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digitalmars.D.bugs - [Issue 1456] New: Cannot use a constant with alias template parameters

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=1456

           Summary: Cannot use a constant with alias template parameters
           Product: D
           Version: 1.020
          Platform: PC
        OS/Version: Windows
            Status: NEW
          Severity: blocker
          Priority: P2
         Component: DMD
        AssignedTo: bugzilla digitalmars.com
        ReportedBy: samukha voliacable.com


<code>
const int i = 20;

template Foo(alias bar)
{
}

alias Foo!(i) foo;
</code>
Error: template instance Foo!(20) does not match any template declaration

Please note that the compiler handles the situation correctly
if the initializer for i is left out:

<code>
const int i;

template Foo(alias bar)
{
  alias bar Foo;
}

alias Foo!(i) foo;
pragma(msg, foo.stringof); // now foo is aliased to i as expected
</code>

D 2.0 has the same problem.


--
Aug 30 2007
next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=1456






I don't think this is a bug. In the second case, the value of i is not known
until runtime. It's really just a variable. But the first case  is identical to

alias Foo!(20) foo;

which shouldn't compile.


--
Sep 13 2007
prev sibling next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=1456






But in the first example the global name i and not 20 is aliased. It is
according to the specs. If it's not a bug, I would expect the following not to
work either:

const int i = 20;
alias i j; // Should fail with an error like "cannot alias 20 to j"? 


--
Sep 13 2007
prev sibling next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=1456


Max Samukha <samukha voliacable.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|blocker                     |normal



PDT ---
Not a blocker but still a bug, IMO. dmd 2.035 handles it right.

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Oct 21 2009
prev sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=1456


Don <clugdbug yahoo.com.au> changed:

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



This is not a bug. The reason it works in D2 is that D2 allows expressions as
template alias parameters.

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Nov 21 2012