[Seol]

The distinction I was trying to make was one between where in the toolchain it lives: error-prone is part of compilation, whereas Findbugs is after-the-fact.

Error-prone is a compiler plugin _mechanism_ - once you have an error-prone compiler, the checks are arguments to the compiler just like APT annotation processors are.

It's built on a standard API - the JavaCompiler mechanism built into the Java SDK - but yes, the code does have further dependencies on com.sun packages. This is a little confusing because why expose the compiler for invocation and extension when extensions have to rely on unsupported code?

So, yes, there are ways where the distinction is important, but they're orthogonal to the point I was trying to make.