http://d.puremagic.com/issues/show_bug.cgi?id=7010

           Summary: Purity of map and filter
           Product: D
           Version: D2
          Platform: x86
        OS/Version: Windows
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: DMD
        AssignedTo: nob...@puremagic.com
        ReportedBy: bearophile_h...@eml.cc


--- Comment #0 from bearophile_h...@eml.cc 2011-11-25 16:39:07 PST ---
There are some important cases where the purity inference of
functions/delegates is not working well enough (DMD 2.057head):


import std.algorithm: map, filter;
int foo(immutable int x) pure nothrow {
    return 1;
}
void main() pure {
    immutable data = [1, 2, 3];
    auto m1 = map!((x){ return 1; })(data);     // OK
    auto m2 = map!((int x){ return 1; })(data); // OK
    auto m3 = map!q{ 1 }(data); // error, map is not pure
    auto m4 = map!foo(data);    // error, map is not pure
    //------------
    auto f1 = filter!((x){ return 1; })(data);     // OK
    auto f2 = filter!((int x){ return 1; })(data); // OK
    auto f3 = filter!q{ 1 }(data); // error, filter is not pure
    auto f4 = filter!foo(data);    // error, filter is not pure
}

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