result mappings in before/after bindings should be illegal

[stephan]

The original example in #286 contains non-sensical code: an after callin binding defines a parameter mapping including a mapping for result.

However, before/after callin bindings do not pass any value to the base side.

In the current implementation such useless result mappings are simply ignored, but the language definition should preferable prohibit this situation. This is especially relevant for after bindings, since they can indeed expose the base result to the role method. Programmers should be alerted that the opposite direction is not possible.

[stephan]

Paragraph 4.4(c) has been updated accordingly in r21944.

[stephan]

Replying to stephan:

Paragraph 4.4(c) has been updated accordingly in r21944.

OTJLD link should have been OTJLD §4.4(c).

[stephan]

Test for new compiler message is 4.3.1-otjld-parameter-mapping-16.

Implemented in r21949.