Analyzer Diagnostics

The Thinktecture.Runtime.Extensions library includes Roslyn analyzers that validate correct usage of Smart Enums, Value Objects, and Discriminated Unions at compile time. These analyzers catch common mistakes early, before they become runtime errors. There are 59 diagnostic rules across the categories below.

The library ships two analyzers:

• ThinktectureRuntimeExtensionsAnalyzer -- Validates correct declaration and usage of all type categories.
• ThinktectureRuntimeExtensionsInternalUsageAnalyzer -- Prevents external use of internal infrastructure APIs.

• Diagnostic Rules
  • General / Shared
  • Smart Enum
  • Value Object
  • Discriminated Union
  • Object Factory
  • Internal Errors
  • Internal API Usage
  • Switch/Map Usage
• Suppressing Diagnostics

Diagnostic Rules

General / Shared

These rules apply across multiple type categories (Smart Enums, Value Objects, Unions).

ID	Severity	Title	Guidance
TTRESG001	Error	Field must be read-only	Add the readonly modifier to the field.
TTRESG003	Error	Property must be read-only	Remove the setter or make the property get-only.
TTRESG004	Error	The type must be a class or a struct	Change the type declaration to a class or struct.
TTRESG006	Error	Type must be partial	Add the partial modifier to the type declaration.
TTRESG009	Error	The constructors must be private	Mark all constructors as private.
TTRESG017	Error	The key member must not be nullable	Change the key member type to a non-nullable type.
TTRESG034	Error	Field of the base class must be read-only	Add the readonly modifier to the base class field.
TTRESG035	Error	Property of the base class must be read-only	Remove the setter from the base class property.
TTRESG041	Error	The type of the comparer doesn't match the type of the member	Ensure the comparer generic type argument matches the member type.
TTRESG042	Error	Property 'init' accessor must be private	Mark the init accessor as private.
TTRESG043	Error	Primary constructor is not allowed	Remove the primary constructor and use a regular private constructor instead.
TTRESG046	Error	The arguments of 'Switch' and 'Map' must be named	Use named arguments when calling Switch or Map methods. See also Switch/Map Usage.
TTRESG047	Error	Variable must be initialized with non-default value	Initialize the variable using a factory method (e.g., Create) instead of default.
TTRESG063	Error	Type must not have more than one ValueObject/SmartEnum/Union-attribute	Remove duplicate attributes; only one category attribute is allowed per type.

Smart Enum

See Smart Enums and Smart Enums Customization for detailed documentation.

ID	Severity	Title	Guidance
TTRESG002	Error	Smart Enum item must be public	Mark the static readonly field as public.
TTRESG012	Error	Provided key member name is not allowed	Choose a different key member name via KeyMemberName.
TTRESG014	Error	Inner Smart Enum on first level must be private	Mark the first-level derived inner Smart Enum as private.
TTRESG015	Error	Inner Smart Enum on non-first level must be public	Mark deeper-level derived inner Smart Enums as public.
TTRESG036	Error	The key type must not be nullable	Use a non-nullable type for the SmartEnumAttribute<T> type argument.
TTRESG037	Error	Smart Enum without derived types must be sealed	Add the sealed modifier to the Smart Enum, or add derived inner types.
TTRESG060	Error	Smart Enums with ObjectFactoryAttribute must not have HasCorrespondingConstructor = true	Set HasCorrespondingConstructor = false or remove the property. Smart Enums do not use constructors for item creation.
TTRESG064	Error	Type must not have more than one SmartEnumAttribute	Remove duplicate SmartEnumAttribute declarations.
TTRESG100	Warning	The Smart Enum has no items	Add at least one public static readonly field of the Smart Enum type.
TTRESG101	Warning	Static properties are not considered Smart Enum items, use a field instead	Change the static property to a static readonly field.

Value Object

See Value Objects and Value Objects Customization for detailed documentation.

ID	Severity	Title	Guidance
TTRESG044	Error	Custom implementation of the key member not found	Implement a field or property matching the expected key member name. Use KeyMemberName to change the name.
TTRESG045	Error	Key member type mismatch	Change the key member type to match the type specified in the attribute.
TTRESG048	Warning	String-based Value Object needs equality comparer	Add [KeyMemberEqualityComparer<ComparerAccessors.StringOrdinalIgnoreCase, string>] or another appropriate comparer.
TTRESG049	Warning	Complex Value Object with string members needs equality comparer	Set DefaultStringComparison on the attribute, e.g., [ComplexValueObject(DefaultStringComparison = StringComparison.OrdinalIgnoreCase)].
TTRESG057	Error	'AllowDefaultStructs' must be 'false' if Value Object is a struct but key type is a reference type	Set AllowDefaultStructs = false because default would produce a null key.
TTRESG058	Error	'AllowDefaultStructs' must be 'false' if some members disallow default values	Set AllowDefaultStructs = false because some members implement IDisallowDefaultValue.
TTRESG065	Error	Type must not have more than one ValueObjectAttribute/ComplexValueObjectAttribute	Remove duplicate Value Object attributes.
TTRESG102	Warning	The type has a comparer defined but no equality comparer	Add an equality comparer alongside the comparer for consistent behavior.
TTRESG103	Warning	The type has an equality comparer defined but no comparer	Add a comparer alongside the equality comparer for consistent behavior.
TTRESG104	Warning	The member must be marked as 'required' to ensure proper initialization	Add the required modifier to the member to prevent uninitialized usage. Does not apply to interface properties, which cannot be required.
TTRESG105	Warning	Comparison and equality operators settings mismatch	Set ComparisonOperators and EqualityComparisonOperators to the same value.

