0.13.11 regression: incremental compiler misses when macro expansion references another source

[eed3si9n]

steps

1. Macro expansion in A.scala references another source B.scala.
2. Change B.scala.

problem

A.scala doesn't get compiled.

expectation

A.scala gets compiled.

notes

This can be confirmed when "member reference internal dependencies" doesn't contain the entry from A.scala to B.scala.

This was caused by 0f61629:

   override def traverse(tree: Tree): Unit = tree match {
     ....
      case MacroExpansionOf(original) if inspectedOriginalTrees.add(original) => traverse(original)
      case other => super.traverse(other)
    }

This won't traverse into an Apply tree, for instance if it has MacroExpansionAttachment. The fix is to call super.traverse(tree) for MacroExpansionOf case as well.

[gkossakowski]

Do you know why existing scripted tests for macros didn't catch the regression?

[eed3si9n]

@gkossakowski See the new repro in #2563. The existing scripted tests didn't catch this because the macro is too simple, and it doesn't introduce new member ref beyond the original tree.