http://d.puremagic.com/issues/show_bug.cgi?id=11308
Summary: Don't use Voldemort types for std.process output
Product: D
Version: D2
Platform: All
OS/Version: All
Status: NEW
Severity: normal
Priority: P2
Component: Phobos
AssignedTo: [email protected]
ReportedBy: [email protected]
CC: [email protected]
--- Comment #0 from Andrej Mitrovic <[email protected]> 2013-10-20
13:02:41 PDT ---
-----
import std.process;
void main()
{
auto res = executeShell("dmd");
if (res.status) { }
if (res.output) { }
// ok, reuse variable
res = executeShell("rdmd");
if (res.status) { }
if (res.output) { }
// NG. Even though return types are the same
res = execute(["dmd"]);
}
-----
$ dmd test.d
> Error: cannot implicitly convert expression (execute(["dmd"], null,
> cast(Config)0, 4294967295u)) of type ProcessOutput to ProcessOutput
The voldemort situation makes reusing variables impossible, even though the
same exact type is returned (the only difference being the template is
instantiated differently).
As a reduced test-case:
-----
auto foo(T)()
{
struct S { int x; }
return S(1);
}
void main()
{
auto res = foo!int();
res = foo!int();
// NG: Error: cannot implicitly convert expression (foo()) of type S to S
res = foo!double();
}
-----
This is a borderline compiler bug. Kenji I've CC'ed you to see if this is
something worth thinking about, could the compiler be smart enough to deduce
that the two Voldemort types are really the same type?
But even so, using `auto` for these process functions makes it very hard to
figure out what the return type of a function is. We might as well use a proper
non-voldemort struct.
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