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 | Posted by Jonathan M Davis |  Permalink Reply |
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Jonathan M Davis 
| http://d.puremagic.com/issues/show_bug.cgi?id=4972
Summary: to!() needs a template constraint
Product: D
Version: unspecified
Platform: Other
OS/Version: Linux
Status: NEW
Severity: enhancement
Priority: P2
Component: Phobos
AssignedTo: nobody@puremagic.com
ReportedBy: jmdavisProg@gmx.com
--- Comment #0 from Jonathan M Davis <jmdavisProg@gmx.com> 2010-10-01 22:58:28 PDT ---
The following program
import std.conv;
import std.stdio;
void main()
{
dchar[7] numStr = "1234567";
writeln(to!long(numStr));
}
fails compilation with this error
/home/jmdavis/Downloaded_Files/dmd/dmd2/linux/bin/../../src/phobos/std/conv.d(95):
Error: template std.conv.toImpl(T,S) if (!implicitlyConverts!(S,T) &&
isSomeString!(T) && isInputRange!(Unqual!(S)) && isSomeChar!(ElementType!(S)))
toImpl(T,S) if (!implicitlyConverts!(S,T) && isSomeString!(T) &&
isInputRange!(Unqual!(S)) && isSomeChar!(ElementType!(S))) matches more than
one template declaration,
/home/jmdavis/Downloaded_Files/dmd/dmd2/linux/bin/../../src/phobos/std/conv.d(217):toImpl(T,S)
if (isStaticArray!(S)) and
/home/jmdavis/Downloaded_Files/dmd/dmd2/linux/bin/../../src/phobos/std/conv.d(588):toImpl(T,S)
if ((is(S : const(wchar)[]) || is(S : const(dchar)[])) && !isSomeString!(T))
jmdavis@Lyonel ~/Programming/D/datetime [master]$ gvim
/home/jmdavis/Downloaded_Files/dmd/dmd2/src/phobos/std/conv.d
The error gives no indication whatsoever where the actual error is. The problem
is not in to!() but in the code that tried to instantiate to!(), and the error
gives no way to find that code. Ideally, bug # 4970 would be fixed and the
error would correctly indicate where to!() was used, but really, to!() should
have a template constraint of its own. As it stands, it's guaranteed that any
error instantiating to!() is not going to report the actual location of the
error. Copying or moving toImpl!()'s template constraint to to!() would fix the
problem quite easily, and I don't see much reason not to do it. It would
certainly make errors with using to!() easier to fix.
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