[INFO] --- gwt-maven-plugin:1.0-rc-6:compile (default-compile) @ closure-compiler-gwt ---
[INFO] Compiling module com.google.JsComp
[INFO]    [ERROR] Hint: Check that your module inherits 'com.google.gwt.core.Core' either directly or indirectly (most often by inheriting module 'com.google.gwt.user.User')
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Summary:
[INFO]
[INFO] Closure Compiler Parent ............................ SUCCESS [  0.310 s]
[INFO] Closure Compiler Externs ........................... SUCCESS [  1.130 s]
[INFO] Closure Compiler GWT App ........................... FAILURE [ 43.368 s]
[INFO] Closure Compiler Main .............................. SKIPPED
[INFO] Closure Compiler Linter ............................ SKIPPED
[INFO] Closure Compiler Unshaded .......................... SKIPPED
[INFO] Closure Compiler ................................... SKIPPED
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 46.002 s
[INFO] Finished at: 2018-02-07T16:33:02+08:00
[INFO] Final Memory: 19M/65M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal net.ltgt.gwt.maven:gwt-maven-plugin:1.0-rc-6:compile (default-compile) on project closure-compiler-gwt: GWT Compiler exited with status 1 -> [Help 1]
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoExecutionException
[ERROR]
[ERROR] After correcting the problems, you can resume the build with the command
[ERROR]   mvn <goals> -rf :closure-compiler-gwt
==> ERROR: A failure occurred in build().
    Aborting...