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' Licensed to the .NET Foundation under one or more agreements.
' The .NET Foundation licenses this file to you under the MIT license.
' See the LICENSE file in the project root for more information.
Imports System.Collections.Immutable
Imports Microsoft.CodeAnalysis.PooledObjects
Imports Microsoft.CodeAnalysis.Symbols
Imports Microsoft.CodeAnalysis.VisualBasic.Symbols
Imports System.Runtime.InteropServices
Namespace Microsoft.CodeAnalysis.VisualBasic.Symbols
' TypeParameters are always directly contained in a NamedTypeDefinition,
' and always have referenced identity (assuming the NamedTypeDefinition also
' has reference identity, which seems true.)
''' <summary>
''' Represents a type parameter in a generic type or generic method.
''' </summary>
Friend MustInherit Class TypeParameterSymbol
Inherits TypeSymbol
Implements ITypeParameterSymbol, ITypeParameterSymbolInternal
' !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
' Changes to the public interface of this class should remain synchronized with the C# version.
' Do not make any changes to the public interface without making the corresponding change
' to the C# version.
' !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
''' <summary>
''' Get the original definition of this symbol. If this symbol is derived from another
''' symbol by (say) type substitution, this gets the original symbol, as it was defined
''' in source or metadata.
''' </summary>
Public Overridable Shadows ReadOnly Property OriginalDefinition As TypeParameterSymbol
Get
' Default implements returns Me.
Return Me
End Get
End Property
Protected NotOverridable Overrides ReadOnly Property OriginalTypeSymbolDefinition As TypeSymbol
Get
Return Me.OriginalDefinition
End Get
End Property
''' <summary>
''' Gets the ordinal order of this type parameter. The first type parameter has ordinal zero.
''' </summary>
Public MustOverride ReadOnly Property Ordinal As Integer
Friend Overridable Function GetConstraintsUseSiteInfo() As UseSiteInfo(Of AssemblySymbol)
Return Nothing
End Function
''' <summary>
''' Get the types that were directly specified as constraints on this type parameter.
''' Duplicates and cycles are removed, although the collection may include redundant
''' constraints where one constraint is a base type of another.
''' </summary>
Friend MustOverride ReadOnly Property ConstraintTypesNoUseSiteDiagnostics As ImmutableArray(Of TypeSymbol)
Friend Function ConstraintTypesWithDefinitionUseSiteDiagnostics(<[In], Out> ByRef useSiteInfo As CompoundUseSiteInfo(Of AssemblySymbol)) As ImmutableArray(Of TypeSymbol)
Dim result = ConstraintTypesNoUseSiteDiagnostics
Me.AddConstraintsUseSiteInfo(useSiteInfo)
For Each constraint In result
constraint.OriginalDefinition.AddUseSiteInfo(useSiteInfo)
Next
Return result
End Function
''' <summary>
''' Returns whether the parameterless constructor constraint was specified.
''' </summary>
Public MustOverride ReadOnly Property HasConstructorConstraint As Boolean Implements ITypeParameterSymbol.HasConstructorConstraint
' Type parameters do not have members.
Public NotOverridable Overrides Function GetMembers() As ImmutableArray(Of Symbol)
Return ImmutableArray(Of Symbol).Empty
End Function
' Type parameters do not have members.
Public NotOverridable Overrides Function GetMembers(name As String) As ImmutableArray(Of Symbol)
Return ImmutableArray(Of Symbol).Empty
End Function
Public MustOverride ReadOnly Property TypeParameterKind As TypeParameterKind Implements ITypeParameterSymbol.TypeParameterKind
''' <summary>
''' The method that declares this type parameter
''' </summary>
Public ReadOnly Property DeclaringMethod As MethodSymbol
Get
Return TryCast(Me.ContainingSymbol, MethodSymbol)
End Get
End Property
''' <summary>
''' The type that declares this type parameter
''' </summary>
Public ReadOnly Property DeclaringType As NamedTypeSymbol
Get
Return TryCast(Me.ContainingSymbol, NamedTypeSymbol)
End Get
End Property
' Type parameters do not have members.
