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Conversions.vb
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Conversions.vb
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' Copyright (c) Microsoft. All Rights Reserved. Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
Imports System.Collections.Immutable
Imports System.Runtime.InteropServices
Imports Microsoft.CodeAnalysis.Operations
Imports Microsoft.CodeAnalysis.PooledObjects
Imports Microsoft.CodeAnalysis.VisualBasic.Symbols
Imports Microsoft.CodeAnalysis.VisualBasic.Symbols.TypeSymbolExtensions
Namespace Microsoft.CodeAnalysis.VisualBasic
''' <summary>
''' Summarizes whether a conversion is allowed, and if so, which kind of conversion (and in some cases, the
''' associated symbol).
''' </summary>
Public Structure Conversion
Implements IEquatable(Of Conversion), IConvertibleConversion
Private ReadOnly _convKind As ConversionKind
Private ReadOnly _method As MethodSymbol
Friend Sub New(conv As KeyValuePair(Of ConversionKind, MethodSymbol))
_convKind = conv.Key
_method = conv.Value
End Sub
Friend ReadOnly Property Kind As ConversionKind
Get
Return _convKind
End Get
End Property
''' <summary>
''' Returns True if the conversion exists, either as a widening or narrowing conversion.
''' </summary>
''' <remarks>
''' If this returns True, exactly one of <see cref="IsNarrowing"/> or <see cref="IsWidening"/> will return True.
''' If this returns False, neither <see cref="IsNarrowing"/> or <see cref="IsWidening"/> will return True.
''' </remarks>
Public ReadOnly Property Exists As Boolean
Get
Return Not Conversions.NoConversion(_convKind)
End Get
End Property
''' <summary>
''' Returns True if this conversion a narrowing conversion, and not a widening conversion.
''' </summary>
Public ReadOnly Property IsNarrowing As Boolean
Get
Return Conversions.IsNarrowingConversion(_convKind)
End Get
End Property
''' <summary>
''' Returns True if this conversion is a widening conversion, and not a narrowing conversion.
''' </summary>
Public ReadOnly Property IsWidening As Boolean
Get
Return Conversions.IsWideningConversion(_convKind)
End Get
End Property
''' <summary>
''' Returns True if this conversion is an identity conversion.
''' </summary>
''' <remarks>
''' Note that identity conversion are also considered widening conversions.
''' </remarks>
Public ReadOnly Property IsIdentity As Boolean
Get
Return Conversions.IsIdentityConversion(_convKind)
End Get
End Property
''' <summary>
''' Returns True if this conversion is a default conversion (a conversion from the "Nothing" literal).
''' </summary>
''' <remarks>Note that default conversions are considered widening conversions.</remarks>
Public ReadOnly Property IsDefault As Boolean
Get
Return (_convKind And ConversionKind.WideningNothingLiteral) = ConversionKind.WideningNothingLiteral
End Get
End Property
''' <summary>
''' Returns True if this conversion is a widening numeric conversion or a narrowing numeric conversion, as defined in
''' section 8.3.
''' </summary>
Public ReadOnly Property IsNumeric As Boolean
Get
Return (_convKind And ConversionKind.Numeric) <> 0
End Get
End Property
''' <summary>
''' Returns True if this conversion is a narrowing boolean conversion, as defined in section 8.2.
''' </summary>
Public ReadOnly Property IsBoolean As Boolean
Get
Return (_convKind And ConversionKind.Boolean) <> 0
End Get
End Property
''' <summary>
''' Returns True if this conversion is a widening reference conversion or narrowing reference conversion, as defined in
''' section 8.4.
''' </summary>
Public ReadOnly Property IsReference As Boolean
Get
Return (_convKind And ConversionKind.Reference) <> 0
End Get
End Property
''' <summary>
''' Returns True if this conversion is a widening anonymous delegate conversion as defined in section 8.8, or a
''' narrowing anonymous delegate conversion as defined in section 8.9.
''' </summary>
Public ReadOnly Property IsAnonymousDelegate As Boolean
Get
Return (_convKind And ConversionKind.AnonymousDelegate) <> 0
End Get
End Property
''' <summary>
''' Returns True if this is a lambda conversion.
