TEST CASE:
---
auto foo()
{
    typeof(return) result;
    return result;
}
---

PATCH: TypeReturn::semantic(), mtype.c, line 5236

Type *TypeReturn::semantic(Loc loc, Scope *sc)
{
    Type *t;
    if (!sc->func)
    {	error(loc, "typeof(return) must be inside function");
	goto Lerr;
    }
    t = sc->func->type->nextOf();
+    if (!t)
+    {   error(loc, "typeof(return) cannot infer type");
+        goto Lerr;
+    }
    t = t->addMod(mod);