[perl #39173] Multi-Dispatch Incompatible with :flat Params

[via RT]

# New Ticket Created by  chromatic 
# Please include the string:  [perl #39173]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org/rt3/Ticket/Display.html?id=39173 >


The multi-dispatch signature checking code in src/mmd.c does not know anything 
about :flat calls when it constructs the signature tuple for dispatching.  
Here is code to demonstrate this:

.sub main :main
    .local pmc int_pmc
    int_pmc = new .Integer
    int_pmc = 3

    .local pmc args
    args = new .ResizablePMCArray
    push args, int_pmc
    'foo'( args :flat )

    .local pmc string_pmc
    string_pmc = new .String
    string_pmc = 'hello'

    args = new .ResizablePMCArray
    push args, string_pmc
    'foo'( args :flat )
    end
.end

.sub 'foo' :multi(Integer)
    print "foo(Integer)\n"
.end

.sub 'foo' :multi(String)
    print "foo(String)\n"
.end

I'll add this as a TODO test to t/pmc/mmd.t as soon as I get an RT number.

-- c