repro.vb

Imports System

Module Program
    Sub Main()
        Dim e = ConversionKind.DelegateRelaxationLevelNone 
        Console.WriteLine(e.ToString())
    End Sub
End Module

<Flags()>
Friend Enum ConversionKind
    ' If there is a conversion, either [Widening] or [Narrowing] bit must be set, but not both.
    ' All VB conversions are either Widening or Narrowing.
    '
    ' To indicate the fact that no conversion exists:
    '    1) Neither [Widening] nor [Narrowing] are set.
    '    2) Additional flags may be set in order to provide specific reason.
    '
    ' Bits from the following values are never set at the same time :
    ' Identity, Numeric, Nullable, Reference, Array, TypeParameter, Value, [String], WideningNothingLiteral, InterpolatedString

    FailedDueToNumericOverflow = 1 << 31 ' Failure flag
    FailedDueToIntegerOverflow = FailedDueToNumericOverflow Or (1 << 30) ' Failure flag
    FailedDueToNumericOverflowMask = FailedDueToNumericOverflow Or FailedDueToIntegerOverflow
    FailedDueToQueryLambdaBodyMismatch = 1 << 29 ' Failure flag to indicate that conversion failed because body of a query lambda couldn't be converted to the target delegate return type.
    FailedDueToArrayLiteralElementConversion = 1 << 28 ' Failed because array literal element could not be converted to the target element type.

    ' If there is a conversion, one and only one of the following two bits must be set.
    ' All VB conversions are either Widening or Narrowing.
    [Widening] = 1 << 0
    [Narrowing] = 1 << 1

    ''' <summary>
    ''' Because flags can be combined, use the method IsIdentityConversion when testing for ConversionKind.Identity
    ''' </summary>
    ''' <remarks></remarks>
    Identity = [Widening] Or 1 << 2 ' According to VB spec, identity conversion is Widening

    Numeric = 1 << 3
    WideningNumeric = [Widening] Or Numeric
    NarrowingNumeric = [Narrowing] Or Numeric

    ''' <summary>
    ''' Can be combined with <see cref="ConversionKind.Tuple"/> to indicate that the underlying value conversion is a predefined tuple conversion
    ''' </summary>
    Nullable = 1 << 4
    WideningNullable = [Widening] Or Nullable
    NarrowingNullable = [Narrowing] Or Nullable

    Reference = 1 << 5
    WideningReference = [Widening] Or Reference
    NarrowingReference = [Narrowing] Or Reference

    Array = 1 << 6
    WideningArray = [Widening] Or Array
    NarrowingArray = [Narrowing] Or Array

    TypeParameter = 1 << 7
    WideningTypeParameter = [Widening] Or TypeParameter
    NarrowingTypeParameter = [Narrowing] Or TypeParameter

    Value = 1 << 8
    WideningValue = [Widening] Or Value
    NarrowingValue = [Narrowing] Or Value

    [String] = 1 << 9
    WideningString = [Widening] Or [String]
    NarrowingString = [Narrowing] Or [String]

    [Boolean] = 1 << 10
    ' Note: there are no widening boolean conversions.
    NarrowingBoolean = [Narrowing] Or [Boolean]

    WideningNothingLiteral = [Widening] Or (1 << 11)

    ' Compiler might be interested in knowing if constant numeric conversion involves narrowing
    ' for constant's original type. When user-defined conversions are involved, this flag can be
    ' combined with widening conversions other than WideningNumericConstant.
    '
    ' If this flag is combined with Narrowing, there should be no other reasons to treat
    ' conversion as narrowing. In some scenarios overload resolution is likely to dismiss
    ' narrowing in presence of this flag. Also, it appears that with Option Strict On, Dev10
    ' compiler does not report errors for narrowing conversions from an integral constant
    ' expression to an integral type (assuming integer overflow checks are disabled) or from a
    ' floating constant to a floating type.
    InvolvesNarrowingFromNumericConstant = 1 << 12

    ' This flag is set when conversion involves conversion enum <-> underlying type,
    ' or conversion between two enums, etc 
    InvolvesEnumTypeConversions = 1 << 13

    ' Lambda conversion
    Lambda = 1 << 14

    ' Delegate relaxation levels for Lambda and Delegate conversions
    DelegateRelaxationLevelNone = 0 ' Identity / Whidbey
    DelegateRelaxationLevelWidening = 1 << 15
    DelegateRelaxationLevelWideningDropReturnOrArgs = 2 << 15
    DelegateRelaxationLevelWideningToNonLambda = 3 << 15
    DelegateRelaxationLevelNarrowing = 4 << 15  ' OrcasStrictOff
    DelegateRelaxationLevelInvalid = 5 << 15 ' Keep invalid the biggest number

    DelegateRelaxationLevelMask = 7 << 15 ' Three bits used!

    'Can be combined with Narrowing
    VarianceConversionAmbiguity = 1 << 18

    ' This bit can be combined with NoConversion to indicate that, even though there is no conversion
    ' from the language point of view, there is a slight chance that conversion might succeed at run-time
    ' under the right circumstances. It is used to detect possibly ambiguous variance conversions to an
    ' interface, so it is set only for scenarios that are relevant to variance conversions to an
    ' interface. 
    MightSucceedAtRuntime = 1 << 19

    AnonymousDelegate = 1 << 20
    NeedAStub = 1 << 21
    ConvertedToExpressionTree = 1 << 22   ' Combined with Lambda, indicates a conversion of lambda to Expression(Of T).

    UserDefined = 1 << 23

    ' Some variance delegate conversions are treated as special narrowing (Dev10 #820752).
    ' This flag is combined with Narrowing to indicate the fact.
    NarrowingDueToContraVarianceInDelegate = 1 << 24

    ' Interpolated string conversions
    InterpolatedString = [Widening] Or (1 << 25)

    ' Tuple conversions
    ''' <summary>
    ''' Can be combined with <see cref="ConversionKind.Nullable"/> to indicate that the underlying value conversion is a predefined tuple conversion
    ''' </summary>
    Tuple = (1 << 26)
    WideningTuple = [Widening] Or Tuple
    NarrowingTuple = [Narrowing] Or Tuple
    WideningNullableTuple = WideningNullable Or Tuple
    NarrowingNullableTuple = NarrowingNullable Or Tuple

    ' Bits 28 - 31 are reserved for failure flags.
End Enum