Shortcut evaluation for hierarchy of in contracts

[Walter Bright]

On 6/30/2011 3:42 AM, Jens Mueller wrote:
> The shortcut evaluation is specified in TDPL. That's why I assume the
> behavior is intended.

The behavior is both intended and crucial to the notion of contract inheritance.

The 'in' contract must pass at least one of the 'in' contracts of its 
inheritance hierarchy.
Derived functions "loosen" the requirements for input.

The 'out' contract must pass all of the 'out' contracts.
Derived functions "tighten" the requirements for output.