Spourious unused renamed import warning

[nicolasstucki]

Compiler version

3.3.3, 3.4.0,

Minimized code

//> using options -Wunused:all

def test(list: List[Int]): Int =
  import list.{head => first}
  first

Output

4 |  import list.{head => first}
  |               ^^^^^^^^^^^^^
  |               unused import

Expectation

Should not warn

[nicolasstucki]

Found regression in ReactiveMongo/ReactiveMongo#1297.

[noti0na1]

When importing a term and renaming it, we will translate the usage of the renamed term into the original selection in typer.

In this case, first becomes list.head; hence, the import checker couldn't find the usage of first.