Bug with missing semicolon after if block about motoko-base

[ggreif]

{ P.unreachable(); } f () is interpreted as a (curried) function application. The if expression terminates at the penultimate line.

N.B.: The -dt option to moc will dump the type-checked AST in doubt.

[rossberg]

Interesting! Wow, you have to be really unlucky to run into this, I don't think it's possible without dead code of type None.

We could try to warn about this, though I'm not sure on what condition. Hm...

[ggreif]

This moc session reproduces it:

$ src/moc
Motoko compiler (revision 654ab7c4-dirty)
> func f () : () -> () = func () {};
let f : () -> () -> () = func
> if false { f } () ();

[rossberg]

@ggreif, that's a less critical example, though, because () () is not meaningful as a separate statement.

[rossberg]

One way to prevent this gotcha would be giving block expressions much lower precedence, so that they cannot be used as nullary expressions (without extra parens). Is it worth it?

A prerequisite would be a disjoint syntax for objects, though, as in #1725.

[ggreif]

Throwing in Any will do:

$ src/moc
Motoko compiler (revision 654ab7c4-dirty)
> func f (_ : Any) : () -> () = func () {};
let f : Any -> () -> () = func
> if false { f } f();

But this is clearly code that nobody will write.