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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 System.Threading
Imports Microsoft.CodeAnalysis.Completion.Providers
Imports Microsoft.CodeAnalysis.VisualBasic.Extensions.ContextQuery
Imports Microsoft.CodeAnalysis.VisualBasic.Syntax
Namespace Microsoft.CodeAnalysis.VisualBasic.Completion.KeywordRecommenders.Declarations
Friend Class GenericConstraintsKeywordRecommender
Inherits AbstractKeywordRecommender
Protected Overrides Function RecommendKeywords(context As VisualBasicSyntaxContext, cancellationToken As CancellationToken) As ImmutableArray(Of RecommendedKeyword)
If context.FollowsEndOfStatement Then
Return ImmutableArray(Of RecommendedKeyword).Empty
End If
Dim targetToken = context.TargetToken
Dim recommendations As New List(Of RecommendedKeyword)
recommendations.Add(New RecommendedKeyword("Class", VBFeaturesResources.Constrains_a_generic_type_parameter_to_require_that_any_type_argument_passed_to_it_be_a_reference_type))
recommendations.Add(New RecommendedKeyword("Structure", VBFeaturesResources.Constrains_a_generic_type_parameter_to_require_that_any_type_argument_passed_to_it_be_a_value_type))
recommendations.Add(New RecommendedKeyword("New", VBFeaturesResources.Specifies_a_constructor_constraint_on_a_generic_type_parameter))
If targetToken.IsChildToken(Of TypeParameterSingleConstraintClauseSyntax)(Function(constraint) constraint.AsKeyword) Then
Return recommendations.ToImmutableArray()
ElseIf TypeOf targetToken.Parent Is TypeParameterMultipleConstraintClauseSyntax Then
Dim multipleConstraint = DirectCast(targetToken.Parent, TypeParameterMultipleConstraintClauseSyntax)
If targetToken = multipleConstraint.OpenBraceToken OrElse targetToken.Kind = SyntaxKind.CommaToken Then
Dim previousConstraints = multipleConstraint.Constraints.Where(Function(c) c.Span.End < context.Position).ToList()
' Structure can only be listed with previous type constraints
If previousConstraints.Any(Function(constraint) Not constraint.IsKind(SyntaxKind.TypeConstraint)) Then
recommendations.RemoveAll(Function(k) k.Keyword = "Structure")
End If
If previousConstraints.Any(Function(constraint) constraint.IsKind(SyntaxKind.ClassConstraint, SyntaxKind.StructureConstraint)) Then
recommendations.RemoveAll(Function(k) k.Keyword = "Class")
End If
If previousConstraints.Any(Function(constraint) constraint.IsKind(SyntaxKind.NewConstraint, SyntaxKind.StructureConstraint)) Then
recommendations.RemoveAll(Function(k) k.Keyword = "New")
End If
Return recommendations.ToImmutableArray()
End If
End If
Return ImmutableArray(Of RecommendedKeyword).Empty
End Function
End Class
End Namespace
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