[Issue 11722] New: Qualifier-only casts should not invoke opCast

[d-bugmail at puremagic.com]

https://d.puremagic.com/issues/show_bug.cgi?id=11722

           Summary: Qualifier-only casts should not invoke opCast
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Keywords: wrong-code
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody at puremagic.com
        ReportedBy: k.hara.pg at gmail.com


--- Comment #0 from Kenji Hara <k.hara.pg at gmail.com> 2013-12-10 17:17:25 PST ---
This is a spin-off issue from bug 5747.

D has a cast syntax for modifying just only the type qualifier of the operand.

http://dlang.org/expression#CastExpression

CastExpression:
    cast ( Type ) UnaryExpression
    cast ( CastQual ) UnaryExpression   <--
    cast ( ) UnaryExpression            <--

However, if the operand is class or struct, and has opCast member function, the
qualifier-cast cast(qual)exp is translated to cast(qual(typeof(exp))exp, then
it will unintendedly invoke opCast. For example, following code wrongly asserts
in C.opCast.

class C
{
    T opCast(T)() { assert(0); }
}
void main()
{
    C c = new C();
    shared C sc = cast(shared)c;
}

I think this is not good behavior in generic code, and should be fixed.

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