5.15 Function Declaration

SCP / rule 1 / premise 2
"statEnv1 = statEnv + funcType(expanded-QName => FunctionDecl)"
    statEnv.funcType maps an expanded-QName to a *set* of function
    *signatures*, not a single FunctionDecl. So you'll need premises like:

        statEnv |- [[ SequenceType1 ]]_sequencetype = Type1
        ...
        statEnv |- [[ SequenceTypen ]]_sequencetype = Typen
        statEnv |- [[ SequenceTyper ]]_sequencetype = Typer
        Sig = define function QName( Type1, ..., Typen ) return Typer
        statEnv.funcType(expanded-QName) = {Sig1, ..., Sigk}
        statEnv1 = statEnv + funcType(expanded-QName => {Sig1, ..., Sigk, Sig})

    (Note that you can drop the set-related stuff if you change funcType
    to map to a single signature. See Bug 1580.)