Uncurried mode regression 11.0.0-rc.6

[DZakh]

After migrating to uncurried mode I've got an unexpected runtime error:

https://rescript-lang.org/try?version=v11.0.0-rc.6&code=DYUwLgBAZgdhC8EDGAjBA+CBvAUBZKAFAJQ4C+OOshAzhhAFI0B0wA9gOaEDEUbbtYkJwB6ERADi4CACIAqjCQBDAK4cAFpABKIKCABOIRSACi+-W30AuCHQCWdGG0gATXXZggXMnEA

[WhyThat]

I think it's related to this too
https://forum.rescript-lang.org/t/the-big-migration-thread-for-rescript-v11-and-uncurried-mode/4769/36

[cristianoc]

Probably related to this optimisation:
#6131

where type inference gives the function unit type

let fn = cb => {
  cb()
}

fn(s => Js.log(#foo(s)))

[cristianoc]

Both issues reported above have in fact the same cause -- fixed in #6507