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digitalmars.D.bugs - [Issue 8701] New: One case of template type deduction

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=8701

           Summary: One case of template type deduction
           Product: D
           Version: D2
          Platform: x86
        OS/Version: Windows
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: DMD
        AssignedTo: nobody puremagic.com
        ReportedBy: bearophile_hugs eml.cc


--- Comment #0 from bearophile_hugs eml.cc 2012-09-20 10:17:13 PDT ---
Is this supposed to work? If the answer is negative, maybe it's a good idea to
support this:


struct Foo(T) {}
void bar(Spam, T)(Spam!T y) {}
void main() {
    Foo!int x;
    bar(x);
}


DMD 2.061alpha gives:

temp.d(5): Error: template temp.bar does not match any function template
declaration
temp.d(5): Error: template temp.bar(Spam,T) cannot deduce template function
from argument types !()(Foo!(int))

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parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=8701


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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |INVALID


--- Comment #1 from Kenji Hara <k.hara.pg gmail.com> 2012-09-20 18:18:33 PDT ---
(In reply to comment #0)

 Is this supposed to work? If the answer is negative, maybe it's a good idea to
 support this:
 
 struct Foo(T) {}
 void bar(Spam, T)(Spam!T y) {}
 void main() {
     Foo!int x;
     bar(x);
 }


Compiler would infer Spam as a template symbol in IFTI, but it is
TemplateTypeParameter. Therefore this doesn't work.

Correct code is here:

struct Foo(T) {}
void bar(alias Spam, T)(Spam!T y) {}
void main() {
    Foo!int x;
    bar(x);
}

You can receive deduced template symbol by TemplateAliasParamerter. Then all
works.

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