[Issue 6857] Precondition contract checks should be statically bound.

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=6857



--- Comment #47 from Walter Bright <bugzilla at digitalmars.com> 2012-05-05 02:02:48 PDT ---
(In reply to comment #46)
> Now, change F from a struct to a class. We believe that the code should still
> fail to compile.

A theorem prover could not produce a compile time error, because it could not
prove that f is actually an F, and not of a class derived from F.

OOP is runtime polymorphism, not compile time. A struct type is fundamentally
different from a class type.

And lastly, your request is quite different from Example #1, which is asserting
that the contract for A.foo() must always pass, even if it's calling B.foo().

I know I sound like a broken record, but please read Meyer's book. He shows how
the behavior of contracts is a derived consequence from OOP principles. It is
not a separate invention with separate rules. Hence it is not a matter of
belief - it is a matter of proof.

--- Comment #48 from Walter Bright <bugzilla at digitalmars.com> 2012-05-05 02:03:05 PDT ---
(In reply to comment #46)
> Now, change F from a struct to a class. We believe that the code should still
> fail to compile.

A theorem prover could not produce a compile time error, because it could not
prove that f is actually an F, and not of a class derived from F.

OOP is runtime polymorphism, not compile time. A struct type is fundamentally
different from a class type.

And lastly, your request is quite different from Example #1, which is asserting
that the contract for A.foo() must always pass, even if it's calling B.foo().

I know I sound like a broken record, but please read Meyer's book. He shows how
the behavior of contracts is a derived consequence from OOP principles. It is
not a separate invention with separate rules. Hence it is not a matter of
belief - it is a matter of proof.

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