(match customAttrs with None -> x.CustomAttrs | Some attrs -> attrs))

    member x.CustomAttrs = x.CustomAttrsStored.GetCustomAttrs metadataIndex

    member x.SecurityDecls = x.SecurityDeclsStored.GetSecurityDecls x.MetadataIndex

    member x.ParameterTypes = typesOfILParams x.Parameters

    member md.Code =
          match md.Body.Contents with
          | MethodBody.IL il-> Some il.Code
          | _ -> None

    member x.IsIL = match x.Body.Contents with | MethodBody.IL _ -> true | _ -> false

    member x.Locals = match x.Body.Contents with | MethodBody.IL il -> il.Locals | _ -> []

    member x.MethodBody = match x.Body.Contents with MethodBody.IL il -> il | _ -> failwith "not IL"

    member x.SourceMarker = x.MethodBody.SourceMarker

    member x.MaxStack = x.MethodBody.MaxStack

    member x.IsZeroInit = x.MethodBody.IsZeroInit

    member md.CallingSignature = mkILCallSig (md.CallingConv, md.ParameterTypes, md.Return.Type)

    member x.IsClassInitializer = x.Name = ".cctor"
    member x.IsConstructor = x.Name = ".ctor"

    member x.Access = memberAccessOfFlags (int x.Attributes)
    member x.IsStatic = x.Attributes &&& MethodAttributes.Static <> enum 0
    member x.IsNonVirtualInstance = not x.IsStatic && not x.IsVirtual
    member x.IsVirtual = x.Attributes &&& MethodAttributes.Virtual <> enum 0
    member x.IsFinal = x.Attributes &&& MethodAttributes.Final <> enum 0
    member x.IsNewSlot = x.Attributes &&& MethodAttributes.NewSlot <> enum 0
    member x.IsCheckAccessOnOverride= x.Attributes &&& MethodAttributes.CheckAccessOnOverride <> enum 0
    member x.IsAbstract = x.Attributes &&& MethodAttributes.Abstract <> enum 0
    member x.IsHideBySig = x.Attributes &&& MethodAttributes.HideBySig <> enum 0
    member x.IsSpecialName = x.Attributes &&& MethodAttributes.SpecialName <> enum 0
    member x.IsUnmanagedExport = x.Attributes &&& MethodAttributes.UnmanagedExport <> enum 0
    member x.IsReqSecObj = x.Attributes &&& MethodAttributes.RequireSecObject <> enum 0
    member x.HasSecurity = x.Attributes &&& MethodAttributes.HasSecurity <> enum 0

    member x.IsManaged = x.ImplAttributes &&& MethodImplAttributes.Managed <> enum 0
    member x.IsForwardRef = x.ImplAttributes &&& MethodImplAttributes.ForwardRef <> enum 0
    member x.IsInternalCall = x.ImplAttributes &&& MethodImplAttributes.InternalCall <> enum 0
    member x.IsPreserveSig = x.ImplAttributes &&& MethodImplAttributes.PreserveSig <> enum 0
    member x.IsSynchronized = x.ImplAttributes &&& MethodImplAttributes.Synchronized <> enum 0
    member x.IsNoInline = x.ImplAttributes &&& MethodImplAttributes.NoInlining <> enum 0
    member x.IsAggressiveInline= x.ImplAttributes &&& MethodImplAttributes.AggressiveInlining <> enum 0
    member x.IsMustRun = x.ImplAttributes &&& MethodImplAttributes.NoOptimization <> enum 0

    member x.WithSpecialName = x.With(attributes = (x.Attributes ||| MethodAttributes.SpecialName))
    member x.WithHideBySig() =
        x.With(attributes = (
                if x.IsVirtual then x.Attributes &&& ~~~MethodAttributes.CheckAccessOnOverride ||| MethodAttributes.HideBySig
                else failwith "WithHideBySig"))
    member x.WithHideBySig(condition) = x.With(attributes = (x.Attributes |> conditionalAdd condition MethodAttributes.HideBySig))
    member x.WithFinal(condition) = x.With(attributes = (x.Attributes |> conditionalAdd condition MethodAttributes.Final))
    member x.WithAbstract(condition) = x.With(attributes = (x.Attributes |> conditionalAdd condition MethodAttributes.Abstract))
    member x.WithAccess(access) = x.With(attributes = (x.Attributes &&& ~~~MethodAttributes.MemberAccessMask ||| convertMemberAccess access))
    member x.WithNewSlot = x.With(attributes = (x.Attributes ||| MethodAttributes.NewSlot))
    member x.WithSecurity(condition) = x.With(attributes = (x.Attributes |> conditionalAdd condition MethodAttributes.HasSecurity))
    member x.WithPInvoke(condition) = x.With(attributes = (x.Attributes |> conditionalAdd condition MethodAttributes.PinvokeImpl))
    member x.WithPreserveSig(condition) = x.With(implAttributes = (x.ImplAttributes |> conditionalAdd condition MethodImplAttributes.PreserveSig))
    member x.WithSynchronized(condition) = x.With(implAttributes = (x.ImplAttributes |> conditionalAdd condition MethodImplAttributes.Synchronized))
    member x.WithNoInlining(condition) = x.With(implAttributes = (x.ImplAttributes |> conditionalAdd condition MethodImplAttributes.NoInlining))
    member x.WithAggressiveInlining(condition) = x.With(implAttributes = (x.ImplAttributes |> conditionalAdd condition MethodImplAttributes.AggressiveInlining))
    member x.WithRuntime(condition) = x.With(implAttributes = (x.ImplAttributes |> conditionalAdd condition MethodImplAttributes.Runtime))

/// Index table by name and arity.
type MethodDefMap = Map<string, ILMethodDef list>

[<Sealed>]
type ILMethodDefs(f : (unit -> ILMethodDef[])) =

    let mutable array = InlineDelayInit<_>(f)
    let mutable dict = InlineDelayInit<_>(fun () ->
            let arr = array.Value
            let t = Dictionary<_, _>()
            for i = arr.Length - 1 downto 0 do
                let y = arr.[i]
                let key = y.Name
                match t.TryGetValue key with
                | true, m -> t.[key] <- y :: m
                | _ -> t.[key] <- [y]
            t)

    interface IEnumerable with
        member x.GetEnumerator() = ((x :> IEnumerable<ILMethodDef>).GetEnumerator() :> IEnumerator)

    interface IEnumerable<ILMethodDef> with
        member x.GetEnumerator() = (array.Value :> IEnumerable<ILMethodDef>).GetEnumerator()

    member x.AsArray = array.Value

    member x.AsList = array.Value|> Array.toList

    member x.FindByName nm =
        match dict.Value.TryGetValue nm with
        | true, m -> m
        | _ -> []

    member x.FindByNameAndArity (nm, arity) = x.FindByName nm |> List.filter (fun x -> List.length x.Parameters = arity)

[<NoComparison; NoEquality; StructuredFormatDisplay("{DebugText}")>]
type ILEventDef(eventType: ILType option, name: string, attributes: EventAttributes,
                addMethod: ILMethodRef, removeMethod: ILMethodRef, fireMethod: ILMethodRef option,
                otherMethods: ILMethodRef list, customAttrsStored: ILAttributesStored, metadataIndex: int32) =

    new (eventType, name, attributes, addMethod, removeMethod, fireMethod, otherMethods, customAttrs) =
        ILEventDef(eventType, name, attributes, addMethod, removeMethod, fireMethod, otherMethods, storeILCustomAttrs customAttrs, NoMetadataIdx)

    member __.EventType = eventType
    member __.Name = name
    member __.Attributes = attributes
    member __.AddMethod = addMethod
    member __.RemoveMethod = removeMethod
    member __.FireMethod = fireMethod
    member __.OtherMethods = otherMethods
    member __.CustomAttrsStored = customAttrsStored
    member __.MetadataIndex = metadataIndex
    member x.CustomAttrs = customAttrsStored.GetCustomAttrs x.MetadataIndex

    member x.With(?eventType, ?name, ?attributes, ?addMethod, ?removeMethod, ?fireMethod, ?otherMethods, ?customAttrs) =
        ILEventDef(eventType= defaultArg eventType x.EventType,
                   name= defaultArg name x.Name,
                   attributes= defaultArg attributes x.Attributes,
                   addMethod=defaultArg addMethod x.AddMethod,
                   removeMethod=defaultArg removeMethod x.RemoveMethod,
                   fireMethod= defaultArg fireMethod x.FireMethod,
                   otherMethods= defaultArg otherMethods x.OtherMethods,
                   customAttrs=(match customAttrs with None -> x.CustomAttrs | Some attrs -> attrs))

    member x.IsSpecialName = (x.Attributes &&& EventAttributes.SpecialName) <> enum<_>(0)
    member x.IsRTSpecialName = (x.Attributes &&& EventAttributes.RTSpecialName) <> enum<_>(0)

    /// For debugging
    [<DebuggerBrowsable(DebuggerBrowsableState.Never)>]
    member x.DebugText = x.ToString()

    override x.ToString() = "event " + x.Name

[<NoEquality; NoComparison>]
type ILEventDefs =
    | ILEvents of LazyOrderedMultiMap<string, ILEventDef>

    member x.AsList = let (ILEvents t) = x in t.Entries()

    member x.LookupByName s = let (ILEvents t) = x in t.[s]

[<NoComparison; NoEquality; StructuredFormatDisplay("{DebugText}")>]
type ILPropertyDef(name: string, attributes: PropertyAttributes, setMethod: ILMethodRef option,
                   getMethod: ILMethodRef option, callingConv: ILThisConvention, propertyType: ILType,
                   init: ILFieldInit option, args: ILTypes, customAttrsStored: ILAttributesStored, metadataIndex: int32) =

    new (name, attributes, setMethod, getMethod, callingConv, propertyType, init, args, customAttrs) =
       ILPropertyDef(name, attributes, setMethod, getMethod, callingConv, propertyType, init, args, storeILCustomAttrs customAttrs, NoMetadataIdx)

    member x.Name = name
    member x.Attributes = attributes
    member x.GetMethod = getMethod
    member x.SetMethod = setMethod
    member x.CallingConv = callingConv
    member x.PropertyType = propertyType
    member x.Init = init
    member x.Args = args
    member x.CustomAttrsStored = customAttrsStored
    member x.CustomAttrs = customAttrsStored.GetCustomAttrs x.MetadataIndex
    member x.MetadataIndex = metadataIndex

    member x.With(?name, ?attributes, ?setMethod, ?getMethod, ?callingConv, ?propertyType, ?init, ?args, ?customAttrs) =
      ILPropertyDef(name=defaultArg name x.Name,
                    attributes=defaultArg attributes x.Attributes,
                    setMethod=defaultArg setMethod x.SetMethod,
                    getMethod=defaultArg getMethod x.GetMethod,
                    callingConv=defaultArg callingConv x.CallingConv,
                    propertyType=defaultArg propertyType x.PropertyType,
                    init=defaultArg init x.Init,
                    args=defaultArg args x.Args,
                    customAttrs=(match customAttrs with None -> x.CustomAttrs | Some attrs -> attrs))


    member x.IsSpecialName = (x.Attributes &&& PropertyAttributes.SpecialName) <> enum<_>(0)
    member x.IsRTSpecialName = (x.Attributes &&& PropertyAttributes.RTSpecialName) <> enum<_>(0)

    /// For debugging
    [<DebuggerBrowsable(DebuggerBrowsableState.Never)>]
    member x.DebugText = x.ToString()

    override x.ToString() = "property " + x.Name

// Index table by name.
[<NoEquality; NoComparison>]
type ILPropertyDefs =
    | ILProperties of LazyOrderedMultiMap<string, ILPropertyDef>
    member x.AsList = let (ILProperties t) = x in t.Entries()
    member x.LookupByName s = let (ILProperties t) = x in t.[s]

let convertFieldAccess (ilMemberAccess: ILMemberAccess) =
    match ilMemberAccess with
    | ILMemberAccess.Assembly -> FieldAttributes.Assembly
    | ILMemberAccess.CompilerControlled -> enum<FieldAttributes>(0)
    | ILMemberAccess.FamilyAndAssembly -> FieldAttributes.FamANDAssem
    | ILMemberAccess.FamilyOrAssembly -> FieldAttributes.FamORAssem
    | ILMemberAccess.Family -> FieldAttributes.Family
    | ILMemberAccess.Private -> FieldAttributes.Private
    | ILMemberAccess.Public -> FieldAttributes.Public

[<NoComparison; NoEquality>]
type ILFieldDef(name: string, fieldType: ILType, attributes: FieldAttributes, data: byte[] option,
                literalValue: ILFieldInit option, offset: int32 option, marshal: ILNativeType option,
                customAttrsStored: ILAttributesStored, metadataIndex: int32) =

    new (name, fieldType, attributes, data, literalValue, offset, marshal, customAttrs) =
        ILFieldDef(name, fieldType, attributes, data, literalValue, offset, marshal, storeILCustomAttrs customAttrs, NoMetadataIdx)
    member __.Name=name
    member __.FieldType = fieldType
    member __.Attributes=attributes
    member __.Data=data
    member __.LiteralValue=literalValue
    member __.Offset=offset
    member __.Marshal=marshal
    member x.CustomAttrsStored = customAttrsStored
    member x.CustomAttrs = customAttrsStored.GetCustomAttrs x.MetadataIndex
    member x.MetadataIndex = metadataIndex

    member x.With(?name: string, ?fieldType: ILType, ?attributes: FieldAttributes, ?data: byte[] option, ?literalValue: ILFieldInit option, ?offset: int32 option, ?marshal: ILNativeType option, ?customAttrs: ILAttributes) =
        ILFieldDef(name=defaultArg name x.Name,
                   fieldType=defaultArg fieldType x.FieldType,
                   attributes=defaultArg attributes x.Attributes,
                   data=defaultArg data x.Data,
                   literalValue=defaultArg literalValue x.LiteralValue,
                   offset=defaultArg offset x.Offset,
                   marshal=defaultArg marshal x.Marshal,
                   customAttrs=defaultArg customAttrs x.CustomAttrs)
    member x.IsStatic = x.Attributes &&& FieldAttributes.Static <> enum 0
    member x.IsSpecialName = x.Attributes &&& FieldAttributes.SpecialName <> enum 0
    member x.IsLiteral = x.Attributes &&& FieldAttributes.Literal <> enum 0
    member x.NotSerialized = x.Attributes &&& FieldAttributes.NotSerialized <> enum 0
    member x.IsInitOnly = x.Attributes &&& FieldAttributes.InitOnly <> enum 0
    member x.Access = memberAccessOfFlags (int x.Attributes)
    member x.WithAccess(access) = x.With(attributes = (x.Attributes &&& ~~~FieldAttributes.FieldAccessMask ||| convertFieldAccess access))
    member x.WithInitOnly(condition) = x.With(attributes = (x.Attributes |> conditionalAdd condition FieldAttributes.InitOnly))
    member x.WithStatic(condition) = x.With(attributes = (x.Attributes |> conditionalAdd condition FieldAttributes.Static))
    member x.WithSpecialName(condition) = x.With(attributes = (x.Attributes |> conditionalAdd condition (FieldAttributes.SpecialName ||| FieldAttributes.RTSpecialName)))
    member x.WithNotSerialized(condition) = x.With(attributes = (x.Attributes |> conditionalAdd condition FieldAttributes.NotSerialized))
    member x.WithLiteralDefaultValue(literal) = x.With(literalValue = literal, attributes = (x.Attributes |> conditionalAdd literal.IsSome (FieldAttributes.Literal ||| FieldAttributes.HasDefault)))
    member x.WithFieldMarshal(marshal) = x.With(marshal = marshal, attributes = (x.Attributes |> conditionalAdd marshal.IsSome FieldAttributes.HasFieldMarshal))

// Index table by name. Keep a canonical list to make sure field order is not disturbed for binary manipulation.
type ILFieldDefs =
    | ILFields of LazyOrderedMultiMap<string, ILFieldDef>

    member x.AsList = let (ILFields t) = x in t.Entries()

    member x.LookupByName s = let (ILFields t) = x in t.[s]

type ILMethodImplDef =
    { Overrides: ILOverridesSpec
      OverrideBy: ILMethodSpec }

