Test plan for "record structs"

[jcouv]

Championed issue: dotnet/csharplang#4334
Spec: https://github.com/dotnet/csharplang/blob/master/proposals/csharp-10.0/record-structs.md

Relates to parameterless ctor and field initializers in structs: dotnet/csharplang#99

Compiler

• Syntax tests
  • 'record' 'struct'
  • 'record' 'class'
  • Appropriate language version checks are in place
  • Etc.
• Type kind, validate Record Struct is a struct and has treatment appropriate to a struct
  • 'default'
  • Creation
  • Generic constraint checks (see TypeDeclaration_IsStruct_InConstraints, TypeDeclaration_IsStruct_Unmanaged)
  • Derives from ValueType (see TypeDeclaration_IsStruct)
  • Etc.
• Record struct members
  • A member named "Clone" is disallowed (see Clone_DisallowedInSource)
  • A field inside a Record Struct cannot have an unsafe type (see RestrictedTypesAndPointerTypes)
  • Destructors are not allowed (see TypeDeclaration_NoDestructor)
  • Equality members (explicit declaration / implicit declaration and code generation)
    • Equals for this type (see Equality_xy)
    • Equals for object type (see Equality_01 and ObjectEquals_06 for user-defined)
    • GetHashCode (see RecordEquals_xy, GetHashCode_UserDefined
    • == and != operators for this type (see EqualityOperators_xy)
  • Printing members (explicit declaration / implicit declaration and code generation)
    • PrintMembers
    • ToString
  • Primary Constructor
    • Parameter-less Primary Constructor is disallowed (see RecordProperties_01_EmptyParameterList, TypeDeclaration_NoParameterlessConstructor, TypeDeclaration_NoInstanceInitializers)
    • Test a signature conflict with an explicitly declared constructor (see RecordProperties_02)
    • Any user-defined constructor must have an explicit this constructor initializer. (see RecordProperties_02)
    • A warning is produced if a parameter of the primary constructor is not read. (see RecordProperties_03)
    • The definite assignment rules for struct instance constructors apply to the primary constructor of record structs.
    • XML Doc comments on the type declaration can be used to document parameters and can refer to the parameters (see XmlDoc)
  • Positional struct members
    • Conditionally synthesized based on Primary Constructor's signature
    • A public get and init auto-property is created if the record struct has readonly modifier, get and set otherwise. (see RecordProperties_01_Readonly)
    • The auto-property is initialized to the value of the corresponding primary constructor parameter. (see RecordProperties_01)
    • Attributes can be applied to the synthesized auto-property and its backing field by using property: or field: targets for attributes syntactically applied to the corresponding record struct parameter. (see AttributesOnPrimaryConstructorParameters_01)
    • Etc.
  • Deconstruct
    • Synthesized for a positional record struct with at least one parameter, unless explicitly declared
  • Instance field initializers
    • Parameters of the primary constructor as well as members of the record struct are in scope within initializers of instance fields or properties. Instance members would be an error in these locations
    • If there is a Primary Constructor, only the primary constructor executes the instance initializers appearing in the record-struct-body.
    • If there is no primary constructor, the instance initializers execute as part of the parameter-less constructor.
    • We have an open design issue around instance initializers in record structs which we should close on, perhaps under umbrella of "Parameter-less struct constructors" feature.
• with expression on structs
  • Test on regular struct instances
  • Test in generic context on type parameters with appropriate constraints
• Allow user-defined positional members of records to be fields
  • Appropriate language version checks are in place
  • Etc.
• SemanticModel around new syntax
• IOperation around new syntax
• Analyzer actions around new syntax and new members
• SymbolDisplay

