SymbolAnalyzer¶

SymbolAnalyzer<TSymbol> is the primary base class for analyzers that check a single condition on a symbol and report one diagnostic.

Quick Start¶

[Reports("RK1002", "Type with [AutoNotify] must be partial",
    Description = "Source generators require partial types.",
    Category = "Usage",
    Severity = DiagnosticSeverity.Error)]
public sealed class MustBePartialAnalyzer : TypeAnalyzer
{
    protected override bool ShouldReport(ValidSymbol<INamedTypeSymbol> type)
        => type.HasAttribute<AutoNotifyAttribute>() && !type.IsPartial;
}

The base class handles Initialize, ConfigureGeneratedCodeAnalysis, EnableConcurrentExecution, SupportedDiagnostics, and RegisterSymbolAction. You only implement ShouldReport.

How It Works¶

Declare the diagnostic via [Reports] on the class
The base class infers the SymbolKind from the TSymbol type parameter
On each symbol, wraps it in ValidSymbol<TSymbol> and calls ShouldReport
If true, reports the diagnostic at the symbol's location

Specialized Aliases¶

These non-generic aliases save you from specifying the symbol type:

Alias	Equivalent To	Symbol Type
`TypeAnalyzer`	`SymbolAnalyzer<INamedTypeSymbol>`	Classes, structs, interfaces, enums
`MethodAnalyzer`	`SymbolAnalyzer<IMethodSymbol>`	Methods
`PropertyAnalyzer`	`SymbolAnalyzer<IPropertySymbol>`	Properties
`FieldAnalyzer`	`SymbolAnalyzer<IFieldSymbol>`	Fields
`EventAnalyzer`	`SymbolAnalyzer<IEventSymbol>`	Events
`ParameterAnalyzer`	`SymbolAnalyzer<IParameterSymbol>`	Parameters
`NamespaceAnalyzer`	`SymbolAnalyzer<INamespaceSymbol>`	Namespaces
`TypeParameterAnalyzer`	`SymbolAnalyzer<ITypeParameterSymbol>`	Generic type parameters

Abstract & Virtual Members¶

Member	Kind	Default	Description
`ShouldReport(symbol)`	abstract	—	Return `true` to report the diagnostic
`GetMessageArgs(symbol)`	virtual	`[symbol.Name]`	Message format arguments
`GetLocation(symbol)`	virtual	`symbol.Location`	Diagnostic location

Properties¶

Property	Type	Description
`Rule`	`DiagnosticDescriptor`	The diagnostic descriptor created from `[Reports]`

Examples¶

Must Be Sealed¶

[Reports("EFF001", "Effects module should be sealed",
    Category = "Design",
    Severity = DiagnosticSeverity.Warning)]
public sealed class ModuleShouldBeSealedAnalyzer : TypeAnalyzer
{
    protected override bool ShouldReport(ValidSymbol<INamedTypeSymbol> type)
        => type.HasAttribute<EffectsModuleAttribute>()
           && type.IsClass && !type.IsSealed && !type.IsAbstract;
}

Async Method Naming¶

[Reports("ASYNC001", "Async method should have 'Async' suffix",
    Category = "Naming",
    Severity = DiagnosticSeverity.Warning)]
public sealed class AsyncNamingAnalyzer : MethodAnalyzer
{
    protected override bool ShouldReport(ValidSymbol<IMethodSymbol> method)
        => method.HasAttribute<AsyncAttribute>()
           && method.IsAsync && !method.Name.EndsWith("Async");
}

Backing Field Must Be Private¶

[Reports("RK1003", "Backing field must be private",
    Category = "Encapsulation",
    Severity = DiagnosticSeverity.Error)]
public sealed class FieldMustBePrivateAnalyzer : FieldAnalyzer
{
    protected override bool ShouldReport(ValidSymbol<IFieldSymbol> field)
        => field.HasAttribute<NotifyAttribute>()
           && field.DeclaredAccessibility != Accessibility.Private;
}

Custom Message Args¶

[Reports("SER001", "Serializable type must have parameterless constructor",
    Message = "Type '{0}' has no parameterless constructor",
    Category = "Serialization",
    Severity = DiagnosticSeverity.Error)]
public sealed class NeedsCtorAnalyzer : TypeAnalyzer
{
    protected override bool ShouldReport(ValidSymbol<INamedTypeSymbol> type)
        => type.HasAttribute<SerializableAttribute>()
           && !type.Constructors.Any(c => c.Parameters.IsEmpty && !c.IsStatic);

    protected override object[] GetMessageArgs(ValidSymbol<INamedTypeSymbol> type)
        => [type.ToDisplayString()];
}

Using Projection Layer¶

[Reports("RK1005", "AutoNotify type must have at least one notifiable field",
    Category = "Usage",
    Severity = DiagnosticSeverity.Warning)]
public sealed class MustHaveFieldsAnalyzer : TypeAnalyzer
{
    protected override bool ShouldReport(ValidSymbol<INamedTypeSymbol> type)
    {
        var model = type.QueryAutoNotify();
        return model is null || model.Properties.IsEmpty;
    }
}