''' </summary>
Public ReadOnly Property IsLambda As Boolean
Get
Return (_convKind And ConversionKind.Lambda) <> 0
End Get
End Property
''' <summary>
''' Returns True if this conversion is a widening array conversion or a narrowing array conversion, as defined in
''' section 8.5.
''' </summary>
Public ReadOnly Property IsArray As Boolean
Get
Return (_convKind And ConversionKind.Array) <> 0
End Get
End Property
''' <summary>
''' Returns True if this conversion a widening value type conversion or a narrowing value type conversion as defined in
''' section 8.6.
''' </summary>
Public ReadOnly Property IsValueType As Boolean
Get
Return (_convKind And ConversionKind.Value) <> 0
End Get
End Property
''' <summary>
''' Returns True if this conversion a widening nullable value type conversion or a narrowing nullable value type
''' conversion as defined in section 8.6.1.
''' </summary>
Public ReadOnly Property IsNullableValueType As Boolean
Get
Return (_convKind And ConversionKind.Nullable) <> 0
End Get
End Property
''' <summary>
''' Returns True if this conversion a widening string conversion or a narrowing string conversion as defined in section
''' 8.7.
''' </summary>
Public ReadOnly Property IsString As Boolean
Get
Return (_convKind And ConversionKind.String) <> 0
End Get
End Property
''' <summary>
''' Returns True if this conversion a widening type parameter or a narrowing type parameter conversion, as defined in
''' section 8.10.
''' </summary>
Public ReadOnly Property IsTypeParameter As Boolean
Get
Return (_convKind And ConversionKind.TypeParameter) <> 0
End Get
End Property
''' <summary>
''' Returns True if this conversion a widening user defined or a narrowing user defined conversion, as defined in
''' section 8.11.
''' </summary>
''' <remarks>
''' If this returns True, the involved conversion method can be obtained with the <see cref="Method"/>
''' property.
''' </remarks>
Public ReadOnly Property IsUserDefined As Boolean
Get
Return (_convKind And ConversionKind.UserDefined) <> 0
End Get
End Property
Friend ReadOnly Property Method As MethodSymbol
Get
Return _method
End Get
End Property
''' <summary>
''' Returns the method that defines the user defined conversion, if any. Otherwise returns Nothing.
''' </summary>
Public ReadOnly Property MethodSymbol As IMethodSymbol
Get
Return _method
End Get
End Property
''' <summary>
''' Returns True if two <see cref="Conversion"/> values are equal.
''' </summary>
''' <param name="left">The left value.</param>
''' <param name="right">The right value.</param>
Public Shared Operator =(left As Conversion, right As Conversion) As Boolean
Return left.Equals(right)
End Operator
''' <summary>
''' Returns True if two <see cref="Conversion"/> values are not equal.
''' </summary>
''' <param name="left">The left value.</param>
''' <param name="right">The right value.</param>
Public Shared Operator <>(left As Conversion, right As Conversion) As Boolean
Return Not (left = right)
End Operator
''' <summary>
''' Creates a <seealso cref="CommonConversion"/> from this Visual Basic conversion.
''' </summary>
''' <returns>The <see cref="CommonConversion"/> that represents this conversion.</returns>
''' <remarks>
''' This is a lossy conversion; it is not possible to recover the original <see cref="Conversion"/>
''' from the <see cref="CommonConversion"/> struct.
''' </remarks>
Public Function ToCommonConversion() As CommonConversion Implements IConvertibleConversion.ToCommonConversion
Return New CommonConversion(Exists, IsIdentity, IsNumeric, IsReference, IsWidening, MethodSymbol)
End Function
''' <summary>
''' Determines whether the specified object is equal to the current object.
''' </summary>
''' <param name="obj">
''' The object to compare with the current object.
''' </param>
Public Overloads Overrides Function Equals(obj As Object) As Boolean
Return TypeOf obj Is Conversion AndAlso
Me = DirectCast(obj, Conversion)
End Function
''' <summary>
''' Determines whether the specified object is equal to the current object.
''' </summary>
''' <param name="other">
''' The object to compare with the current object.
''' </param>
Public Overloads Function Equals(other As Conversion) As Boolean Implements IEquatable(Of Conversion).Equals
Return Me._convKind = other._convKind AndAlso Me.Method = other.Method
End Function
''' <summary>
''' Returns a hash code for the current object.
