codegen: Move typecheck of self down to methods vfunc
codegen: Move typecheck of self down to methods vfunc

tjol/vala-tjol,kamanashisroy/aroop,GNOME/vala,rvu95/vala,Distrotech/vala,Distrotech/vala,GNOME/vala,spidermonkdust/vala,frida/vala,jessevdk/vala,rvu95/vala,jessevdk/vala,flobrosch/vala-fixes,xdave/pvala,severinh/vala,GNOME/vala,frida/vala,frida/vala,flobrosch/vala-fixes,flobrosch/vala-fixes,severinh/vala,rvu95/vala,spidermonkdust/vala,frida/vala,playya/vala,kamanashisroy/aroop,GNOME/vala,playya/vala,kamanashisroy/aroop,severinh/vala,jessevdk/vala,Distrotech/vala,frida/vala,tjol/vala-tjol,playya/vala,tjol/vala-tjol,spidermonkdust/vala