private static Task <Document> UsePatternMatchingAsync(
Document document,
SwitchStatementSyntax switchStatement,
CancellationToken cancellationToken)
{
SyntaxList <SwitchSectionSyntax> newSections = switchStatement.Sections.Select(section =>
{
if (!(section.Labels.Single() is CaseSwitchLabelSyntax label))
{
return(section);
}
SyntaxList <StatementSyntax> statements = section.Statements;
StatementSyntax statement = statements[0];
if (statement is BlockSyntax block)
{
statement = block.Statements.FirstOrDefault();
}
SingleLocalDeclarationStatementInfo localInfo = SyntaxInfo.SingleLocalDeclarationStatementInfo((LocalDeclarationStatementSyntax)statement);
var castExpression = (CastExpressionSyntax)localInfo.Value;
CasePatternSwitchLabelSyntax newLabel = CasePatternSwitchLabel(
DeclarationPattern(
castExpression.Type,
SingleVariableDesignation(localInfo.Identifier)),
label.ColonToken);
SwitchSectionSyntax newSection = section.RemoveStatement(localInfo.Statement);
newSection = newSection.WithLabels(newSection.Labels.ReplaceAt(0, newLabel));
return(newSection.WithFormatterAnnotation());
})
.ToSyntaxList();
ExpressionSyntax expression = switchStatement.Expression;
ExpressionSyntax newExpression = expression;
LocalDeclarationStatementSyntax localDeclaration = null;
if (expression.IsKind(SyntaxKind.InvocationExpression))
{
SimpleMemberInvocationExpressionInfo invocationInfo = SyntaxInfo.SimpleMemberInvocationExpressionInfo(expression);
newExpression = invocationInfo.Expression;
}
else
{
localDeclaration = (LocalDeclarationStatementSyntax)switchStatement.PreviousStatement();
SingleLocalDeclarationStatementInfo localInfo = SyntaxInfo.SingleLocalDeclarationStatementInfo(localDeclaration);
SimpleMemberInvocationExpressionInfo invocationInfo = SyntaxInfo.SimpleMemberInvocationExpressionInfo(localInfo.Value);
newExpression = invocationInfo.Expression;
}
SwitchStatementSyntax newSwitchStatement = switchStatement
.WithExpression(newExpression.WithTriviaFrom(expression))
.WithSections(newSections);
if (localDeclaration != null)
{
StatementListInfo statementsInfo = SyntaxInfo.StatementListInfo(switchStatement);
newSwitchStatement = newSwitchStatement.WithLeadingTrivia(localDeclaration.GetLeadingTrivia());
SyntaxList <StatementSyntax> newStatements = statementsInfo.Statements
.Replace(switchStatement, newSwitchStatement)
.RemoveAt(statementsInfo.IndexOf(localDeclaration));
return(document.ReplaceStatementsAsync(statementsInfo, newStatements, cancellationToken));
}
else
{
return(document.ReplaceNodeAsync(switchStatement, newSwitchStatement, cancellationToken));
}
}