// Index table by name and arity.
type ILMethodImplDefs =
    | ILMethodImpls of Lazy<MethodImplsMap>

    member x.AsList = let (ILMethodImpls ltab) = x in Map.foldBack (fun _x y r -> y@r) (ltab.Force()) []

and MethodImplsMap = Map<string * int, ILMethodImplDef list>

[<RequireQualifiedAccess>]
type ILTypeDefLayout =
    | Auto
    | Sequential of ILTypeDefLayoutInfo
    | Explicit of ILTypeDefLayoutInfo (* REVIEW: add field info here *)

and ILTypeDefLayoutInfo =
    { Size: int32 option
      Pack: uint16 option }

[<RequireQualifiedAccess>]
type ILTypeInit =
    | BeforeField
    | OnAny

[<RequireQualifiedAccess>]
type ILDefaultPInvokeEncoding =
    | Ansi
    | Auto
    | Unicode

type ILTypeDefAccess =
    | Public
    | Private
    | Nested of ILMemberAccess

let typeAccessOfFlags flags =
    let f = (flags &&& 0x00000007)
    if f = 0x00000001 then ILTypeDefAccess.Public
    elif f = 0x00000002 then ILTypeDefAccess.Nested ILMemberAccess.Public
    elif f = 0x00000003 then ILTypeDefAccess.Nested ILMemberAccess.Private
    elif f = 0x00000004 then ILTypeDefAccess.Nested ILMemberAccess.Family
    elif f = 0x00000006 then ILTypeDefAccess.Nested ILMemberAccess.FamilyAndAssembly
    elif f = 0x00000007 then ILTypeDefAccess.Nested ILMemberAccess.FamilyOrAssembly
    elif f = 0x00000005 then ILTypeDefAccess.Nested ILMemberAccess.Assembly
    else ILTypeDefAccess.Private

let typeEncodingOfFlags flags =
    let f = (flags &&& 0x00030000)
    if f = 0x00020000 then ILDefaultPInvokeEncoding.Auto
    elif f = 0x00010000 then ILDefaultPInvokeEncoding.Unicode
    else ILDefaultPInvokeEncoding.Ansi

[<RequireQualifiedAccess>]
type ILTypeDefKind =
    | Class
    | ValueType
    | Interface
    | Enum
    | Delegate

let typeKindOfFlags nm _mdefs _fdefs (super: ILType option) flags =
    if (flags &&& 0x00000020) <> 0x0 then ILTypeDefKind.Interface
    else
         let isEnum, isDelegate, isMulticastDelegate, isValueType =
            match super with
            | None -> false, false, false, false
            | Some ty ->
                ty.TypeSpec.Name = "System.Enum",
                ty.TypeSpec.Name = "System.Delegate",
                ty.TypeSpec.Name = "System.MulticastDelegate",
                ty.TypeSpec.Name = "System.ValueType" && nm <> "System.Enum"
         let selfIsMulticastDelegate = nm = "System.MulticastDelegate"
         if isEnum then ILTypeDefKind.Enum
         elif (isDelegate && not selfIsMulticastDelegate) || isMulticastDelegate then ILTypeDefKind.Delegate
         elif isValueType then ILTypeDefKind.ValueType
         else ILTypeDefKind.Class

let convertTypeAccessFlags access =
    match access with
    | ILTypeDefAccess.Public -> TypeAttributes.Public
    | ILTypeDefAccess.Private -> TypeAttributes.NotPublic
    | ILTypeDefAccess.Nested ILMemberAccess.Public -> TypeAttributes.NestedPublic
    | ILTypeDefAccess.Nested ILMemberAccess.Private -> TypeAttributes.NestedPrivate
    | ILTypeDefAccess.Nested ILMemberAccess.Family -> TypeAttributes.NestedFamily
    | ILTypeDefAccess.Nested ILMemberAccess.CompilerControlled -> TypeAttributes.NestedPrivate
    | ILTypeDefAccess.Nested ILMemberAccess.FamilyAndAssembly -> TypeAttributes.NestedFamANDAssem
    | ILTypeDefAccess.Nested ILMemberAccess.FamilyOrAssembly -> TypeAttributes.NestedFamORAssem
    | ILTypeDefAccess.Nested ILMemberAccess.Assembly -> TypeAttributes.NestedAssembly

let convertTypeKind kind =
    match kind with
    | ILTypeDefKind.Class -> TypeAttributes.Class
    | ILTypeDefKind.ValueType -> TypeAttributes.Class
    | ILTypeDefKind.Interface -> TypeAttributes.Abstract ||| TypeAttributes.Interface
    | ILTypeDefKind.Enum -> TypeAttributes.Class
    | ILTypeDefKind.Delegate -> TypeAttributes.Class

let convertLayout layout =
    match layout with
    | ILTypeDefLayout.Auto -> TypeAttributes.AutoLayout
    | ILTypeDefLayout.Sequential _ -> TypeAttributes.SequentialLayout
    | ILTypeDefLayout.Explicit _ -> TypeAttributes.ExplicitLayout

let convertEncoding encoding =
    match encoding with
    | ILDefaultPInvokeEncoding.Auto -> TypeAttributes.AutoClass
    | ILDefaultPInvokeEncoding.Ansi -> TypeAttributes.AnsiClass
    | ILDefaultPInvokeEncoding.Unicode -> TypeAttributes.UnicodeClass

let convertToNestedTypeAccess (ilMemberAccess: ILMemberAccess) =
    match ilMemberAccess with
    | ILMemberAccess.Assembly -> TypeAttributes.NestedAssembly
    | ILMemberAccess.CompilerControlled -> failwith "Method access compiler controlled."
    | ILMemberAccess.FamilyAndAssembly -> TypeAttributes.NestedFamANDAssem
    | ILMemberAccess.FamilyOrAssembly -> TypeAttributes.NestedFamORAssem
    | ILMemberAccess.Family -> TypeAttributes.NestedFamily
    | ILMemberAccess.Private -> TypeAttributes.NestedPrivate
    | ILMemberAccess.Public -> TypeAttributes.NestedPublic

let convertInitSemantics (init: ILTypeInit) =
    match init with
    | ILTypeInit.BeforeField -> TypeAttributes.BeforeFieldInit
    | ILTypeInit.OnAny -> enum 0

[<NoComparison; NoEquality>]
type ILTypeDef(name: string, attributes: TypeAttributes, layout: ILTypeDefLayout, implements: ILTypes, genericParams: ILGenericParameterDefs,
               extends: ILType option, methods: ILMethodDefs, nestedTypes: ILTypeDefs, fields: ILFieldDefs, methodImpls: ILMethodImplDefs,
               events: ILEventDefs, properties: ILPropertyDefs, securityDeclsStored: ILSecurityDeclsStored, customAttrsStored: ILAttributesStored, metadataIndex: int32) =

    let mutable customAttrsStored = customAttrsStored

    new (name, attributes, layout, implements, genericParams, extends, methods, nestedTypes, fields, methodImpls, events, properties, securityDecls, customAttrs) =
       ILTypeDef (name, attributes, layout, implements, genericParams, extends, methods, nestedTypes, fields, methodImpls, events, properties, storeILSecurityDecls securityDecls, storeILCustomAttrs customAttrs, NoMetadataIdx)

    member __.Name = name
    member __.Attributes = attributes
    member __.GenericParams = genericParams
    member __.Layout = layout
    member __.NestedTypes = nestedTypes
    member __.Implements = implements
    member __.Extends = extends
    member __.Methods = methods
    member __.SecurityDeclsStored = securityDeclsStored
    member __.Fields = fields
    member __.MethodImpls = methodImpls
    member __.Events = events
    member __.Properties = properties
    member __.CustomAttrsStored = customAttrsStored
    member __.MetadataIndex = metadataIndex

    member x.With(?name, ?attributes, ?layout, ?implements, ?genericParams, ?extends, ?methods, ?nestedTypes, ?fields, ?methodImpls, ?events, ?properties, ?customAttrs, ?securityDecls) =
        ILTypeDef(name=defaultArg name x.Name,
                  attributes=defaultArg attributes x.Attributes,
                  layout=defaultArg layout x.Layout,
                  genericParams = defaultArg genericParams x.GenericParams,
                  nestedTypes = defaultArg nestedTypes x.NestedTypes,
                  implements = defaultArg implements x.Implements,
                  extends = defaultArg extends x.Extends,
                  methods = defaultArg methods x.Methods,
                  securityDecls = defaultArg securityDecls x.SecurityDecls,
                  fields = defaultArg fields x.Fields,
                  methodImpls = defaultArg methodImpls x.MethodImpls,
                  events = defaultArg events x.Events,
                  properties = defaultArg properties x.Properties,
                  customAttrs = defaultArg customAttrs x.CustomAttrs)

    member x.CustomAttrs =
        match customAttrsStored with
        | ILAttributesStored.Reader f ->
            let res = ILAttributes(f x.MetadataIndex)
            customAttrsStored <- ILAttributesStored.Given res
            res
        | ILAttributesStored.Given res ->
            res

    member x.SecurityDecls = x.SecurityDeclsStored.GetSecurityDecls x.MetadataIndex

    member x.IsClass = (typeKindOfFlags x.Name x.Methods x.Fields x.Extends (int x.Attributes)) = ILTypeDefKind.Class
    member x.IsStruct = (typeKindOfFlags x.Name x.Methods x.Fields x.Extends (int x.Attributes)) = ILTypeDefKind.ValueType
    member x.IsInterface = (typeKindOfFlags x.Name x.Methods x.Fields x.Extends (int x.Attributes)) = ILTypeDefKind.Interface
    member x.IsEnum = (typeKindOfFlags x.Name x.Methods x.Fields x.Extends (int x.Attributes)) = ILTypeDefKind.Enum
    member x.IsDelegate = (typeKindOfFlags x.Name x.Methods x.Fields x.Extends (int x.Attributes)) = ILTypeDefKind.Delegate
    member x.Access = typeAccessOfFlags (int x.Attributes)
    member x.IsAbstract = x.Attributes &&& TypeAttributes.Abstract <> enum 0
    member x.IsSealed = x.Attributes &&& TypeAttributes.Sealed <> enum 0
    member x.IsSerializable = x.Attributes &&& TypeAttributes.Serializable <> enum 0
    member x.IsComInterop = x.Attributes &&& TypeAttributes.Import <> enum 0 (* Class or interface generated for COM interop *)
    member x.IsSpecialName = x.Attributes &&& TypeAttributes.SpecialName <> enum 0
    member x.HasSecurity = x.Attributes &&& TypeAttributes.HasSecurity <> enum 0
    member x.Encoding = typeEncodingOfFlags (int x.Attributes)
    member x.IsStructOrEnum = x.IsStruct || x.IsEnum
    member x.WithAccess(access) = x.With(attributes=(x.Attributes &&& ~~~TypeAttributes.VisibilityMask ||| convertTypeAccessFlags access))
    member x.WithNestedAccess(access) = x.With(attributes=(x.Attributes &&& ~~~TypeAttributes.VisibilityMask ||| convertToNestedTypeAccess access))
    member x.WithSealed(condition) = x.With(attributes=(x.Attributes |> conditionalAdd condition TypeAttributes.Sealed))
    member x.WithSerializable(condition) = x.With(attributes=(x.Attributes |> conditionalAdd condition TypeAttributes.Serializable))
    member x.WithAbstract(condition) = x.With(attributes=(x.Attributes |> conditionalAdd condition TypeAttributes.Abstract))
    member x.WithImport(condition) = x.With(attributes=(x.Attributes |> conditionalAdd condition TypeAttributes.Import))
    member x.WithHasSecurity(condition) = x.With(attributes=(x.Attributes |> conditionalAdd condition TypeAttributes.HasSecurity))
    member x.WithLayout(layout) = x.With(attributes=(x.Attributes ||| convertLayout layout), layout = layout)
    member x.WithKind(kind) = x.With(attributes=(x.Attributes ||| convertTypeKind kind), extends = match kind with ILTypeDefKind.Interface -> None | _ -> x.Extends)
    member x.WithEncoding(encoding) = x.With(attributes=(x.Attributes &&& ~~~TypeAttributes.StringFormatMask ||| convertEncoding encoding))
    member x.WithSpecialName(condition) = x.With(attributes=(x.Attributes |> conditionalAdd condition TypeAttributes.SpecialName))
    member x.WithInitSemantics(init) = x.With(attributes=(x.Attributes ||| convertInitSemantics init))

and [<Sealed>] ILTypeDefs(f : unit -> ILPreTypeDef[]) =

    let mutable array = InlineDelayInit<_>(f)

    let mutable dict = InlineDelayInit<_>(fun () ->
        let arr = array.Value
        let t = Dictionary<_, _>(HashIdentity.Structural)
        for pre in arr do
            let key = pre.Namespace, pre.Name
            t.[key] <- pre
        t)

    member x.AsArray = [| for pre in array.Value -> pre.GetTypeDef() |]

    member x.AsList = [ for pre in array.Value -> pre.GetTypeDef() ]

    interface IEnumerable with
        member x.GetEnumerator() = ((x :> IEnumerable<ILTypeDef>).GetEnumerator() :> IEnumerator)

    interface IEnumerable<ILTypeDef> with
        member x.GetEnumerator() =
            (seq { for pre in array.Value -> pre.GetTypeDef() }).GetEnumerator()

    member x.AsArrayOfPreTypeDefs = array.Value

    member x.FindByName nm =
        let ns, n = splitILTypeName nm
        dict.Value.[(ns, n)].GetTypeDef()


and [<NoEquality; NoComparison>] ILPreTypeDef =
    abstract Namespace: string list
    abstract Name: string
    abstract GetTypeDef: unit -> ILTypeDef


/// This is a memory-critical class. Very many of these objects get allocated and held to represent the contents of .NET assemblies.
and [<Sealed>] ILPreTypeDefImpl(nameSpace: string list, name: string, metadataIndex: int32, storage: ILTypeDefStored) =
    let mutable store : ILTypeDef = Unchecked.defaultof<_>

    interface ILPreTypeDef with
        member __.Namespace = nameSpace
        member __.Name = name

        member x.GetTypeDef() =
            match box store with
            | null ->
                match storage with
                | ILTypeDefStored.Given td ->
                    store <- td
                    td
                | ILTypeDefStored.Computed f ->
                    LazyInitializer.EnsureInitialized<ILTypeDef>(&store, Func<_>(fun () -> f()))
                | ILTypeDefStored.Reader f ->
                    LazyInitializer.EnsureInitialized<ILTypeDef>(&store, Func<_>(fun () -> f metadataIndex))
            | _ -> store

and ILTypeDefStored =
    | Given of ILTypeDef
    | Reader of (int32 -> ILTypeDef)
    | Computed of (unit -> ILTypeDef)

let mkILTypeDefReader f = ILTypeDefStored.Reader f

type ILNestedExportedType =
    { Name: string
      Access: ILMemberAccess
      Nested: ILNestedExportedTypes
      CustomAttrsStored: ILAttributesStored
      MetadataIndex: int32 }

    member x.CustomAttrs = x.CustomAttrsStored.GetCustomAttrs x.MetadataIndex

and ILNestedExportedTypes =
    | ILNestedExportedTypes of Lazy<Map<string, ILNestedExportedType>>

    member x.AsList = let (ILNestedExportedTypes ltab) = x in Map.foldBack (fun _x y r -> y :: r) (ltab.Force()) []

and [<NoComparison; NoEquality>]
    ILExportedTypeOrForwarder =
    { ScopeRef: ILScopeRef
      Name: string
      Attributes: TypeAttributes
      Nested: ILNestedExportedTypes
      CustomAttrsStored: ILAttributesStored
      MetadataIndex: int32 }

    member x.Access = typeAccessOfFlags (int x.Attributes)

    member x.IsForwarder = x.Attributes &&& enum<TypeAttributes>(0x00200000) <> enum 0

    member x.CustomAttrs = x.CustomAttrsStored.GetCustomAttrs x.MetadataIndex

and ILExportedTypesAndForwarders =
    | ILExportedTypesAndForwarders of Lazy<Map<string, ILExportedTypeOrForwarder>>

    member x.AsList = let (ILExportedTypesAndForwarders ltab) = x in Map.foldBack (fun _x y r -> y :: r) (ltab.Force()) []

[<RequireQualifiedAccess>]
type ILResourceAccess =
    | Public
    | Private

[<RequireQualifiedAccess>]
type ILResourceLocation =
    | LocalIn of string * int * int
    | LocalOut of byte[]
    | File of ILModuleRef * int32
    | Assembly of ILAssemblyRef

type ILResource =
    { Name: string
      Location: ILResourceLocation
      Access: ILResourceAccess
      CustomAttrsStored: ILAttributesStored
      MetadataIndex: int32 }

