assert semantic change proposal

[John Carter via Digitalmars-d]

On Sunday, 3 August 2014 at 19:47:27 UTC, David Bregman wrote:

> Walter has proposed a change to D's assert function as follows 
> [1]:
> "The compiler can make use of assert expressions to improve 
> optimization, even in -release mode."

Hmm. I really really do like that idea.

I suspect it is one of those ideas of Walter's that has 
consequences that reach further than anyone foresees..... but 
that's OK, because it is fundamentally the correct course of 
action, it's implications foreseen and unforeseen will be correct.

One "near term" implication is to permit deeper static checking 
of the code.

Both in terms of "Well, actually there is a code path in which 
the assert expression could be false, flag it with a warning" and 
in terms of "There is a code path which is unused / incorrect / 
erroneous is the assert expression is true", flag as an 
error/warning.

Furthermore, in the presence of the deeper compile time function 
evaluation, I suspect we will get deeper and even more suprising 
consequences from this decision.

Suddenly we have, at compile time, an expression we know to be 
true, always, at run time. Thus where possible, the compiler can 
infer as much as it can from this.

The implications of that will be very very interesting and far 
reaching.

As I said, this choice will have very far reaching and unforeseen 
and unforeseeable consequences.... but that's OK, since it is 
fundamentally the correct choice, those consequences will be 
correct too.