ev3 code generation too weak - general problem with workers/visitors

[rbudde]

the following ev3 program crashes:

ev3-advanced-lists-too-complex.txt

reason:

• the type derived in the code generator is captured and not int as expected.

• this shows that the expression is too complex for out code generator and

• that type inferencing is needed for complex expressions

• btw: the generated code cannot be compiled due to an type error

• if this is compensated in Ev3Visitor#visitListSetIndex e.g. it becomes obvious, that the worker AbstractLanguageGeneratorWorker expects error-free results and sets the result to success in any case.

• making this worker error-aware crashes arduino tests, that rely on that wrong behavior.

todo:

• the way worker and visitors interact has to be refactored soon.
• error handling has to be easy and consistent.
• a type inferencer has to store the inferred type into each phrase, so that this can be used in code generation (the first two topics are much more urgent)

[rbudde]

related to #306