    /// Read the bytes from a resource local to an assembly
    member r.GetBytes() =
        match r.Location with
        | ILResourceLocation.LocalIn (file, start, len) ->
            File.ReadBinaryChunk(file, start, len)
        | ILResourceLocation.LocalOut bytes -> bytes
        | _ -> failwith "GetBytes"

    member x.CustomAttrs = x.CustomAttrsStored.GetCustomAttrs x.MetadataIndex

type ILResources =
    | ILResources of ILResource list

    member x.AsList = let (ILResources ltab) = x in ltab

// --------------------------------------------------------------------
// One module in the "current" assembly
// --------------------------------------------------------------------

[<RequireQualifiedAccess>]
type ILAssemblyLongevity =
    | Unspecified
    | Library
    | PlatformAppDomain
    | PlatformProcess
    | PlatformSystem


type ILAssemblyManifest =
    { Name: string
      AuxModuleHashAlgorithm: int32
      SecurityDeclsStored: ILSecurityDeclsStored
      PublicKey: byte[] option
      Version: ILVersionInfo option
      Locale: Locale option
      CustomAttrsStored: ILAttributesStored

      AssemblyLongevity: ILAssemblyLongevity
      DisableJitOptimizations: bool
      JitTracking: bool
      IgnoreSymbolStoreSequencePoints: bool
      Retargetable: bool

      /// Records the types implemented by other modules.
      ExportedTypes: ILExportedTypesAndForwarders

      /// Records whether the entrypoint resides in another module.
      EntrypointElsewhere: ILModuleRef option
      MetadataIndex: int32
    }

    member x.CustomAttrs = x.CustomAttrsStored.GetCustomAttrs x.MetadataIndex

    member x.SecurityDecls = x.SecurityDeclsStored.GetSecurityDecls x.MetadataIndex

[<RequireQualifiedAccess>]
type ILNativeResource =
    | In of fileName: string * linkedResourceBase: int * linkedResourceStart: int * linkedResourceLength: int
    | Out of unlinkedResource: byte[]

type ILModuleDef =
    { Manifest: ILAssemblyManifest option
      Name: string
      TypeDefs: ILTypeDefs
      SubsystemVersion : int * int
      UseHighEntropyVA : bool
      SubSystemFlags: int32
      IsDLL: bool
      IsILOnly: bool
      Platform: ILPlatform option
      StackReserveSize: int32 option
      Is32Bit: bool
      Is32BitPreferred: bool
      Is64Bit: bool
      VirtualAlignment: int32
      PhysicalAlignment: int32
      ImageBase: int32
      MetadataVersion: string
      Resources: ILResources
      /// e.g. win32 resources
      NativeResources: ILNativeResource list
      CustomAttrsStored: ILAttributesStored
      MetadataIndex: int32
    }
    member x.ManifestOfAssembly =
        match x.Manifest with
        | Some m -> m
        | None -> failwith "no manifest"

    member m.HasManifest =
        match m.Manifest with None -> false | _ -> true

    member x.CustomAttrs = x.CustomAttrsStored.GetCustomAttrs x.MetadataIndex

// --------------------------------------------------------------------
// Add fields and types to tables, with decent error messages
// when clashes occur...
// --------------------------------------------------------------------

let mkILEmptyGenericParams = ([]: ILGenericParameterDefs)

let emptyILGenericArgsList = ([]: ILType list)

// --------------------------------------------------------------------
// Make ILTypeRefs etc.
// --------------------------------------------------------------------


let mkILNestedTyRef (scope, l, nm) = ILTypeRef.Create (scope, l, nm)

let mkILTyRef (scope, nm) = mkILNestedTyRef (scope, [], nm)

type ILGenericArgsList = ILType list

let mkILTySpec (tref, inst) = ILTypeSpec.Create (tref, inst)

let mkILNonGenericTySpec tref = mkILTySpec (tref, [])

let mkILTyRefInTyRef (tref: ILTypeRef, nm) =
    mkILNestedTyRef (tref.Scope, tref.Enclosing@[tref.Name], nm)

let mkILTy boxed tspec =
    match boxed with AsObject -> mkILBoxedType tspec | _ -> ILType.Value tspec

let mkILNamedTy vc tref tinst = mkILTy vc (ILTypeSpec.Create (tref, tinst))

let mkILValueTy tref tinst = mkILNamedTy AsValue tref tinst

let mkILBoxedTy tref tinst = mkILNamedTy AsObject tref tinst

let mkILNonGenericValueTy tref = mkILNamedTy AsValue tref []

let mkILNonGenericBoxedTy tref = mkILNamedTy AsObject tref []

let mkSimpleAssemblyRef n =
  ILAssemblyRef.Create (n, None, None, false, None, None)

let mkSimpleModRef n =
    ILModuleRef.Create (n, true, None)

// --------------------------------------------------------------------
// The toplevel class of a module is called "<Module>"
// --------------------------------------------------------------------

let typeNameForGlobalFunctions = "<Module>"

let mkILTypeForGlobalFunctions scoref = mkILBoxedType (mkILNonGenericTySpec (ILTypeRef.Create (scoref, [], typeNameForGlobalFunctions)))

let isTypeNameForGlobalFunctions d = (d = typeNameForGlobalFunctions)

let mkILMethRef (tref, callconv, nm, gparams, args, rty) =
    { mrefParent=tref
      mrefCallconv=callconv
      mrefGenericArity=gparams
      mrefName=nm
      mrefArgs=args
      mrefReturn=rty}

let mkILMethSpecForMethRefInTy (mref, ty, minst) =
    { mspecMethodRef=mref
      mspecDeclaringType=ty
      mspecMethodInst=minst }

let mkILMethSpec (mref, vc, tinst, minst) = mkILMethSpecForMethRefInTy (mref, mkILNamedTy vc mref.DeclaringTypeRef tinst, minst)

let mkILMethSpecInTypeRef (tref, vc, cc, nm, args, rty, tinst, minst) =
    mkILMethSpec (mkILMethRef ( tref, cc, nm, List.length minst, args, rty), vc, tinst, minst)

let mkILMethSpecInTy (ty: ILType, cc, nm, args, rty, minst: ILGenericArgs) =
    mkILMethSpecForMethRefInTy (mkILMethRef (ty.TypeRef, cc, nm, minst.Length, args, rty), ty, minst)

let mkILNonGenericMethSpecInTy (ty, cc, nm, args, rty) =
    mkILMethSpecInTy (ty, cc, nm, args, rty, [])

let mkILInstanceMethSpecInTy (ty: ILType, nm, args, rty, minst) =
    mkILMethSpecInTy (ty, ILCallingConv.Instance, nm, args, rty, minst)

let mkILNonGenericInstanceMethSpecInTy (ty: ILType, nm, args, rty) =
    mkILInstanceMethSpecInTy (ty, nm, args, rty, [])

let mkILStaticMethSpecInTy (ty, nm, args, rty, minst) =
    mkILMethSpecInTy (ty, ILCallingConv.Static, nm, args, rty, minst)

let mkILNonGenericStaticMethSpecInTy (ty, nm, args, rty) =
    mkILStaticMethSpecInTy (ty, nm, args, rty, [])

let mkILCtorMethSpec (tref, args, cinst) =
    mkILMethSpecInTypeRef (tref, AsObject, ILCallingConv.Instance, ".ctor", args, ILType.Void, cinst, [])

let mkILCtorMethSpecForTy (ty, args) =
  mkILMethSpecInTy (ty, ILCallingConv.Instance, ".ctor", args, ILType.Void, [])

let mkILNonGenericCtorMethSpec (tref, args) =
  mkILCtorMethSpec (tref, args, [])

// --------------------------------------------------------------------
// Make references to fields
// --------------------------------------------------------------------

let mkILFieldRef (tref, nm, ty) = { DeclaringTypeRef=tref; Name=nm; Type=ty}

let mkILFieldSpec (tref, ty) = { FieldRef= tref; DeclaringType=ty }

let mkILFieldSpecInTy (ty: ILType, nm, fty) =
    mkILFieldSpec (mkILFieldRef (ty.TypeRef, nm, fty), ty)


let andTailness x y =
  match x with Tailcall when y -> Tailcall | _ -> Normalcall

// --------------------------------------------------------------------
// Basic operations on code.
// --------------------------------------------------------------------

let formatCodeLabel (x: int) = "L"+string x

//  ++GLOBAL MUTABLE STATE (concurrency safe)
let codeLabelCount = ref 0
let generateCodeLabel() = Interlocked.Increment codeLabelCount

let instrIsRet i =
    match i with
    | I_ret -> true
    | _ -> false

let nonBranchingInstrsToCode instrs : ILCode =
    let instrs = Array.ofList instrs
    let instrs =
        if instrs.Length <> 0 && instrIsRet (Array.last instrs) then instrs
        else Array.append instrs [| I_ret |]

    { Labels = Dictionary()
      Instrs = instrs
      Exceptions = []
      Locals = [] }


// --------------------------------------------------------------------
//
// --------------------------------------------------------------------

let mkILTyvarTy tv = ILType.TypeVar tv

let mkILSimpleTypar nm =
   { Name=nm
     Constraints = []
     Variance=NonVariant
     HasReferenceTypeConstraint=false
     HasNotNullableValueTypeConstraint=false
     HasDefaultConstructorConstraint=false
     CustomAttrsStored = storeILCustomAttrs emptyILCustomAttrs
     MetadataIndex = NoMetadataIdx }

let gparam_of_gactual (_ga: ILType) = mkILSimpleTypar "T"

let mkILFormalTypars (x: ILGenericArgsList) = List.map gparam_of_gactual x

let mkILFormalGenericArgs numtypars (gparams: ILGenericParameterDefs) =
    List.mapi (fun n _gf -> mkILTyvarTy (uint16 (numtypars + n))) gparams

let mkILFormalBoxedTy tref gparams = mkILBoxedTy tref (mkILFormalGenericArgs 0 gparams)

let mkILFormalNamedTy bx tref gparams = mkILNamedTy bx tref (mkILFormalGenericArgs 0 gparams)

// --------------------------------------------------------------------
// Operations on class etc. defs.
// --------------------------------------------------------------------

let mkRefForNestedILTypeDef scope (enc: ILTypeDef list, td: ILTypeDef) =
    mkILNestedTyRef (scope, (enc |> List.map (fun etd -> etd.Name)), td.Name)

// --------------------------------------------------------------------
// Operations on type tables.
// --------------------------------------------------------------------

let mkILPreTypeDef (td: ILTypeDef) =
    let ns, n = splitILTypeName td.Name
    ILPreTypeDefImpl (ns, n, NoMetadataIdx, ILTypeDefStored.Given td) :> ILPreTypeDef
let mkILPreTypeDefComputed (ns, n, f) =
    ILPreTypeDefImpl (ns, n, NoMetadataIdx, ILTypeDefStored.Computed f) :> ILPreTypeDef
let mkILPreTypeDefRead (ns, n, idx, f) =
    ILPreTypeDefImpl (ns, n, idx, f) :> ILPreTypeDef


let addILTypeDef td (tdefs: ILTypeDefs) = ILTypeDefs (fun () -> [| yield mkILPreTypeDef td; yield! tdefs.AsArrayOfPreTypeDefs |])
let mkILTypeDefsFromArray (l: ILTypeDef[]) = ILTypeDefs (fun () -> Array.map mkILPreTypeDef l)
let mkILTypeDefs l = mkILTypeDefsFromArray (Array.ofList l)
let mkILTypeDefsComputed f = ILTypeDefs f
let emptyILTypeDefs = mkILTypeDefsFromArray [| |]

// --------------------------------------------------------------------
// Operations on method tables.
// --------------------------------------------------------------------

let mkILMethodsFromArray xs = ILMethodDefs (fun () -> xs)
let mkILMethods xs = xs |> Array.ofList |> mkILMethodsFromArray
let mkILMethodsComputed f = ILMethodDefs f
let emptyILMethods = mkILMethodsFromArray [| |]

let filterILMethodDefs f (mdefs: ILMethodDefs) =
    ILMethodDefs (fun () -> mdefs.AsArray |> Array.filter f)

// --------------------------------------------------------------------
// Operations and defaults for modules, assemblies etc.
// --------------------------------------------------------------------

let defaultSubSystem = 3 (* this is what comes out of ILDASM on 30/04/2001 *)
let defaultPhysAlignment = 512 (* this is what comes out of ILDASM on 30/04/2001 *)
let defaultVirtAlignment = 0x2000 (* this is what comes out of ILDASM on 30/04/2001 *)
let defaultImageBase = 0x034f0000 (* this is what comes out of ILDASM on 30/04/2001 *)

// --------------------------------------------------------------------
// Array types
// --------------------------------------------------------------------

let mkILArrTy (ty, shape) = ILType.Array (shape, ty)

let mkILArr1DTy ty = mkILArrTy (ty, ILArrayShape.SingleDimensional)

let isILArrTy ty = match ty with ILType.Array _ -> true| _ -> false

let destILArrTy ty =
    match ty with
    | ILType.Array (shape, ty) -> (shape, ty)
    | _ -> failwith "destILArrTy"

// --------------------------------------------------------------------
// Sigs of special types built-in
// --------------------------------------------------------------------

[<Literal>]
let tname_Object = "System.Object"

[<Literal>]
let tname_String = "System.String"

[<Literal>]
let tname_Array = "System.Array"

[<Literal>]
let tname_Type = "System.Type"

[<Literal>]
let tname_Int64 = "System.Int64"

[<Literal>]
let tname_UInt64 = "System.UInt64"

[<Literal>]
let tname_Int32 = "System.Int32"

[<Literal>]
let tname_UInt32 = "System.UInt32"

[<Literal>]
let tname_Int16 = "System.Int16"

[<Literal>]
let tname_UInt16 = "System.UInt16"

[<Literal>]
let tname_SByte = "System.SByte"

[<Literal>]
let tname_Byte = "System.Byte"

[<Literal>]
let tname_Single = "System.Single"

[<Literal>]
let tname_Double = "System.Double"

[<Literal>]
let tname_Bool = "System.Boolean"

[<Literal>]
let tname_Char = "System.Char"

[<Literal>]
let tname_IntPtr = "System.IntPtr"

[<Literal>]
let tname_UIntPtr = "System.UIntPtr"

[<NoEquality; NoComparison; StructuredFormatDisplay("{DebugText}")>]
// This data structure needs an entirely delayed implementation
type ILGlobals(primaryScopeRef) =

    let m_mkSysILTypeRef nm = mkILTyRef (primaryScopeRef, nm)

    let m_typ_Object = mkILBoxedType (mkILNonGenericTySpec (m_mkSysILTypeRef tname_Object))
    let m_typ_String = mkILBoxedType (mkILNonGenericTySpec (m_mkSysILTypeRef tname_String))
    let m_typ_Array = mkILBoxedType (mkILNonGenericTySpec (m_mkSysILTypeRef tname_Array))
    let m_typ_Type = mkILBoxedType (mkILNonGenericTySpec (m_mkSysILTypeRef tname_Type))
    let m_typ_SByte = ILType.Value (mkILNonGenericTySpec (m_mkSysILTypeRef tname_SByte))
    let m_typ_Int16 = ILType.Value (mkILNonGenericTySpec (m_mkSysILTypeRef tname_Int16))
    let m_typ_Int32 = ILType.Value (mkILNonGenericTySpec (m_mkSysILTypeRef tname_Int32))
    let m_typ_Int64 = ILType.Value (mkILNonGenericTySpec (m_mkSysILTypeRef tname_Int64))
    let m_typ_Byte = ILType.Value (mkILNonGenericTySpec (m_mkSysILTypeRef tname_Byte))
    let m_typ_UInt16 = ILType.Value (mkILNonGenericTySpec (m_mkSysILTypeRef tname_UInt16))
    let m_typ_UInt32 = ILType.Value (mkILNonGenericTySpec (m_mkSysILTypeRef tname_UInt32))
    let m_typ_UInt64 = ILType.Value (mkILNonGenericTySpec (m_mkSysILTypeRef tname_UInt64))
    let m_typ_Single = ILType.Value (mkILNonGenericTySpec (m_mkSysILTypeRef tname_Single))
    let m_typ_Double = ILType.Value (mkILNonGenericTySpec (m_mkSysILTypeRef tname_Double))
    let m_typ_Bool = ILType.Value (mkILNonGenericTySpec (m_mkSysILTypeRef tname_Bool))
    let m_typ_Char = ILType.Value (mkILNonGenericTySpec (m_mkSysILTypeRef tname_Char))
    let m_typ_IntPtr = ILType.Value (mkILNonGenericTySpec (m_mkSysILTypeRef tname_IntPtr))
    let m_typ_UIntPtr = ILType.Value (mkILNonGenericTySpec (m_mkSysILTypeRef tname_UIntPtr))

    member x.primaryAssemblyScopeRef = m_typ_Object.TypeRef.Scope
    member x.primaryAssemblyName = m_typ_Object.TypeRef.Scope.AssemblyRef.Name
    member x.typ_Object = m_typ_Object
    member x.typ_String = m_typ_String
    member x.typ_Array = m_typ_Array
    member x.typ_Type = m_typ_Type
    member x.typ_IntPtr = m_typ_IntPtr
    member x.typ_UIntPtr = m_typ_UIntPtr
    member x.typ_Byte = m_typ_Byte
    member x.typ_Int16 = m_typ_Int16
    member x.typ_Int32 = m_typ_Int32
    member x.typ_Int64 = m_typ_Int64
    member x.typ_SByte = m_typ_SByte
    member x.typ_UInt16 = m_typ_UInt16
    member x.typ_UInt32 = m_typ_UInt32
    member x.typ_UInt64 = m_typ_UInt64
    member x.typ_Single = m_typ_Single
    member x.typ_Double = m_typ_Double
    member x.typ_Bool = m_typ_Bool
    member x.typ_Char = m_typ_Char

