www.digitalmars.com         C & C++   DMDScript  

digitalmars.D.bugs - [Issue 10008] New: Inconsistent inference of template and non-template function attributes

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=10008

           Summary: Inconsistent inference of template and non-template
                    function attributes
           Product: D
           Version: unspecified
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody puremagic.com
        ReportedBy: maxim maxim-fomin.ru



---
struct S()
{
    void foo(){}
}

struct Z
{
    void foo(){}
}

void main()  safe
{
    auto x = &Z.foo;
    auto y = &S!().foo;
    pragma(msg, typeof(x));
    pragma(msg, typeof(y));
    x();
    y();
}

Member function of templated struct is deduced to be pure nothrow  safe while
non-templated struct function is not. Either both should be rejected or none of
them.

-- 
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
Apr 29 2013
next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=10008




This is a new D feature from 2.063.

For the *instantiated* non-virtual member functions, compiler now infers their
function attributes as same as normal template functions.

This is useful template based structures, such as std.algorithm and std.range.
Now, most of ranges and algorithms would work in safe/pure/nothrow functions.

import std.algorithm, std.range;
void main()  safe pure nothrow {
    auto r = [1,2,3].map!(a => a*2).retro;
}

-- 
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
Apr 29 2013
prev sibling next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=10008




---
OK, this explains why function from templated struct is deduced to have all
attributes. But this tells nothing about another case. I understand that Z.foo
is not required to be  safe/pure/nothrow because it isn't marked as such, but
on the other hand S.foo() is also not marked and clearly there is contradiction
here.

-- 
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
Apr 29 2013
prev sibling next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=10008






 OK, this explains why function from templated struct is deduced to have all
 attributes. But this tells nothing about another case. I understand that Z.foo
 is not required to be  safe/pure/nothrow because it isn't marked as such, but
 on the other hand S.foo() is also not marked and clearly there is contradiction
 here.


Short answer is that it is just same as the difference between:
  void foo() {}
and
  void bar()() {}

Both don't have attributes explicitly, but bar would be inferred to
 safe/pure/nothrow when it is instantiated.

---

There is an essential difference between template functions and non-template
ones. For the former, the actual function attributes of instantiated code is
not pre-deterministic. Ultimately, it would depend on the arguments which is
given on the template parameters. Attribute inference for the instantiated
functions is necessary for making function attributes more convenient.

On the other hand, the functions out of the template declaration should be "as
is". You can hide the function body in the library file for the separate
compilation, and just only declaring function signatures in di file. Therefore,
we cannot/should not apply attribute inference for normal functions.

The contradiction you feel comes from the essential difference that I described
in above. Thanks.

-- 
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
Apr 29 2013
prev sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=10008


Maxim Fomin <maxim maxim-fomin.ru> changed:

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



---
I see, mark it as RESOLVED INVALID.

-- 
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
Apr 29 2013