On Friday, 1 April 2016 at 21:46:35 UTC, ag0aep6g wrote:
On 01.04.2016 22:59, Simen Kjaeraas wrote:
The usual way to fix it would be to include __FILE__ and
__LINE__ in the
template arguments:
Right, no mixin this way. I wouldn't call this "truly nice",
though.
It depends on code formatting to work. Put everything on one
line and it breaks. Significant whitespace is a pain when
generating code. Though this is not nearly as bad as
significant indentation, of course.
__FILE__ also kind of breaks separate compilation. All object
files have to be compiled from the same directory. Otherwise
__FILE__ will be different.
__LINE__ has a similar (maybe even more obscure) issue. Add or
remove a newline before compiling dependent modules and things
break. Usually, one recompiles all dependents when a dependency
changes, but a significant newline, really?
I kinda agree. And looking at https://dlang.org/spec/traits.html,
I see there's __MODULE__, which would probably be a better choice
than __FILE__.
As for __LINE__, what we'd want is basically something like
__CONTEXT__, which doesn't exist, but might be the .mangleof of
the surrounding scope:
struct S(string ctx = __CONTEXT__) {
pragma(msg, ctx);
}
S!() a; // "3foo"
void bar() {
S!() b; // "_D3foo3barFZv"
}
struct S2 {
S!() c; // "S3foo2S2"
void baz() {
S!() d; // "_D3foo2S23bazMFZv"
}
}
That'd remove the problem of significant whitespace. In fact,
it'd also eliminate the need for __MODULE__ in this case.
Still though, that's not enough if we want this to work:
void foo() {
alias a = Foo!(); alias b = Foo!();
assert(!isSame!(a, b));
}
We could also add __COLUMN__, which would be the horizontal index
of the instantiation's beginning:
foo(3, Bar!3.baz);
// ^Here. Position 11.
Next problem:
void main() {
pragma(msg, __LINE__);
mixin("pragma(msg, __LINE__);\npragma(msg, __LINE__);");
pragma(msg, __LINE__);
}
That prints '4' twice - once for the actual line 4, the other for
the second line of the mixin. However, __FILE__ is different, so
I guess __CONTEXT__ could also be.
--
Simen