''' </summary>
Public Overrides Function GetHashCode() As Integer
Return Hash.Combine(Method, CInt(_convKind))
End Function
''' <summary>
''' Returns a string that represents the current object.
''' </summary>
Public Overrides Function ToString() As String
Return _convKind.ToString()
End Function
End Structure
<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
<Flags()>
Friend Enum MethodConversionKind
Identity = &H0
OneArgumentIsVbOrBoxWidening = &H1
OneArgumentIsClrWidening = &H2
OneArgumentIsNarrowing = &H4
' TODO: It looks like Dev10 MethodConversionKinds for return are badly named because
' they appear to give classification in the direction opposite to the data
' flow. This is very confusing. However, I am not going to rename them just yet.
' Will do this when all parts are ported and working together, otherwise it will
' be very hard to port the rest of the feature.
ReturnIsWidening = &H8
ReturnIsClrNarrowing = &H10
ReturnIsIsVbOrBoxNarrowing = &H20
ReturnValueIsDropped = &H40
AllArgumentsIgnored = &H80
ExcessOptionalArgumentsOnTarget = &H100
Error_ByRefByValMismatch = &H200
Error_Unspecified = &H400
Error_IllegalToIgnoreAllArguments = &H800
Error_RestrictedType = &H1000
Error_SubToFunction = &H2000
Error_ReturnTypeMismatch = &H4000
Error_OverloadResolution = &H8000
Error_StubNotSupported = &H10000
AllErrorReasons = Error_ByRefByValMismatch Or
Error_Unspecified Or
Error_IllegalToIgnoreAllArguments Or
Error_RestrictedType Or
Error_SubToFunction Or
Error_ReturnTypeMismatch Or
Error_OverloadResolution Or
Error_StubNotSupported
End Enum
''' <summary>
''' The purpose of this class is to answer questions about convertibility of one type to another.
''' It also answers questions about conversions from an expression to a type.
'''
''' The code is organized such that each method attempts to implement exactly one section of the
''' specification.
''' </summary>
''' <remarks></remarks>
Friend NotInheritable Class Conversions
Public Shared ReadOnly Identity As New KeyValuePair(Of ConversionKind, MethodSymbol)(ConversionKind.Identity, Nothing)
Private Sub New()
Throw ExceptionUtilities.Unreachable
End Sub
Friend Class ConversionEasyOut
' There are situations in which we know that there is no unusual conversion going on (such as a conversion involving constants,
' enumerated types, and so on.) In those situations we can classify conversions via a simple table lookup:
' PERF: Use Integer instead of ConversionKind so the compiler can use array literal initialization.
' The most natural type choice, Enum arrays, are not blittable due to a CLR limitation.
Private Shared ReadOnly s_convkind As Integer(,)
Shared Sub New()
Const NOC As Integer = Nothing 'ConversionKind.NoConversion
Const IDN As Integer = ConversionKind.Identity
Const NUM As Integer = ConversionKind.WideningNumeric
Const NNM As Integer = ConversionKind.NarrowingNumeric
Const IRF As Integer = ConversionKind.WideningReference
Const NRF As Integer = ConversionKind.NarrowingReference
Const WIV As Integer = ConversionKind.WideningValue
Const NAV As Integer = ConversionKind.NarrowingValue
Const NST As Integer = ConversionKind.NarrowingString
Const WST As Integer = ConversionKind.WideningString
Const NBO As Integer = ConversionKind.NarrowingBoolean
' TO TYPE
