On Thursday, 15 December 2016 at 03:26:24 UTC, Meta wrote:
On Tuesday, 13 December 2016 at 22:33:24 UTC, Andrei
Alexandrescu wrote:
Destroy.
https://github.com/dlang/DIPs/pull/51/files
Andrei
What's the main goal with this proposal? Is it to introduce
DCDs into the language or is it to clean up some warts of the
local import pattern, i.e.:
int doSomething(T)(T t) //std.range is lazily imported but
{ //can't be used in the signature
import std.range;
//...
}
struct Test(R) //Ditto
{
import std.algorithm;
//etc...
}
I'm assuming it's the former, or there wouldn't be any talk
about introducing any new syntax. Imports would just be made
completely lazy and we wouldn't have to change the language at
all otherwise. So other than the fact that you can move the
declaration anywhere without breaking it due to missing
imports, are the advantages that DCDs provide really worth it
enough to introduce yet another clause that can be put on any
declaration? Especially when we have another solution (lazy
imports) that does exactly what you want but excludes the DCD
aspect?
I think there is a case to be made to use the import in the
symbol's signature, which is currently not possible. Not sure it
pays for itself to add a feature in the language just for this.
The tooling case is moot IMO. The languages keeps being fubared
with obtuse complexities, which makes tooling harder to write,
and then this is used an an excuse to fubar it even more. This
isn't leading to a good place.
Now there are some ways I see this happen leveraging the 'with'
creating a "with import" construct.
void foo(R)(R r) if (isInputRange!R) with import std.range {
// ...
}
The good thing here is that the import syntax doesn't need to be
altered in any way. You can still do "with import foo.bar : buzz".
