DIFL is a tool to evaluate changes between different versions of FIDL libraries. It describes the changes in terms of their impact on compatibility
TODO
In the Fuchsia tree the easiest way to test is by invoking a test script via:
fx build garnet/public/lib/fidl/tools/difl_test_fidl
As well as running tests this will generate some test FIDL libraries. Then you can run the regular difl tool like:
scripts/difl --before \ out/default/gen/garnet/public/lib/fidl/tools/difl_test_fidl/before.fidl.json \ --after \ out/default/gen/garnet/public/lib/fidl/tools/difl_test_fidl/after.fidl.json