Test Plan for "Ref Struct Interfaces" feature

[AlekseyTs]

Championed proposal: dotnet/csharplang#7608
Speclet: https://github.com/dotnet/csharplang/blob/main/proposals/csharp-13.0/ref-struct-interfaces.md
Feature branch: https://github.com/dotnet/roslyn/tree/features/RefStructInterfaces

Compiler

• language version
  • interface implementation
  • allows ref struct
  • generic type substitution
  • using, foreach, etc. with ref like type interface implementation
• target runtime support: RuntimeFeature.ByRefLikeGenerics
  • allows ref struct
• ref struct interface implementation
  • implicit / explicit implementation
  • default interface methods, properties, indexers, events, with virtual / sealed modifiers (see *_DefaultImplementation)
• allows ref struct constraint (see AllowsConstraint_*)
  • must be last
  • duplicated constraint
  • with struct, class, new(), unmanaged, notnull, default, interface, class
  • on partial type / method
  • on override
  • on implicit / explicit implementation
  • constraint emitted to metadata
  • constraint emitted to ref assembly (Fill some gaps in Test Plan for "Ref Struct Interfaces" feature #74389, AllowsConstraint_01_SimpleTypeTypeParameter)
• calling instance members on value of type parameter with allows ref struct
  • error calling System.Object methods
  • error calling non-virtual default interface member (ERR_BadNonVirtualInterfaceMemberAccessOnAllowsRefLike error CS9246: A non-virtual instance interface member cannot be accessed on a type parameter that allows ref struct.)
  • (open design question) warning calling virtual, non-abstract default interface member
• conversions
  • from: ref struct
  • from: type parameter with allows ref struct, with/without struct constraint
  • from: implemented/unimplemented interface
  • to: System.Object
  • to: ref struct
  • to: implemented/unimplemented interface
  • to: same type parameter (IdentityConversion_01 .. IdentityConversion_04)
  • to: type parameter with/without allows ref struct, with/without struct constraint
  • to: type parameter with allows ref struct, with/without struct constraint, with implemented interface constraint
  • to: type parameter with allows ref struct, with/without struct constraint, with unimplemented interface constraint
  • to: type parameter with/without allows ref struct, with/without struct constraint, where T : U/where U : T`
• is operator: value is Type (see IsOperator_*)
  • value: ref struct with/without interface implementation
  • value: interface
  • value: type parameter with/without allows ref struct, with/without struct constraint, with/without interface constraint
  • type: ref struct
  • type: interface
  • type: same type parameter
  • type: type parameter with/without allows ref struct, with/without struct constraint, with/without interface constraint
  • type: type parameter with class constraint, with/without interface constraint (Fill some gaps in Test Plan for "Ref Struct Interfaces" feature #74389, IsOperator_05, IsOperator_07)
  • type: type parameter with/without allows ref struct, with/without struct constraint, where T : U/where U : T`
• is pattern: value is Type t (see IsPattern_*)
  • see cases from is operator above
• as operator: value as Type (see AsOperator_*)
  • see cases from is operator above
• generic type substitution
  • ref struct substituted for type parameter
    • without allows ref struct
    • with allows ref struct
    • with satisfied interface constraints
    • with unsatisfied interface constraints
    • with valid variance (Fill some gaps in Test Plan for "Ref Struct Interfaces" feature #74389, ImplementAnInterface_05_Variance)
    • with invalid variance (Fill some gaps in Test Plan for "Ref Struct Interfaces" feature #74389, ImplementAnInterface_12_Variance_ErrorScenarios)
  • type parameter with allows ref struct substituted for type parameter (Fill some gaps in Test Plan for "Ref Struct Interfaces" feature #74389, ImplementAnInterface_03)
    • see cases above
  • type parameter without allows ref struct substituted for type parameter (ConstraintsCheck_04)
    • see cases above
  • delegate type variance (...?)
• field / auto-property using type parameter with allows ref struct
  • instance field / auto-propertyin ref struct (allowed)
  • instance field / auto-propertyin struct, class (disallowed)
  • static field / auto-property (disallowed)
  • record primary constructor parameter (disallowed)
  • ref struct primary constructor parameter (disallowed)
• using type parameter with allows ref struct (extend IsRefLikeType checks)
  • value in anonymous type initializer (disallowed)
  • in LINQ query with implicit anonymous type
  • value in makeref (disallowed)
  • type of ref field (disallowed)
  • array element type (disallowed)
  • inline array element type (disallowed)
  • async parameter type (disallowed)
  • value in expression tree (disallowed)
  • delegate receiver (disallowed)
  • conditional access ?. result type, with struct constraint (disallowed)
  • conditional access ?. receiver type, without struct constraint
  • type argument to dynamic call (disallowed)
  • receiver to dynamic call (disallowed)
  • captured in lambda or local function (disallowed)
  • error for method signature with T? when where T : struct, allows ref struct (ConstraintsCheck_06)
• ref safety analysis for instance of allows ref struct (extend IsRefLikeType checks)
  • new T() instance
  • scoped T instance
  • cannot assign instance to static field (Field, AutoProperty ?)
  • cannot create T[] (InArrayType_01)
  • return only scope (see Return*)
  • method arguments must match (see MethodArgumentsMustMatch_*)
• null checking with value of type parameter with allows ref struct (see NullCheck_*)
  • value == null, value != null, !(value == null), !(value != null)
  • value is null, value is not null, !(value is null), !(value is not null)
  • value == null when type parameter has struct constraint
• object creation: new T() (see ObjectCreation_*)
  • with object initializer
  • within object initializer
  • with struct constraint
  • with Activator.CreateInstance<T>() with/without allows ref struct (see SystemActivatorCreateInstance_*)
  • collection expression target type
• scoped with type parameter with allows ref struct
  • local
  • method parameter
  • lambda and local function parameters (Fill some gaps in Test Plan for "Ref Struct Interfaces" feature #74389, ScopedTypeParameter_01)
  • params T implicitly scoped
  • scoped mismatch in override
  • scoped mismatch in partial method (Fill some gaps in Test Plan for "Ref Struct Interfaces" feature #74389, ScopedTypeParameter_03)
  • scoped mismatch in delegate (Fill some gaps in Test Plan for "Ref Struct Interfaces" feature #74389, ScopedTypeParameter_04)
• [UnscopedRef] on interface members (see UnscopedRefIn*)
  • language version: [UnscopedRef] on interface members, interface implementations
  • on interface methods, properties, indexers, accessors
  • on member with no modifier, abstract, virtual, sealed
  • implemented on class, struct, ref struct, interface
  • implemented explicitly (UnscopedRefInImplementation_*)
  • implemented implicitly with/without [UnscopedRef] (UnscopedRefInImplementation_*)
  • diagnostic for unsafe [UnscopedRef] mismatch with implicit implementation
  • ref safety analysis at callsite with instance of interface constrained/not constrained to struct (see MethodArgumentsMustMatch_*, etc. cloned from RefFieldTests.cs)
  • defensive copy with instance of interface constrained/not constrained to struct (see DefensiveCopy_*)
• using: implementing IDisposable and/or pattern Dispose() (see Using_*)
  • with ref struct implementing interface with/without pattern
  • with type parameter with allows ref struct implementing interface and/or pattern, with/without struct constraint
• foreach (see Foreach_*)
  • IEnumerable: see cases in using above
  • IEnumerable<T>: see cases in using above
  • IEnumerator: see cases in using above
  • IEnumerator<T>: see cases in using above
  • IDisposable: see cases in using above
• await using (see AwaitUsing_*)
  • IAsyncDisposable: see cases in using above
• await foreach (see AwaitForeach_*)
  • IAsyncEnumerable<T>: see cases in using above
  • IAsyncEnumerator<T>: see cases in using above (is explicit implementation only tested?) (AwaitForeach_IAsyncEnumerableT_03?)
  • IAsyncDisposable: see cases in using above
• anonymous delegates (see AnonymousDelegateType_*)
  • with ref struct parameter types
  • with allows ref struct parameter types
  • System.Func<> and System.Action<> with/without allows ref struct constraints
  • synthesized delegate type parameter has allows ref struct constraint if needed
• -langversion:12 and earlier: consuming generic types and methods with type parameters with allows ref struct
  • construct generic type with non ref struct (ConstraintsCheck_07)
  • call generic method with non ref struct (ConstraintsCheck_02)
• public API
  • ITypeParameterSymbol.AllowsRefLikeType
  • RuntimeCapability.ByRefLikeGenerics
• VB
  • public API supported
  • consuming generic types and methods with type parameters with allows ref struct
    • construct generic type with non ref struct (AllowsConstraint_01)
    • call generic method with non ref struct (AllowsConstraint_01)
  • error overriding or implementing generic methods with type parameters with allows ref struct
• open questions for Language Design
  • allows or allow?
  • other open questions?

