https://issues.dlang.org/show_bug.cgi?id=21018

          Issue ID: 21018
           Summary: Assert fails glue.d(1560) using -allinst due to an
                    error making it into codegen
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: critical
          Priority: P1
         Component: dmd
          Assignee: nobody@puremagic.com
          Reporter: uplink.coder@gmail.com

compile the following code with allinst.

template Tuple(Specs)
{
    struct Tuple
    {
        this()
        {
        }

        ref opAssign(R)(R )
        if (isTuple!R)
        {
        }
    }
}

enum isTuple(T) = __traits(compiles,
                           {
                               void f(Specs)(Specs ) {}
                               f(T.init);
                           } );

pragma(msg, is(Tuple!int));

Reduced version of: https://issues.dlang.org/show_bug.cgi?id=21017

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