When building the classpath container, ivyDE does not include source jars on the classpath. This is well in good in most situations, but with a GWT application this can cause issues where the GWT hosted mode compiler can not see source jars on the classpath that are required.
Expected behavior would be, if that any jar, source or not, included in the retrieval pattern, would b included on the classpath.
If a dependency is resolved in the workspace as an open project, then the classpath container should also add the source folders of that project to classpath.
Configure project with facet of Dynamic Web Application and point to correct war/WebContent folder.
Configure Ivy Project settings to retrieve jars with the pattern: war/WEB-INF/lib/[artifact]
This will add the Web App Libraries classpath container which will appropriately read all the jars in teh war/WEB-INF/lib folder.