Ah, I noticed that as well. Seems like Java 7 collapses several diagnostics for the same method/line.

Instead of having a separate `ExpectedCompilationOutcomeJDK6` annotation, what do you think about adding this as attribute to `@Diagnostic` (the default would be any JDK version):

    @Diagnostic(
        type = ErroneousSourceTargetMapper.class,
        kind = Kind.ERROR,
        line = 29,
        messageRegExp = "...",
        javaVersion = SourceVersion.RELEASE_6
    )

(with `SourceVersion` from `javax.lang.model.*`).