`UnnecessaryConversionTest` failing in latest Scala community build

[saeltz]

See scala/community-build#1677.

The Scala compiler is now constant-folding integer literals and our tests like 3.toInt don't warn anymore because the expression is already constant folded in the typer phase of the compiler after which scapegoat is invoked.

It's good that the compiler is now constant folding. We should adjust somehow.

[som-snytt]

This is in typer, and the change for .toInt is a backport from Scala 3. // background

I've forgotten the details, but Scaladoc has a flag to reduce constant inlining for documentation purposes. Maybe something similar would be useful for 3rd party tooling?

For some reason, I've also forgotten the outcome of not changing trees for constant folding but only types. I've forgotten the context, maybe Scaladoc or maybe some other tool wanted to witness "the original tree".

[SethTisue]

Note that a compiler plugin may introduce multiple phases — perhaps you could insert an additional phase pre-typer.