Discriminated Union

See Discriminated Unions and Discriminated Unions Customization for detailed documentation.

ID	Severity	Title	Guidance
TTRESG053	Error	Derived type of a union must not be generic	Remove generic type parameters from the derived union type.
TTRESG054	Error	Discriminated union must be sealed or have private constructors only	Either seal the union type or make all constructors private.
TTRESG055	Error	Discriminated union implemented using a record must be sealed	Seal the record-based union. Use a class instead if you need nested unions.
TTRESG056	Error	Non-abstract derived union is less accessible than base union	Increase the accessibility of the derived union to match or exceed the base union.
TTRESG066	Error	Type must not have more than one UnionAttribute/AdHocUnionAttribute	Remove duplicate union attributes.
TTRESG067	Error	Ad hoc union must define at least two member types	Add at least two type arguments to the union attribute.
TTRESG071	Error	TypeParamRef index exceeds the number of type parameters	The TypeParamRef index is higher than the union's type parameter count. Use a TypeParamRef that matches an existing type parameter.
TTRESG072	Error	TypeParamRef cannot be used on non-generic ad-hoc union	The union must declare its own type parameters for TypeParamRef placeholders to reference. Either make the union generic or replace the TypeParamRef with a concrete type.
TTRESG073	Error	Ad-hoc unions do not support allows ref struct type parameters	Remove the allows ref struct anti-constraint from the type parameter. Ref structs cannot be boxed, which conflicts with equality, the Value property, and Switch/Map delegate patterns.
TTRESG074	Error	Type parameter used via TypeParamRef must have notnull constraint	When using TypeParamRef to reference a generic type parameter as the key type of a Smart Enum or keyed Value Object, the type parameter must have a notnull constraint (or struct/class, which imply non-null). Add where T : notnull to the type declaration.
TTRESG106	Warning	Inner type should derive from union type	Make the inner type derive from the enclosing union type.
TTRESG107	Warning	Generic ad-hoc union does not reference any type parameter via TypeParamRef	The union is generic but none of its member types use TypeParamRef. Reference at least one type parameter via TypeParamRef1–TypeParamRef5.

Object Factory

See Object Factories for detailed documentation.

ID	Severity	Title	Guidance
TTRESG050	Error	Method with UseDelegateFromConstructorAttribute must be partial	Add the partial modifier to the method.
TTRESG051	Error	Method with UseDelegateFromConstructorAttribute must not have generics	Remove generic type parameters from the method. Use the inheritance approach instead.
TTRESG059	Error	Type with ObjectFactoryAttribute and HasCorrespondingConstructor = true must have a matching constructor	Add a constructor with a single parameter of the object factory's type argument.
TTRESG061	Error	Type with ObjectFactoryAttribute must implement static Validate method	Add a static Validate method with the required signature (see error message for details).
TTRESG062	Error	Type with ObjectFactoryAttribute must implement ToValue method	Add an instance ToValue() method when UseForSerialization is not None or UseWithEntityFramework is true.
TTRESG068	Error	Multiple ObjectFactoryAttribute instances cannot have UseWithEntityFramework = true	Set UseWithEntityFramework = true on only one ObjectFactoryAttribute.
TTRESG069	Error	Multiple ObjectFactoryAttribute instances cannot have UseForModelBinding = true	Set UseForModelBinding = true on only one ObjectFactoryAttribute.
TTRESG070	Error	Multiple ObjectFactoryAttribute instances cannot specify overlapping serialization frameworks	Ensure each serialization framework is used by only one ObjectFactoryAttribute.

Internal Errors

These diagnostics indicate problems within the source generator itself and are not typically caused by user code.

ID	Severity	Title	Guidance
TTRESG097	Error	Error during analysis of referenced modules	Check that all referenced Thinktecture integration packages are compatible with the installed version of the core library.
TTRESG098	Warning	Error during code analysis	Report the issue if it persists. The error message contains details about the affected type.
TTRESG099	Error	Error during code generation	Report the issue if it persists. The error message contains details about the affected type.

Internal API Usage

ID	Severity	Title	Guidance
TTRESG1000	Warning	Internal Thinktecture.Runtime.Extensions API usage	Do not use types or members from the Thinktecture.Internal namespace. These are internal infrastructure APIs that may change or be removed without notice.

Switch/Map Usage

See also TTRESG046 in General / Shared for the requirement that Switch/Map arguments must be named.

ID	Severity	Title	Guidance
TTRESG1001	Info	Consider using a static lambda	Lambda passed to Switch/Map should be static. Use a static lambda to avoid unnecessary allocations, or use the state overload to pass captured variables explicitly.

Suppressing Diagnostics

If you need to suppress a specific diagnostic, you can use one of the following approaches:

Using #pragma directives:

#pragma warning disable TTRESG048 // String-based Value Object needs equality comparer
[ValueObject<string>]
public partial class MyValueObject
{
   // ...
}
#pragma warning restore TTRESG048

Using [SuppressMessage] attribute:

using System.Diagnostics.CodeAnalysis;

[SuppressMessage("ThinktectureRuntimeExtensionsAnalyzer", "TTRESG048")]
[ValueObject<string>]
public partial class MyValueObject
{
   // ...
}

Note: TTRESG1000 uses a different category: "ThinktectureRuntimeExtensionsInternalUsageAnalyzer".

In .editorconfig:

[*.cs]
dotnet_diagnostic.TTRESG048.severity = none

Note: Suppressing Error-level diagnostics is generally not recommended, as these indicate conditions that will cause incorrect code generation or runtime failures.