Re: bikeshed: Typed Aliases

On Sat, Sep 7, 2024, at 7:42 AM, Mike Schinkel wrote: >> On Sep 6, 2024, at 4:45 PM, Larry Garfield <larry@garfieldtech.com> wrote: >> Aliases can then be used only in parameter, return, property, and instanceof types. >> Extends and implements are out of scope entirely. > > Is there a strong technical reason why extends and implements should be > out of scope? > > There is definite utility for this, to create a local alias in a > namespace that can be used throughout the namespace rather than having > to refer to the external namespace in many different places. Because it quickly can produce nonsensical syntax. class A {} class B {} typealias AB: A|B; // This is logically nonsensical. class C extends AB {} While there are edge cases where that might be logical (if A and B are interfaces and &-ed together, then it's kinda sorta the same as C implements A, B), separating those out and allowing just that subset sounds like a lot of work for dubious gain, and introducing surprise inconsistency. Better to just avoid that entirely. --Larry Garfield