Overload resolution for extension methods fails in some cases where named parameters are involved.

[rmgk]

Compiler version

3.1.3-RC3, 3.2.0-RC1-bin-20220519-ee9cc8f-NIGHTLY-git-ee9cc8f

Minimized code

extension (x: Char)
  def f(someParam: String): String = "a"
  def f(min: Boolean, max: Int = 4): String = "b"

@main def run() = 'c'.f(false)

Output

Test.scala:7:19: value f is not a member of Char.
An extension method was tried, but could not be fully constructed:

    extensionOverload.f()    failed with

        value f: <overloaded extensionOverload.f> does not take parameters [7:19]

Expectation

Compile just fine, return "b"

[pikinier20]

Invoking f as a standard method:

f('c')(false)

fails with:

[error] ./cli.scala:5:19: None of the overloaded alternatives of method f with types
[error]  (x: Char)(min: Boolean, max: Int): String
[error]  (x: Char)(someParam: String): String
[error] match arguments (('c' : Char))
[error] @main def run() = f('c')(false)

After specyfing default parameter explicitely, everything compiles

[pikinier20]

This problem occurs also for standard methods:

def f(x: Char)(someParam: String): String = "a"
def f(x: Char)(min: Boolean, max: Int = 4): String = "b"

@main def run() = f('c')(false)

[pikinier20]

The problem is that compiler expects the default getter name: f$default$2 when actually it is: f$default$3

[pikinier20]

I give up on this as it turned out to be too complicated case. Resolving overloaded methods for curried methods goes param clause per param clause and it's not aware how it should work with default parameters for further parameter clauses.

[odersky]

One way to fix this for now is to reject overloaded extension methods that have default arguments.

[odersky]

I have decided not to attack errors involving default parameters using the old scheme of default parameters any more. It's better to focus on fixing the scheme to use inline which would fix lots of other problems as well. If people want fixes now, someone else should take this on, or we move to backlog.