I'm sitting here trying to figure out why I can't combine join
pathSplitter components with pathSeparator.
import std.range, std.path;
void bug()
{
auto comps = pathSplitter("foo/bar");
auto path = join(comps, pathSeparator);
}
This is the error message:
path.d(6): Error: template std.array.join does not match any function
template declaration. Candidates are:
DPL/dmd/src/../../phobos/std/array.d(1559): std.array.join(RoR,
R)(RoR ror, R sep) if (isInputRange!RoR &&
isInputRange!(ElementType!RoR) && isInputRange!R &&
is(Unqual!(ElementType!(ElementType!RoR)) == Unqual!(ElementType!R)))
DPL/dmd/src/../../phobos/std/array.d(1606):
std.array.join(RoR)(RoR ror) if (isInputRange!RoR &&
isInputRange!(ElementType!RoR))
path.d(6): Error: template std.array.join(RoR, R)(RoR ror, R sep) if
(isInputRange!RoR && isInputRange!(ElementType!RoR) && isInputRange!R &&
is(Unqual!(ElementType!(ElementType!RoR)) == Unqual!(ElementType!R)))
cannot deduce template function from argument types !()(PathSplitter,
string)
This is what I currently have to do to figure out what is going on.
// declare types of arguments
alias RoR = typeof(comps);
alias R = typeof(pathSeparator);
// static assert each constraint
static assert(isInputRange!RoR);
// Bingo!
static assert(isInputRange!(ElementType!RoR));
// path.d(9): Error: static assert (isInputRange!(const(char[])))
is false
static assert(isInputRange!R);
static assert(is(Unqual!(ElementType!(ElementType!RoR)) ==
Unqual!(ElementType!R)));
A useful error message should be something along this line.
path.d(6): Error: Can't call template function 'join' because the
element type of 'comps' is not an input range.
path.d(6): Error: Can't call template function 'join' because the
following constraint failed.
isInputRange!(ElementType!RoR), RoR == const(char[]) deduced from
argument 'comps'.
