[Issue 1780] New: Type tuple deduction failure for class templates

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=1780

           Summary: Type tuple deduction failure for class templates
           Product: D
           Version: 2.009
          Platform: PC
        OS/Version: Windows
            Status: NEW
          Keywords: rejects-valid
          Severity: major
          Priority: P2
         Component: DMD
        AssignedTo: bugzilla at digitalmars.com
        ReportedBy: paul_m_doc at hotmail.com


Type arguments of class templates should be deducible with the following:

template Tuple(Ts ...) { alias Ts Tuple; }

template Decode( T )                            { alias Tuple!() Types; }
template Decode( T : TT!(Us), alias TT, Us... ) { alias Us Types; }

struct S2(T1, T2) {}

// should extract tuple (bool,short) but matches the first specialisation

alias Decode!( S2!(bool,short) ).Types SQ2;  // --> SQ2 is empty tuple!

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Issue #1779 tries to workaround this failure by decoding a fixed number of
arguments but even that crashes the compiler.


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