http://d.puremagic.com/issues/show_bug.cgi?id=9971

           Summary: eponymous function is not an lvalue
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody@puremagic.com
        ReportedBy: ellery-newcomer@utulsa.edu


--- Comment #0 from Ellery Newcomer <ellery-newcomer@utulsa.edu> 2013-04-20 15:56:31 PDT ---
the code:

void main() {
    goo!()();
}

void goo()() {
    auto g = &goo; // not ok
}
void goo2() {
    auto g = &goo2; // ok
}

the fireworks:

Error: goo()() is not an lvalue

dmd 2.063-devel.

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Maxim Fomin <maxim@maxim-fomin.ru> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |maxim@maxim-fomin.ru


--- Comment #1 from Maxim Fomin <maxim@maxim-fomin.ru> 2013-04-20 21:19:50 PDT ---
I think it does not work because &goo is address of raw template and dmd does not instantiate it, so you should use pointer to instantiated function. I am not sure this is bug (but it may be an enhancement request).

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--- Comment #2 from Ellery Newcomer <ellery-newcomer@utulsa.edu> 2013-04-20 22:17:10 PDT ---
(In reply to comment #1)
> I think it does not work because &goo is address of raw template and dmd does not instantiate it, so you should use pointer to instantiated function. I am not sure this is bug (but it may be an enhancement request).

It is inconsistent with the way templated structs and classes work:

void main() {
    alias T!(int) t1;
}

struct T(j) {
    pragma(msg, "a struct ",T); // T is the struct
}
pragma(msg, "a template ", T); // T is the template

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--- Comment #3 from Maxim Fomin <maxim@maxim-fomin.ru> 2013-04-20 22:32:39 PDT ---
(In reply to comment #2)
> It is inconsistent with the way templated structs and classes work:
> 
> void main() {
>     alias T!(int) t1;
> }
> 
> struct T(j) {
>     pragma(msg, "a struct ",T); // T is the struct
> }
> pragma(msg, "a template ", T); // T is the template

Sorry I don't see your point. Note, that second message is printed irrespective to instantiation and none of the messages is sensitive to what T is really is.

void main() {
    alias T!(int) t1;
}

struct T(j) {
    //pragma(msg, "a struct ",T); // T is the struct
    pragma(msg, T.stringof);
}
//pragma(msg, "a template ", T); // T is the template
pragma(msg, T.stringof);

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--- Comment #4 from Ellery Newcomer <ellery-newcomer@utulsa.edu> 2013-04-20 22:45:05 PDT ---
(In reply to comment #3)
> 
> Sorry I don't see your point. Note, that second message is printed irrespective to instantiation and none of the messages is sensitive to what T is really is.

My point is that inside the struct template, T without any template instantiation refers to the instantiated struct:

import std.traits;
void main() {
    alias T!(int) t1;
}

struct T(j) {
    T foo() {
        T t;
        return t;
    }
}
static assert(is(ReturnType!(T!int.foo) == T!int));
static assert(is(ReturnType!(T!double.foo) == T!double));

But in a templated function, T refers to the template:

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deadalnix <deadalnix@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |deadalnix@gmail.com


--- Comment #5 from deadalnix <deadalnix@gmail.com> 2013-04-20 22:49:27 PDT ---
(In reply to comment #1)
> I think it does not work because &goo is address of raw template and dmd does not instantiate it, so you should use pointer to instantiated function. I am not sure this is bug (but it may be an enhancement request).

No, within the function, the function must be resolve before the template.

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--- Comment #6 from Kenji Hara <k.hara.pg@gmail.com> 2013-04-20 23:10:56 PDT ---
I think this is a bug.
Inside template function, the name 'goo' should be resolved to the instantiated
function 1st, then rewritten to template 'goo' if needed.

For example, this code should work.

void main() {
    goo(1);                // 1. instantiate goo!int
}
void goo(T...)(T args) {
    auto g = &goo;         // 2. &goo!int == void function(int)
                           // 4. &goo!() == void function()
    pragma(msg, typeof(g));
    static if (T.length)
        goo(args[1..$]);   // 3. instantiate goo!()
}

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--- Comment #7 from Maxim Fomin <maxim@maxim-fomin.ru> 2013-04-20 23:41:27 PDT ---
Yes, you are both right.

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Kenji Hara <k.hara.pg@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |pull, rejects-valid


--- Comment #8 from Kenji Hara <k.hara.pg@gmail.com> 2013-05-06 04:52:56 PDT ---
https://github.com/D-Programming-Language/dmd/pull/1970

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--- Comment #9 from github-bugzilla@puremagic.com 2013-05-06 20:41:58 PDT ---
Commits pushed to master at https://github.com/D-Programming-Language/dmd

https://github.com/D-Programming-Language/dmd/commit/f34c77f6f19ea516c19842f2aff0e43a7d94c3ef fix Issue 9971 - eponymous function is not an lvalue

https://github.com/D-Programming-Language/dmd/commit/654de7808e89204d20bac6f7f228fe07e3dd2c7a Merge pull request #1970 from 9rnsr/fix9971

Issue 9971 - eponymous function is not an lvalue

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