fail hard on logic errors

src/macros.h

@@ -141,6 +141,8 @@ const char* sqlite_code_string(int code);
     Statement* stmt = baton->stmt;
 
 #define STATEMENT_END()                                                        \
+    assert(stmt->locked);                                                      \
+    assert(stmt->db->pending)                                                  \
     stmt->locked = false;                                                      \
     stmt->db->pending--;                                                       \
     stmt->Process();                                                           \

src/statement.cc

@@ -64,6 +64,8 @@ void Statement::Schedule(EIO_Callback callback, Baton* baton) {
 
 template <class T> void Statement::Error(T* baton) {
     Statement* stmt = baton->stmt;
+    // Fail hard on logic errors.
+    assert(stmt->status != 0);
     EXCEPTION(String::New(stmt->message.c_str()), stmt->status, exception);
 
     if (!baton->callback.IsEmpty() && baton->callback->IsFunction()) {