[Issue 7529] IFTI does not support template argument dependent template alias instances as parameter types
https://issues.dlang.org/show_bug.cgi?id=7529 Walter Bright changed: What|Removed |Added See Also||https://issues.dlang.org/sh ||ow_bug.cgi?id=1807 --
[Issue 7529] IFTI does not support template argument dependent template alias instances as parameter types
http://d.puremagic.com/issues/show_bug.cgi?id=7529
--- Comment #7 from d...@dawgfoto.de 2012-02-17 06:52:19 PST ---
void foo(T)(Unsigned!T val)
{
}
foo(2u);
???
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[Issue 7529] IFTI does not support template argument dependent template alias instances as parameter types
http://d.puremagic.com/issues/show_bug.cgi?id=7529 --- Comment #8 from timon.g...@gmx.ch 2012-02-17 06:54:08 PST --- Unsigned is not an alias template. Your example is unrelated to this enhancement. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email --- You are receiving this mail because: ---
[Issue 7529] IFTI does not support template argument dependent template alias instances as parameter types
http://d.puremagic.com/issues/show_bug.cgi?id=7529
--- Comment #9 from Kenji Hara k.hara...@gmail.com 2012-02-17 07:10:54 PST ---
I think this is invalid issue.
Reduced case:
void f(T)(T, T) { pragma(msg, T); }
void main()
{
f(0L, 0); // first argument is long, and second one is int
// Error: template test.f(T) does not match any function template declaration
}
In IFTI, arguments don't have any dependencies each other about the deduction.
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[Issue 7529] IFTI does not support template argument dependent template alias instances as parameter types
http://d.puremagic.com/issues/show_bug.cgi?id=7529
--- Comment #10 from timon.g...@gmx.ch 2012-02-17 07:20:59 PST ---
If you think it is invalid you misunderstand the issue. This is about extending
IFTI so that it can match templated aliases.
template Alias(T){ alias Foo!T Alias;}
void foo(T)(Alias!T x){ pragma(msg, T); }
foo(Foo!int); // prints 'int'
What effectively would need to be done at the compiler side:
- If a template parameter type is a template, check whether it is an eponymous
alias template (like template Alias(T){ alias Foo!T Alias; }
- If so, expand the template without knowing the type it is instantiated with
void foo(T)(Alias!T x){ ... } = void foo(T)(Foo!T x){ ... }
This is always a valid transformation for eponymous alias templates.
This does not introduce any dependencies across parameters.
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[Issue 7529] IFTI does not support template argument dependent template alias instances as parameter types
http://d.puremagic.com/issues/show_bug.cgi?id=7529
--- Comment #11 from d...@dawgfoto.de 2012-02-17 07:25:35 PST ---
Is that what you mean by alias template.
template Wrap(T) { alias T Wrap; } // no members, no static if
This has a bidirectional mapping, but you can't change the type any longer.
'void foo(T)(Wrap!T val)' would always be equal to 'void foo(T)(T val)'
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[Issue 7529] IFTI does not support template argument dependent template alias instances as parameter types
http://d.puremagic.com/issues/show_bug.cgi?id=7529
--- Comment #12 from timon.g...@gmx.ch 2012-02-17 07:35:44 PST ---
An alias template is like a function template, just for aliases.
Those are all alias templates:
template A(T){alias T A;}
template B(T){alias Foo!T B;}
template C(T){alias foo.bar.Qux!T C;}
template D(T){alias Foo!(Bar!(Qux!T)) D;}
Those are functions that use them:
void fooa(T)(A!T a){ ... }
void foob(T)(B!T b){ ... }
void fooc(T)(C!T c){ ... }
void food(T)(D!T d){ ... }
Those are the versions that do exactly the same thing but work with IFTI:
void fooa(T)(T a){ ... }
void foob(T)(Foo!T b){ ... }
void fooc(T)(foo.bar.Qux!T c){ ... }
void food(T)(Foo!(Bar!(Qux!T)) d){ ... }
What I am asking for is for IFTI to work the same for the former and latter
versions of the functions. This is easy to implement and matches what most
programmers would expect the language to be capable of.
