Protected function arguments cause confusing error message

[Per Östlund]

When instantiating a model such as this:

function fn
  protected Real r;
  input Real inR;
  output Real outR;
algorithm
  outR := inR;
end fn;

model test
  Real r, r2;
equation
  r = fn(r2);
end test;

the error message given is:

[protarg.mo:12:3-12:13:writable] Error: Failed to instantiate equation r = fn(r2);

The problem is that protected denotes a whole section and not a single variable, so the input and output parameters of the function is also protected. A protected input or output parameter doesn't really make much sense I think, but I can't see anything about it in the standard. We should probably print a warning either that you shouldn't protected input and output parameters, or an error that the number of arguments doesn't match the function definition.

[Martin Sjölund]

I'll also add errors for functions containing equations.
Note: We can not make this an error because MSL uses public bidirectional variables even though they are not allowed in the specification.

[Martin Sjölund]

Fixed in r7470