I identified this problem while diagnosing a bug reported against Spring Boot.
It's probably best described with an example:
Compiling the above, and running it with a file named foo.groovy in the current working directory with the contents:
will produce the output:
I believe the problem lies in org.codehaus.groovy.ast.ModuleNode.extractClassFromFileDescription() as it does not consider a URL that contains no slashes. As a result it never strips off the file: prefix.