# C# Language Design Notes for 2018

Overview of meetings and agendas for 2018


## Jan 3, 2018
[C# Language Design Notes for Jan 3, 2018](LDM-2018-01-03.md)

1. Scoping of expression variables in constructor initializer
2. Scoping of expression variables in field initializer
3. Scoping of expression variables in query clauses
4. Caller argument expression attribute
5. Other caller attributes
6. New constraints


## Jan 10, 2018
[C# Language Design Notes for Jan 10, 2018](LDM-2018-01-10.md)

1. Ranges and endpoint types


## Jan 18, 2018 
[C# Language Design Notes for Jan 18, 2018](LDM-2018-01-18.md)

We discussed the range operator in C# and the underlying types for it.

1. Scope of the feature
2. Range types
3. Type name
4. Open-ended ranges
5. Empty ranges
6. Enumerability
7. Language questions


## Jan 22, 2018
[C# Language Design Notes for Jan 22, 2018](LDM-2018-01-22.md)

We continued to discuss the range operator in C# and the underlying types for it.

1. Inclusive or exclusive?
2. Natural type of range expressions
3. Start/length notation


## Jan 24, 2018
[C# Language Design Notes for Jan 24, 2018](LDM-2018-01-24.md)

1. Ref reassignment
2. New constraints
3. Target typed stackalloc initializers
4. Deconstruct as ref extension method

## July 9, 2018
[C# Language Design Notes for July 9, 2018](LDM-2018-07-09.md)

1. `using var` feature
   1. Overview
   2. Tuple deconstruction grammar form
   3. `using expr;` grammar form
   4. Flow control safety
2. Pattern-based Dispose in the `using` statement
3. Relax Multiline interpolated string syntax (`$@`)

## July 11, 2018
[C# Language Design Notes for July 11, 2018](LDM-2018-07-11.md)

1. Controlling nullable reference types with feature flags
1. Interaction with NonNullTypesAttribute
1. Feature flag and 'warning waves'
1. How 'oblivious' null types interact with generics
1. Nullable and interface generic constraints

## July 16, 2018
[C# Language Design Notes for July 16, 2018](LDM-2018-07-16.md)

1. Null-coalescing assignment
   1. User-defined operators
   1. Unconstrained type parameters
   1. Throw expression the right-hand side
1. Nullable await
1. Nullable pointer access
1. Non-nullable reference types feature flag follow-up

##  August 20, 2018

[C# Language Design Notes for August 20, 2018](LDM-2018-08-20.md)

1. Remaining questions on [suppression operator](https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fdotnet%2Froslyn%2Fissues%2F28271&data=02%7C01%7C%7C6defe1e21ab54cce8d0008d606be5d23%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636703812006445395&sdata=DAdh5dev1mnr%2F5zxtvuJVcHP%2Bzewrzz4z9iuGkl%2BUHg%3D&reserved=0) (and possibly cast)
2. Does a dereference update the null-state?
3. Null contract attributes
4. Expanding the feature
5. Is T? where T : class? allowed or meaningful?
6. Typing judgments containing oblivious types
7. Unconstrained T in List<T> then `FirstOrDefault()`. What attribute to annotate `FirstOrDefault`?

## August 22, 2018

[C# Language Design Notes for August 22, 2018](LDM-2018-08-22.md)

1. Target-typed new
1. Clarification on constraints with nullable reference types enabled

## September 5, 2018

[C# Language Design Notes for September 5, 2018](LDM-2018-09-05.md)

1. Index operator: is it a unary operator?
1. Compiler intrinsics

## September 10, 2018

[C# Language Design Notes for September 10, 2018](LDM-2018-09-10.md)

1. Nullability of constraints in inheritance and interface implementation
2. Static local functions

## Sep 19, 2018

[C# Language Design Notes for September 19, 2018](LDM-2018-09-19.md)

Triage:

1. XML doc comment features
2. New `foreach` pattern using `Length` and indexer
3. Object initializers for `readonly` members
4. `readonly` struct methods
5. `params Span<T>`
6. Nullable reference type features on `Nullable<T>`

## Sep 24, 2018

[C# Language Design Notes for September 24, 2018](LDM-2018-09-24.md)

Combined C#/F# LDM

1. What new C# features are going to require work to get F# support?
2. How can the design of C# features play well with the broader .NET environment?

