swift234

[SE-0091] Require member operators to refer to the enclosing nominal type.

Member operators should be placed within a nominal type (or extension
thereof) that they operate on. Aside from being good style, enforcing
this in the type checker can help with dependency tracking. Addresses
rdar://problem/27536066.

(cherry picked from commit a15c485193c4dcb61c330be8c2d869758fff2c45)