Don't chain conversions when looking for import suggestions

[smarter]

Fixes #12394.

[soronpo]

@smarter I can confirm this PR solves the reentry issue, but the compiler does not report the error thrown with report.throwError, like it does for non-transparent macros. Is that deliberate or a bug? Should I file a separate issue?

[smarter]

I don't think so, if an error is thrown when trying to type your implicit conversion, then that means it's not a valid implicit conversion so the compile rolls back. For a non-transparent inline the error will not be found until after typechecking, at that point it's too late to roll back so the error gets displayed to the user.

[soronpo]

IIRC, in Scala 2 the implicit conversion macros controlled the error message. Why should it be different in Scala 3?

[smarter]

I don't know anything about Scala 2 macros so I can't say, but this discussion isn't related to this PR, feel free to open a separate discussion thread with examples.