Extension method on aliased path dependent type is not found

[ftucky]

Compiler version

3.3.1-RC1

Minimized code

trait A:
	type X = Int
	extension (x:X) def foo : String = "foo"

def bar(a:A)(x:a.X) = x.foo // <-- ERROR : value foo is not a member of a.X

Output

Does not compile :

value foo is not a member of a.X

Expectation

Should compile

observations:

Following flavors behave as expected:

trait A:
	type X 

trait A:
	type X >: Int <: Int // Strictly Bounded

[smarter]

I believe this is intentional, extension methods are found using the same mechanism as implicit search which will look for members in the anchors of the types as defined in https://dotty.epfl.ch/docs/reference/changed-features/implicit-resolution.html, this explicitly excludes non-opaque type aliases. The reason for doing so is that type aliases are easily lost (in particular via type inference) and it'd be confusing for implicit search to give different results when that happens. It's maybe something we could revisit if we tried harder to keep type aliases (as proposed in #14586), but it would be a language change.