[INFO] Validating units:
              [INFO]    Ignored 53 units with compilation errors in first pass.
              [INFO] Compile with -strict or with -logLevel set to TRACE or DEBUG to see all errors.

            Turning up the log level, we see that GWT is trying to compile classes from other
            packages, like RangeTest. The reason for this is that GWT doesn't distinguish between

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                     https://errorprone.info/docs/installation#maven) if it can
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                <arg>-J--add-exports=jdk.compiler/com.sun.tools.javac.api=ALL-UNNAMED</arg>

                <!-- TODO(cpovirk): Use .mvn/jvm.config instead (per
                     https://errorprone.info/docs/installation#maven) if it can
                     be made not to interfere with JDK8 or if we stop building
                     with JDK8. -->
                <arg>-J--add-exports=jdk.compiler/com.sun.tools.javac.api=ALL-UNNAMED</arg>