Matching enums is more limited after multiple enum value changes

Originally posted on our forums: https://www.eclipse.org/forums/index.php/t/1116860/

With the implementation of enumerated items with multiple possible values (#633 (closed)) the compiler has more difficulties determining the types of the operands of 'match' operations.

Example:

type enumerated Enum { e1, e2 };

function f(boolean b) return Enum {
  if (b) { return e1; }
  else { return e2; }
}

...

if (match(f(true), e1)) {
...

In this case the compiler can't determine whether its operands are references or enum items. This was not an issue in version 10.1.1, because 'f(true)' was clearly a reference to a function call, but now it can also be an enum item with multiple possible values.

/cc @aknappqwt @mmagyari