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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.Statements
''' <summary>
''' Recommends the "Else" keyword for the statement context.
''' </summary>
Friend Class ElseKeywordRecommender
Inherits AbstractKeywordRecommender
Protected Overrides Function RecommendKeywords(context As VisualBasicSyntaxContext, cancellationToken As CancellationToken) As ImmutableArray(Of RecommendedKeyword)
Dim targetToken = context.TargetToken
Dim parent = targetToken.GetAncestor(Of SingleLineIfStatementSyntax)()
If parent IsNot Nothing AndAlso Not parent.Statements.IsEmpty() Then
If context.IsFollowingCompleteStatement(Of SingleLineIfStatementSyntax)(Function(ifStatement) ifStatement.Statements.Last()) Then
Return ImmutableArray.Create(New RecommendedKeyword("Else", VBFeaturesResources.Introduces_a_group_of_statements_in_an_If_statement_that_is_executed_if_no_previous_condition_evaluates_to_True))
End If
End If
If context.IsStatementContext AndAlso
IsDirectlyInIfOrElseIf(context) Then
Return ImmutableArray.Create(New RecommendedKeyword("Else", VBFeaturesResources.Introduces_a_group_of_statements_in_an_If_statement_that_is_executed_if_no_previous_condition_evaluates_to_True))
End If
' Determine whether we can offer "Else" after "Case" in a Select block.
If targetToken.Kind = SyntaxKind.CaseKeyword AndAlso targetToken.Parent.IsKind(SyntaxKind.CaseStatement) Then
' Next, grab the parenting "Select" block and ensure that it doesn't have any Case Else statements
Dim selectBlock = targetToken.GetAncestor(Of SelectBlockSyntax)()
If selectBlock IsNot Nothing AndAlso
Not selectBlock.CaseBlocks.Any(Function(cb) cb.CaseStatement.Kind = SyntaxKind.CaseElseStatement) Then
' Finally, ensure this case statement is the last one in the parenting "Select" block.
If selectBlock.CaseBlocks.Last().CaseStatement Is targetToken.Parent Then
Return ImmutableArray.Create(New RecommendedKeyword("Else", VBFeaturesResources.Introduces_the_statements_to_run_if_none_of_the_previous_cases_in_the_Select_Case_statement_returns_True))
End If
End If
End If
Return ImmutableArray(Of RecommendedKeyword).Empty
End Function
Private Shared Function IsDirectlyInIfOrElseIf(context As VisualBasicSyntaxContext) As Boolean
' Maybe we're after the Then keyword
If context.TargetToken.IsKind(SyntaxKind.ThenKeyword) AndAlso
context.TargetToken.Parent?.Parent.IsKind(SyntaxKind.MultiLineIfBlock, SyntaxKind.ElseIfBlock) Then
Return True
End If
Dim statement = context.TargetToken.Parent.GetAncestor(Of StatementSyntax)
Return If(statement?.Parent.IsKind(SyntaxKind.MultiLineIfBlock, SyntaxKind.ElseIfBlock), False)
End Function
End Class
End Namespace
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