[Issue 18541] comparison `==` of two typeid() should always be rewritten as a "is"

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=18541

Jonathan M Davis <issues.dlang at jmdavisProg.com> changed:

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--- Comment #7 from Jonathan M Davis <issues.dlang at jmdavisProg.com> ---
(In reply to Basile B. from comment #6)
> (In reply to Steven Schveighoffer from comment #5)
> > Note that == will shortcut and return true if the two instances are the same
> > object.
> 
> With someone yesterday we have verified that it's really not the case. In a
> specific hotspot, using "==" instead of "is" made something running in 7
> minutes instead of 4 !
> 
> This is exactly why i opened this issue but unfortunately i understand now
> that it's not applicable, we just take care to use "is".

The very first thing in the implementation of the free function opEquals is

    if (lhs is rhs) return true;

So, it most definitely shortcuts. Now, that doesn't mean that it's as
efficient, since unless it's inlined, you're calling a function that isn't
called if you use is directly, but the shortcut definitely happens.

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