Check model reports errors for correct models and vice versa.

[dhedberg]

The kernel fails to recognize the modification of x in the extends clause in model B, resulting in an error that A.x is not identical to B.x when checking model B.

model A
  Integer x;
end A;

model B
  extends A(x=2);
  Integer x=2;
end B;

Kernel reports the following error:
Check of B failed
Error: Duplicate elements (due to inherited elements) not identical, first element is: Integer x = 2; from baseclass: <nothing>
, second element is: Integer x; from baseclass: A

Error: Error occured while flattening model B

The error itself could be re-structured with line breaks etc, also the comment " from baseclass: <nothing>" could be improved. The element is locally declared and not inherited at all.

For the same reason the kernel incorrectly reports the erronous model B below as correct when checking it:

model A
  Integer x=2;
end A;

model B
  extends A(x=3);
  Integer x=2;
end B;

[dhedberg]

The corresponding ticket in MathCore Track is 1944.

[adrpo]

Similar to almost duplicate of [BUG:1126].

[perost]

The new frontend handles this correctly.