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[Issue 7529] IFTI does not support template argument dependent template alias instances as parameter types
http://d.puremagic.com/issues/show_bug.cgi?id=7529
--- Comment #13 from d...@dawgfoto.de 2012-02-17 07:47:33 PST ---
MidAir collision but thanks for the clarification.
Most of those cases can be handled by aliasing
the template declaration rather than the instance.
alias Foo Alias;
void foo(T)(Alias!T x){ pragma(msg, T); }
foo(Foo!int.init);
Which wouldn't work for recursion.
template D(T){alias Foo!(Bar!(Qux!T)) D;}
It seems to me that what you want is an AST macro not a template expansion.
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[Issue 7529] IFTI does not support template argument dependent template alias instances as parameter types
http://d.puremagic.com/issues/show_bug.cgi?id=7529
--- Comment #14 from Kenji Hara k.hara...@gmail.com 2012-02-17 07:59:59 PST
---
(In reply to comment #12)
An alias template is like a function template, just for aliases.
Those are all alias templates:
template A(T){alias T A;}
template B(T){alias Foo!T B;}
template C(T){alias foo.bar.Qux!T C;}
template D(T){alias Foo!(Bar!(Qux!T)) D;}
Those are functions that use them:
void fooa(T)(A!T a){ ... }
void foob(T)(B!T b){ ... }
void fooc(T)(C!T c){ ... }
void food(T)(D!T d){ ... }
Those are the versions that do exactly the same thing but work with IFTI:
void fooa(T)(T a){ ... }
void foob(T)(Foo!T b){ ... }
void fooc(T)(foo.bar.Qux!T c){ ... }
void food(T)(Foo!(Bar!(Qux!T)) d){ ... }
What I am asking for is for IFTI to work the same for the former and latter
versions of the functions. This is easy to implement and matches what most
programmers would expect the language to be capable of.
OK, I almost understand what you expects.
When the two declarations exist,
template B(T){alias Foo!T B;}
void foob(T)(B!T b){ ... }
and calling foob with IFTI like follows:
Foo!int x;
foob(x); // foob(T)(B!T) is converted to foob(T)(Foo!T)
// *with expanding template B*, then foob deduces T as int.
OK?
-
There is some problems about this enhancement.
1) This enhancement requires adding a phase to expanding eponymous templates
used as function parameter type. This makes IFTI process more complicate.
2) Some eponymous templates are not one liner.
template X(T) {
template Y(U) { ... } // massive type calculation
alias Y!T X; // also eponymous template
}
void foo(T)(X!T) { ... }
Should compiler calculate T from X!T? It is almost impossible!
If it only works with one-linear eponymous template, it is less benefit than
the semantic complexity.
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[Issue 7529] IFTI does not support template argument dependent template alias instances as parameter types
http://d.puremagic.com/issues/show_bug.cgi?id=7529
--- Comment #16 from timon.g...@gmx.ch 2012-02-17 08:06:44 PST ---
(In reply to comment #13)
MidAir collision but thanks for the clarification.
Most of those cases can be handled by aliasing
the template declaration rather than the instance.
alias Foo Alias;
void foo(T)(Alias!T x){ pragma(msg, T); }
foo(Foo!int.init);
Which wouldn't work for recursion.
template D(T){alias Foo!(Bar!(Qux!T)) D;}
It seems to me that what you want is an AST macro not a template expansion.
IFTI matching already works that way.
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[Issue 7529] IFTI does not support template argument dependent template alias instances as parameter types
http://d.puremagic.com/issues/show_bug.cgi?id=7529
--- Comment #15 from timon.g...@gmx.ch 2012-02-17 08:05:50 PST ---
(In reply to comment #14)
OK?
Yes.
-
There is some problems about this enhancement.
1) This enhancement requires adding a phase to expanding eponymous templates
used as function parameter type. This makes IFTI process more complicate.
It can presumably be done while semantically analyzing the parameter types.
2) Some eponymous templates are not one liner.
template X(T) {
template Y(U) { ... } // massive type calculation
alias Y!T X; // also eponymous template
}
void foo(T)(X!T) { ... }
Should compiler calculate T from X!T? It is almost impossible!