    /// For debugging
    [<DebuggerBrowsable(DebuggerBrowsableState.Never)>]
    member x.DebugText = x.ToString()

    override x.ToString() = "<ILGlobals>"

let mkILGlobals primaryScopeRef = ILGlobals primaryScopeRef

let mkNormalCall mspec = I_call (Normalcall, mspec, None)

let mkNormalCallvirt mspec = I_callvirt (Normalcall, mspec, None)

let mkNormalCallconstraint (ty, mspec) = I_callconstraint (Normalcall, ty, mspec, None)

let mkNormalNewobj mspec = I_newobj (mspec, None)

/// Comment on common object cache sizes:
/// mkLdArg - I can't imagine any IL method we generate needing more than this
/// mkLdLoc - I tried 256, and there were LdLoc allocations left, so I upped it o 512. I didn't check again.
/// mkStLoc - it should be the same as LdLoc (where there's a LdLoc there must be a StLoc)
/// mkLdcInt32 - just a guess

let ldargs = [| for i in 0 .. 128 -> I_ldarg (uint16 i) |]

let mkLdarg i = if 0us < i && i < uint16 ldargs.Length then ldargs.[int i] else I_ldarg i

let mkLdarg0 = mkLdarg 0us

let ldlocs = [| for i in 0 .. 512 -> I_ldloc (uint16 i) |]

let mkLdloc i = if 0us < i && i < uint16 ldlocs.Length then ldlocs.[int i] else I_ldloc i

let stlocs = [| for i in 0 .. 512 -> I_stloc (uint16 i) |]

let mkStloc i = if 0us < i && i < uint16 stlocs.Length then stlocs.[int i] else I_stloc i

let ldi32s = [| for i in 0 .. 256 -> AI_ldc (DT_I4, ILConst.I4 i) |]

let mkLdcInt32 i = if 0 < i && i < ldi32s.Length then ldi32s.[i] else AI_ldc (DT_I4, ILConst.I4 i)

let tname_CompilerGeneratedAttribute = "System.Runtime.CompilerServices.CompilerGeneratedAttribute"

let tname_DebuggableAttribute = "System.Diagnostics.DebuggableAttribute"

(* NOTE: ecma_ prefix refers to the standard "mscorlib" *)
let ecmaPublicKey = PublicKeyToken (Bytes.ofInt32Array [|0xde; 0xad; 0xbe; 0xef; 0xca; 0xfe; 0xfa; 0xce |])

let isILBoxedTy = function ILType.Boxed _ -> true | _ -> false

let isILValueTy = function ILType.Value _ -> true | _ -> false

let isPrimaryAssemblyTySpec (tspec: ILTypeSpec) n =
    let tref = tspec.TypeRef
    let scoref = tref.Scope
    (tref.Name = n) &&
    match scoref with
    | ILScopeRef.Assembly n -> PrimaryAssembly.IsSomePrimaryAssembly n.Name
    | ILScopeRef.Module _ -> false
    | ILScopeRef.Local -> true

let isILBoxedPrimaryAssemblyTy (ty: ILType) n =
  isILBoxedTy ty && isPrimaryAssemblyTySpec ty.TypeSpec n

let isILValuePrimaryAssemblyTy (ty: ILType) n =
  isILValueTy ty && isPrimaryAssemblyTySpec ty.TypeSpec n

let isILObjectTy ty = isILBoxedPrimaryAssemblyTy ty tname_Object

let isILStringTy ty = isILBoxedPrimaryAssemblyTy ty tname_String

let isILTypedReferenceTy ty = isILValuePrimaryAssemblyTy ty "System.TypedReference"

let isILSByteTy ty = isILValuePrimaryAssemblyTy ty tname_SByte

let isILByteTy ty = isILValuePrimaryAssemblyTy ty tname_Byte

let isILInt16Ty ty = isILValuePrimaryAssemblyTy ty tname_Int16

let isILUInt16Ty ty = isILValuePrimaryAssemblyTy ty tname_UInt16

let isILInt32Ty ty = isILValuePrimaryAssemblyTy ty tname_Int32

let isILUInt32Ty ty = isILValuePrimaryAssemblyTy ty tname_UInt32

let isILInt64Ty ty = isILValuePrimaryAssemblyTy ty tname_Int64

let isILUInt64Ty ty = isILValuePrimaryAssemblyTy ty tname_UInt64

let isILIntPtrTy ty = isILValuePrimaryAssemblyTy ty tname_IntPtr

let isILUIntPtrTy ty = isILValuePrimaryAssemblyTy ty tname_UIntPtr

let isILBoolTy ty = isILValuePrimaryAssemblyTy ty tname_Bool

let isILCharTy ty = isILValuePrimaryAssemblyTy ty tname_Char

let isILSingleTy ty = isILValuePrimaryAssemblyTy ty tname_Single

let isILDoubleTy ty = isILValuePrimaryAssemblyTy ty tname_Double

// --------------------------------------------------------------------
// Rescoping
// --------------------------------------------------------------------

let rescopeILScopeRef scoref scoref1 =
    match scoref, scoref1 with
    | _, ILScopeRef.Local -> scoref
    | ILScopeRef.Local, _ -> scoref1
    | _, ILScopeRef.Module _ -> scoref
    | ILScopeRef.Module _, _ -> scoref1
    | _ -> scoref1

let rescopeILTypeRef scoref (tref1: ILTypeRef) =
    let scoref1 = tref1.Scope
    let scoref2 = rescopeILScopeRef scoref scoref1
    if scoref1 === scoref2 then tref1
    else ILTypeRef.Create (scoref2, tref1.Enclosing, tref1.Name)

// ORIGINAL IMPLEMENTATION (too many allocations
//         { tspecTypeRef=rescopeILTypeRef scoref tref
//           tspecInst=rescopeILTypes scoref tinst }
let rec rescopeILTypeSpec scoref (tspec1: ILTypeSpec) =
    let tref1 = tspec1.TypeRef
    let tinst1 = tspec1.GenericArgs
    let tref2 = rescopeILTypeRef scoref tref1

    // avoid reallocation in the common case
    if tref1 === tref2 then
        if isNil tinst1 then tspec1 else
        let tinst2 = rescopeILTypes scoref tinst1
        if tinst1 === tinst2 then tspec1 else
        ILTypeSpec.Create (tref2, tinst2)
    else
        let tinst2 = rescopeILTypes scoref tinst1
        ILTypeSpec.Create (tref2, tinst2)

and rescopeILType scoref ty =
    match ty with
    | ILType.Ptr t -> ILType.Ptr (rescopeILType scoref t)
    | ILType.FunctionPointer t -> ILType.FunctionPointer (rescopeILCallSig scoref t)
    | ILType.Byref t -> ILType.Byref (rescopeILType scoref t)
    | ILType.Boxed cr1 ->
        let cr2 = rescopeILTypeSpec scoref cr1
        if cr1 === cr2 then ty else
        mkILBoxedType cr2
    | ILType.Array (s, ety1) ->
        let ety2 = rescopeILType scoref ety1
        if ety1 === ety2 then ty else
        ILType.Array (s, ety2)
    | ILType.Value cr1 ->
        let cr2 = rescopeILTypeSpec scoref cr1
        if cr1 === cr2 then ty else
        ILType.Value cr2
    | ILType.Modified (b, tref, ty) -> ILType.Modified (b, rescopeILTypeRef scoref tref, rescopeILType scoref ty)
    | x -> x

and rescopeILTypes scoref i =
    if isNil i then i
    else List.mapq (rescopeILType scoref) i

and rescopeILCallSig scoref csig =
    mkILCallSig (csig.CallingConv, rescopeILTypes scoref csig.ArgTypes, rescopeILType scoref csig.ReturnType)

let rescopeILMethodRef scoref (x: ILMethodRef) =
    { mrefParent = rescopeILTypeRef scoref x.DeclaringTypeRef
      mrefCallconv = x.mrefCallconv
      mrefGenericArity=x.mrefGenericArity
      mrefName=x.mrefName
      mrefArgs = rescopeILTypes scoref x.mrefArgs
      mrefReturn= rescopeILType scoref x.mrefReturn }

let rescopeILFieldRef scoref x =
    { DeclaringTypeRef = rescopeILTypeRef scoref x.DeclaringTypeRef
      Name= x.Name
      Type= rescopeILType scoref x.Type }

// --------------------------------------------------------------------
// Instantiate polymorphism in types
// --------------------------------------------------------------------

let rec instILTypeSpecAux numFree inst (tspec: ILTypeSpec) =
    ILTypeSpec.Create (tspec.TypeRef, instILGenericArgsAux numFree inst tspec.GenericArgs)

and instILTypeAux numFree (inst: ILGenericArgs) ty =
    match ty with
    | ILType.Ptr t -> ILType.Ptr (instILTypeAux numFree inst t)
    | ILType.FunctionPointer t -> ILType.FunctionPointer (instILCallSigAux numFree inst t)
    | ILType.Array (a, t) -> ILType.Array (a, instILTypeAux numFree inst t)
    | ILType.Byref t -> ILType.Byref (instILTypeAux numFree inst t)
    | ILType.Boxed cr -> mkILBoxedType (instILTypeSpecAux numFree inst cr)
    | ILType.Value cr -> ILType.Value (instILTypeSpecAux numFree inst cr)
    | ILType.TypeVar v ->
        let v = int v
        let top = inst.Length
        if v < numFree then ty else
        if v - numFree >= top then
            ILType.TypeVar (uint16 (v - top))
        else
            List.item (v - numFree) inst
    | x -> x

and instILGenericArgsAux numFree inst i = List.map (instILTypeAux numFree inst) i

and instILCallSigAux numFree inst csig =
  mkILCallSig (csig.CallingConv, List.map (instILTypeAux numFree inst) csig.ArgTypes, instILTypeAux numFree inst csig.ReturnType)

let instILType i t = instILTypeAux 0 i t

// --------------------------------------------------------------------
// MS-IL: Parameters, Return types and Locals
// --------------------------------------------------------------------

let mkILParam (name, ty) : ILParameter =
    { Name=name
      Default=None
      Marshal=None
      IsIn=false
      IsOut=false
      IsOptional=false
      Type=ty
      CustomAttrsStored=storeILCustomAttrs emptyILCustomAttrs
      MetadataIndex = NoMetadataIdx }

let mkILParamNamed (s, ty) = mkILParam (Some s, ty)

let mkILParamAnon ty = mkILParam (None, ty)

let mkILReturn ty : ILReturn =
    { Marshal=None
      Type=ty
      CustomAttrsStored=storeILCustomAttrs emptyILCustomAttrs
      MetadataIndex = NoMetadataIdx }

let mkILLocal ty dbgInfo : ILLocal =
    { IsPinned=false
      Type=ty
      DebugInfo=dbgInfo }

type ILFieldSpec with
    member fr.ActualType =
        let env = fr.DeclaringType.GenericArgs
        instILType env fr.FormalType

// --------------------------------------------------------------------
// Make a method mbody
// --------------------------------------------------------------------

let mkILMethodBody (zeroinit, locals, maxstack, code, tag) : ILMethodBody =
    { IsZeroInit=zeroinit
      MaxStack=maxstack
      NoInlining=false
      AggressiveInlining=false
      Locals= locals
      Code= code
      SourceMarker=tag }

let mkMethodBody (zeroinit, locals, maxstack, code, tag) = MethodBody.IL (mkILMethodBody (zeroinit, locals, maxstack, code, tag))

// --------------------------------------------------------------------
// Make a constructor
// --------------------------------------------------------------------

let mkILVoidReturn = mkILReturn ILType.Void

let methBodyNotAvailable = mkMethBodyAux MethodBody.NotAvailable

let methBodyAbstract = mkMethBodyAux MethodBody.Abstract

let methBodyNative = mkMethBodyAux MethodBody.Native

let mkILCtor (access, args, impl) =
    ILMethodDef(name=".ctor",
                attributes=(convertMemberAccess access ||| MethodAttributes.SpecialName ||| MethodAttributes.RTSpecialName),
                implAttributes=MethodImplAttributes.Managed,
                callingConv=ILCallingConv.Instance,
                parameters = args,
                ret= mkILVoidReturn,
                body= mkMethBodyAux impl,
                securityDecls=emptyILSecurityDecls,
                isEntryPoint=false,
                genericParams=mkILEmptyGenericParams,
                customAttrs = emptyILCustomAttrs)

// --------------------------------------------------------------------
// Do-nothing ctor, just pass on to monomorphic superclass
// --------------------------------------------------------------------

let mkCallBaseConstructor (ty, args: ILType list) =
    [ mkLdarg0 ] @
    List.mapi (fun i _ -> mkLdarg (uint16 (i+1))) args @
    [ mkNormalCall (mkILCtorMethSpecForTy (ty, [])) ]

let mkNormalStfld fspec = I_stfld (Aligned, Nonvolatile, fspec)

let mkNormalStsfld fspec = I_stsfld (Nonvolatile, fspec)

let mkNormalLdsfld fspec = I_ldsfld (Nonvolatile, fspec)

let mkNormalLdfld fspec = I_ldfld (Aligned, Nonvolatile, fspec)

let mkNormalLdflda fspec = I_ldflda fspec

let mkNormalLdobj dt = I_ldobj (Aligned, Nonvolatile, dt)

let mkNormalStobj dt = I_stobj (Aligned, Nonvolatile, dt)

let mkILNonGenericEmptyCtor tag superTy =
    let ctor = mkCallBaseConstructor (superTy, [])
    mkILCtor (ILMemberAccess.Public, [], mkMethodBody (false, [], 8, nonBranchingInstrsToCode ctor, tag))

// --------------------------------------------------------------------
// Make a static, top level monomophic method - very useful for
// creating helper ILMethodDefs for internal use.
// --------------------------------------------------------------------

let mkILStaticMethod (genparams, nm, access, args, ret, impl) =
    ILMethodDef(genericParams=genparams,
                name=nm,
                attributes=(convertMemberAccess access ||| MethodAttributes.Static),
                implAttributes=MethodImplAttributes.Managed,
                callingConv = ILCallingConv.Static,
                parameters = args,
                ret= ret,
                securityDecls=emptyILSecurityDecls,
                isEntryPoint=false,
                customAttrs = emptyILCustomAttrs,
                body= mkMethBodyAux impl)

let mkILNonGenericStaticMethod (nm, access, args, ret, impl) =
    mkILStaticMethod (mkILEmptyGenericParams, nm, access, args, ret, impl)

let mkILClassCtor impl =
    ILMethodDef(name=".cctor",
                attributes=(MethodAttributes.Private ||| MethodAttributes.Static ||| MethodAttributes.SpecialName ||| MethodAttributes.RTSpecialName),
                implAttributes=MethodImplAttributes.Managed,
                callingConv=ILCallingConv.Static,
                genericParams=mkILEmptyGenericParams,
                parameters = [],
                ret=mkILVoidReturn,
                isEntryPoint=false,
                securityDecls=emptyILSecurityDecls,
                customAttrs=emptyILCustomAttrs,
                body= mkMethBodyAux impl)

