private Symbol firstDirectIncompatibility(DiagnosticPosition pos, Type t1, Type t2, Type site) {
for (Scope.Entry e1 = t1.tsym.members().elems; e1 != null; e1 = e1.sibling) {
Symbol s1 = e1.sym;
Type st1 = null;
if (s1.kind != MTH || !s1.isInheritedIn(site.tsym, types) ||
(s1.flags() & SYNTHETIC) != 0) continue;
Symbol impl = ((MethodSymbol)s1).implementation(site.tsym, types, false);
if (impl != null && (impl.flags() & ABSTRACT) == 0) continue;
for (Scope.Entry e2 = t2.tsym.members().lookup(s1.name); e2.scope != null; e2 = e2.next()) {
Symbol s2 = e2.sym;
if (s1 == s2) continue;