Order of the source files changes the compilation result

[adpi2]

While compiling scala3doc I found surprising that the order of the source files change the compilation result.

Minimized code

I minimized it to 3 files.

// Context.scala
trait Context:
  type Symbol

trait SymOps[C <: Context](val c: C):
  extension (sym: c.Symbol):
    def getVisibility(): Int = 0

// Parser.scala
case class Parser(ctx: Context) extends BasicSupport

// BasicSupport.scala
trait BasicSupport:
  self: Parser =>

  object SymOps extends SymOps[ctx.type](ctx)
  export SymOps._

  def parse(sym: ctx.Symbol): Int =
    sym.getVisibility()

Output

BasicSupport.scala Context.scala Parser.scala compiles successfully.

But Parser.scala Context.scala BasicSupport.scala compiles in error:

[info] cannot take signature of (sym: Parser.this.SymOps.c.Symbol)(): Int
[error] -- [E008] Not Found Error: /home/piquerez/lampepfl/dotty-issue/src/main/scala/tasty/BasicSupport.scala:8:8 
[error] 8 |    sym.getVisibility()
[error]   |    ^^^^^^^^^^^^^^^^^
[error]   |    value getVisibility is not a member of BasicSupport.this.ctx.Symbol.
[error]   |    An extension method was tried, but could not be fully constructed:
[error]   |
[error]   |        sym
[error] one error found

Expectation

The order of the source files should not change the compilation result.

[adpi2]

@b-studios I am not sure this is only a doctool bug since I don't expect the compiler result to depend on the order of the source files. But maybe I am wrong.

[sjrd]

Indeed, this is definitely a compiler bug (failing to compile the doctool), not a doctool bug.

[dwijnand]

$ rm *.class *.tasty; scalac3 BasicSupport.scala Context.scala      Parser.scala        # OK
$ rm *.class *.tasty; scalac3 BasicSupport.scala Parser.scala       Context.scala       # OK
$ rm *.class *.tasty; scalac3 Context.scala      BasicSupport.scala Parser.scala        # OK
$ rm *.class *.tasty; scalac3 Context.scala      Parser.scala       BasicSupport.scala  # KO
$ rm *.class *.tasty; scalac3 Parser.scala       BasicSupport.scala Context.scala       # KO
$ rm *.class *.tasty; scalac3 Parser.scala       Context.scala      BasicSupport.scala  # KO

Looks like it's necessary for BasicSupport.scala to precede Parser.scala.

Remembering that the error is in BasicSupport this means that processing Parser before BasicSupport breaks BasicSupport.

[odersky]

With #10902 we get more info:

> sc Context.scala Parser.scala BasicSupport.scala 
cannot take signature of (sym: Parser.this.SymOps.c.Symbol)(): Int

-- [E008] Not Found Error: BasicSupport.scala:9:8 ------------------------------
9 |    sym.getVisibility()
  |    ^^^^^^^^^^^^^^^^^
  |    value getVisibility is not a member of BasicSupport.this.ctx.Symbol.
  |    Extension methods were tried, but the search failed with:
  |
  |        cannot resolve reference to type Parser.this.SymOps.c.type.Symbol