// --------------------------------------------------------------------
// Make a virtual method, where the overriding is simply the default
// (i.e. overrides by name/signature)
// --------------------------------------------------------------------

let mk_ospec (ty: ILType, callconv, nm, genparams, formal_args, formal_ret) =
  OverridesSpec (mkILMethRef (ty.TypeRef, callconv, nm, genparams, formal_args, formal_ret), ty)

let mkILGenericVirtualMethod (nm, access, genparams, actual_args, actual_ret, impl) =
    ILMethodDef(name=nm,
                attributes=
                  (convertMemberAccess access |||
                   MethodAttributes.CheckAccessOnOverride |||
                   (match impl with MethodBody.Abstract -> MethodAttributes.Abstract ||| MethodAttributes.Virtual | _ -> MethodAttributes.Virtual)),
                implAttributes=MethodImplAttributes.Managed,
                genericParams=genparams,
                callingConv=ILCallingConv.Instance,
                parameters=actual_args,
                ret=actual_ret,
                isEntryPoint=false,
                securityDecls=emptyILSecurityDecls,
                customAttrs = emptyILCustomAttrs,
                body= mkMethBodyAux impl)

let mkILNonGenericVirtualMethod (nm, access, args, ret, impl) =
    mkILGenericVirtualMethod (nm, access, mkILEmptyGenericParams, args, ret, impl)

let mkILGenericNonVirtualMethod (nm, access, genparams, actual_args, actual_ret, impl) =
    ILMethodDef(name=nm,
                attributes=(convertMemberAccess access ||| MethodAttributes.HideBySig),
                implAttributes=MethodImplAttributes.Managed,
                genericParams=genparams,
                callingConv=ILCallingConv.Instance,
                parameters=actual_args,
                ret=actual_ret,
                isEntryPoint=false,
                securityDecls=emptyILSecurityDecls,
                customAttrs = emptyILCustomAttrs,
                body= mkMethBodyAux impl)

let mkILNonGenericInstanceMethod (nm, access, args, ret, impl) =
  mkILGenericNonVirtualMethod (nm, access, mkILEmptyGenericParams, args, ret, impl)


// --------------------------------------------------------------------
// Add some code to the end of the .cctor for a type. Create a .cctor
// if one doesn't exist already.
// --------------------------------------------------------------------

let ilmbody_code2code f (il: ILMethodBody) =
  {il with Code = f il.Code}

let mdef_code2code f (md: ILMethodDef) =
    let il =
        match md.Body.Contents with
        | MethodBody.IL il-> il
        | _ -> failwith "mdef_code2code - method not IL"
    let b = MethodBody.IL (ilmbody_code2code f il)
    md.With(body = mkMethBodyAux b)

let prependInstrsToCode (instrs: ILInstr list) (c2: ILCode) =
    let instrs = Array.ofList instrs
    let n = instrs.Length
    match c2.Instrs.[0] with
    // If there is a sequence point as the first instruction then keep it at the front
    | I_seqpoint _ as i0 ->
        let labels =
            let dict = Dictionary.newWithSize c2.Labels.Count
            for kvp in c2.Labels do dict.Add (kvp.Key, if kvp.Value = 0 then 0 else kvp.Value + n)
            dict
        { c2 with Labels = labels
                  Instrs = Array.concat [| [|i0|] ; instrs ; c2.Instrs.[1..] |] }
    | _ ->
        let labels =
            let dict = Dictionary.newWithSize c2.Labels.Count
            for kvp in c2.Labels do dict.Add (kvp.Key, kvp.Value + n)
            dict
        { c2 with Labels = labels
                  Instrs = Array.append instrs c2.Instrs }

let prependInstrsToMethod new_code md =
    mdef_code2code (prependInstrsToCode new_code) md

// Creates cctor if needed
let cdef_cctorCode2CodeOrCreate tag f (cd: ILTypeDef) =
    let mdefs = cd.Methods
    let cctor =
        match mdefs.FindByName ".cctor" with
        | [mdef] -> mdef
        | [] -> mkILClassCtor (mkMethodBody (false, [], 1, nonBranchingInstrsToCode [ ], tag))
        | _ -> failwith "bad method table: more than one .cctor found"

    let methods = ILMethodDefs (fun () -> [| yield f cctor; for md in mdefs do if md.Name <> ".cctor" then yield md |])
    cd.With(methods = methods)


let code_of_mdef (md: ILMethodDef) =
    match md.Code with
    | Some x -> x
    | None -> failwith "code_of_mdef: not IL"

let mkRefToILMethod (tref, md: ILMethodDef) =
    mkILMethRef (tref, md.CallingConv, md.Name, md.GenericParams.Length, md.ParameterTypes, md.Return.Type)

let mkRefToILField (tref, fdef: ILFieldDef) = mkILFieldRef (tref, fdef.Name, fdef.FieldType)

let mkRefForILMethod scope (tdefs, tdef) mdef = mkRefToILMethod (mkRefForNestedILTypeDef scope (tdefs, tdef), mdef)

let mkRefForILField scope (tdefs, tdef) (fdef: ILFieldDef) = mkILFieldRef (mkRefForNestedILTypeDef scope (tdefs, tdef), fdef.Name, fdef.FieldType)

// Creates cctor if needed
let prependInstrsToClassCtor instrs tag cd =
    cdef_cctorCode2CodeOrCreate tag (prependInstrsToMethod instrs) cd

let mkILField (isStatic, nm, ty, (init: ILFieldInit option), (at: byte [] option), access, isLiteral) =
     ILFieldDef(name=nm,
                fieldType=ty,
                attributes=
                    (convertFieldAccess access |||
                     (if isStatic then FieldAttributes.Static else enum 0) |||
                     (if isLiteral then FieldAttributes.Literal else enum 0) |||
                     (if init.IsSome then FieldAttributes.HasDefault else enum 0) |||
                     (if at.IsSome then FieldAttributes.HasFieldRVA else enum 0)),
                literalValue = init,
                data=at,
                offset=None,
                marshal=None,
                customAttrs=emptyILCustomAttrs)

let mkILInstanceField (nm, ty, init, access) = mkILField (false, nm, ty, init, None, access, false)

let mkILStaticField (nm, ty, init, at, access) = mkILField (true, nm, ty, init, at, access, false)

let mkILLiteralField (nm, ty, init, at, access) = mkILField (true, nm, ty, Some init, at, access, true)

// --------------------------------------------------------------------
// Scopes for allocating new temporary variables.
// --------------------------------------------------------------------

type ILLocalsAllocator (numPrealloc: int) =
    let newLocals = ResizeArray<ILLocal>()
    member tmps.AllocLocal loc =
        let locn = uint16 (numPrealloc + newLocals.Count)
        newLocals.Add loc
        locn

    member tmps.Close() = ResizeArray.toList newLocals

let mkILFieldsLazy l = ILFields (LazyOrderedMultiMap ((fun (f: ILFieldDef) -> f.Name), l))

let mkILFields l = mkILFieldsLazy (notlazy l)

let emptyILFields = mkILFields []

let mkILEventsLazy l = ILEvents (LazyOrderedMultiMap ((fun (e: ILEventDef) -> e.Name), l))

let mkILEvents l = mkILEventsLazy (notlazy l)

let emptyILEvents = mkILEvents []

let mkILPropertiesLazy l = ILProperties (LazyOrderedMultiMap ((fun (p: ILPropertyDef) -> p.Name), l) )

let mkILProperties l = mkILPropertiesLazy (notlazy l)

let emptyILProperties = mkILProperties []

let addExportedTypeToTable (y: ILExportedTypeOrForwarder) tab = Map.add y.Name y tab

let mkILExportedTypes l = ILExportedTypesAndForwarders (notlazy (List.foldBack addExportedTypeToTable l Map.empty))

let mkILExportedTypesLazy (l: Lazy<_>) = ILExportedTypesAndForwarders (lazy (List.foldBack addExportedTypeToTable (l.Force()) Map.empty))

let addNestedExportedTypeToTable (y: ILNestedExportedType) tab =
    Map.add y.Name y tab

let mkTypeForwarder scopeRef name nested customAttrs access =
    { ScopeRef=scopeRef
      Name=name
      Attributes=enum<TypeAttributes>(0x00200000) ||| convertTypeAccessFlags access
      Nested=nested
      CustomAttrsStored=storeILCustomAttrs customAttrs
      MetadataIndex = NoMetadataIdx }

let mkILNestedExportedTypes l =
    ILNestedExportedTypes (notlazy (List.foldBack addNestedExportedTypeToTable l Map.empty))

let mkILNestedExportedTypesLazy (l: Lazy<_>) =
    ILNestedExportedTypes (lazy (List.foldBack addNestedExportedTypeToTable (l.Force()) Map.empty))

let mkILResources l = ILResources l

let addMethodImplToTable y tab =
    let key = (y.Overrides.MethodRef.Name, y.Overrides.MethodRef.ArgTypes.Length)
    let prev = Map.tryFindMulti key tab
    Map.add key (y :: prev) tab

let mkILMethodImpls l = ILMethodImpls (notlazy (List.foldBack addMethodImplToTable l Map.empty))

let mkILMethodImplsLazy l = ILMethodImpls (lazy (List.foldBack addMethodImplToTable (Lazy.force l) Map.empty))

let emptyILMethodImpls = mkILMethodImpls []

/// Make a constructor that simply takes its arguments and stuffs
/// them in fields. preblock is how to call the superclass constructor....
let mkILStorageCtorWithParamNames (tag, preblock, ty, extraParams, flds, access) =
    mkILCtor(access,
            (flds |> List.map (fun (pnm, _, ty) -> mkILParamNamed (pnm, ty))) @ extraParams,
            mkMethodBody
              (false, [], 2,
               nonBranchingInstrsToCode
                 begin
                   (match tag with Some x -> [I_seqpoint x] | None -> []) @
                   preblock @
                   List.concat (List.mapi (fun n (_pnm, nm, fieldTy) ->
                     [ mkLdarg0
                       mkLdarg (uint16 (n+1))
                       mkNormalStfld (mkILFieldSpecInTy (ty, nm, fieldTy))
                     ]) flds)
                 end, tag))

let mkILSimpleStorageCtorWithParamNames (tag, baseTySpec, ty, extraParams, flds, access) =
    let preblock =
      match baseTySpec with
        None -> []
      | Some tspec ->
          ([ mkLdarg0
             mkNormalCall (mkILCtorMethSpecForTy (mkILBoxedType tspec, [])) ])
    mkILStorageCtorWithParamNames (tag, preblock, ty, extraParams, flds, access)

let addParamNames flds =
    flds |> List.map (fun (nm, ty) -> (nm, nm, ty))

let mkILSimpleStorageCtor (tag, baseTySpec, ty, extraParams, flds, access) =
    mkILSimpleStorageCtorWithParamNames (tag, baseTySpec, ty, extraParams, addParamNames flds, access)

let mkILStorageCtor (tag, preblock, ty, flds, access) = mkILStorageCtorWithParamNames (tag, preblock, ty, [], addParamNames flds, access)

let mkILGenericClass (nm, access, genparams, extends, impl, methods, fields, nestedTypes, props, events, attrs, init) =
    ILTypeDef(name=nm,
              attributes=(convertTypeAccessFlags access ||| TypeAttributes.AutoLayout ||| TypeAttributes.Class |||
                          (match init with | ILTypeInit.BeforeField -> TypeAttributes.BeforeFieldInit | _ -> enum 0) ||| TypeAttributes.AnsiClass),
              genericParams= genparams,
              implements = impl,
              layout=ILTypeDefLayout.Auto,
              extends = Some extends,
              methods= methods,
              fields= fields,
              nestedTypes=nestedTypes,
              customAttrs=attrs,
              methodImpls=emptyILMethodImpls,
              properties=props,
              events=events,
              securityDecls=emptyILSecurityDecls)

let mkRawDataValueTypeDef (iltyp_ValueType: ILType) (nm, size, pack) =
    ILTypeDef(name = nm,
              genericParams= [],
              attributes = (TypeAttributes.NotPublic ||| TypeAttributes.Sealed ||| TypeAttributes.ExplicitLayout |||
                            TypeAttributes.BeforeFieldInit ||| TypeAttributes.AnsiClass),
              implements = [],
              extends = Some iltyp_ValueType,
              layout=ILTypeDefLayout.Explicit { Size=Some size; Pack=Some pack },
              methods= emptyILMethods,
              fields= emptyILFields,
              nestedTypes=emptyILTypeDefs,
              customAttrs=emptyILCustomAttrs,
              methodImpls=emptyILMethodImpls,
              properties=emptyILProperties,
              events=emptyILEvents,
              securityDecls=emptyILSecurityDecls)


let mkILSimpleClass (ilg: ILGlobals) (nm, access, methods, fields, nestedTypes, props, events, attrs, init) =
  mkILGenericClass (nm, access, mkILEmptyGenericParams, ilg.typ_Object, [], methods, fields, nestedTypes, props, events, attrs, init)

let mkILTypeDefForGlobalFunctions ilg (methods, fields) =
    mkILSimpleClass ilg (typeNameForGlobalFunctions, ILTypeDefAccess.Public, methods, fields, emptyILTypeDefs, emptyILProperties, emptyILEvents, emptyILCustomAttrs, ILTypeInit.BeforeField)

let destTypeDefsWithGlobalFunctionsFirst ilg (tdefs: ILTypeDefs) =
  let l = tdefs.AsList
  let top, nontop = l |> List.partition (fun td -> td.Name = typeNameForGlobalFunctions)
  let top2 = if isNil top then [ mkILTypeDefForGlobalFunctions ilg (emptyILMethods, emptyILFields) ] else top
  top2@nontop

let mkILSimpleModule assemblyName modname dll subsystemVersion useHighEntropyVA tdefs hashalg locale flags exportedTypes metadataVersion =
    let manifest =
        { Name=assemblyName
          AuxModuleHashAlgorithm= match hashalg with | Some alg -> alg | _ -> 0x8004 // SHA1
          SecurityDeclsStored=emptyILSecurityDeclsStored
          PublicKey= None
          Version= None
          Locale=locale
          CustomAttrsStored=storeILCustomAttrs emptyILCustomAttrs
          AssemblyLongevity=ILAssemblyLongevity.Unspecified
          DisableJitOptimizations = 0 <> (flags &&& 0x4000)
          JitTracking = (0 <> (flags &&& 0x8000)) // always turn these on
          IgnoreSymbolStoreSequencePoints = (0 <> (flags &&& 0x2000))
          Retargetable = (0 <> (flags &&& 0x100))
          ExportedTypes=exportedTypes
          EntrypointElsewhere=None
          MetadataIndex = NoMetadataIdx }
    { Manifest= Some manifest
      CustomAttrsStored=storeILCustomAttrs emptyILCustomAttrs
      Name=modname
      NativeResources=[]
      TypeDefs=tdefs
      SubsystemVersion = subsystemVersion
      UseHighEntropyVA = useHighEntropyVA
      SubSystemFlags=defaultSubSystem
      IsDLL=dll
      IsILOnly=true
      Platform=None
      StackReserveSize=None
      Is32Bit=false
      Is32BitPreferred=false
      Is64Bit=false
      PhysicalAlignment=defaultPhysAlignment
      VirtualAlignment=defaultVirtAlignment
      ImageBase=defaultImageBase
      MetadataVersion=metadataVersion
      Resources=mkILResources []
      MetadataIndex = NoMetadataIdx
    }


//-----------------------------------------------------------------------
// [instructions_to_code] makes the basic block structure of code from
// a primitive array of instructions. We
// do this be iterating over the instructions, pushing new basic blocks
// everytime we encounter an address that has been recorded
// [bbstartToCodeLabelMap].
//-----------------------------------------------------------------------


// REVIEW: this function shows up on performance traces. If we eliminated the last ILX->IL rewrites from the
// F# compiler we could get rid of this structured code representation from Abstract IL altogether and
// never convert F# code into this form.
let buildILCode (_methName: string) lab2pc instrs tryspecs localspecs : ILCode =
    { Labels = lab2pc
      Instrs = instrs
      Exceptions = tryspecs
      Locals = localspecs }


