(issue with extension methods) context param(s) preceding receiver break *unqualified* calls from different methods within the same group

[irfanstract]

an issue with extension methods, where context param(s) preceding receiver break unqualified calls from different methods within the same group/clause.

extension (/* either remove this, or move this to the end, and everything comes back to work! */ using ... ) (x: String)

  def m1(): String = ...
  def m2(): String = m1().m1()

Compiler version

3.9.0-RC4
3.8.4
3.3.8 and 3.3.2

Minimized code

extension (/* either remove this, or move this to the end, and everything comes back to work! */ using String <:< String ) (x: String)

  def dropFirstChar(): String = x.drop(1)
  def dropFirstTwoChars(): String = dropFirstChar().dropFirstChar()


val d = "[[Ljava/util/List;"
println(s"mode: ${d}")
println(s"mode: ${d.dropFirstTwoChars()}")

Output

3.9.0-RC4 and 3.8.4 and 3.3.8:

value dropFirstChar is not a member of String <:< String.
Extension methods were tried, but could not be fully constructed:

    <:<.refl[String <:< String].apply(x$1)

    Playground.dropFirstChar(x$1)(x$1)

    failed with:

        Found:    (x$1 : String <:< String)
        Required: String

Expectation

for it to compile and run (behave) equivalently as if the (using String <:< String) were instead at the end or gotten rid of entirely.
specifically, for it to run and print:

mode: [[Ljava/util/List;
mode: Ljava/util/List;

Notes

at some point
I also found a case where a similar pattern (unqualified call to someOtherExtMethod() in-turn defined with inferred type) surprisingly failed with recursive value needs type complaint, where an equivalent qualified call (bar.someOtherExtMethod(), which is, the former plus an extra implicit search!) worked.