Planning: Working Set Themes

[MadsTorgersen]

Working Set themes

For planning purposes, here's a list of the language features in the Working Set milestone sorted loosely by themes. It's important to note that there are way more features here than can fit in any one release! Also, while all are intended to get further language design scrutiny, that doesn't mean they'll make it all the way into a shipping version of C#.

Initialization and immutability

• [Proposal]: Direct constructor parameters #4024 Direct constructor parameters
• [Proposal]: Support readonly modifier for classes and records #3885 Support readonly modifier for classes and records
• [Proposal] Required Properties #3630 Required Properties
• [Proposal] Extend with expression to anonymous type #3530 Extend with-expression to anonymous type
• Primary Constructors #2691 Primary Constructors
• Champion "pattern-based with expressions" #162 Pattern-based with expressions
• Proposal: record structs #4334 Record structs
• Inherit between records and other classes

Pattern matching

• Proposal: Permit variable declarations under disjunctive patterns #4018 Permit variable declarations under disjunctive patterns
• Proposal: list pattern #3435 list pattern

Scope

• [Proposal]: [call local static functions in base constructor] #3980 Call local static functions in base constructor
• Support for method parameter names in nameof() #373 Support for method parameter names in nameof()

Nullable

• [Proposal]: Nullable analysis of LINQ queries #3951 Nullable analysis of LINQ queries
• [Proposal]: Task<T> nullability covariance #3950 Task<T> nullability covariance
• Champion: Simplified parameter null validation code #2145 Simplified parameter null validation code

Boilerplate reduction

• [Proposal] Add ability to declare global usings for namespaces, types and aliases by using a command line switch #3428 Global usings for namespaces, types and aliases with command line switch
• Proposal: File scoped namespaces #137 File scoped namespaces

Closed and grouped types

• Proposal: "Closed" enum types #3179 "Closed" enum types
• Champion: Name lookup for simple name when target type known #2926 Name lookup for simple name when target type known
• Champion "Discriminated Unions" #113 Discriminated Unions

Statements in expressions

• Proposal: Sequence Expressions #377 Sequence Expressions
• Proposal: Expression blocks #3086 Expression blocks

Switch enhancements

• Proposal: Enhanced switch statements #3038 Enhanced switch statements
• Proposal: Block-bodied switch expression arms #3037 Block-bodied switch expression arms
• Champion: Switch expression as a statement expression #2632 Switch expression as a statement expression

Span and ref

• Efficient Params and String Formatting #2302 Efficient Params and String Formatting
• Switching ReadOnlySpan<char> with constant strings #1881 Switching ReadOnlySpan with constant strings
• generic constraint: where T : ref struct  #1148 where T : ref struct
• allow references to structs to be stored in fields of ref structs #1147 allow references to structs to be stored in fields of ref structs

Fixed

• Permit a fixed field to be declared inside a readonly struct. #1793 Permit a fixed field to be declared inside a readonly struct
• Five ideas for improving working with fixed buffers #1502 Five ideas for improving working with fixed buffers

Type classes

• Exploration: Roles, extension interfaces and static interface members #1711 Roles, extension interfaces and static interface members
• Champion "Type Classes (aka Concepts, Structural Generic Constraints)" #110 Type Classes (aka Concepts, Structural Generic Constraints)

Deconstruction

• [Proposal]: Nominal and Collection Deconstruction #4082 Nominal and Collection Deconstruction
• C# Feature Request: Allow value tuple deconstruction with default keyword #1358 Allow value tuple deconstruction with default keyword
• Champion "Mix Declarations and Variables in Deconstruction" #125 Mix Declarations and Variables in Deconstruction

Auto-properties

• Proposal: field keyword in properties #140 Semi-Auto-Properties; field keyword
• Proposal: Property-Scoped Fields #133 Property-Scoped Fields

Misc

• Proposal: Repeated Attributes in Partial Members #3658 Repeated Attributes in Partial Members
• Allow omitting unused parameters #2180 Allow omitting unused parameters
• Proposal: Allow [AsyncMethodBuilder(...)] on methods #1407 Allow [AsyncMethodBuilder(...)] on methods
• Champion "CallerArgumentExpression" #287 CallerArgumentExpression
• Champion "Allow Generic Attributes" #124 Allow Generic Attributes