Should property patterns be capable of referencing an indexed property?

[gafter]

If we want property patterns to be capable of referencing an indexed property, we will need to extend the bound nodes that represent them. Similarly for dynamic indexers and events. See also #9515.

[AdamSpeight2008]

What would (if any) be on the index?

• Constants P { X[ 0 ] is var x }
• Reference P { X[ index ] is var x }
• What about the checking of the index bounds? Index <0 || Index >= X.Length
• (VB) Is the dictionary lookup operator also allowed? P { X!foo is var x }

[gafter]

@AdamSpeight2008

If we do it, certainly constant indices would be allowed. However, given that indexed properties are not supported in a first-class way in C#, it seems unlikely we would do it.

We would not support VB operators in C#.

[AdamSpeight2008]

My comment was more about, what would be allowed should pattern-matching be brought into VB

[alrz]

If we had support for indexer itself P { [0] is var x } then indexed properties can be matched with:

obj is P { X is T { [0] is var x } }

As long as it's analogous with indexer initializers, the following also makes sense,

obj is P { [0][1] is var x }

In addition to obj is P { X[0] is var x }, I think this on would be also helpful:

obj is P { Prop1.Prop2 is var x }
// instead of
obj is P { Prop1 is { Prop2 is var x } }