Pattern match not return matched F-bounded type

[yaqiz01]

I'm trying this example in scala 2.12.8

class B[N<:B[N]] { def foo(x:N) = println(s"$x") } 
class A extends B[A] 
def bar[N<:B[N]](n:N, v:A) = { n match { case n:A => n.foo(v); case _ => } }

The above example gives folllowing error

error: type mismatch;
 found   : this.A
 required: _1
def bar[N<:B[N]](n:N, v:A) = { n match { case n:A => n.foo(v); case _ => } }
                                                           ^

However, this compiles

def bar[N<:B[N]](n:N, v:A) = { n match { case n:A => n.asInstanceOf[A].foo(v); case _ => } }

Why does not n have type A after matched to A. This only occurs when N in B has bound N<:B[N].

[ashwinbhaskar]

@yaqiz01 : interesting..But I don't think this is a fault in pattern matching. The below code gives the same error
def bar[N<:B[N]](n:N, v:A) = n.foo(v)

[SethTisue]

@ashwinbhaskar I think the compiler is correct to reject your variant. you should be able to arrive at that conclusion by reasoning (the compiler has been given no evidence that N and A are related, except via their common super type B); but as further support, note that Dotty accepts Yaqi's code but rejects your variant.

[ashwinbhaskar]

@SethTisue :Got it:)