' Obj Str Bool Char SByt Shrt Int Long Byte UShr UInt ULng Sngl Dbl Dec Date
s_convkind = New Integer(,) { ' FROM TYPE
{IDN, NRF, NAV, NAV, NAV, NAV, NAV, NAV, NAV, NAV, NAV, NAV, NAV, NAV, NAV, NAV}, ' Obj
{IRF, IDN, NST, NST, NST, NST, NST, NST, NST, NST, NST, NST, NST, NST, NST, NST}, ' Str
{WIV, NST, IDN, NOC, NBO, NBO, NBO, NBO, NBO, NBO, NBO, NBO, NBO, NBO, NBO, NOC}, ' Bool
{WIV, WST, NOC, IDN, NOC, NOC, NOC, NOC, NOC, NOC, NOC, NOC, NOC, NOC, NOC, NOC}, ' Char
{WIV, NST, NBO, NOC, IDN, NUM, NUM, NUM, NNM, NNM, NNM, NNM, NUM, NUM, NUM, NOC}, ' SByt
{WIV, NST, NBO, NOC, NNM, IDN, NUM, NUM, NNM, NNM, NNM, NNM, NUM, NUM, NUM, NOC}, ' Shrt
{WIV, NST, NBO, NOC, NNM, NNM, IDN, NUM, NNM, NNM, NNM, NNM, NUM, NUM, NUM, NOC}, ' Int
{WIV, NST, NBO, NOC, NNM, NNM, NNM, IDN, NNM, NNM, NNM, NNM, NUM, NUM, NUM, NOC}, ' Long
{WIV, NST, NBO, NOC, NNM, NUM, NUM, NUM, IDN, NUM, NUM, NUM, NUM, NUM, NUM, NOC}, ' Byte
{WIV, NST, NBO, NOC, NNM, NNM, NUM, NUM, NNM, IDN, NUM, NUM, NUM, NUM, NUM, NOC}, ' UShr
{WIV, NST, NBO, NOC, NNM, NNM, NNM, NUM, NNM, NNM, IDN, NUM, NUM, NUM, NUM, NOC}, ' UInt
{WIV, NST, NBO, NOC, NNM, NNM, NNM, NNM, NNM, NNM, NNM, IDN, NUM, NUM, NUM, NOC}, ' ULng
{WIV, NST, NBO, NOC, NNM, NNM, NNM, NNM, NNM, NNM, NNM, NNM, IDN, NUM, NNM, NOC}, ' Sngl
{WIV, NST, NBO, NOC, NNM, NNM, NNM, NNM, NNM, NNM, NNM, NNM, NNM, IDN, NNM, NOC}, ' Dbl
{WIV, NST, NBO, NOC, NNM, NNM, NNM, NNM, NNM, NNM, NNM, NNM, NUM, NUM, IDN, NOC}, ' Dec
{WIV, NST, NOC, NOC, NOC, NOC, NOC, NOC, NOC, NOC, NOC, NOC, NOC, NOC, NOC, IDN} ' Date
}
' Obj Str Bool Char SByt Shrt Int Long Byte UShr UInt ULng Sngl Dbl Dec Date
End Sub
Public Shared Function ClassifyPredefinedConversion(source As TypeSymbol, target As TypeSymbol) As ConversionKind?
If source Is Nothing OrElse target Is Nothing Then
Return Nothing
End If
' First, dig through Nullable
Dim sourceNullableUnderlying = source.GetNullableUnderlyingTypeOrSelf()
Dim sourceIsNullable As Boolean = (sourceNullableUnderlying IsNot source)
Dim targetNullableUnderlying = target.GetNullableUnderlyingTypeOrSelf()
Dim targetIsNullable As Boolean = (targetNullableUnderlying IsNot target)
' Now dig through Enum
Dim sourceEnumUnderlying = sourceNullableUnderlying.GetEnumUnderlyingTypeOrSelf()
Dim sourceIsEnum As Boolean = (sourceEnumUnderlying IsNot sourceNullableUnderlying)
Dim targetEnumUnderlying = targetNullableUnderlying.GetEnumUnderlyingTypeOrSelf()
Dim targetIsEnum As Boolean = (targetEnumUnderlying IsNot targetNullableUnderlying)
' Filter out unexpected underlying types for Nullable and enum types
If (sourceIsEnum OrElse sourceIsNullable) AndAlso
(sourceEnumUnderlying.IsStringType() OrElse sourceEnumUnderlying.IsObjectType()) Then
Return Nothing
End If
If (targetIsEnum OrElse targetIsNullable) AndAlso
(targetEnumUnderlying.IsStringType() OrElse targetEnumUnderlying.IsObjectType()) Then
Return Nothing
End If
' Classify conversion between underlying types.
Dim sourceIndex As Integer? = TypeToIndex(sourceEnumUnderlying)
If sourceIndex Is Nothing Then
Return Nothing
End If
Dim targetIndex As Integer? = TypeToIndex(targetEnumUnderlying)
If targetIndex Is Nothing Then
Return Nothing
End If
' Table lookup for underlying type doesn't give correct classification
' for Nullable <=> Object conversion. Need to check them explicitly.
