https://issues.dlang.org/show_bug.cgi?id=18426

Andrei Alexandrescu <andrei@erdani.com> changed:

           What    |Removed                     |Added
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           Assignee|nobody@puremagic.com        |greensunny12@gmail.com

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https://issues.dlang.org/show_bug.cgi?id=18426

--- Comment #1 from Seb <greensunny12@gmail.com> ---
A minimal testcase

---
alias point = Tuple!(int, "x",  int, "y");
static assert(point(2, 2)[0] == 0);
---

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https://issues.dlang.org/show_bug.cgi?id=18426

--- Comment #2 from Seb <greensunny12@gmail.com> ---
And a stripped down version of std.typecons.Tuple:

https://gist.github.com/wilzbach/0a55a571f1c46e9d59420cf158354b85

> A better implementation would be to have the Tuple with named fields use the Tuple with no named fields as its only member variable; then, "alias this" needs to simply return a reference to that member.

This is already done:


struct Tuple
{
   Types expand; // e.g. AliasSeq!(int, int)
}


However, if `alias expand this` is used, this stops to work:

---
auto t1 = Tuple!(int, "x", string, "y")(1, "a");
void foo(Tuple!(int, string) t2) {}
foo(t1);
---

foo.d(149): Error: function foo.__unittest_L143_C7.foo(Tuple!(int, string) t2)
is not callable using argument types (Tuple!(int, "x", string, "y"))
foo.d(149):        cannot pass argument t1 of type Tuple!(int, "x", string,
"y") to parameter Tuple!(int, string) t2

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https://issues.dlang.org/show_bug.cgi?id=18426

--- Comment #3 from Andrei Alexandrescu <andrei@erdani.com> ---
(In reply to Seb from comment #2)
> And a stripped down version of std.typecons.Tuple:
> 
> https://gist.github.com/wilzbach/0a55a571f1c46e9d59420cf158354b85
> 
> > A better implementation would be to have the Tuple with named fields use the Tuple with no named fields as its only member variable; then, "alias this" needs to simply return a reference to that member.
> 
> This is already done:

Nonono, we need to do this:

Tuple!(int, "x", int, "y") should have as its only state Tuple!(int, int). In
the form of a data member that is. Call that field impl. Then:

alias impl this;

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https://issues.dlang.org/show_bug.cgi?id=18426

Iain Buclaw <ibuclaw@gdcproject.org> changed:

           What    |Removed                     |Added
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           Priority|P1                          |P4

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https://issues.dlang.org/show_bug.cgi?id=18426

Basile-z <b2.temp@gmx.com> changed:

           What    |Removed                     |Added
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          Component|dmd                         |phobos

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