Type inference not working for extension method using prefixless extension

[prolativ]

Compiler version

3.4.0-RC1-bin-20230822-3783220-NIGHTLY and before

Minimized code

extension (s: String)
  def doubled = s ++ s
  def quadrupled = doubled ++ doubled

Output

[error] FakeRecursiveExtension.scala:3:20
[error] Overloaded or recursive method quadrupled needs return type
[error]   def quadrupled = doubled ++ doubled
[error]                    ^

Expectation

I would expect the compiler to be able to infer the type of quadrupled so that the snippet above compiles successfully. Interestingly, the problem doesn't occur if the extension method is used with a prefix: def quadrupled = s.doubled ++ s.doubled.
If for some surprising reason the inference problem cannot be fixed easily, at least the error message should be improved.

[nicolasstucki]

Minimized

extension (s: String)
  def s1: String = "a"
  def s2 = s1
//         ^ Overloaded or recursive method s2 needs return type