[Pitch] Allow generic extension for struct

[frogcjn]

Since SE-0346 allow

extension Collection<String> { ... }

why don't we allow

extension Optional<String> { ... }

?

[Nevin]

@frogcjn

Since SE-0346 allow

extension Collection<String> { ... }

why don't we allow

extension Optional<String> { ... }

?

SE–0361 Extensions on bound generic types

[frogcjn]

Thanks!
I added Other Swift Flags "-enable-experimental-bound-generic-extensions" to my project.