Custom ImpexFindUsagesProvider breaks reference search

[mlytvyn]

Create Impex file

INSERT MyProduct;

Create FXS file

select * from {MyProduct}

Define custom type:

<itemtype code="MyProduct">
</itemtype>

Execute action "Find Usages" on code attribute of the newly defined item type.

Current behaviour
Impex is not included in the search, while FXS is

Expected behaviour
Impex is properly indexed and parsed, references registered via Contributors available in the Find Usages results.

docs:

• https://plugins.jetbrains.com/docs/intellij/find-usages.html
• https://plugins.jetbrains.com/docs/intellij/find-usages-provider.html