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digitalmars.D.bugs - [Issue 1536] New: Literal '0' is improperly used to deduce an implicit template parameter

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=1536

           Summary: Literal '0' is improperly used to deduce an implicit
                    template parameter
           Product: D
           Version: 1.021
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: bugzilla digitalmars.com
        ReportedBy: webmaster villagersonline.com


EXAMPLE CODE
  void delegate() CurryAll(A...)(void delegate(A) dg, A args)
  {
    return null; // dummy function
  }
  struct S
  {
    void foo()
    {
      uint u = 0;
      int i = 0;

      // these work
      auto a = CurryAll       (&this.baz, 0);
      auto b = CurryAll!(uint)(&this.bar, 0);
      auto c = CurryAll       (&this.bar, u);
      auto d = CurryAll       (&this.baz, i);
      auto e = CurryAll!(uint)(&this.bar, i);
      auto f = CurryAll!( int)(&this.baz, u);

      // these don't
      auto z = CurryAll       (&this.bar, 0);
    }

    void bar(uint u) { return; }
    void baz( int i) { return; }
  }

DMD OUTPUT
  implicit_instantiation_and_implicit_cast.d(21): function
implicit_instantiation_and_implicit_cast.CurryAll!(int).CurryAll (void
delegate(int i),(int _param_1)) does not match parameter types (void
delegate((uint _param_1)),int)
  implicit_instantiation_and_implicit_cast.d(21): Error: cannot implicitly
convert expression (&(*this).bar) of type void delegate((uint _param_1)) to
void delegate(int i)

ANALYSIS

It appears that when DMD encounters the literal '0', it is jumping to the
conclusion that that literal '0' *must* be of type int, even though it could be
other types (uint, real, etc.).  In the case of the example z from above, this
is bad because the delegate argument quite clearly requires that the template
be deduced to have parameter uint.


--
Sep 28 2007
next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=1536






A decimal literal within the range of 0 .. 2_147_483_647 is assumed to be of
type int, it's in the docs:

http://www.digitalmars.com/d/lex.html#integerliteral

"The type of the integer is resolved as follows:

Decimal Literal         Type
0 .. 2_147_483_647      int
2_147_483_648 .. 9_223_372_036_854_775_807L     long

Decimal Literal, L Suffix       Type
0L .. 9_223_372_036_854_775_807L        long

Decimal Literal, U Suffix       Type
0U .. 4_294_967_296U    uint
4_294_967_296U .. 18_446_744_073_709_551_615UL  ulong

Decimal Literal, UL Suffix      Type
0UL .. 18_446_744_073_709_551_615UL     ulong
"


--
Sep 28 2007
prev sibling next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=1536






Seems that I was wrong about what is written in the spec; I thought that the
type of literal was considered ambiguous until it was forced, by context, to be
something (such as assigning it to a variable, or passing it as a parameter).

So, let's make this bug more of a question about the language itself: Perhaps
we need to change integer literals to have their type inferred from context,
just like string literals.  IMHO, the code below looks pretty simple and seems
like it *ought* to work.  Is there a technical reason (other than just "it is
easier") why integer literals *shouldn't* be polysemous?


--
Sep 28 2007
prev sibling next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=1536


thomas-dloop kuehne.cn changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement
         OS/Version|Linux                       |All
           Platform|PC                          |All




--
Sep 30 2007
prev sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=1536


Don <clugdbug yahoo.com.au> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |clugdbug yahoo.com.au



This example is unnecessarily complicated.

void CurryAll(A)(A x, A y)
{ }

void foo()
{
       uint u = 0;
       CurryAll(u, 0);
}

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