Comment #0 by snarwin+bugzilla — 2024-11-25T15:46:38Z
As of DMD 2.109.1, the following program fails to compile:
---
enum E { One }
inout(E) fun(inout(E) e)
{
import std.conv;
auto s = e.to!string;
return e;
}
---
The error message is:
---
/usr/include/dmd/phobos/std/conv.d(1227): Error: variable `std.conv.value` - only parameters or stack-based variables can be `inout`
/usr/include/dmd/phobos/std/conv.d(210): Error: template instance `std.conv.toImpl!(string, inout(E))` error instantiating
bug.d(6): instantiated from here: `to!(inout(E))`
---
This error occurs because toImpl attempts to pass an inout(E) value as an argument to the template enumRep. The instantiation fails because inout values cannot be used as template arguments:
---
enum E { One }
enum example(T, T value) = true;
alias test = example!(inout(E), E.One);
// Error: only parameters or stack-based variables can be `inout
---
Comment #1 by dfj1esp02 — 2024-11-26T18:45:25Z
private template enumRep(T, S, S value)
if (is (T == immutable) && isExactSomeString!T && is(S == enum))
{
static T enumRep = toStr!T(value);
}
If I mark the argument as immutable, then it compiles:
private template enumRep(T, S, immutable S value)
Presumably for enums it should be fine.
Invoking with enumRep!(immutable(T), immutable(S), member) works too.
Comment #2 by robert.schadek — 2024-12-01T16:43:16Z