The poem "Neutral Tones" by Thomas Hardy was written in 1867 and published in the 1898 collection Wessex Poems and Other Verses. It contains the stanza:
The smile on your mouth was the deadest thing
Alive enough to have strength to die;
And a grin of bitterness swept thereby
Like an ominous bird a-wing….
I would like to ask which figure of speech does the phrase "alive enough to have strength to die" contain?