// --------------------------------------------------------------------
// Detecting Delegates
// --------------------------------------------------------------------

let mkILDelegateMethods (access) (ilg: ILGlobals) (iltyp_AsyncCallback, iltyp_IAsyncResult) (parms, rtv: ILReturn) =
    let rty = rtv.Type
    let one nm args ret =
        let mdef = mkILNonGenericVirtualMethod (nm, access, args, mkILReturn ret, MethodBody.Abstract)
        mdef.WithAbstract(false).WithHideBySig(true).WithRuntime(true)
    let ctor = mkILCtor (access, [ mkILParamNamed("object", ilg.typ_Object); mkILParamNamed("method", ilg.typ_IntPtr) ], MethodBody.Abstract)
    let ctor = ctor.WithRuntime(true).WithHideBySig(true)
    [ ctor
      one "Invoke" parms rty
      one "BeginInvoke" (parms @ [mkILParamNamed ("callback", iltyp_AsyncCallback); mkILParamNamed ("objects", ilg.typ_Object) ] ) iltyp_IAsyncResult
      one "EndInvoke" [mkILParamNamed ("result", iltyp_IAsyncResult)] rty ]


let mkCtorMethSpecForDelegate (ilg: ILGlobals) (ty: ILType, useUIntPtr) =
    let scoref = ty.TypeRef.Scope
    mkILInstanceMethSpecInTy (ty, ".ctor", [rescopeILType scoref ilg.typ_Object
                                            rescopeILType scoref (if useUIntPtr then ilg.typ_UIntPtr else ilg.typ_IntPtr)],
                              ILType.Void, emptyILGenericArgsList)

type ILEnumInfo =
    { enumValues: (string * ILFieldInit) list
      enumType: ILType }

let getTyOfILEnumInfo info = info.enumType

let computeILEnumInfo (mdName, mdFields: ILFieldDefs) =
    match (List.partition (fun (fd: ILFieldDef) -> fd.IsStatic) mdFields.AsList) with
    | staticFields, [vfd] ->
        { enumType = vfd.FieldType
          enumValues = staticFields |> List.map (fun fd -> (fd.Name, match fd.LiteralValue with Some i -> i | None -> failwith ("info_of_enum_tdef: badly formed enum "+mdName+": static field does not have an default value"))) }
    | _, [] -> failwith ("info_of_enum_tdef: badly formed enum "+mdName+": no non-static field found")
    | _, _ -> failwith ("info_of_enum_tdef: badly formed enum "+mdName+": more than one non-static field found")

//---------------------------------------------------------------------
// Primitives to help read signatures. These do not use the file cursor, but
// pass around an int index
//---------------------------------------------------------------------

let sigptr_get_byte bytes sigptr =
    Bytes.get bytes sigptr, sigptr + 1

let sigptr_get_bool bytes sigptr =
    let b0, sigptr = sigptr_get_byte bytes sigptr
    (b0 = 0x01), sigptr

let sigptr_get_u8 bytes sigptr =
    let b0, sigptr = sigptr_get_byte bytes sigptr
    byte b0, sigptr

let sigptr_get_i8 bytes sigptr =
    let i, sigptr = sigptr_get_u8 bytes sigptr
    sbyte i, sigptr

let sigptr_get_u16 bytes sigptr =
    let b0, sigptr = sigptr_get_byte bytes sigptr
    let b1, sigptr = sigptr_get_byte bytes sigptr
    uint16 (b0 ||| (b1 <<< 8)), sigptr

let sigptr_get_i16 bytes sigptr =
    let u, sigptr = sigptr_get_u16 bytes sigptr
    int16 u, sigptr

let sigptr_get_i32 bytes sigptr =
    let b0, sigptr = sigptr_get_byte bytes sigptr
    let b1, sigptr = sigptr_get_byte bytes sigptr
    let b2, sigptr = sigptr_get_byte bytes sigptr
    let b3, sigptr = sigptr_get_byte bytes sigptr
    b0 ||| (b1 <<< 8) ||| (b2 <<< 16) ||| (b3 <<< 24), sigptr

let sigptr_get_u32 bytes sigptr =
    let u, sigptr = sigptr_get_i32 bytes sigptr
    uint32 u, sigptr

let sigptr_get_i64 bytes sigptr =
    let b0, sigptr = sigptr_get_byte bytes sigptr
    let b1, sigptr = sigptr_get_byte bytes sigptr
    let b2, sigptr = sigptr_get_byte bytes sigptr
    let b3, sigptr = sigptr_get_byte bytes sigptr
    let b4, sigptr = sigptr_get_byte bytes sigptr
    let b5, sigptr = sigptr_get_byte bytes sigptr
    let b6, sigptr = sigptr_get_byte bytes sigptr
    let b7, sigptr = sigptr_get_byte bytes sigptr
    int64 b0 ||| (int64 b1 <<< 8) ||| (int64 b2 <<< 16) ||| (int64 b3 <<< 24) |||
    (int64 b4 <<< 32) ||| (int64 b5 <<< 40) ||| (int64 b6 <<< 48) ||| (int64 b7 <<< 56),
    sigptr

let sigptr_get_u64 bytes sigptr =
    let u, sigptr = sigptr_get_i64 bytes sigptr
    uint64 u, sigptr

let float32_of_bits (x: int32) = BitConverter.ToSingle (BitConverter.GetBytes x, 0)

let float_of_bits (x: int64) = BitConverter.Int64BitsToDouble x

let sigptr_get_ieee32 bytes sigptr =
    let u, sigptr = sigptr_get_i32 bytes sigptr
    float32_of_bits u, sigptr

let sigptr_get_ieee64 bytes sigptr =
    let u, sigptr = sigptr_get_i64 bytes sigptr
    float_of_bits u, sigptr

let sigptr_get_intarray n (bytes: byte[]) sigptr =
    let res = Bytes.zeroCreate n
    for i = 0 to n - 1 do
        res.[i] <- bytes.[sigptr + i]
    res, sigptr + n

let sigptr_get_string n bytes sigptr =
    let intarray, sigptr = sigptr_get_intarray n bytes sigptr
    Encoding.UTF8.GetString (intarray, 0, intarray.Length), sigptr

let sigptr_get_z_i32 bytes sigptr =
    let b0, sigptr = sigptr_get_byte bytes sigptr
    if b0 <= 0x7F then b0, sigptr
    elif b0 <= 0xbf then
        let b0 = b0 &&& 0x7f
        let b1, sigptr = sigptr_get_byte bytes sigptr
        (b0 <<< 8) ||| b1, sigptr
    else
        let b0 = b0 &&& 0x3f
        let b1, sigptr = sigptr_get_byte bytes sigptr
        let b2, sigptr = sigptr_get_byte bytes sigptr
        let b3, sigptr = sigptr_get_byte bytes sigptr
        (b0 <<< 24) ||| (b1 <<< 16) ||| (b2 <<< 8) ||| b3, sigptr

let sigptr_get_serstring bytes sigptr =
    let len, sigptr = sigptr_get_z_i32 bytes sigptr
    sigptr_get_string ( len) bytes sigptr

let sigptr_get_serstring_possibly_null bytes sigptr =
    let b0, new_sigptr = sigptr_get_byte bytes sigptr
    if b0 = 0xFF then // null case
        None, new_sigptr
    else  // throw away new_sigptr, getting length & text advance
        let len, sigptr = sigptr_get_z_i32 bytes sigptr
        let s, sigptr = sigptr_get_string len bytes sigptr
        Some s, sigptr

//---------------------------------------------------------------------
// Get the public key token from the public key.
//---------------------------------------------------------------------

let mkRefToILAssembly (m: ILAssemblyManifest) =
    ILAssemblyRef.Create (m.Name, None, (match m.PublicKey with Some k -> Some (PublicKey.KeyAsToken k) | None -> None), m.Retargetable, m.Version, m.Locale)

let z_unsigned_int_size n =
    if n <= 0x7F then 1
    elif n <= 0x3FFF then 2
    else 3

let z_unsigned_int n =
    if n >= 0 && n <= 0x7F then [| byte n |]
    elif n >= 0x80 && n <= 0x3FFF then [| byte (0x80 ||| (n >>>& 8)); byte (n &&& 0xFF) |]
    else [| byte (0xc0 ||| (n >>>& 24))
            byte ((n >>>& 16) &&& 0xFF)
            byte ((n >>>& 8) &&& 0xFF)
            byte (n &&& 0xFF) |]

let string_as_utf8_bytes (s: string) = Encoding.UTF8.GetBytes s

(* Little-endian encoding of int64 *)
let dw7 n = byte ((n >>> 56) &&& 0xFFL)

let dw6 n = byte ((n >>> 48) &&& 0xFFL)

let dw5 n = byte ((n >>> 40) &&& 0xFFL)

let dw4 n = byte ((n >>> 32) &&& 0xFFL)

let dw3 n = byte ((n >>> 24) &&& 0xFFL)

let dw2 n = byte ((n >>> 16) &&& 0xFFL)

let dw1 n = byte ((n >>> 8) &&& 0xFFL)

let dw0 n = byte (n &&& 0xFFL)

let u8AsBytes (i: byte) = [| i |]

let u16AsBytes x = let n = (int x) in [| byte (b0 n); byte (b1 n) |]

let i32AsBytes i = [| byte (b0 i); byte (b1 i); byte (b2 i); byte (b3 i) |]

let i64AsBytes i = [| dw0 i; dw1 i; dw2 i; dw3 i; dw4 i; dw5 i; dw6 i; dw7 i |]

let i8AsBytes (i: sbyte) = u8AsBytes (byte i)

let i16AsBytes (i: int16) = u16AsBytes (uint16 i)

let u32AsBytes (i: uint32) = i32AsBytes (int32 i)

let u64AsBytes (i: uint64) = i64AsBytes (int64 i)

let bits_of_float32 (x: float32) = BitConverter.ToInt32 (BitConverter.GetBytes x, 0)

let bits_of_float (x: float) = BitConverter.DoubleToInt64Bits x

let ieee32AsBytes i = i32AsBytes (bits_of_float32 i)

let ieee64AsBytes i = i64AsBytes (bits_of_float i)

let et_END = 0x00uy
let et_VOID = 0x01uy
let et_BOOLEAN = 0x02uy
let et_CHAR = 0x03uy
let et_I1 = 0x04uy
let et_U1 = 0x05uy
let et_I2 = 0x06uy
let et_U2 = 0x07uy
let et_I4 = 0x08uy
let et_U4 = 0x09uy
let et_I8 = 0x0Auy
let et_U8 = 0x0Buy
let et_R4 = 0x0Cuy
let et_R8 = 0x0Duy
let et_STRING = 0x0Euy
let et_PTR = 0x0Fuy
let et_BYREF = 0x10uy
let et_VALUETYPE = 0x11uy
let et_CLASS = 0x12uy
let et_VAR = 0x13uy
let et_ARRAY = 0x14uy
let et_WITH = 0x15uy
let et_TYPEDBYREF = 0x16uy
let et_I = 0x18uy
let et_U = 0x19uy
let et_FNPTR = 0x1Buy
let et_OBJECT = 0x1Cuy
let et_SZARRAY = 0x1Duy
let et_MVAR = 0x1Euy
let et_CMOD_REQD = 0x1Fuy
let et_CMOD_OPT = 0x20uy

let formatILVersion (version: ILVersionInfo) = sprintf "%d.%d.%d.%d" (int version.Major) (int version.Minor) (int version.Build) (int version.Revision)

let encodeCustomAttrString s =
    let arr = string_as_utf8_bytes s
    Array.concat [ z_unsigned_int arr.Length; arr ]

let rec encodeCustomAttrElemType x =
    match x with
    | ILType.Value tspec when tspec.Name = tname_SByte -> [| et_I1 |]
    | ILType.Value tspec when tspec.Name = tname_Byte -> [| et_U1 |]
    | ILType.Value tspec when tspec.Name = tname_Int16 -> [| et_I2 |]
    | ILType.Value tspec when tspec.Name = tname_UInt16 -> [| et_U2 |]
    | ILType.Value tspec when tspec.Name = tname_Int32 -> [| et_I4 |]
    | ILType.Value tspec when tspec.Name = tname_UInt32 -> [| et_U4 |]
    | ILType.Value tspec when tspec.Name = tname_Int64 -> [| et_I8 |]
    | ILType.Value tspec when tspec.Name = tname_UInt64 -> [| et_U8 |]
    | ILType.Value tspec when tspec.Name = tname_Double -> [| et_R8 |]
    | ILType.Value tspec when tspec.Name = tname_Single -> [| et_R4 |]
    | ILType.Value tspec when tspec.Name = tname_Char -> [| et_CHAR |]
    | ILType.Value tspec when tspec.Name = tname_Bool -> [| et_BOOLEAN |]
    | ILType.Boxed tspec when tspec.Name = tname_String -> [| et_STRING |]
    | ILType.Boxed tspec when tspec.Name = tname_Object -> [| 0x51uy |]
    | ILType.Boxed tspec when tspec.Name = tname_Type -> [| 0x50uy |]
    | ILType.Value tspec -> Array.append [| 0x55uy |] (encodeCustomAttrString tspec.TypeRef.QualifiedName)
    | ILType.Array (shape, elemType) when shape = ILArrayShape.SingleDimensional ->
          Array.append [| et_SZARRAY |] (encodeCustomAttrElemType elemType)
    | _ -> failwith "encodeCustomAttrElemType: unrecognized custom element type"

/// Given a custom attribute element, work out the type of the .NET argument for that element.
let rec encodeCustomAttrElemTypeForObject x =
    match x with
    | ILAttribElem.String _ -> [| et_STRING |]
    | ILAttribElem.Bool _ -> [| et_BOOLEAN |]
    | ILAttribElem.Char _ -> [| et_CHAR |]
    | ILAttribElem.SByte _ -> [| et_I1 |]
    | ILAttribElem.Int16 _ -> [| et_I2 |]
    | ILAttribElem.Int32 _ -> [| et_I4 |]
    | ILAttribElem.Int64 _ -> [| et_I8 |]
    | ILAttribElem.Byte _ -> [| et_U1 |]
    | ILAttribElem.UInt16 _ -> [| et_U2 |]
    | ILAttribElem.UInt32 _ -> [| et_U4 |]
    | ILAttribElem.UInt64 _ -> [| et_U8 |]
    | ILAttribElem.Type _ -> [| 0x50uy |]
    | ILAttribElem.TypeRef _ -> [| 0x50uy |]
    | ILAttribElem.Null _ -> [| et_STRING |]// yes, the 0xe prefix is used when passing a "null" to a property or argument of type "object" here
    | ILAttribElem.Single _ -> [| et_R4 |]
    | ILAttribElem.Double _ -> [| et_R8 |]
    | ILAttribElem.Array (elemTy, _) -> [| yield et_SZARRAY; yield! encodeCustomAttrElemType elemTy |]

let rec decodeCustomAttrElemType (ilg: ILGlobals) bytes sigptr x =
    match x with
    | x when x = et_I1 -> ilg.typ_SByte, sigptr
    | x when x = et_U1 -> ilg.typ_Byte, sigptr
    | x when x = et_I2 -> ilg.typ_Int16, sigptr
    | x when x = et_U2 -> ilg.typ_UInt16, sigptr
    | x when x = et_I4 -> ilg.typ_Int32, sigptr
    | x when x = et_U4 -> ilg.typ_UInt32, sigptr
    | x when x = et_I8 -> ilg.typ_Int64, sigptr
    | x when x = et_U8 -> ilg.typ_UInt64, sigptr
    | x when x = et_R8 -> ilg.typ_Double, sigptr
    | x when x = et_R4 -> ilg.typ_Single, sigptr
    | x when x = et_CHAR -> ilg.typ_Char, sigptr
    | x when x = et_BOOLEAN -> ilg.typ_Bool, sigptr
    | x when x = et_STRING -> ilg.typ_String, sigptr
    | x when x = et_OBJECT -> ilg.typ_Object, sigptr
    | x when x = et_SZARRAY ->
         let et, sigptr = sigptr_get_u8 bytes sigptr
         let elemTy, sigptr = decodeCustomAttrElemType ilg bytes sigptr et
         mkILArr1DTy elemTy, sigptr
    | x when x = 0x50uy -> ilg.typ_Type, sigptr
    | _ -> failwithf "decodeCustomAttrElemType ilg: unrecognized custom element type: %A" x