Productivity

• Colorization for allows ref struct
• completion for allows ref struct
  • for allows (with Add AllowsKeywordRecommender to KeywordCompletionProvider #73608 in place)
  • for ref
  • for struct
• Language version upgrade is offered
• F1 for allows ref struct (tracked by F1 help for allows ref struct constraint #74604)
  • on allows (doesn't work at the moment)
  • on ref (goes to a wrong page at the moment)
  • on struct (goes to a wrong page at the moment)
• Hovering over a declaration displays the constraint in the tooltip.
• Implement interface on ref struct
  • implicitly
  • explicitly
• GoToImplementation on an interface finds implementation on a ref struct
• GoToImplementation on an interface method finds implicit/explicit implementation within a ref struct
• FindAllReferences on an interface finds implementation on a ref struct
• FindAllReferences on an interface method finds implicit/explicit implementation within a ref struct
• GoToDefinition on an interface implemented by a ref struct goes to the interface
• GoToDefinition on an implicit/explicit implementation of an interface method within a ref struct goes to the method in the interface
• completion for override of generic method with allows ref struct constraint is offered and generates correct code
• GoToImplementation on a virtual generic method with allows ref struct constraint finds an override
• FindAllReferences on a virtual generic method with allows ref struct constraint finds a call site
• GoToDefinition on an override goes to the overridden generic method with allows ref struct constraint
• Implement generic interface method with allows ref struct constraint
  • implicitly (doesn't copy the allows ref struct constraint at the moment) (tracked by Implement generic interface method with allows ref struct constraint #74605)
  • explicitly
• GoToImplementation on a generic method with allows ref struct constraint finds an explicit/implicit implementation
• FindAllReferences on a generic method with allows ref struct constraint finds an explicit/implicit implementation
• GoToDefinition on an explicit/implicit implementation goes to the implemented generic method with allows ref struct constraint

[AlekseyTs]

CC @cston, @jjonescz