If sourceIsNullable Then
If target.IsObjectType() Then
Return ConversionKind.WideningValue
End If
ElseIf targetIsNullable Then
If source.IsObjectType() Then
Return ConversionKind.NarrowingValue
End If
End If
Dim conv As ConversionKind = CType(s_convkind(sourceIndex.Value, targetIndex.Value), ConversionKind)
If Conversions.NoConversion(conv) Then
Return conv
End If
' Adjust classification for enum conversions first, but don't adjust conversions enum <=> Object.
If ((sourceIsEnum AndAlso Not target.IsObjectType()) OrElse
(targetIsEnum AndAlso Not source.IsObjectType())) Then
'§8.8 Widening Conversions
'• From an enumerated type to its underlying numeric type, or to a numeric type
' that its underlying numeric type has a widening conversion to.
'§8.9 Narrowing Conversions
'• From a numeric type to an enumerated type.
'• From an enumerated type to a numeric type its underlying numeric type has a narrowing conversion to.
'• From an enumerated type to another enumerated type.
'!!! Spec doesn't mention this, but VB also supports conversions between enums and non-numeric intrinsic types.
Dim sourceEnum = sourceNullableUnderlying
Dim targetEnum = targetNullableUnderlying
If sourceIsEnum Then
If targetIsEnum Then
If Not (Conversions.IsIdentityConversion(conv) AndAlso sourceEnum.IsSameTypeIgnoringAll(targetEnum)) Then
'• From an enumerated type to another enumerated type.
conv = ConversionKind.NarrowingNumeric Or ConversionKind.InvolvesEnumTypeConversions
End If
ElseIf Conversions.IsWideningConversion(conv) Then
'• From an enumerated type to its underlying numeric type, or to a type
' that its underlying numeric type has a widening conversion to.
conv = conv Or ConversionKind.InvolvesEnumTypeConversions
If (conv And ConversionKind.Identity) <> 0 Then
conv = (conv And Not ConversionKind.Identity) Or ConversionKind.Widening Or ConversionKind.Numeric
End If
Else
Debug.Assert(Conversions.IsNarrowingConversion(conv))
'• From an enumerated type to a numeric type its underlying numeric type has a narrowing conversion to.
conv = conv Or ConversionKind.InvolvesEnumTypeConversions
End If
Else
Debug.Assert(targetIsEnum)
'• From a type convertible to underlying type to an enumerated type.
conv = (conv And Not ConversionKind.Widening) Or ConversionKind.Narrowing Or ConversionKind.InvolvesEnumTypeConversions
If (conv And ConversionKind.Identity) <> 0 Then
conv = (conv And Not ConversionKind.Identity) Or ConversionKind.Numeric
End If
End If
Debug.Assert(Conversions.IsIdentityConversion(conv) OrElse (conv And ConversionKind.InvolvesEnumTypeConversions) <> 0)
End If
' Now adjust classification for Nullable conversions.
If sourceIsNullable OrElse targetIsNullable Then
Debug.Assert(Not source.IsObjectType() AndAlso Not target.IsObjectType())
'§8.8 Widening Conversions
'• From a type T to the type T?.
'• From a type T? to a type S?, where there is a widening conversion from the type T to the type S.
'• From a type T to a type S?, where there is a widening conversion from the type T to the type S.
'• From a type T? to an interface type that the type T implements.
'§8.9 Narrowing Conversions
'• From a type T? to a type T.
'• From a type T? to a type S?, where there is a narrowing conversion from the type T to the type S.
'• From a type T to a type S?, where there is a narrowing conversion from the type T to the type S.
'• From a type S? to a type T, where there is a conversion from the type S to the type T.
Dim sourceNullable = source
Dim targetNullable = target
If sourceIsNullable Then
If targetIsNullable Then
If Conversions.IsNarrowingConversion(conv) Then
'• From a type T? to a type S?, where there is a narrowing conversion from the type T to the type S.
conv = ConversionKind.NarrowingNullable
ElseIf Not Conversions.IsIdentityConversion(conv) Then
Debug.Assert(Conversions.IsWideningConversion(conv))
'• From a type T? to a type S?, where there is a widening conversion from the type T to the type S.
conv = ConversionKind.WideningNullable
Else
Debug.Assert(Conversions.IsIdentityConversion(conv) AndAlso sourceNullable.IsSameTypeIgnoringAll(targetNullable))
End If
Else
'• From a type T? to a type T.
