Structural (sub-)typing or Implicit interfaces

[gulshan]

This are basically interfaces which are implemented implicitly by having the members.
This will bring a degree of flexibility to C#. C# will still be statically typed with this.
This is how types work in TypeScript.
The syntax can simply be adding the implicit keyword as a modifier for interfaces.

[huoyaoyuan]

TypeScript uses structural typing because there is no typing in JavaScript. It has to act as facade to describe existential members in the wild.
CLR has a typed object system. All the members of an object are described by its type.

See also #1647 #5863 #5849

[gulshan]

Just to clarify, I am not proposing the change the behavior of existing interfaces, which are explicitly implemented. It is proposal for a new kind of interfaces which are marked as implicit and are implemented implicitly.

Also, this is not about dynamic typing. I am not proposing JS/TS like typing in C#. These implicit interfaces would be statically typed. i.e. the objects will still have their own types (class or struct), which may implement the implicit interfaces.

[huoyaoyuan]

This has already been explicitly rejected for multiple times.

There is interest about working on implicitly typed data (#5863), and explicitly providing additional interface implementation on existing types (the extended goal of roles).