[Issue 24005] New: UFCS: The non-member function call can be uniform/universal, too
d-bugmail at puremagic.com
d-bugmail at puremagic.com
Wed Jun 21 09:12:25 UTC 2023
https://issues.dlang.org/show_bug.cgi?id=24005
Issue ID: 24005
Summary: UFCS: The non-member function call can be
uniform/universal, too
Product: D
Version: D2
Hardware: All
OS: All
Status: NEW
Severity: enhancement
Priority: P1
Component: dmd
Assignee: nobody at puremagic.com
Reporter: qs.il.paperinik at gmail.com
UFCS makes it possible to call a non-member function as if it were a member
function of the first parameter’s type. The reverse is not true, however. A
member function cannot be called as if it were a non-member function that takes
the aggregate type that contains it as the first parameter explicitly:
```d
struct S
{
void mem() {}
}
void nonmem(S) {}
void main()
{
S s;
s.mem(); // ok
mem(s); // fails
s.nonmem(); // ok (UFCS)
nonmem(s); // ok
}
```
I suggest to make the non-member call syntax universal as well. The same as
preferring the member function in member function syntax over an eponymous
non-member function in scope, we prefer the non-member function in the
non-member function call syntax over an eponymous member function of the type
of the first argument.
This, plus https://issues.dlang.org/show_bug.cgi?id=24004, would make it
unnecessary to remember if a functionality is provided via a non-member or
member function in quite a lot of cases.
A bit of nomenclature:
UNFCS: Universal non-member function call syntax. The (new) mechanic that
`mem(obj)` works because `obj` has a member `mem`.
UMFCS: Universal member function call syntax: The (already present) mechanic
that `obj.nonmem` works because a non-member function takes `typeof(obj)` as
its first parameter.
UFCS: Umbrella term for both UNFCS and UMFCS.
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