Public NotOverridable Overrides Function GetTypeMembers() As ImmutableArray(Of NamedTypeSymbol)
Return ImmutableArray(Of NamedTypeSymbol).Empty
End Function
' Type parameters do not have members.
Public NotOverridable Overrides Function GetTypeMembers(name As String) As ImmutableArray(Of NamedTypeSymbol)
Return ImmutableArray(Of NamedTypeSymbol).Empty
End Function
' Type parameters do not have members.
Public NotOverridable Overrides Function GetTypeMembers(name As String, arity As Integer) As ImmutableArray(Of NamedTypeSymbol)
Return ImmutableArray(Of NamedTypeSymbol).Empty
End Function
Friend Overrides Function Accept(Of TArgument, TResult)(visitor As VisualBasicSymbolVisitor(Of TArgument, TResult), arg As TArgument) As TResult
Return visitor.VisitTypeParameter(Me, arg)
End Function
' Only the compiler can create instances of TypeParameter.
Friend Sub New()
End Sub
Public NotOverridable Overrides ReadOnly Property DeclaredAccessibility As Accessibility
Get
Return Accessibility.NotApplicable
End Get
End Property
Public NotOverridable Overrides ReadOnly Property Kind As SymbolKind
Get
Return SymbolKind.TypeParameter
End Get
End Property
Public NotOverridable Overrides ReadOnly Property TypeKind As TypeKind
Get
Return TypeKind.TypeParameter
End Get
End Property
Friend NotOverridable Overrides ReadOnly Property BaseTypeNoUseSiteDiagnostics As NamedTypeSymbol
Get
Return Nothing
End Get
End Property
Friend NotOverridable Overrides ReadOnly Property InterfacesNoUseSiteDiagnostics As ImmutableArray(Of NamedTypeSymbol)
Get
Return ImmutableArray(Of NamedTypeSymbol).Empty
End Get
End Property
''' <summary>
''' Called by ConstraintTypes and Interfaces
''' to allow derived classes to ensure constraints within the containing
''' type or method are resolved in a consistent order, regardless of the
''' order the callers query individual type parameters.
''' </summary>
Friend MustOverride Sub EnsureAllConstraintsAreResolved()
''' <summary>
''' Helper method to force type parameter constraints to be resolved.
''' </summary>
Friend Shared Sub EnsureAllConstraintsAreResolved(typeParameters As ImmutableArray(Of TypeParameterSymbol))
For Each typeParameter In typeParameters
typeParameter.ResolveConstraints(ConsList(Of TypeParameterSymbol).Empty)
Next
End Sub
''' <summary>
''' Get all constraints, with optional source location for each. This method
''' is provided for constraint checking only, and should only be invoked
''' for SourceTypeParameterSymbol or ErrorTypeParameterSymbol directly.
''' There is currently no need to invoke this method for PETypeParameterSymbol.
''' </summary>
Friend Sub GetConstraints(constraintsBuilder As ArrayBuilder(Of TypeParameterConstraint))
constraintsBuilder.AddRange(GetConstraints())
End Sub
Friend Overridable Function GetConstraints() As ImmutableArray(Of TypeParameterConstraint)
Throw ExceptionUtilities.Unreachable
End Function
''' <summary>
''' Resolve constraints, binding and checking for conflicts as necessary. This is an
''' internal method for resolving dependent sets of constraints and handling cycles.
''' It will be called indirectly for core implementations (SourceTypeParameterSymbol and
''' PETypeParameterSymbol) as a result of accessing constraint properties on this class.
''' </summary>
Friend Overridable Sub ResolveConstraints(inProgress As ConsList(Of TypeParameterSymbol))
Throw ExceptionUtilities.Unreachable
End Sub
Friend Shared Function GetConstraintTypesOnly(constraints As ImmutableArray(Of TypeParameterConstraint)) As ImmutableArray(Of TypeSymbol)
If constraints.IsEmpty Then
Return ImmutableArray(Of TypeSymbol).Empty
End If
Dim builder = ArrayBuilder(Of TypeSymbol).GetInstance()
For Each constraint In constraints
Dim constraintType = constraint.TypeConstraint
If constraintType IsNot Nothing Then
builder.Add(constraintType)
End If
Next
Return builder.ToImmutableAndFree()
End Function
Public NotOverridable Overrides ReadOnly Property IsReferenceType As Boolean
Get
If (Me.HasReferenceTypeConstraint) Then
Return True
End If
Return IsReferenceTypeIgnoringIsClass()
End Get
End Property
' From typedesc.cpp :
' > A recursive helper that helps determine whether this variable is constrained as ObjRef.
