Fix test failures in continuous distribution build: CheckProjectStructure test collects all modules found under MPS distribution to fill a project to run tests against. Jars under lib/ (e.g. mps-closures.jar) contain msd files (e.g. modules/closures.runtime/closures.runtime.msd) and are treated as regular modules, and models in there (e.g. runtime.mpb) are queried for last generation hash that they obviously lack. I'd say the right fix is to avoid collecting modules from under lib/, but present fix (check isReadOnly) brings it to the state it was prior to change in GeneratableSModel#isGeneratable() logic (it used to check read-only in there, but updated perception is even read-only models may be generated).
Do not infer outer type based on use of some genContext operation. E.g. we get a cryptic message on a LOOP macro when some reference macro deep inside use typed LabelMapping to access output by loop node.