Need a help with OT code :)

Have two versions of ligatures, s_t, and s_t.salt for example.

I write code

feature dlig { # or liga
sub s t by s_t;
} dlig;

feature salt {
sub s_t by s_t.salt;
} salt;

with this code replacing of s_t not work when I turn on both features.

Maybe someone known how to do?

Thanks in advance!