It shouldn't, because it *is* impossible.
If it only works with one-linear eponymous template, it is less benefit than
the semantic complexity.
I disagree. There is almost no semantic complexity.
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[Issue 7529] IFTI does not support template argument dependent template alias instances as parameter types
http://d.puremagic.com/issues/show_bug.cgi?id=7529 --- Comment #17 from d...@dawgfoto.de 2012-02-17 08:44:58 PST --- IFTI matching already works that way. No it does not. With IFTI and structs you recursively match template arguments. Foo!(Bar!(Baz!T))) Foo!(Bar!(Baz!int))) With the alias you need to instantiate the template, probably using a bottom type and then do the above. Foo!(Bar!(Baz!(T))) = Result!T Result!int -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email --- You are receiving this mail because: ---
[Issue 7529] IFTI does not support template argument dependent template alias instances as parameter types
http://d.puremagic.com/issues/show_bug.cgi?id=7529 timon.g...@gmx.ch changed: What|Removed |Added Status|NEW |RESOLVED Resolution||DUPLICATE --- Comment #19 from timon.g...@gmx.ch 2012-02-17 14:20:37 PST --- Good catch. *** This issue has been marked as a duplicate of issue 1807 *** -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email --- You are receiving this mail because: ---
[Issue 7529] IFTI does not support template argument dependent template alias instances as parameter types
http://d.puremagic.com/issues/show_bug.cgi?id=7529 timon.g...@gmx.ch changed: What|Removed |Added CC||timon.g...@gmx.ch Summary|IFTI does not support |IFTI does not support |aliases |template argument dependent ||template alias instances as ||parameter types Severity|normal |enhancement --- Comment #1 from timon.g...@gmx.ch 2012-02-16 20:23:46 PST --- This is an enhancement, a very desirable one. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email --- You are receiving this mail because: ---
[Issue 7529] IFTI does not support template argument dependent template alias instances as parameter types
http://d.puremagic.com/issues/show_bug.cgi?id=7529
d...@dawgfoto.de changed:
What|Removed |Added
CC||d...@dawgfoto.de
--- Comment #2 from d...@dawgfoto.de 2012-02-16 20:49:38 PST ---
The issue is what do you make of related cases.
// not deducible
void f(T)(Type!T) {}
f(0);
// ?
void f(T)(Type!T, T) {}
f(0, 0);
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[Issue 7529] IFTI does not support template argument dependent template alias instances as parameter types
http://d.puremagic.com/issues/show_bug.cgi?id=7529
--- Comment #3 from timon.g...@gmx.ch 2012-02-16 21:24:43 PST ---
Both of those(In reply to comment #2)
The issue is what do you make of related cases.
// not deducible
void f(T)(Type!T) {}
f(0);
// ?
void f(T)(Type!T, T) {}
f(0, 0);
Both of those should work. The enhancement demands special treatment of
templated aliases.
For example, this would work too:
template LList(T){alias Lazy!(List!T)) LList;}
alias f(T)(LList!T){}
f(new LList);
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[Issue 7529] IFTI does not support template argument dependent template alias instances as parameter types
http://d.puremagic.com/issues/show_bug.cgi?id=7529
--- Comment #4 from timon.g...@gmx.ch 2012-02-16 21:25:43 PST ---
I meant
void f(T)(LList!T){}
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[Issue 7529] IFTI does not support template argument dependent template alias instances as parameter types
http://d.puremagic.com/issues/show_bug.cgi?id=7529
--- Comment #5 from d...@dawgfoto.de 2012-02-16 22:03:04 PST ---
The reason why this works with structs but not with templates is that a struct
preserves the full type information while an alias template transforms a type.
void bar(Ty)(Ty) { pragma(msg, Ty); }
struct SList(T) {}
template TList(T) { alias T TList; }
void main()
{
bar(SList!int.init); // type SList!int = SList!int is preserved
bar(TList!int.init); // type int = TList!int is lost
}
Now if you take a function void foo(T)(TList!T) {} and gives you 'TList(T) =
int'.
What your asking for is an inverted template 'TList^-1(int) = T'.
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