/// Given a custom attribute element, encode it to a binary representation according to the rules in Ecma 335 Partition II.
let rec encodeCustomAttrPrimValue ilg c =
    match c with
    | ILAttribElem.Bool b -> [| (if b then 0x01uy else 0x00uy) |]
    | ILAttribElem.String None
    | ILAttribElem.Type None
    | ILAttribElem.TypeRef None
    | ILAttribElem.Null -> [| 0xFFuy |]
    | ILAttribElem.String (Some s) -> encodeCustomAttrString s
    | ILAttribElem.Char x -> u16AsBytes (uint16 x)
    | ILAttribElem.SByte x -> i8AsBytes x
    | ILAttribElem.Int16 x -> i16AsBytes x
    | ILAttribElem.Int32 x -> i32AsBytes x
    | ILAttribElem.Int64 x -> i64AsBytes x
    | ILAttribElem.Byte x -> u8AsBytes x
    | ILAttribElem.UInt16 x -> u16AsBytes x
    | ILAttribElem.UInt32 x -> u32AsBytes x
    | ILAttribElem.UInt64 x -> u64AsBytes x
    | ILAttribElem.Single x -> ieee32AsBytes x
    | ILAttribElem.Double x -> ieee64AsBytes x
    | ILAttribElem.Type (Some ty) -> encodeCustomAttrString ty.QualifiedName
    | ILAttribElem.TypeRef (Some tref) -> encodeCustomAttrString tref.QualifiedName
    | ILAttribElem.Array (_, elems) ->
         [| yield! i32AsBytes elems.Length; for elem in elems do yield! encodeCustomAttrPrimValue ilg elem |]

and encodeCustomAttrValue ilg ty c =
    match ty, c with
    | ILType.Boxed tspec, _ when tspec.Name = tname_Object ->
       [| yield! encodeCustomAttrElemTypeForObject c; yield! encodeCustomAttrPrimValue ilg c |]
    | ILType.Array (shape, _), ILAttribElem.Null when shape = ILArrayShape.SingleDimensional ->
       [| yield! i32AsBytes 0xFFFFFFFF |]
    | ILType.Array (shape, elemType), ILAttribElem.Array (_, elems) when shape = ILArrayShape.SingleDimensional ->
       [| yield! i32AsBytes elems.Length; for elem in elems do yield! encodeCustomAttrValue ilg elemType elem |]
    | _ ->
       encodeCustomAttrPrimValue ilg c

let encodeCustomAttrNamedArg ilg (nm, ty, prop, elem) =
   [| yield (if prop then 0x54uy else 0x53uy)
      yield! encodeCustomAttrElemType ty
      yield! encodeCustomAttrString nm
      yield! encodeCustomAttrValue ilg ty elem |]

let encodeCustomAttrArgs (ilg: ILGlobals) (mspec: ILMethodSpec) (fixedArgs: list<_>) (namedArgs: list<_>) =
    let argtys = mspec.MethodRef.ArgTypes
    [| yield! [| 0x01uy; 0x00uy; |]
       for (argty, fixedArg) in Seq.zip argtys fixedArgs do
          yield! encodeCustomAttrValue ilg argty fixedArg
       yield! u16AsBytes (uint16 namedArgs.Length)
       for namedArg in namedArgs do
           yield! encodeCustomAttrNamedArg ilg namedArg |]

let encodeCustomAttr (ilg: ILGlobals) (mspec: ILMethodSpec, fixedArgs: list<_>, namedArgs: list<_>) =
    let args = encodeCustomAttrArgs ilg mspec fixedArgs namedArgs
    ILAttribute.Encoded (mspec, args, fixedArgs @ (namedArgs |> List.map (fun (_, _, _, e) -> e)))

let mkILCustomAttribMethRef (ilg: ILGlobals) (mspec: ILMethodSpec, fixedArgs: list<_>, namedArgs: list<_>) =
    encodeCustomAttr ilg (mspec, fixedArgs, namedArgs)

let mkILCustomAttribute ilg (tref, argtys, argvs, propvs) =
    encodeCustomAttr ilg (mkILNonGenericCtorMethSpec (tref, argtys), argvs, propvs)

let getCustomAttrData (ilg: ILGlobals) cattr =
    match cattr with
    | ILAttribute.Encoded (_, data, _) -> data
    | ILAttribute.Decoded (mspec, fixedArgs, namedArgs) ->
        encodeCustomAttrArgs ilg mspec fixedArgs namedArgs

let MscorlibScopeRef = ILScopeRef.Assembly (ILAssemblyRef.Create ("mscorlib", None, Some ecmaPublicKey, true, None, None))

let EcmaMscorlibILGlobals = mkILGlobals MscorlibScopeRef

// ILSecurityDecl is a 'blob' having the following format:
// - A byte containing a period (.).
// - A compressed int32 containing the number of attributes encoded in the blob.
// - An array of attributes each containing the following:
// - A String, which is the fully-qualified type name of the attribute. (Strings are encoded
//      as a compressed int to indicate the size followed by an array of UTF8 characters.)
// - A set of properties, encoded as the named arguments to a custom attribute would be (as
//      in §23.3, beginning with NumNamed).
let mkPermissionSet (ilg: ILGlobals) (action, attributes: list<(ILTypeRef * (string * ILType * ILAttribElem) list)>) =
    let bytes =
        [| yield (byte '.')
           yield! z_unsigned_int attributes.Length
           for (tref: ILTypeRef, props) in attributes do
              yield! encodeCustomAttrString tref.QualifiedName
              let bytes =
                  [| yield! z_unsigned_int props.Length
                     for (nm, ty, value) in props do
                         yield! encodeCustomAttrNamedArg ilg (nm, ty, true, value)|]
              yield! z_unsigned_int bytes.Length
              yield! bytes |]

    ILSecurityDecl.ILSecurityDecl (action, bytes)

// Parse an IL type signature argument within a custom attribute blob
type ILTypeSigParser (tstring : string) =

    let mutable startPos = 0
    let mutable currentPos = 0

    let reset() = startPos <- 0 ; currentPos <- 0
    let nil = '\r' // cannot appear in a type sig

    // take a look at the next value, but don't advance
    let peek() = if currentPos < (tstring.Length-1) then tstring.[currentPos+1] else nil
    let peekN skip = if currentPos < (tstring.Length - skip) then tstring.[currentPos+skip] else nil
    // take a look at the current value, but don't advance
    let here() = if currentPos < tstring.Length then tstring.[currentPos] else nil
    // move on to the next character
    let step() = currentPos <- currentPos+1
    // ignore the current lexeme
    let skip() = startPos <- currentPos
    // ignore the current lexeme, advance
    let drop() = skip() ; step() ; skip()
    // return the current lexeme, advance
    let take() =
        let s = if currentPos < tstring.Length then tstring.[startPos..currentPos] else ""
        drop()
        s

    // The format we accept is
    // "<type name>{`<arity>[<type>, +]}{<array rank>}{<scope>}" E.g.,
    //
    // System.Collections.Generic.Dictionary
    //     `2[
    //         [System.Int32, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089],
    //         dev.virtualearth.net.webservices.v1.search.CategorySpecificPropertySet],
    // mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"
    //
    // Note that
    //   Since we're only reading valid IL, we assume that the signature is properly formed
    //   For type parameters, if the type is non-local, it will be wrapped in brackets ([])
    //   Still needs testing with jagged arrays and byref parameters
    member private x.ParseType() =

        // Does the type name start with a leading '['? If so, ignore it
        // (if the specialization type is in another module, it will be wrapped in bracket)
        if here() = '[' then drop()

        // 1. Iterate over beginning of type, grabbing the type name and determining if it's generic or an array
        let typeName =
            while (peek() <> '`') && (peek() <> '[') && (peek() <> ']') && (peek() <> ',') && (peek() <> nil) do step()
            take()

        // 2. Classify the type

        // Is the type generic?
        let typeName, specializations =
            if here() = '`' then
                drop() // step to the number
                // fetch the arity
                let arity =
                    while (int(here()) >= (int('0'))) && (int(here()) <= ((int('9')))) && (int(peek()) >= (int('0'))) && (int(peek()) <= ((int('9')))) do step()
                    Int32.Parse(take())
                // skip the '['
                drop()
                // get the specializations
                typeName+"`"+(arity.ToString()), Some(([for _i in 0..arity-1 do yield x.ParseType()]))
            else
                typeName, None

        // Is the type an array?
        let rank =
            if here() = '[' then
                let mutable rank = 0

                while here() <> ']' do
                    rank <- rank + 1
                    step()
                drop()

                Some(ILArrayShape(List.replicate rank (Some 0, None)))
            else
                None

        // Is there a scope?
        let scope =
            if (here() = ',' || here() = ' ') && (peek() <> '[' && peekN 2 <> '[') then
                let grabScopeComponent() =
                    if here() = ',' then drop() // ditch the ','
                    if here() = ' ' then drop() // ditch the ' '

                    while (peek() <> ',' && peek() <> ']' && peek() <> nil) do step()
                    take()

                let scope =
                    [ yield grabScopeComponent() // assembly
                      yield grabScopeComponent() // version
                      yield grabScopeComponent() // culture
                      yield grabScopeComponent() // public key token
                    ] |> String.concat ","
                ILScopeRef.Assembly(ILAssemblyRef.FromAssemblyName(AssemblyName scope))
            else
                ILScopeRef.Local

        // strip any extraneous trailing brackets or commas
        if (here() = ']') then drop()
        if (here() = ',') then drop()

        // build the IL type
        let tref = mkILTyRef (scope, typeName)
        let genericArgs =
            match specializations with
            | None -> []
            | Some genericArgs -> genericArgs
        let tspec = ILTypeSpec.Create (tref, genericArgs)
        let ilty =
            match tspec.Name with
            | "System.SByte"
            | "System.Byte"
            | "System.Int16"
            | "System.UInt16"
            | "System.Int32"
            | "System.UInt32"
            | "System.Int64"
            | "System.UInt64"
            | "System.Char"
            | "System.Double"
            | "System.Single"
            | "System.Boolean" -> ILType.Value tspec
            | _ -> ILType.Boxed tspec

        // if it's an array, wrap it - otherwise, just return the IL type
        match rank with
        | Some r -> ILType.Array (r, ilty)
        | _ -> ilty

    member x.ParseTypeSpec() =
        reset()
        let ilty = x.ParseType()
        ILAttribElem.Type (Some ilty)

let decodeILAttribData (ilg: ILGlobals) (ca: ILAttribute) =
    match ca with
    | ILAttribute.Decoded (_, fixedArgs, namedArgs) -> fixedArgs, namedArgs
    | ILAttribute.Encoded (_, bytes, _) ->

    let sigptr = 0
    let bb0, sigptr = sigptr_get_byte bytes sigptr
    let bb1, sigptr = sigptr_get_byte bytes sigptr
    if not (bb0 = 0x01 && bb1 = 0x00) then failwith "decodeILAttribData: invalid data"

    let rec parseVal argty sigptr =
      match argty with
      | ILType.Value tspec when tspec.Name = "System.SByte" ->
          let n, sigptr = sigptr_get_i8 bytes sigptr
          ILAttribElem.SByte n, sigptr
      | ILType.Value tspec when tspec.Name = "System.Byte" ->
          let n, sigptr = sigptr_get_u8 bytes sigptr
          ILAttribElem.Byte n, sigptr
      | ILType.Value tspec when tspec.Name = "System.Int16" ->
          let n, sigptr = sigptr_get_i16 bytes sigptr
          ILAttribElem.Int16 n, sigptr
      | ILType.Value tspec when tspec.Name = "System.UInt16" ->
          let n, sigptr = sigptr_get_u16 bytes sigptr
          ILAttribElem.UInt16 n, sigptr
      | ILType.Value tspec when tspec.Name = "System.Int32" ->
          let n, sigptr = sigptr_get_i32 bytes sigptr
          ILAttribElem.Int32 n, sigptr
      | ILType.Value tspec when tspec.Name = "System.UInt32" ->
          let n, sigptr = sigptr_get_u32 bytes sigptr
          ILAttribElem.UInt32 n, sigptr
      | ILType.Value tspec when tspec.Name = "System.Int64" ->
          let n, sigptr = sigptr_get_i64 bytes sigptr
          ILAttribElem.Int64 n, sigptr
      | ILType.Value tspec when tspec.Name = "System.UInt64" ->
          let n, sigptr = sigptr_get_u64 bytes sigptr
          ILAttribElem.UInt64 n, sigptr
      | ILType.Value tspec when tspec.Name = "System.Double" ->
          let n, sigptr = sigptr_get_ieee64 bytes sigptr
          ILAttribElem.Double n, sigptr
      | ILType.Value tspec when tspec.Name = "System.Single" ->
          let n, sigptr = sigptr_get_ieee32 bytes sigptr
          ILAttribElem.Single n, sigptr
      | ILType.Value tspec when tspec.Name = "System.Char" ->
          let n, sigptr = sigptr_get_u16 bytes sigptr
          ILAttribElem.Char (char (int32 n)), sigptr
      | ILType.Value tspec when tspec.Name = "System.Boolean" ->
          let n, sigptr = sigptr_get_byte bytes sigptr
          ILAttribElem.Bool (not (n = 0)), sigptr
      | ILType.Boxed tspec when tspec.Name = "System.String" ->
          let n, sigptr = sigptr_get_serstring_possibly_null bytes sigptr
          ILAttribElem.String n, sigptr
      | ILType.Boxed tspec when tspec.Name = "System.Type" ->
          let nOpt, sigptr = sigptr_get_serstring_possibly_null bytes sigptr
          match nOpt with
          | None -> ILAttribElem.TypeRef None, sigptr
          | Some n ->
            try
                let parser = ILTypeSigParser n
                parser.ParseTypeSpec(), sigptr
            with e ->
                failwith (sprintf "decodeILAttribData: error parsing type in custom attribute blob: %s" e.Message)
      | ILType.Boxed tspec when tspec.Name = "System.Object" ->
          let et, sigptr = sigptr_get_u8 bytes sigptr
          if et = 0xFFuy then
              ILAttribElem.Null, sigptr
          else
              let ty, sigptr = decodeCustomAttrElemType ilg bytes sigptr et
              parseVal ty sigptr
      | ILType.Array (shape, elemTy) when shape = ILArrayShape.SingleDimensional ->
          let n, sigptr = sigptr_get_i32 bytes sigptr
          if n = 0xFFFFFFFF then ILAttribElem.Null, sigptr else
          let rec parseElems acc n sigptr =
            if n = 0 then List.rev acc, sigptr else
            let v, sigptr = parseVal elemTy sigptr
            parseElems (v :: acc) (n-1) sigptr
          let elems, sigptr = parseElems [] n sigptr
          ILAttribElem.Array (elemTy, elems), sigptr
      | ILType.Value _ -> (* assume it is an enumeration *)
          let n, sigptr = sigptr_get_i32 bytes sigptr
          ILAttribElem.Int32 n, sigptr
      | _ -> failwith "decodeILAttribData: attribute data involves an enum or System.Type value"
    let rec parseFixed argtys sigptr =
      match argtys with
        [] -> [], sigptr
      | h :: t ->
          let nh, sigptr = parseVal h sigptr
          let nt, sigptr = parseFixed t sigptr
          nh :: nt, sigptr
    let fixedArgs, sigptr = parseFixed ca.Method.FormalArgTypes sigptr
    let nnamed, sigptr = sigptr_get_u16 bytes sigptr
    let rec parseNamed acc n sigptr =
      if n = 0 then List.rev acc else
      let isPropByte, sigptr = sigptr_get_u8 bytes sigptr
      let isProp = (int isPropByte = 0x54)
      let et, sigptr = sigptr_get_u8 bytes sigptr
      // We have a named value
      let ty, sigptr =
        if ( (* 0x50 = (int et) || *) 0x55 = (int et)) then
            let qualified_tname, sigptr = sigptr_get_serstring bytes sigptr
            let unqualified_tname, rest =
                let pieces = qualified_tname.Split (',')
                if pieces.Length > 1 then
                    pieces.[0], Some (String.concat "," pieces.[1..])
                else
                    pieces.[0], None
            let scoref =
                match rest with
                | Some aname -> ILScopeRef.Assembly (ILAssemblyRef.FromAssemblyName (AssemblyName aname))
                | None -> ilg.primaryAssemblyScopeRef

            let tref = mkILTyRef (scoref, unqualified_tname)
            let tspec = mkILNonGenericTySpec tref
            ILType.Value tspec, sigptr
        else
            decodeCustomAttrElemType ilg bytes sigptr et
      let nm, sigptr = sigptr_get_serstring bytes sigptr
      let v, sigptr = parseVal ty sigptr
      parseNamed ((nm, ty, isProp, v) :: acc) (n-1) sigptr
    let named = parseNamed [] (int nnamed) sigptr
    fixedArgs, named


