In this example (extracted from https://digitalmars.com/articles/b68.html), this works:

class C {
  int a;
  int foo(int i) { return i + a; }
}

auto mfp = (C self, int i)=>self.foo(i);

void main(){
  auto c = new C;
  assert( c.mfp(20)==20);
}

but this fails

class C {
  int a;
  int foo(int i) { return i + a; }
}

void main(){
  auto mfp = (C self, int i)=>self.foo(i);
  auto c = new C;
  assert( c.mfp(20)==20);
}

onlineapp.d(9): Error: no property mfp for type onlineapp.C

I supossed that mfp(c,20) and c.mfp(20) should be equivalent because UFCS in second example, but it is not... why?

On Thursday, 8 July 2021 at 22:24:26 UTC, Antonio wrote:

UFCS does not work for nested functions.

https://dlang.org/spec/function.html#pseudo-member

On Thursday, 8 July 2021 at 22:24:26 UTC, Antonio wrote:

https://dlang.org/spec/function.html#pseudo-member

6. Functions declared in a local scope are not found when searching for a matching UFCS function.

On Thursday, 8 July 2021 at 22:24:26 UTC, Antonio wrote:

UFCS only works with functions defined at top level, not nested inside other functions. That's just how it is defined i don't really know why.

On Thursday, 8 July 2021 at 22:31:49 UTC, Dennis wrote:

Thanks.

I read the example and the assumption of "name conflict" does not seem to be justified (from my point of view)

i.e. Without dot notation, this example must fail

int front(int[] arr) { return arr[0]; }
void main()
{
    int[] a =[1,2,3];
    auto front = 1;       // front is now a variable
    auto y = front(a);   // Error, front is not a function
}

Changing to y = a.front() should not change the behavior (it is only a notation change )... but it does!!!

int front(int[] arr) { return arr[0]; }
void main()
{
    int[] a =[1,2,3];
    auto front = 1;       // front is now a variable
    auto y = a.front()     // NO ERROR!!!
}

"It works as described in the manual, not as expected" (from MySQL haters club :-p) .

On Thursday, 8 July 2021 at 23:31:57 UTC, Antonio wrote:

Yeah, 50/285 people answering the question "What language features do you miss?" chose "UFCS for local symbols" in the State of D survey (2018), but no one has championed a language change for it yet.