Subtyping failure involving ExprType and unions of singleton types

[OlivierBlanvillain]

object Test {
  def foo(x: 0 | 1) = ()
  def bar: 0 | 1 = 0
  foo(bar)
}

Fails with:

4 |  foo(bar)                
  |      ^^^                 
  |      Found:    (Test.bar : => (0 : Int) | (1 : Int))  
  |      Required: (0 : Int) | (1 : Int)                  

Here are the relevant part of the logs with trancing enabled, it looks like there might be a missing case missing in type comparer?:

==> isSubType (Test.bar : => (0 : Int) | (1 : Int)) <:< (0 : Int) | (1 : Int) ?
  ==> isSubType (Test.bar : => (0 : Int) | (1 : Int)) <:< Nothing ?
    ==> isSubType => (0 : Int) | (1 : Int) <:< Nothing LoApprox?
    <== isSubType => (0 : Int) | (1 : Int) <:< Nothing LoApprox = false
  <== isSubType (Test.bar : => (0 : Int) | (1 : Int)) <:< Nothing  = false
<== isSubType (Test.bar : => (0 : Int) | (1 : Int)) <:< (0 : Int) | (1 : Int)  = false

[smarter]

The following works:

object Test {
  def foo(x: 0 | 1) = ()
  def bar(): 0 | 1 = 0
  foo(bar())
}

So it's probably an issue with the subtyping checks involving ExprType on the left