Work items

• parameters less primary constructor, including field initializers (tracking issue Allow parameterless constructors in record structs #52240)
• Consider improving parsing recovery of struct Point(int x, int y);
• Consider improving parsing error for record interface C(int X, int Y); (RecordInterfaceParsing)
• LDM: Emitting GetHashCode and Equals as readonly (conditionally) (answer: yes, issue Record structs: emit readonly modifier for synthesized members #54419)
• left and right parameter names in equality/inequality operators (PR Merge latest bits from main into record-structs #52236)
• with on structs (PR Allow 'with' expression on value types #52319)
• allowing record positional members to be implemented as fields (PR Records: allow positional members to be implemented with fields #52480)
• take C# 9 compat break on hidden positional members (tracking issue Records: Should produce an error when member we pick as positional member is hidden  #52630)
• with expressions on anonymous types (PR Allow with on anonymous types #53248)
• SyntaxNormalizer
• public API: metadata scenario for IsRecord (tracking issue Implement IsRecord on record structs #52233, PR Record-structs: Address some PROTOTYPE markers #52256)
• LDM: Should records implement ISpanFormattable? (answer: no)
• LDM: Should ToString/PrintMembers use InterpolatedStringBuilder? (discussion) (answer: no)
• LDM: Confirm we'll allow parameterless primary constructor (answer: yes)
• LDM: What about initializers when no primary constructor? (question relates to parameterless constructors in structs)
• LDM: Confirm that Equals(R) API doesn't need in (answer: we won't add in overloads, too heuristic-dependant)
• LDM: Confirm with on generic structs (did we have LDM notes and/or decision already? current behavior is fine )
• LDM: Confirm whether GetHashCode should include a hash of the type (this isn't needed per email thread, current behavior is fine)
• LDM: Confirm whether property should come first, or field from current type should come before property from base
• remove PROTOTYPE markers
• EnC: EnC: support for record structs #51200

Productivity

• completion (done in Recommend struct and class keywords after record #51304)
• formatting
• Intellisense
• QuickInfo (PR Record-structs: adjust symbol display and QuickInfo #52455)
• Should appear correctly in solution explorer. (see Fix graph query for records #48451 where this was done for C# 9.0 records)
• Also name suggestion for positional parameters should be PascalCased. (see Treat record positional parameters as properties #48329)
• Also destructor intellisense. (see Add destructor intellisense test for record #48297)
• Also navigation. (see Add records support in navigate to #48116)
• Make type abstract. (see Extend make type abstract to include records #48227)
• FAR works like for record classes
• record structs in help service (similar to F1 help for private protected and protected internal go to their expected places #46343)
• Complete statement command will need to handle the new RecordStructDeclarationSyntax node. (see Support abstract methods and records in complete statement command #48128)
• CodeLens support (issue Add support for record structs in CodeLens #52430)
• GoToTypes support (issue "Go to all" and "Go to types" don't work for records #51672)
• Make sure that explicit PrintMembers isn't reported as unused by IDE analyzers. See PrintMembers method in record is unused #52421
• attribute target completion (see issue Completion don't provide property target in record parameter  #51756)
• Add ConvertTupleToRecordStruct
• IDE to handle xml docs (PR Handle records in documentation comments in IDE side #52737 for records)

[Youssef1313]

Have the implementation of the feature started?

[jcouv]

It's about to

[Youssef1313]

Posting few things that are easy to forget:

[jcouv: thanks for the scenarios. I moved them into OP]

[jcouv]

PR #52261 added the coverage and fixes suggested by @Youssef1313. Thanks!
I'll do some manual validation in next few days.

[Youssef1313]

One more minor scenario:
[jcouv: thanks for the scenario. I moved it into OP]

[Youssef1313]

Moved to OP.

[Youssef1313]

@jcouv Make type abstract. is marked as done, but it doesn't seem to:

https://github.com/dotnet/roslyn/blob/features/record-structs/src/Features/CSharp/Portable/MakeTypeAbstract/CSharpMakeTypeAbstractCodeFixProvider.cs#L55

[jcouv]

@Youssef1313 MakeTypeAbstract is "done" because a test was added, but purposefully not supporting because structs can't be abstract.

[Youssef1313]

@jcouv Can you add handling record structs in help service to the original issue? This is something that should be done a little bit late (after a doc page is created in dotnet/docs with f1_keywords recordstruct_CSharpKeyword). This will be similar to #46343. Thanks.

[jcouv]

@Youssef1313 Added. Thanks

[jcouv]

Remaining issues are tracked as separate issues (linked). I'll go ahead and close this.