Multi-module export of methods: default parameters are not honoured

[benhutchison]

Compiler version

3.3.1

Minimized code

Problem only seems to show when compiling incrementally, ie across multiple SBT subprojects

https://github.com/benhutchison/export_default_param_repro

See also initial discussion at https://users.scala-lang.org/t/does-multi-module-incremental-compilation-affect-scala-3-compiler-semantics-behavior/9576/4

Output

[error] -- [E171] Type Error: /Users/ben/workspace/export_default_param_repro/module2/Module2.scala:1:22
[error] 1 |val x = Module1.method()
[error]   |        ^^^^^^^^^^^^^^^^
[error]   |missing argument for parameter param of method method in object Module1: (param: String): Unit
[error] one error found

Expectation

Code compiles correctly

[sjrd]

Vulpix-style minimization:

// Exporter_1.scala

object Exporter:
  export Exportee.*

object Exportee:
  def method(param: String = "defaultValue"): Unit = ???

// Test_2.scala

object Test:
  val x = Exporter.method()

  val y = Exportee.method()
end Test

Output:

[E171] Type Error: tests/pos/i18767/Test_2.scala:2:25 ---------------------------------------------------------------
2 |  val x = Exporter.method()
  |          ^^^^^^^^^^^^^^^^^
  |          missing argument for parameter param of method method in object Exporter: (param: String): Unit

[bishabosha]

So the default argument is exported as can be seen:

~/workspace/scripts/qux » cs launch scalac:3.3.1 -- -d out -Xprint:typer -Ydebug-flags Exporter_1.scala
[[syntax trees at end of                     typer]] // Exporter_1.scala
package <empty> {
  final lazy module <stable> <touched> val Exporter: Exporter = new Exporter()
  final module <touched> class Exporter <method> <touched>() extends Object() {
    this: Exporter.type =>
    export Exportee.*
    final <method> exported <has-default-params> def method(
      <param> param: String): Unit = Exportee.method(param)
    final <method> exported <no-default-params> def method$default$1:
      String @uncheckedVariance = Exportee.method$default$1
  }
  final lazy module <stable> <touched> val Exportee: Exportee = new Exportee()
  final module <noinits> <touched> class Exportee <method> <stable> <touched>()
     extends Object() { this: Exportee.type =>
    <method> <touched> <has-default-params> def method(
      <param> <hasdefault> <touched> param: String): Unit = ???
    <method> <touched> <no-default-params> def method$default$1:
      String @uncheckedVariance = "defaultValue"
  }
}

it seems that only in a second compilation run (and not in REPL) that the compiler doesn't find the default argument - it is probably because Exporter.method()#param doesnt have the <hasdefault> flag