View mode: basic / threaded / horizontal-split · Log in · Help
November 14, 2009
[Issue 3510] New: Cannot forward reference a templated type from within a template mixin
http://d.puremagic.com/issues/show_bug.cgi?id=3510

          Summary: Cannot forward reference a templated type from within
                   a template mixin
          Product: D
          Version: 1.051
         Platform: All
       OS/Version: All
           Status: NEW
         Keywords: rejects-valid
         Severity: blocker
         Priority: P2
        Component: DMD
       AssignedTo: nobody@puremagic.com
       ReportedBy: matti.niemenmaa+dbugzilla@iki.fi
           Blocks: 340


--- Comment #0 from Matti Niemenmaa <matti.niemenmaa+dbugzilla@iki.fi> 2009-11-14 12:30:29 PST ---
Simple case:


struct S(int x) {}
template Mix() { Sa s; }

class C {
   mixin Mix!();
   alias S!(0) Sa;
}

foo.d(2): Error: forward reference to 'S!(0)'
foo.d(2): Error: Sa is used as a type
foo.d(2): Error: variable foo.C.Mix!().s voids have no value
foo.d(5): Error: mixin foo.C.Mix!() error instantiating


Move the mixin of Mix!() below the alias of S!() and it compiles.

For the following code, that move alone isn't enough:


template Tuple(T...) { alias T Tuple; }

struct S(size_t x) {}
template Mix() { Sa s; }

class C {
   mixin Mix!();
   alias Tuple!("foo") T;
   alias S!(T.length) Sa;
}

[same errors as above]


Moving the mixin below the alias of S!() gives:

foo.d(8): Error: identifier 'length' of 'T.length' is not defined
foo.d(8): Error: template instance S!(int) does not match template declaration
S(uint x)
foo.d(4): Error: template instance S!(int) is used as a type
foo.d(4): Error: variable foo.C.Mix!().s voids have no value
foo.d(9): Error: mixin foo.C.Mix!() error instantiating

After moving the mixin, the code can still be made to compile by introducing a
constant to hold the length. The following class C works:

alias Tuple!("foo") T;
const size_t Tlength = T.length;
alias S!(Tlength) Sa;
mixin Mix!();

Unfortunately, in my case T depends on Mix in ways the compiler can't figure
out without having Mix mixed in before T (Bug 3509), so this is a blocker for
me.

-- 
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
March 13, 2012
[Issue 3510] Cannot forward reference a templated type from within a template mixin
http://d.puremagic.com/issues/show_bug.cgi?id=3510



--- Comment #1 from github-bugzilla@puremagic.com 2012-03-12 20:02:19 PDT ---
Commit pushed to master at https://github.com/D-Programming-Language/dmd

https://github.com/D-Programming-Language/dmd/commit/2c3e9a8b007d62493c52ca601173ff2cd9cd9c0a
fix Issue 3510 - Cannot forward reference a templated type from within a
template mixin

-- 
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
March 13, 2012
[Issue 3510] Cannot forward reference a templated type from within a template mixin
http://d.puremagic.com/issues/show_bug.cgi?id=3510



--- Comment #2 from github-bugzilla@puremagic.com 2012-03-12 20:02:40 PDT ---
Commit pushed to dmd-1.x at https://github.com/D-Programming-Language/dmd

https://github.com/D-Programming-Language/dmd/commit/1ac0b1021b77190f512399a2bde9bfac7e05f940
fix Issue 3510 - Cannot forward reference a templated type from within a
template mixin

-- 
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
March 13, 2012
[Issue 3510] Cannot forward reference a templated type from within a template mixin
http://d.puremagic.com/issues/show_bug.cgi?id=3510


Walter Bright <bugzilla@digitalmars.com> changed:

          What    |Removed                     |Added
----------------------------------------------------------------------------
            Status|NEW                         |RESOLVED
                CC|                            |bugzilla@digitalmars.com
        Resolution|                            |FIXED


-- 
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
Top | Discussion index | About this forum | D home