// --------------------------------------------------------------------
// Functions to collect up all the references in a full module or
// assembly manifest. The process also allocates
// a unique name to each unique internal assembly reference.
// --------------------------------------------------------------------

type ILReferences =
    { AssemblyReferences: ILAssemblyRef list
      ModuleReferences: ILModuleRef list }

type ILReferencesAccumulator =
    { refsA: HashSet<ILAssemblyRef>
      refsM: HashSet<ILModuleRef> }

let emptyILRefs =
    { AssemblyReferences=[]
      ModuleReferences = [] }

(* Now find references. *)
let refs_of_assemblyRef (s: ILReferencesAccumulator) x = s.refsA.Add x |> ignore

let refs_of_modref (s: ILReferencesAccumulator) x = s.refsM.Add x |> ignore

let refs_of_scoref s x =
    match x with
    | ILScopeRef.Local -> ()
    | ILScopeRef.Assembly assemblyRef -> refs_of_assemblyRef s assemblyRef
    | ILScopeRef.Module modref -> refs_of_modref s modref

let refs_of_tref s (x: ILTypeRef) = refs_of_scoref s x.Scope

let rec refs_of_typ s x =
    match x with
    | ILType.Void | ILType.TypeVar _ -> ()
    | ILType.Modified (_, ty1, ty2) -> refs_of_tref s ty1; refs_of_typ s ty2
    | ILType.Array (_, ty)
    | ILType.Ptr ty | ILType.Byref ty -> refs_of_typ s ty
    | ILType.Value tr | ILType.Boxed tr -> refs_of_tspec s tr
    | ILType.FunctionPointer mref -> refs_of_callsig s mref

and refs_of_inst s i = refs_of_tys s i

and refs_of_tspec s (x: ILTypeSpec) = refs_of_tref s x.TypeRef; refs_of_inst s x.GenericArgs

and refs_of_callsig s csig = refs_of_tys s csig.ArgTypes; refs_of_typ s csig.ReturnType

and refs_of_genparam s x = refs_of_tys s x.Constraints

and refs_of_genparams s b = List.iter (refs_of_genparam s) b

and refs_of_dloc s ts = refs_of_tref s ts

and refs_of_mref s (x: ILMethodRef) =
    refs_of_dloc s x.DeclaringTypeRef
    refs_of_tys s x.mrefArgs
    refs_of_typ s x.mrefReturn

and refs_of_fref s x = refs_of_tref s x.DeclaringTypeRef; refs_of_typ s x.Type

and refs_of_ospec s (OverridesSpec (mref, ty)) = refs_of_mref s mref; refs_of_typ s ty

and refs_of_mspec s (x: ILMethodSpec) =
    refs_of_mref s x.MethodRef
    refs_of_typ s x.DeclaringType
    refs_of_inst s x.GenericArgs

and refs_of_fspec s x =
    refs_of_fref s x.FieldRef
    refs_of_typ s x.DeclaringType

and refs_of_tys s l = List.iter (refs_of_typ s) l

and refs_of_token s x =
    match x with
    | ILToken.ILType ty -> refs_of_typ s ty
    | ILToken.ILMethod mr -> refs_of_mspec s mr
    | ILToken.ILField fr -> refs_of_fspec s fr

and refs_of_custom_attr s (cattr: ILAttribute) = refs_of_mspec s cattr.Method

and refs_of_custom_attrs s (cas : ILAttributes) = Array.iter (refs_of_custom_attr s) cas.AsArray

and refs_of_varargs s tyso = Option.iter (refs_of_tys s) tyso

and refs_of_instr s x =
    match x with
    | I_call (_, mr, varargs) | I_newobj (mr, varargs) | I_callvirt (_, mr, varargs) ->
        refs_of_mspec s mr
        refs_of_varargs s varargs
    | I_callconstraint (_, tr, mr, varargs) ->
        refs_of_typ s tr
        refs_of_mspec s mr
        refs_of_varargs s varargs
    | I_calli (_, callsig, varargs) ->
        refs_of_callsig s callsig; refs_of_varargs s varargs
    | I_jmp mr | I_ldftn mr | I_ldvirtftn mr ->
        refs_of_mspec s mr
    | I_ldsfld (_, fr) | I_ldfld (_, _, fr) | I_ldsflda fr | I_ldflda fr | I_stsfld (_, fr) | I_stfld (_, _, fr) ->
        refs_of_fspec s fr
    | I_isinst ty | I_castclass ty | I_cpobj ty | I_initobj ty | I_ldobj (_, _, ty)
    | I_stobj (_, _, ty) | I_box ty |I_unbox ty | I_unbox_any ty | I_sizeof ty
    | I_ldelem_any (_, ty) | I_ldelema (_, _, _, ty) |I_stelem_any (_, ty) | I_newarr (_, ty)
    | I_mkrefany ty | I_refanyval ty
    | EI_ilzero ty -> refs_of_typ s ty
    | I_ldtoken token -> refs_of_token s token
    | I_stelem _|I_ldelem _|I_ldstr _|I_switch _|I_stloc _|I_stind _
    | I_starg _|I_ldloca _|I_ldloc _|I_ldind _
    | I_ldarga _|I_ldarg _|I_leave _|I_br _
    | I_brcmp _|I_rethrow|I_refanytype|I_ldlen|I_throw|I_initblk _ |I_cpblk _
    | I_localloc|I_ret |I_endfilter|I_endfinally|I_arglist
    | I_break
    | AI_add | AI_add_ovf | AI_add_ovf_un | AI_and | AI_div | AI_div_un | AI_ceq | AI_cgt | AI_cgt_un | AI_clt
    | AI_clt_un | AI_conv _ | AI_conv_ovf _ | AI_conv_ovf_un _ | AI_mul | AI_mul_ovf | AI_mul_ovf_un | AI_rem | AI_rem_un
    | AI_shl | AI_shr | AI_shr_un | AI_sub | AI_sub_ovf | AI_sub_ovf_un | AI_xor | AI_or | AI_neg | AI_not
    | AI_ldnull | AI_dup | AI_pop | AI_ckfinite | AI_nop | AI_ldc _
    | I_seqpoint _ | EI_ldlen_multi _ -> ()

and refs_of_il_code s (c: ILCode) =
    c.Instrs |> Array.iter (refs_of_instr s)
    c.Exceptions |> List.iter (fun e -> e.Clause |> (function
        | ILExceptionClause.TypeCatch (ilty, _) -> refs_of_typ s ilty
        | _ -> ()))

and refs_of_ilmbody s (il: ILMethodBody) =
    List.iter (refs_of_local s) il.Locals
    refs_of_il_code s il.Code

and refs_of_local s loc = refs_of_typ s loc.Type

and refs_of_mbody s x =
    match x with
    | MethodBody.IL il -> refs_of_ilmbody s il
    | MethodBody.PInvoke (attr) -> refs_of_modref s attr.Where
    | _ -> ()

and refs_of_mdef s (md: ILMethodDef) =
    List.iter (refs_of_param s) md.Parameters
    refs_of_return s md.Return
    refs_of_mbody s md.Body.Contents
    refs_of_custom_attrs s md.CustomAttrs
    refs_of_genparams s md.GenericParams

and refs_of_param s p = refs_of_typ s p.Type

and refs_of_return s (rt: ILReturn) = refs_of_typ s rt.Type

and refs_of_mdefs s x = Seq.iter (refs_of_mdef s) x

and refs_of_event_def s (ed: ILEventDef) =
    Option.iter (refs_of_typ s) ed.EventType
    refs_of_mref s ed.AddMethod
    refs_of_mref s ed.RemoveMethod
    Option.iter (refs_of_mref s) ed.FireMethod
    List.iter (refs_of_mref s) ed.OtherMethods
    refs_of_custom_attrs s ed.CustomAttrs

and refs_of_events s (x: ILEventDefs) = List.iter (refs_of_event_def s) x.AsList

and refs_of_property_def s (pd: ILPropertyDef) =
    Option.iter (refs_of_mref s) pd.SetMethod
    Option.iter (refs_of_mref s) pd.GetMethod
    refs_of_typ s pd.PropertyType
    refs_of_tys s pd.Args
    refs_of_custom_attrs s pd.CustomAttrs

and refs_of_properties s (x: ILPropertyDefs) = List.iter (refs_of_property_def s) x.AsList

and refs_of_fdef s (fd: ILFieldDef) =
    refs_of_typ s fd.FieldType
    refs_of_custom_attrs s fd.CustomAttrs

and refs_of_fields s fields = List.iter (refs_of_fdef s) fields

and refs_of_method_impls s mimpls = List.iter (refs_of_method_impl s) mimpls

and refs_of_method_impl s m =
    refs_of_ospec s m.Overrides
    refs_of_mspec s m.OverrideBy

and refs_of_tdef_kind _s _k = ()

and refs_of_tdef s (td : ILTypeDef) =
    refs_of_types s td.NestedTypes
    refs_of_genparams s td.GenericParams
    refs_of_tys s td.Implements
    Option.iter (refs_of_typ s) td.Extends
    refs_of_mdefs s td.Methods
    refs_of_fields s td.Fields.AsList
    refs_of_method_impls s td.MethodImpls.AsList
    refs_of_events s td.Events
    refs_of_tdef_kind s td
    refs_of_custom_attrs s td.CustomAttrs
    refs_of_properties s td.Properties

and refs_of_string _s _ = ()

and refs_of_types s (types: ILTypeDefs) = Seq.iter (refs_of_tdef s) types

and refs_of_exported_type s (c: ILExportedTypeOrForwarder) =
    refs_of_custom_attrs s c.CustomAttrs

and refs_of_exported_types s (tab: ILExportedTypesAndForwarders) = List.iter (refs_of_exported_type s) tab.AsList

and refs_of_resource_where s x =
    match x with
    | ILResourceLocation.LocalIn _ -> ()
    | ILResourceLocation.LocalOut _ -> ()
    | ILResourceLocation.File (mref, _) -> refs_of_modref s mref
    | ILResourceLocation.Assembly aref -> refs_of_assemblyRef s aref

and refs_of_resource s x =
    refs_of_resource_where s x.Location
    refs_of_custom_attrs s x.CustomAttrs

and refs_of_resources s (tab: ILResources) = List.iter (refs_of_resource s) tab.AsList

and refs_of_modul s m =
    refs_of_types s m.TypeDefs
    refs_of_resources s m.Resources
    Option.iter (refs_of_manifest s) m.Manifest

and refs_of_manifest s (m: ILAssemblyManifest) =
    refs_of_custom_attrs s m.CustomAttrs
    refs_of_exported_types s m.ExportedTypes

let computeILRefs modul =
    let s =
      { refsA = HashSet<_>(HashIdentity.Structural)
        refsM = HashSet<_>(HashIdentity.Structural) }

    refs_of_modul s modul
    { AssemblyReferences = Seq.fold (fun acc x -> x :: acc) [] s.refsA
      ModuleReferences = Seq.fold (fun acc x -> x :: acc) [] s.refsM }

let tspan = TimeSpan (DateTime.UtcNow.Ticks - DateTime(2000, 1, 1).Ticks)

let parseILVersion (vstr : string) =
    // matches "v1.2.3.4" or "1.2.3.4". Note, if numbers are missing, returns -1 (not 0).
    let mutable vstr = vstr.TrimStart [|'v'|]
    // if the version string contains wildcards, replace them
    let versionComponents = vstr.Split ([|'.'|])

    // account for wildcards
    if versionComponents.Length > 2 then
      let defaultBuild = uint16 tspan.Days % UInt16.MaxValue - 1us
      let defaultRevision = uint16 (DateTime.UtcNow.TimeOfDay.TotalSeconds / 2.0) % UInt16.MaxValue - 1us
      if versionComponents.[2] = "*" then
        if versionComponents.Length > 3 then
          failwith "Invalid version format"
        else
          // set the build number to the number of days since Jan 1, 2000
          versionComponents.[2] <- defaultBuild.ToString()
          // Set the revision number to number of seconds today / 2
          vstr <- String.Join (".", versionComponents) + "." + defaultRevision.ToString()
      elif versionComponents.Length > 3 && versionComponents.[3] = "*" then
        // Set the revision number to number of seconds today / 2
        versionComponents.[3] <- defaultRevision.ToString()
        vstr <- String.Join (".", versionComponents)

    let version = System.Version vstr
    let zero32 n = if n < 0 then 0us else uint16 n
    // since the minor revision will be -1 if none is specified, we need to truncate to 0 to not break existing code
    let minorRevision = if version.Revision = -1 then 0us else uint16 version.MinorRevision
    ILVersionInfo (zero32 version.Major, zero32 version.Minor, zero32 version.Build, minorRevision)

let compareILVersions (version1 : ILVersionInfo) (version2 : ILVersionInfo) =
    let c = compare version1.Major version2.Major
    if c <> 0 then c else
    let c = compare version1.Minor version2.Minor
    if c <> 0 then c else
    let c = compare version1.Build version2.Build
    if c <> 0 then c else
    let c = compare version1.Revision version2.Revision
    if c <> 0 then c else
    0

let unscopeILTypeRef (x: ILTypeRef) = ILTypeRef.Create (ILScopeRef.Local, x.Enclosing, x.Name)

let rec unscopeILTypeSpec (tspec: ILTypeSpec) =
    let tref = tspec.TypeRef
    let tinst = tspec.GenericArgs
    let tref = unscopeILTypeRef tref
    ILTypeSpec.Create (tref, unscopeILTypes tinst)

and unscopeILType ty =
    match ty with
    | ILType.Ptr t -> ILType.Ptr (unscopeILType t)
    | ILType.FunctionPointer t -> ILType.FunctionPointer (unscopeILCallSig t)
    | ILType.Byref t -> ILType.Byref (unscopeILType t)
    | ILType.Boxed cr -> mkILBoxedType (unscopeILTypeSpec cr)
    | ILType.Array (s, ty) -> ILType.Array (s, unscopeILType ty)
    | ILType.Value cr -> ILType.Value (unscopeILTypeSpec cr)
    | ILType.Modified (b, tref, ty) -> ILType.Modified (b, unscopeILTypeRef tref, unscopeILType ty)
    | x -> x

and unscopeILTypes i =
    if List.isEmpty i then i
    else List.map unscopeILType i

and unscopeILCallSig csig =
    mkILCallSig (csig.CallingConv, unscopeILTypes csig.ArgTypes, unscopeILType csig.ReturnType)

let resolveILMethodRefWithRescope r (td: ILTypeDef) (mref: ILMethodRef) =
    let args = mref.ArgTypes
    let nargs = args.Length
    let nm = mref.Name
    let possibles = td.Methods.FindByNameAndArity (nm, nargs)
    if isNil possibles then failwith ("no method named " + nm + " found in type " + td.Name)
    let argTypes = mref.ArgTypes |> List.map r
    let retType : ILType = r mref.ReturnType
    match
      possibles |> List.filter (fun md ->
          mref.CallingConv = md.CallingConv &&
          // REVIEW: this uses equality on ILType. For CMOD_OPTIONAL this is not going to be correct
          (md.Parameters, argTypes) ||> List.lengthsEqAndForall2 (fun p1 p2 -> r p1.Type = p2) &&
          // REVIEW: this uses equality on ILType. For CMOD_OPTIONAL this is not going to be correct
          r md.Return.Type = retType) with
    | [] -> failwith ("no method named "+nm+" with appropriate argument types found in type "+td.Name)
    | [mdef] -> mdef
    | _ -> failwith ("multiple methods named "+nm+" appear with identical argument types in type "+td.Name)

let resolveILMethodRef td mref = resolveILMethodRefWithRescope id td mref

let mkRefToILModule m =
    ILModuleRef.Create (m.Name, true, None)

type ILEventRef =
    { erA: ILTypeRef
      erB: string }

    static member Create (a, b) = {erA=a;erB=b}

    member x.DeclaringTypeRef = x.erA

    member x.Name = x.erB

type ILPropertyRef =
    { prA: ILTypeRef
      prB: string }

    static member Create (a, b) = {prA=a;prB=b}

    member x.DeclaringTypeRef = x.prA

    member x.Name = x.prB