private static bool IsIsKindMethod(
ExpressionSyntax expression,
SemanticModel semanticModel,
CancellationToken cancellationToken)
{
return expression is IdentifierNameSyntax identifierName
&& string.Equals(identifierName.Identifier.ValueText, "IsKind", StringComparison.Ordinal)
&& CSharpSymbolUtility.IsIsKindExtensionMethod(expression, semanticModel, cancellationToken);
}
private static void AnalyzeInvocationExpression(SyntaxNodeAnalysisContext context)
{
var invocationExpression = (InvocationExpressionSyntax)context.Node;
if (invocationExpression.ContainsDiagnostics)
{
return;
}
SimpleMemberInvocationExpressionInfo invocationInfo = SyntaxInfo.SimpleMemberInvocationExpressionInfo(invocationExpression);
if (!invocationInfo.Success)
{
return;
}
ISymbol symbol = null;
string methodName = invocationInfo.NameText;
switch (invocationInfo.Arguments.Count)
{
case 0:
{
switch (methodName)
{
case "First":
{
if (!context.IsAnalyzerSuppressed(DiagnosticDescriptors.UseElementAccess))
{
UseElementAccessInsteadOfCallingFirst();
}
break;
}
}
break;
}
case 1:
{
switch (methodName)
{
case "ElementAt":
{
if (!context.IsAnalyzerSuppressed(DiagnosticDescriptors.UseElementAccess))
{
UseElementAccessInsteadOfCallingElementAt();
}
break;
}
case "IsKind":
{
if (!context.IsAnalyzerSuppressed(DiagnosticDescriptors.UnnecessaryNullCheck))
{
AnalyzeUnnecessaryNullCheck();
}
break;
}
}
break;
}
}
if (!context.IsAnalyzerSuppressed(DiagnosticDescriptors.UseReturnValue) &&
invocationExpression.IsParentKind(SyntaxKind.ExpressionStatement))
{
UseReturnValue();
}
void AnalyzeUnnecessaryNullCheck()
{
ExpressionSyntax expression = invocationInfo.InvocationExpression.WalkUpParentheses();
SyntaxNode parent = expression.Parent;
if (!parent.IsKind(SyntaxKind.LogicalAndExpression))
{
return;
}
var binaryExpression = (BinaryExpressionSyntax)parent;
if (expression != binaryExpression.Right)
{
return;
}
if (binaryExpression.Left.ContainsDirectives)
{
return;
}
if (binaryExpression.OperatorToken.ContainsDirectives)
{
return;
}
NullCheckExpressionInfo nullCheckInfo = SyntaxInfo.NullCheckExpressionInfo(binaryExpression.Left, NullCheckStyles.CheckingNotNull & ~NullCheckStyles.HasValue);
if (!nullCheckInfo.Success)
{
return;
}
if (!CSharpFactory.AreEquivalent(invocationInfo.Expression, nullCheckInfo.Expression))
{
return;
}
if (!CSharpSymbolUtility.IsIsKindExtensionMethod(invocationExpression, context.SemanticModel, context.CancellationToken))
{
return;
}
TextSpan span = TextSpan.FromBounds(binaryExpression.Left.SpanStart, binaryExpression.OperatorToken.Span.End);
DiagnosticHelpers.ReportDiagnostic(
context,
DiagnosticDescriptors.UnnecessaryNullCheck,
Location.Create(invocationInfo.InvocationExpression.SyntaxTree, span));
}
void UseElementAccessInsteadOfCallingFirst()
{
if (!invocationInfo.Expression.GetTrailingTrivia().IsEmptyOrWhitespace())
{
return;
}
symbol = context.SemanticModel.GetSymbol(invocationExpression, context.CancellationToken);
if (symbol?.Kind != SymbolKind.Method ||
symbol.IsStatic ||
symbol.DeclaredAccessibility != Accessibility.Public ||
!RoslynSymbolUtility.IsList(symbol.ContainingType.OriginalDefinition))
{
return;
}
TextSpan span = TextSpan.FromBounds(invocationInfo.Name.SpanStart, invocationExpression.Span.End);
DiagnosticHelpers.ReportDiagnostic(
context,
DiagnosticDescriptors.UseElementAccess,
Location.Create(invocationExpression.SyntaxTree, span));
}
void UseElementAccessInsteadOfCallingElementAt()
{
if (!invocationInfo.Expression.GetTrailingTrivia().IsEmptyOrWhitespace())
{
return;
}
symbol = context.SemanticModel.GetSymbol(invocationExpression, context.CancellationToken);
if (symbol?.Kind != SymbolKind.Method ||
symbol.IsStatic ||
symbol.DeclaredAccessibility != Accessibility.Public ||
!symbol.ContainingType.OriginalDefinition.HasMetadataName(RoslynMetadataNames.Microsoft_CodeAnalysis_SyntaxTriviaList))
{
return;
}
TextSpan span = TextSpan.FromBounds(invocationInfo.Name.SpanStart, invocationExpression.Span.End);
DiagnosticHelpers.ReportDiagnostic(
context,
DiagnosticDescriptors.UseElementAccess,
Location.Create(invocationExpression.SyntaxTree, span));
}
void UseReturnValue()
{
if (symbol == null)
{
symbol = context.SemanticModel.GetSymbol(invocationExpression, context.CancellationToken);
}
if (symbol?.Kind != SymbolKind.Method)
{
return;
}
if (!RoslynSymbolUtility.IsRoslynType(symbol.ContainingType))
{
return;
}
var methodSymbol = (IMethodSymbol)symbol;
if (!RoslynSymbolUtility.IsRoslynType(methodSymbol.ReturnType))
{
return;
}
DiagnosticHelpers.ReportDiagnostic(context, DiagnosticDescriptors.UseReturnValue, invocationExpression);
}
}
