Target-typed static member access

[tmat]

I have recently encountered the following scenario:

class ProjectChanges {
  public ProjectChanges(
              ProjectAnalysisSummary summary,
              ImmutableArray<SemanticEdit> semanticEdits,
              ImmutableArray<(DocumentId, ImmutableArray<LineChange>)> lineChanges,
              ImmutableArray<(DocumentId, ImmutableArray<ActiveStatement>, 
  ImmutableArray<ImmutableArray<LinePositionSpan>>)> newActiveStatements) { }
}

Creating an instance of the ProjectChanges class with empty arrays requires a lot of typing:

new ProjectChanges(summary, ImmutableArray<SemanticEdit>.Empty, 
  ImmutableArray<(DocumentId, ImmutableArray<LineChange>)>.Empty,
  ImmutableArray<(DocumentId, ImmutableArray<ActiveStatement>, 
    ImmutableArray<ImmutableArray<LinePositionSpan>>)>.Empty);

If I wanted to allow null arrays I could write

new ProjectChanges(summary, default, default, default);

But I want those arrays to be non-nullable.

It would be handy if we could express the target type of an expression. For example,

new ProjectChanges(summary, default.Empty, default.Empty, default.Empty);

Accessing member off of default keyword currently disallowed:

Error CS0023 Operator '.' cannot be applied to operand of type 'default'

So the compiler could potentially interpret default as a type, which can be used to access static members.

[TheUnlocked]

var.Empty? We already use var as a "type" so it might make more sense than default here.

[jnm2]

@TheUnlocked It's more consistent to think of var as meaning "declare local variable," especially now that C# doubled down on this semantic difference with expr is Foo foo (excludes null) versus expr is var foo (includes null).