[dmd-beta] D 2.059 beta 3

[Jonathan M Davis]

On Monday, April 09, 2012 10:26:37 kenji hara wrote:
> 2012年4月9日10:07 Jonathan M Davis <jmdavisProg at gmx.com>:
> > There really should be errors for opEquals, opCmp, toString, and toHash
> > with incorrect signatures,
> 
> It is difficult to detect *incorrect signatures*, because compiler
> cannot judge it is a mistake of programmer, or is intended one of him.

It doesn't matter what the programmer intended. If specific signatures are 
required for these functions, then the compiler knows exactly what they should 
look like, and if they don't match, then they're wrong.

> > and for any of them that need multiple overloads, it
> > should complain not only if any of the overloads are incorrect but if any
> > are missing. The fact that it's sort that's complaining makes it very
> > hard to determine what's actually wrong.
> 
> At least, we should fix const system holes (e.g bug1824 - Object not
> const correct) before adding this kind of enforcements. Otherwise
> compiler may block some user codes that picks the const system holes
> but works as expected.

We should enforce whatever is currently required by the compiler. That 
enforcement can change when the requirements change. For instance, if a 
struct's opEquals must currently look like

bool opEquals(const S rhs) const {}
bool opEquals(const ref S rhs) const {}

then it should be an error if it doesn't. And if the requirements change so 
that a struct's opEquals should look like

bool opEquals(const S rhs) @safe const pure nothrow {}
bool opEquals(const ref S rhs) @safe const pure nothrow {}

then at that point, it'll complain if they don't look like that. Right now, 
the compiler is requiring things for these functions but not always giving 
errors when stuff doesn't match (or good ones when it does give errors), making 
it hard to get it right.

Obviously, the compiler can't require that all of these functions look like 
they're going to look a release or two from now, since that's going to change 
as we iron things out to make it possible for them to have the signatures that 
we want, but since the compiler _does_ have requirements for them (even if 
they're incomplete compared to what they will be), I don't see why the 
compiler shouldn't be complaining if they don't match what it currently 
requires.

- Jonathan M Davis