Re: Fixing spurious "statement is not reachable" in template code

[deadalnix via Digitalmars-d]

On Saturday, 24 October 2015 at 17:25:23 UTC, tsbockman wrote:
While improving the DMD front-end's constant folding:
    https://github.com/D-Programming-Language/dmd/pull/5229
I found out about DMD issue 14835:
    https://issues.dlang.org/show_bug.cgi?id=14835
Briefly:
///////////////////////////////
module main;

import std.stdio;

void reachIf(bool x)()
{
    if(!x)
        return;
    writeln("reached"); // Warning: statement is not reachable
}

void main(string[] args) {
    reachIf!true();  // prints "reached"
    reachIf!false(); // triggers warning
}
///////////////////////////////

This is, I think, a big problem.

It is. This is the optimizer leaking into semantic. As far as 
language definition is concerned, this is a runtime if and 
changing it to a compile time one is an optimization.

If this was a static if, then generating a error is reasonable, 
but with a regular if, it isn't.