' > Please note that we do not check the gpReferenceTypeConstraint special constraint here
' > because this property does not propagate up the constraining hierarchy.
' > (e.g. "class A<S, T> where S : T, where T : class" does not guarantee that S is ObjRef)
Private Function IsReferenceTypeIgnoringIsClass() As Boolean
For Each constraint In Me.ConstraintTypesNoUseSiteDiagnostics
If (ConstraintImpliesReferenceType(constraint)) Then
Return True
End If
Next
Return False
End Function
Private Shared Function ConstraintImpliesReferenceType(constraint As TypeSymbol) As Boolean
If (constraint.TypeKind = TypeKind.TypeParameter) Then
Return DirectCast(constraint, TypeParameterSymbol).IsReferenceTypeIgnoringIsClass()
Else
If (constraint.IsReferenceType) Then
If (constraint.IsInterfaceType()) Then
Return False ' can be satisfied by valuetypes
End If
Select Case (constraint.SpecialType)
Case SpecialType.System_Object,
SpecialType.System_ValueType,
SpecialType.System_Enum
Return False ' can be satisfied by valuetypes
End Select
Return True
End If
Return False
End If
End Function
Public Overrides ReadOnly Property IsValueType As Boolean
Get
If Me.HasValueTypeConstraint Then
Return True
End If
' usually value types cannot be used as type constraints. But there is a way to use a
' value type as a type parameter which gets as a constraints to a overriding generic method - et voila: we
' have a value type as type constraint.
'
' Source example:
' Class BaseGeneric(Of S)
' Public Overridable Sub MySub(Of T As S)(param As T)
' End Sub
' End Class
' Class Derived
' Inherits BaseGeneric(Of MyStruct)
' Public Overrides Sub MySub(Of T As MyStruct)(param As T)
' End Sub
' End Class
' Structure MyStruct
' End Structure
'
' therefore we need to check the type constraints for value types as well
For Each constraint In Me.ConstraintTypesNoUseSiteDiagnostics
If (constraint.IsValueType) Then
Return True
End If
Next
Return False
End Get
End Property
''' <summary>
''' Substitute the given type substitution within this type, returning a new type. If the
''' substitution had no effect, return Me.
''' !!! Only code implementing construction of generic types is allowed to call this method !!!
''' !!! All other code should use Construct methods. !!!
''' </summary>
Friend Overrides Function InternalSubstituteTypeParameters(substitution As TypeSubstitution) As TypeWithModifiers
If substitution IsNot Nothing Then
Return substitution.GetSubstitutionFor(Me)
End If
Return New TypeWithModifiers(Me)
End Function
Public MustOverride ReadOnly Property HasReferenceTypeConstraint As Boolean Implements ITypeParameterSymbol.HasReferenceTypeConstraint
Public MustOverride ReadOnly Property HasValueTypeConstraint As Boolean Implements ITypeParameterSymbol.HasValueTypeConstraint
Public MustOverride ReadOnly Property AllowsRefLikeType As Boolean Implements ITypeParameterSymbol.AllowsRefLikeType
Private ReadOnly Property HasUnmanagedTypeConstraint As Boolean Implements ITypeParameterSymbol.HasUnmanagedTypeConstraint
Get
Return False
End Get
End Property
Private ReadOnly Property HasNotNullConstraint As Boolean Implements ITypeParameterSymbol.HasNotNullConstraint
Get
Return False
End Get
End Property
Public MustOverride ReadOnly Property Variance As VarianceKind Implements ITypeParameterSymbol.Variance
''' <summary>
''' If this is a type parameter of a reduced extension method, gets the type parameter definition that
''' this type parameter was reduced from. Otherwise, returns Nothing.