'• From a type S? to a type T, where there is a conversion from the type S to the type T.
conv = ConversionKind.NarrowingNullable
End If
Else
Debug.Assert(targetIsNullable)
If Conversions.IsWideningConversion(conv) Then
'• From a type T to the type T?.
'• From a type T to a type S?, where there is a widening conversion from the type T to the type S.
conv = ConversionKind.WideningNullable
Else
Debug.Assert(Conversions.IsNarrowingConversion(conv))
'• From a type T to a type S?, where there is a narrowing conversion from the type T to the type S.
conv = ConversionKind.NarrowingNullable
End If
End If
End If
Return conv
End Function
End Class
Private Shared Function FastClassifyPredefinedConversion(source As TypeSymbol, target As TypeSymbol) As ConversionKind?
Return ConversionEasyOut.ClassifyPredefinedConversion(source, target)
End Function
''' <summary>
''' Attempts to fold conversion of a constant expression.
'''
''' Returns Nothing if conversion cannot be folded.
'''
''' If conversion failed due to non-integer overflow, ConstantValue.Bad is returned. Consumer
''' is responsible for reporting appropriate diagnostics.
'''
''' If integer overflow occurs, integerOverflow is set to True and ConstantValue for overflowed result is returned.
''' Consumer is responsible for reporting appropriate diagnostics and potentially discarding the result.
''' </summary>
Public Shared Function TryFoldConstantConversion(
source As BoundExpression,
destination As TypeSymbol,
ByRef integerOverflow As Boolean
) As ConstantValue
Debug.Assert(source IsNot Nothing)
Debug.Assert(destination IsNot Nothing)
Debug.Assert(destination.Kind <> SymbolKind.ErrorType)
integerOverflow = False
Dim sourceValue As ConstantValue = source.ConstantValueOpt
If sourceValue Is Nothing OrElse sourceValue.IsBad Then
' Not a constant
Return Nothing
End If
If Not destination.AllowsCompileTimeConversions() Then
Return Nothing
End If
If source.IsNothingLiteral() Then
' A Nothing literal turns into the default value of the target type.
If destination.IsStringType() Then
Return source.ConstantValueOpt
End If
Dim dstDiscriminator As ConstantValueTypeDiscriminator = destination.GetConstantValueTypeDiscriminator()
Debug.Assert((dstDiscriminator <> ConstantValueTypeDiscriminator.Bad) AndAlso (dstDiscriminator <> ConstantValueTypeDiscriminator.Nothing))
Return ConstantValue.Default(dstDiscriminator)
End If
Dim sourceExpressionType = source.Type
If Not sourceExpressionType.AllowsCompileTimeConversions() Then
Return Nothing
End If
Debug.Assert(sourceExpressionType IsNot Nothing)
Debug.Assert(sourceExpressionType.IsValidForConstantValue(sourceValue))
Dim sourceType = sourceExpressionType.GetEnumUnderlyingTypeOrSelf()
Dim targetType = destination.GetEnumUnderlyingTypeOrSelf()
' Shortcut for identity conversions
If sourceType Is targetType Then
Return sourceValue
End If
' Convert the value of the constant to the result type.
If IsStringType(sourceType) Then
If IsCharType(targetType) Then
Dim str As String = If(sourceValue.IsNothing, Nothing, sourceValue.StringValue)
Dim [char] As Char
If str Is Nothing OrElse str.Length = 0 Then
[char] = ChrW(0)
Else
[char] = str(0)
End If
Return ConstantValue.Create([char])
End If
ElseIf IsCharType(sourceType) Then
If IsStringType(targetType) Then
Return ConstantValue.Create(New String(sourceValue.CharValue, 1))
End If
Else
Dim result = TryFoldConstantNumericOrBooleanConversion(
sourceValue,
sourceType,
targetType,
integerOverflow)
Debug.Assert(result Is Nothing OrElse Not result.IsBad OrElse integerOverflow = False)
Return result
End If
Return Nothing
End Function
''' <summary>
''' Attempts to fold conversion of a constant expression.
