IsDefined operator in compiled Rascal broken

[jurgenvinju]

Currently it is implemented by catching Exception (see is_defined_loc_field_access_get in RascalPrimitive) which hides accidental bugs and also expected IO exceptions from URIInputResolvers. Some tests were succeeding because of accidental null pointer exceptions caught by this implementation and turned into false.

The current interpreter has ? implemented specifically for every kind of field or access you can do and checks up front if the requested value is defined. No more exceptions. For now isDefinedLoc4() is ignored by the compiler tests to work around the problem (to be merged soon).

[jurgenvinju]

Apart from this isDefinedLoc4 fails because the is_defined_loc_field_access_get does not check if the file is a directory which makes the test fail now.