On Saturday, 20 June 2026 at 10:28:24 UTC, Ivan Kazmenko wrote:
void main ()
{
auto a = [1, 2, 3];
auto b = a.map !(x => format !("%d") (x)); // ok
auto c = a.map !(format !("%d")); // orphan format specifier
}
```
Why the line with `b` compiles, but the line with `c` does not?
Shouldn't the compiler deduce the type for the format argument
as a.front?
The signature is:
```d
typeof(fmt) format(alias fmt, Args...)(Args args);
```
https://dlang.org/phobos/std_format.html#format
You only provided the `fmt` template argument, so `Args` is
inferred as an empty sequence. Your code could be supported if
`format` was changed to:
```d
template format(alias fmt)
{
typeof(fmt) format(Args...)(Args args) { ... }
}
```
Perhaps file an issue:
https://github.com/dlang/phobos/issues