'''
''' Returns Nothing if conversion cannot be folded, i.e. unexpected source and destination types.
''' Returns Bad value (Discriminator = ConstantValueTypeDiscriminator.Bad) if conversion failed due to non-integer overflow.
'''
''' If integer overflow occurs, integerOverflow is set to True and the overflowed result is returned.
''' </summary>
Private Shared Function TryFoldConstantNumericOrBooleanConversion(
ByRef sourceValue As ConstantValue,
sourceType As TypeSymbol,
targetType As TypeSymbol,
ByRef integerOverflow As Boolean
) As ConstantValue
integerOverflow = False
If IsIntegralType(sourceType) OrElse IsBooleanType(sourceType) Then
If IsNumericType(targetType) OrElse IsBooleanType(targetType) Then
Dim value As Int64 = GetConstantValueAsInt64(sourceValue)
' // Converting True to an arithmetic value produces -1.
If IsBooleanType(sourceType) AndAlso value <> 0 Then
Const BASIC_TRUE As Integer = (-1)
If IsUnsignedIntegralType(targetType) Then
Dim ignoreOverflow As Boolean = False
value = NarrowIntegralResult(BASIC_TRUE, sourceType, targetType, ignoreOverflow)
Else
value = BASIC_TRUE
End If
End If
Return ConvertIntegralValue(value,
sourceValue.Discriminator,
targetType.GetConstantValueTypeDiscriminator(),
integerOverflow)
End If
ElseIf IsFloatingType(sourceType) Then
If IsNumericType(targetType) OrElse IsBooleanType(targetType) Then
Dim result = ConvertFloatingValue(
If(sourceValue.Discriminator = ConstantValueTypeDiscriminator.Double, sourceValue.DoubleValue, sourceValue.SingleValue),
targetType.GetConstantValueTypeDiscriminator(),
integerOverflow)
If result.IsBad Then
integerOverflow = False
End If
Return result
End If
ElseIf IsDecimalType(sourceType) Then
If IsNumericType(targetType) OrElse IsBooleanType(targetType) Then
Dim result = ConvertDecimalValue(
sourceValue.DecimalValue,
targetType.GetConstantValueTypeDiscriminator(),
integerOverflow)
If result.IsBad Then
integerOverflow = False
End If
Return result
End If
End If
Return Nothing
End Function
Public Shared Function TryFoldNothingReferenceConversion(
source As BoundExpression,
conversion As ConversionKind,
targetType As TypeSymbol
) As ConstantValue
Debug.Assert(source IsNot Nothing)
Debug.Assert(targetType IsNot Nothing)
Debug.Assert(targetType.Kind <> SymbolKind.ErrorType)
Dim sourceValue As ConstantValue = source.ConstantValueOpt
Return TryFoldNothingReferenceConversion(sourceValue, conversion, targetType)
End Function
Friend Shared Function TryFoldNothingReferenceConversion(
sourceValue As ConstantValue,
conversion As ConversionKind,
targetType As TypeSymbol
) As ConstantValue
Debug.Assert(targetType IsNot Nothing)
Debug.Assert(targetType.Kind <> SymbolKind.ErrorType)
If sourceValue Is Nothing OrElse Not sourceValue.IsNothing OrElse
targetType.IsTypeParameter() OrElse Not targetType.IsReferenceType() Then
Return Nothing
End If
If conversion = ConversionKind.WideningNothingLiteral OrElse
IsIdentityConversion(conversion) OrElse
(conversion And ConversionKind.WideningReference) = ConversionKind.WideningReference OrElse
(conversion And ConversionKind.WideningArray) = ConversionKind.WideningArray Then
Return sourceValue
End If
Return Nothing
End Function
''' <summary>
''' This function classifies all intrinsic language conversions and user-defined conversions.
