[Issue 7586] New: Equality lambda inference problem on tuples

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=7586

           Summary: Equality lambda inference problem on tuples
           Product: D
           Version: D2
          Platform: x86
        OS/Version: Windows
            Status: NEW
          Keywords: rejects-valid
          Severity: normal
          Priority: P2
         Component: Phobos
        AssignedTo: nobody at puremagic.com
        ReportedBy: bearophile_hugs at eml.cc


--- Comment #0 from bearophile_hugs at eml.cc 2012-02-25 10:08:07 PST ---
I am not sure what's the cause of this problem.


import std.algorithm, std.typecons;
alias Tuple!int T;
void main() {
    const T del = T(1);
    T[] items1 = [T(0), T(1), T(2)];
    auto r1 = filter!(x => x != del)(items1); // OK
    auto r2 = filter!(x => del != x)(items1); // error
    const(T[]) items2 = [T(0), T(1), T(2)];
    auto r3 = filter!(x => x != del)(items2); // error
}



test.d(7): Error: function
std.typecons.Tuple!(int).Tuple.opEquals!(Tuple!(int)).opEquals (Tuple!(int)
rhs) is not callable using argument types (Tuple!(int)) const
...\dmd2\src\phobos\std\algorithm.d(1089): Error: template instance
test.main.__lambda4!(Tuple!(int)) error instantiating
test.d(7):        instantiated from here: filter!(Tuple!(int)[])
test.d(7): Error: template instance
test.main.filter!(__lambda4).filter!(Tuple!(int)[]) error instantiating
test.d(9): Error: function
std.typecons.Tuple!(int).Tuple.opEquals!(const(Tuple!(int))).opEquals
(const(Tuple!(int)) rhs) is not callable using argument types
(const(Tuple!(int))) const
...\dmd2\src\phobos\std\algorithm.d(1089): Error: template instance
test.main.__lambda6!(const(Tuple!(int))) error instantiating
test.d(9):        instantiated from here: filter!(const(Tuple!(int))[])
test.d(9): Error: template instance
test.main.filter!(__lambda6).filter!(const(Tuple!(int))[]) error instantiating


If  x => x != del  works then I think  x => del != x  too should work.
The third case is a filter done on a const(Tuple!(int)[]), I think it's legit
code.

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