Move storage of final vtbl from BaseClass to IrInterface: BaseClass instances are shared! Always use the target's irstruct interfaceMap when building the const initializer. Tango helloworld works again.

module typeinfos2;

import
typeinfo2.ti_AC,
typeinfo2.ti_Adouble,
typeinfo2.ti_Afloat,
typeinfo2.ti_Ag,
typeinfo2.ti_Aint,
typeinfo2.ti_Along,
typeinfo2.ti_Areal,
typeinfo2.ti_Ashort,
typeinfo2.ti_C;