False positive unused import in 3.7 nightly for value only used for export

[mrdziuban]

Compiler version

3.7.0-RC2 and latest nightly 3.7.1-RC1-bin-20250411-98c84c3-NIGHTLY

Minimized code

object test1 {
  object foo {
    type X = Int
  }
}

object test2 {
  import test1.foo

  export foo.X
}

Output

-- [E198] Unused Symbol Warning: -----------------------------------------------
8 |  import test1.foo
  |               ^^^
  |               unused import

Expectation

The import should not be reported unused since it's required for the export foo.X statement.

[Gedochao]

Last good release: 3.7.0-RC1-bin-20250127-89c20f8-NIGHTLY
First bad release: 3.7.0-RC1-bin-20250128-9cb97ec-NIGHTLY
c65d45d is the first bad commit
Seems like you're already on it, @som-snytt, so I'll assign you for now.

[som-snytt]

3.6 used tree traversal for the "bucket" transformOther trees.