''' </summary>
Public Overridable ReadOnly Property ReducedFrom As TypeParameterSymbol
Get
Return Nothing
End Get
End Property
''' <summary>
''' Return an array of substituted type parameters with duplicates removed.
''' </summary>
Friend Shared Function InternalSubstituteTypeParametersDistinct(substitution As TypeSubstitution, types As ImmutableArray(Of TypeSymbol)) As ImmutableArray(Of TypeSymbol)
Return types.SelectAsArray(s_substituteFunc, substitution).Distinct()
End Function
Private Shared ReadOnly s_substituteFunc As Func(Of TypeSymbol, TypeSubstitution, TypeSymbol) = Function(type, substitution) type.InternalSubstituteTypeParameters(substitution).Type
Friend Overrides ReadOnly Property EmbeddedSymbolKind As EmbeddedSymbolKind
Get
Return Me.ContainingSymbol.EmbeddedSymbolKind
End Get
End Property
Friend NotOverridable Overrides ReadOnly Property ObsoleteAttributeData As ObsoleteAttributeData
Get
Return Nothing
End Get
End Property
#Region "ITypeParameterSymbol"
Private ReadOnly Property ITypeParameterSymbol_ReferenceTypeConstraintNullableAnnotation As NullableAnnotation Implements ITypeParameterSymbol.ReferenceTypeConstraintNullableAnnotation
Get
Return NullableAnnotation.None
End Get
End Property
Private ReadOnly Property ITypeParameterSymbol_DeclaringMethod As IMethodSymbol Implements ITypeParameterSymbol.DeclaringMethod
Get
Return Me.DeclaringMethod
End Get
End Property
Private ReadOnly Property ITypeParameterSymbol_DeclaringType As INamedTypeSymbol Implements ITypeParameterSymbol.DeclaringType
Get
Return Me.DeclaringType
End Get
End Property
Private ReadOnly Property ITypeParameterSymbol_Ordinal As Integer Implements ITypeParameterSymbol.Ordinal
Get
Return Me.Ordinal
End Get
End Property
Private ReadOnly Property ITypeParameterSymbol_ConstraintTypes As ImmutableArray(Of ITypeSymbol) Implements ITypeParameterSymbol.ConstraintTypes
Get
Return StaticCast(Of ITypeSymbol).From(Me.ConstraintTypesNoUseSiteDiagnostics)
End Get
End Property
Private ReadOnly Property ITypeParameterSymbol_ConstraintNullableAnnotations As ImmutableArray(Of NullableAnnotation) Implements ITypeParameterSymbol.ConstraintNullableAnnotations
Get
Return Me.ConstraintTypesNoUseSiteDiagnostics.SelectAsArray(Function(t) NullableAnnotation.None)
End Get
End Property
Private ReadOnly Property ITypeParameterSymbol_OriginalDefinition As ITypeParameterSymbol Implements ITypeParameterSymbol.OriginalDefinition
Get
Return Me.OriginalDefinition
End Get
End Property
Private ReadOnly Property ITypeParameterSymbol_ReducedFrom As ITypeParameterSymbol Implements ITypeParameterSymbol.ReducedFrom
Get
Return Me.ReducedFrom
End Get
End Property
Public Overrides Sub Accept(visitor As SymbolVisitor)
visitor.VisitTypeParameter(Me)
End Sub
Public Overrides Function Accept(Of TResult)(visitor As SymbolVisitor(Of TResult)) As TResult
Return visitor.VisitTypeParameter(Me)
End Function
Public Overrides Function Accept(Of TArgument, TResult)(visitor As SymbolVisitor(Of TArgument, TResult), argument As TArgument) As TResult
Return visitor.VisitTypeParameter(Me, argument)
End Function
Public Overrides Sub Accept(visitor As VisualBasicSymbolVisitor)
visitor.VisitTypeParameter(Me)
End Sub
Public Overrides Function Accept(Of TResult)(visitor As VisualBasicSymbolVisitor(Of TResult)) As TResult
Return visitor.VisitTypeParameter(Me)
End Function
#End Region
End Class
End Namespace
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