Original bug ID: 6173
Reporter: @johnwhitington
Assigned to: @garrigue
Status: assigned (set by @johnwhitington on 2015-11-23T21:49:16Z)
Resolution: reopened
Priority: normal
Severity: feature
Version: 4.01.0
Target version: later
Fixed in version: 4.02.0+dev
Category: typing
Has duplicate: #6295
Related to: #5936
Child of: #7338
Monitored by: @gasche @hcarty @dbuenzli

Bug description

OCaml version 4.01.0+rc1
# let f x = x @ [];;
val f : 'a list -> 'a list = <fun>
# f ();;
Error: The variant type list has no constructor ()

Is this related to the new variants work? Is it related to the fact that () is, unusually, a valid constructor (this has been debated before, I know)?

The previous behaviour is much less confusing.

 OCaml version 4.00.1

# let f x = x @ [];;
val f : 'a list -> 'a list = <fun>
# f ();;
Error: This expression has type unit but an expression was expected of type
         'a list