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.