''' </summary>
Public Shared Function ClassifyConversion(source As TypeSymbol, destination As TypeSymbol, <[In], Out> ByRef useSiteDiagnostics As HashSet(Of DiagnosticInfo)) As KeyValuePair(Of ConversionKind, MethodSymbol)
Debug.Assert(source IsNot Nothing)
Debug.Assert(destination IsNot Nothing)
Debug.Assert(source.Kind <> SymbolKind.ErrorType)
Debug.Assert(Not TypeOf source Is ArrayLiteralTypeSymbol)
Debug.Assert(destination.Kind <> SymbolKind.ErrorType)
Dim predefinedConversion As ConversionKind = ClassifyPredefinedConversion(source, destination, useSiteDiagnostics)
If ConversionExists(predefinedConversion) Then
Return New KeyValuePair(Of ConversionKind, MethodSymbol)(predefinedConversion, Nothing)
End If
Return ClassifyUserDefinedConversion(source, destination, useSiteDiagnostics)
End Function
''' <summary>
''' This function classifies all intrinsic language conversions, such as inheritance,
''' implementation, array covariance, and conversions between intrinsic types.
''' </summary>
Public Shared Function ClassifyPredefinedConversion(source As BoundExpression, destination As TypeSymbol, binder As Binder, <[In], Out> ByRef useSiteDiagnostics As HashSet(Of DiagnosticInfo)) As ConversionKind
Return ClassifyPredefinedConversion(source, destination, binder, userDefinedConversionsMightStillBeApplicable:=Nothing, useSiteDiagnostics:=useSiteDiagnostics)
End Function
Private Shared Function ClassifyPredefinedConversion(
source As BoundExpression,
destination As TypeSymbol,
binder As Binder,
<Out()> ByRef userDefinedConversionsMightStillBeApplicable As Boolean,
<[In], Out> ByRef useSiteDiagnostics As HashSet(Of DiagnosticInfo)
) As ConversionKind
Debug.Assert(source IsNot Nothing)
Debug.Assert(destination IsNot Nothing)
Debug.Assert(destination.Kind <> SymbolKind.ErrorType)
userDefinedConversionsMightStillBeApplicable = False
Dim conv As ConversionKind
' Using source.IsConstant for field accesses can result in an infinite loop.
' To resolve the cycle, first call GetConstantValue with the already visited constants from the binder.
' The check for source.IsConstant is still necessary because the node might still
' be considered as a non-constant in some error conditions (a reference before declaration,
' for example).
Dim sourceIsConstant As Boolean = False
If source.Kind = BoundKind.FieldAccess Then
sourceIsConstant = DirectCast(source, BoundFieldAccess).FieldSymbol.GetConstantValue(binder.ConstantFieldsInProgress) IsNot Nothing AndAlso source.IsConstant
ElseIf source.Kind = BoundKind.Local Then
sourceIsConstant = DirectCast(source, BoundLocal).LocalSymbol.GetConstantValue(binder) IsNot Nothing AndAlso source.IsConstant
Else
sourceIsConstant = source.IsConstant
End If
If sourceIsConstant Then
'§8.8 Widening Conversions
'• From the literal Nothing to a type.
conv = ClassifyNothingLiteralConversion(source, destination)
If ConversionExists(conv) Then
Return conv
End If
'§8.8 Widening Conversions
'• From the literal 0 to an enumerated type.
'• From a constant expression of type ULong, Long, UInteger, Integer, UShort, Short, Byte, or SByte to
' a narrower type, provided the value of the constant expression is within the range of the destination type.
conv = ClassifyNumericConstantConversion(source, destination, binder)
If ConversionExists(conv) OrElse FailedDueToNumericOverflow(conv) Then
Return conv
End If
End If
If Not (source.IsValue) Then
Return Nothing 'ConversionKind.NoConversion
End If
Dim sourceType As TypeSymbol = If(source.Kind = BoundKind.TupleLiteral,
DirectCast(source, BoundTupleLiteral).InferredType,
source.Type)
If sourceType Is Nothing Then
Dim mostEnclosing = source.GetMostEnclosedParenthesizedExpression().Kind
userDefinedConversionsMightStillBeApplicable = mostEnclosing = BoundKind.ArrayLiteral OrElse
mostEnclosing = BoundKind.TupleLiteral
' The node doesn't have a type yet and reclassification failed.
Return Nothing ' No conversion
End If
If sourceType.Kind <> SymbolKind.ErrorType Then
Dim predefinedConversion As ConversionKind = ClassifyPredefinedConversion(sourceType, destination, useSiteDiagnostics)
If ConversionExists(predefinedConversion) Then
Return predefinedConversion
End If