x?.y works even when x is not an optional

[kach]

Because of the way ?. is implemented, things like this happen:

ergo$ return {a: 1}?.a;
Response. none
  :  {emit: Unit[], response: Nothing?, state: Unit}?

(This should be a type error, I think, because people will surely try to do this and get confused.)

[jeromesimeon]

I agree. I seem to recall this is the semantics in Swift which I started from, but I don't like it.

[kach]

Can be compiled to (let $opt : Any? = <operand> ; match …), where the let just forces the operand to be of an optional type.

[jeromesimeon]

Looking at the example more carefully, this is definitely not the semantic in Swift. It's certainly a bug.

[jeromesimeon]

Addressed in #502 :

ergo$ return {a: 1}?.a
Compilation error (at line 1 col 7). Cannot match unless against an option type
return {a: 1}?.a
       ^^^^^^^^^
ergo$ return 1?.a
Compilation error (at line 1 col 7). Cannot match unless against an option type
return 1?.a
       ^^^^
ergo$ return some({a:1})?.a
Response. some(1) : Integer?
ergo$ return none?.a
Response. none : Nothing?
ergo$ let x : {a:Integer}? = none; return x?.a
Response. none : Integer?