## Sep 26, 2018

[C# Language Design Notes for September 26, 2018](LDM-2018-09-26.md)

1. Warning waves

## Oct 1, 2018

[C# Language Design Notes for Oct 1, 2018](LDM-2018-10-01.md)

1. Nullable type inference
2. Type parameters and nullability context

## Oct 3, 2018

[C# Language Design Notes for Oct 3, 2018](LDM-2018-10-03.md)

1. How is the nullable context expressed?
2. Async streams - which interface shape?

## Oct 10, 2018

[C# Language Design Notes for Oct 10, 2018](LDM-2018-10-10.md)

1. Pattern matching open questions

## Oct 15, 2018

[C# Language Design Notes for Oct 15, 2018](LDM-2018-10-15.md)

1. Readonly methods in structs
2. Intrinsics update with function pointers
3. Finalize syntax for async-streams. Per [last notes](https://github.com/dotnet/csharplang/blob/95c9267d0d54a9984086ca327b1f892790e6c2cf/meetings/2017/LDM-2017-08-30.md#syntax-options), the current tentative syntax is `foreach await (var x in ...) ...`.

## Oct 17, 2018

[C# Language Design Notes for Oct 17, 2018](LDM-2018-10-17.md)

1. [Open issues](https://github.com/dotnet/csharplang/issues/406) with default interface methods
1. target typed new with default constructors on structs

## Oct 22, 2018

[C# Language Design Notes for Oct 22, 2018](LDM-2018-10-22.md)

Discussion of records proposals:

1. [The existing old one](https://github.com/dotnet/csharplang/blob/master/proposals/records.md)
2. [The data classes proposal](https://github.com/dotnet/csharplang/pull/1667)

## Oct 24, 2018

- [Adding Nullable Reference Type features to Nullable Value Types](https://github.com/dotnet/csharplang/issues/1865)
- Open issues with pattern matching

## Oct 29, 2018

[C# Language Design Notes for Oct 29, 2018](LDM-2018-10-29.md)

- [Source-level opt-in to nullable reference types](https://github.com/dotnet/csharplang/issues/1939)

## Oct 31, 2018

[C# Language Design Notes for Oct 31, 2018](LDM-2018-10-31.md)

- *Design review*

## Nov 5, 2018

[C# Language Design Notes for Nov 5, 2018](LDM-2018-11-05.md)

1. Where can #nullable go?
2. Open issues with pattern matching

## Nov 14, 2018

[C# Language Design Notes for Nov 14, 2018](LDM-2018-11-14.md)

1. Base call syntax for default interface implementations
2. Switch exhaustiveness and null

## Nov 28, 2018

[C# Language Design Notes for Nov 28, 2018](LDM-2018-11-28.md)

1. Are nullable annotations part of array specifiers?
2. Cancellation of async-streams

## Dec 3, 2018

[C# Language Design Notes for Dec 3, 2018](LDM-2018-12-03.md)

1. `using` declaration open issues
2. Return type of `Range` indexer on array and FX types

## Dec 5, 2018

[C# Language Design Notes for Dec 5, 2018](LDM-2018-12-05.md)

- Tracked nullable states, their correspondance to source and the rules they follow in flow analysis

## Dec 12, 2018

[C# Language Design Notes for Dec 12, 2018](LDM-2018-12-12.md)

- Async-streams misc. questions
- Compat issue with Dispose pattern in `foreach`

# Upcoming meetings

## Dec 17, 2018

- Review the [Nullable Reference Types Specification](https://github.com/dotnet/csharplang/blob/master/proposals/nullable-reference-types-specification.md)

## Schedule ASAP

- Async-streams: should we emit one `CancellationToken` check in `GetAsyncEnumerator()` or one per `MoveNextAsync()`?
- Generating null-check for `parameter!` (Jared)

## Schedule when convenient

- Discussion of refreshing language spec (Neal)
- Nullability flow through conditional access when unconstrained generic type parameters are involved. (Aleksey)

## Recurring topics

- *Triage championed features*
- *Triage milestones*
- *Design review*